ht_dec.c

//***************************************************************************/
// This software is released under the 2-Clause BSD license, included
// below.
//
// Copyright (c) 2021, Aous Naman
// Copyright (c) 2021, Kakadu Software Pty Ltd, Australia
// Copyright (c) 2021, The University of New South Wales, Australia
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// 1. Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
// IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
// TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
// PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
// TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//***************************************************************************/
// This file is part of the OpenJpeg software implementation.
// File: ht_dec.c
// Author: Aous Naman
// Date: 01 September 2021
//***************************************************************************/

//***************************************************************************/
/** @file ht_dec.c
 *  @brief implements HTJ2K block decoder
 */

#include <assert.h>
#include <string.h>
#include "opj_includes.h"

#include "t1_ht_luts.h"

/////////////////////////////////////////////////////////////////////////////
// compiler detection
/////////////////////////////////////////////////////////////////////////////
#ifdef _MSC_VER
#define OPJ_COMPILER_MSVC
#elif (defined __GNUC__)
#define OPJ_COMPILER_GNUC
#endif

//************************************************************************/
/** @brief Displays the error message for disabling the decoding of SPP and
  * MRP passes
  */
static OPJ_BOOL only_cleanup_pass_is_decoded = OPJ_FALSE;

//************************************************************************/
/** @brief Generates population count (i.e., the number of set bits)
  *
  *   @param [in]  val is the value for which population count is sought
  */
static INLINE
OPJ_UINT32 population_count(OPJ_UINT32 val)
{
#if defined(OPJ_COMPILER_MSVC) && (defined(_M_IX86) || defined(_M_AMD64))
    return (OPJ_UINT32)__popcnt(val);
#elif (defined OPJ_COMPILER_GNUC)
    return (OPJ_UINT32)__builtin_popcount(val);
#else
    val -= ((val >> 1) & 0x55555555);
    val = (((val >> 2) & 0x33333333) + (val & 0x33333333));
    val = (((val >> 4) + val) & 0x0f0f0f0f);
    val += (val >> 8);
    val += (val >> 16);
    return (OPJ_UINT32)(val & 0x0000003f);
#endif
}

//************************************************************************/
/** @brief Counts the number of leading zeros
  *
  *   @param [in]  val is the value for which leading zero count is sought
  */
#ifdef OPJ_COMPILER_MSVC
#pragma intrinsic(_BitScanReverse)
#endif
static INLINE
OPJ_UINT32 count_leading_zeros(OPJ_UINT32 val)
{
#ifdef OPJ_COMPILER_MSVC
    unsigned long result = 0;
    _BitScanReverse(&result, val);
    return 31U ^ (OPJ_UINT32)result;
#elif (defined OPJ_COMPILER_GNUC)
    return (OPJ_UINT32)__builtin_clz(val);
#else
    val |= (val >> 1);
    val |= (val >> 2);
    val |= (val >> 4);
    val |= (val >> 8);
    val |= (val >> 16);
    return 32U - population_count(val);
#endif
}

//************************************************************************/
/** @brief Read a little-endian serialized UINT32.
  *
  *   @param [in]  dataIn pointer to byte stream to read from
  */
static INLINE OPJ_UINT32 read_le_uint32(const void* dataIn)
{
#if defined(OPJ_BIG_ENDIAN)
    const OPJ_UINT8* data = (const OPJ_UINT8*)dataIn;
    return ((OPJ_UINT32)data[0]) | (OPJ_UINT32)(data[1] << 8) | (OPJ_UINT32)(
               data[2] << 16) | (((
                                      OPJ_UINT32)data[3]) <<
                                 24U);
#else
    return *(OPJ_UINT32*)dataIn;
#endif
}

//************************************************************************/
/** @brief MEL state structure for reading and decoding the MEL bitstream
  *
  *  A number of events is decoded from the MEL bitstream ahead of time
  *  and stored in run/num_runs.
  *  Each run represents the number of zero events before a one event.
  */
typedef struct dec_mel {
    // data decoding machinery
    OPJ_UINT8* data;  //!<the address of data (or bitstream)
    OPJ_UINT64 tmp;   //!<temporary buffer for read data
    int bits;         //!<number of bits stored in tmp
    int size;         //!<number of bytes in MEL code
    OPJ_BOOL unstuff; //!<true if the next bit needs to be unstuffed
    int k;            //!<state of MEL decoder

    // queue of decoded runs
    int num_runs;    //!<number of decoded runs left in runs (maximum 8)
    OPJ_UINT64 runs; //!<runs of decoded MEL codewords (7 bits/run)
} dec_mel_t;

//************************************************************************/
/** @brief Reads and unstuffs the MEL bitstream
  *
  *  This design needs more bytes in the codeblock buffer than the length
  *  of the cleanup pass by up to 2 bytes.
  *
  *  Unstuffing removes the MSB of the byte following a byte whose
  *  value is 0xFF; this prevents sequences larger than 0xFF7F in value
  *  from appearing the bitstream.
  *
  *  @param [in]  melp is a pointer to dec_mel_t structure
  */
static INLINE
void mel_read(dec_mel_t *melp)
{
    OPJ_UINT32 val;
    int bits;
    OPJ_UINT32 t;
    OPJ_BOOL unstuff;

    if (melp->bits > 32) { //there are enough bits in the tmp variable
        return;    // return without reading new data
    }

    val = 0xFFFFFFFF;      // feed in 0xFF if buffer is exhausted
    if (melp->size > 4) {  // if there is more than 4 bytes the MEL segment
        val = read_le_uint32(melp->data);  // read 32 bits from MEL data
        melp->data += 4;           // advance pointer
        melp->size -= 4;           // reduce counter
    } else if (melp->size > 0) { // 4 or less
        OPJ_UINT32 m, v;
        int i = 0;
        while (melp->size > 1) {
            OPJ_UINT32 v = *melp->data++; // read one byte at a time
            OPJ_UINT32 m = ~(0xFFu << i); // mask of location
            val = (val & m) | (v << i);   // put byte in its correct location
            --melp->size;
            i += 8;
        }
        // size equal to 1
        v = *melp->data++;  // the one before the last is different
        v |= 0xF;                         // MEL and VLC segments can overlap
        m = ~(0xFFu << i);
        val = (val & m) | (v << i);
        --melp->size;
    }

    // next we unstuff them before adding them to the buffer
    bits = 32 - melp->unstuff;      // number of bits in val, subtract 1 if
    // the previously read byte requires
    // unstuffing

    // data is unstuffed and accumulated in t
    // bits has the number of bits in t
    t = val & 0xFF;
    unstuff = ((val & 0xFF) == 0xFF); // true if the byte needs unstuffing
    bits -= unstuff; // there is one less bit in t if unstuffing is needed
    t = t << (8 - unstuff); // move up to make room for the next byte

    //this is a repeat of the above
    t |= (val >> 8) & 0xFF;
    unstuff = (((val >> 8) & 0xFF) == 0xFF);
    bits -= unstuff;
    t = t << (8 - unstuff);

    t |= (val >> 16) & 0xFF;
    unstuff = (((val >> 16) & 0xFF) == 0xFF);
    bits -= unstuff;
    t = t << (8 - unstuff);

    t |= (val >> 24) & 0xFF;
    melp->unstuff = (((val >> 24) & 0xFF) == 0xFF);

    // move t to tmp, and push the result all the way up, so we read from
    // the MSB
    melp->tmp |= ((OPJ_UINT64)t) << (64 - bits - melp->bits);
    melp->bits += bits; //increment the number of bits in tmp
}

//************************************************************************/
/** @brief Decodes unstuffed MEL segment bits stored in tmp to runs
  *
  *  Runs are stored in "runs" and the number of runs in "num_runs".
  *  Each run represents a number of zero events that may or may not
  *  terminate in a 1 event.
  *  Each run is stored in 7 bits.  The LSB is 1 if the run terminates in
  *  a 1 event, 0 otherwise.  The next 6 bits, for the case terminating
  *  with 1, contain the number of consecutive 0 zero events * 2; for the
  *  case terminating with 0, they store (number of consecutive 0 zero
  *  events - 1) * 2.
  *  A total of 6 bits (made up of 1 + 5) should have been enough.
  *
  *  @param [in]  melp is a pointer to dec_mel_t structure
  */
static INLINE
void mel_decode(dec_mel_t *melp)
{
    static const int mel_exp[13] = { //MEL exponents
        0, 0, 0, 1, 1, 1, 2, 2, 2, 3, 3, 4, 5
    };

    if (melp->bits < 6) { // if there are less than 6 bits in tmp
        mel_read(melp);    // then read from the MEL bitstream
    }
    // 6 bits is the largest decodable MEL cwd

    //repeat so long that there is enough decodable bits in tmp,
    // and the runs store is not full (num_runs < 8)
    while (melp->bits >= 6 && melp->num_runs < 8) {
        int eval = mel_exp[melp->k]; // number of bits associated with state
        int run = 0;
        if (melp->tmp & (1ull << 63)) { //The next bit to decode (stored in MSB)
            //one is found
            run = 1 << eval;
            run--; // consecutive runs of 0 events - 1
            melp->k = melp->k + 1 < 12 ? melp->k + 1 : 12;//increment, max is 12
            melp->tmp <<= 1; // consume one bit from tmp
            melp->bits -= 1;
            run = run << 1; // a stretch of zeros not terminating in one
        } else {
            //0 is found
            run = (int)(melp->tmp >> (63 - eval)) & ((1 << eval) - 1);
            melp->k = melp->k - 1 > 0 ? melp->k - 1 : 0; //decrement, min is 0
            melp->tmp <<= eval + 1; //consume eval + 1 bits (max is 6)
            melp->bits -= eval + 1;
            run = (run << 1) + 1; // a stretch of zeros terminating with one
        }
        eval = melp->num_runs * 7;                 // 7 bits per run
        melp->runs &= ~((OPJ_UINT64)0x3F << eval); // 6 bits are sufficient
        melp->runs |= ((OPJ_UINT64)run) << eval;   // store the value in runs
        melp->num_runs++;                          // increment count
    }
}

//************************************************************************/
/** @brief Initiates a dec_mel_t structure for MEL decoding and reads
  *         some bytes in order to get the read address to a multiple
  *         of 4
  *
  *  @param [in]  melp is a pointer to dec_mel_t structure
  *  @param [in]  bbuf is a pointer to byte buffer
  *  @param [in]  lcup is the length of MagSgn+MEL+VLC segments
  *  @param [in]  scup is the length of MEL+VLC segments
  */
static INLINE
void mel_init(dec_mel_t *melp, OPJ_UINT8* bbuf, int lcup, int scup)
{
    int num;
    int i;

    melp->data = bbuf + lcup - scup; // move the pointer to the start of MEL
    melp->bits = 0;                  // 0 bits in tmp
    melp->tmp = 0;                   //
    melp->unstuff = OPJ_FALSE;       // no unstuffing
    melp->size = scup - 1;           // size is the length of MEL+VLC-1
    melp->k = 0;                     // 0 for state
    melp->num_runs = 0;              // num_runs is 0
    melp->runs = 0;                  //

    //This code is borrowed; original is for a different architecture
    //These few lines take care of the case where data is not at a multiple
    // of 4 boundary.  It reads 1,2,3 up to 4 bytes from the MEL segment
    num = 4 - (int)((intptr_t)(melp->data) & 0x3);
    for (i = 0; i < num; ++i) { // this code is similar to mel_read
        OPJ_UINT64 d;
        int d_bits;

        assert(melp->unstuff == OPJ_FALSE || melp->data[0] <= 0x8F);
        d = (melp->size > 0) ? *melp->data : 0xFF; // if buffer is consumed
        // set data to 0xFF
        if (melp->size == 1) {
            d |= 0xF;    //if this is MEL+VLC-1, set LSBs to 0xF
        }
        // see the standard
        melp->data += melp->size-- > 0; //increment if the end is not reached
        d_bits = 8 - melp->unstuff; //if unstuffing is needed, reduce by 1
        melp->tmp = (melp->tmp << d_bits) | d; //store bits in tmp
        melp->bits += d_bits;  //increment tmp by number of bits
        melp->unstuff = ((d & 0xFF) == 0xFF); //true of next byte needs
        //unstuffing
    }
    melp->tmp <<= (64 - melp->bits); //push all the way up so the first bit
    // is the MSB
}

//************************************************************************/
/** @brief Retrieves one run from dec_mel_t; if there are no runs stored
  *         MEL segment is decoded
  *
  * @param [in]  melp is a pointer to dec_mel_t structure
  */
static INLINE
int mel_get_run(dec_mel_t *melp)
{
    int t;
    if (melp->num_runs == 0) { //if no runs, decode more bit from MEL segment
        mel_decode(melp);
    }

    t = melp->runs & 0x7F; //retrieve one run
    melp->runs >>= 7;  // remove the retrieved run
    melp->num_runs--;
    return t; // return run
}

//************************************************************************/
/** @brief A structure for reading and unstuffing a segment that grows
  *         backward, such as VLC and MRP
  */
typedef struct rev_struct {
    //storage
    OPJ_UINT8* data;  //!<pointer to where to read data
    OPJ_UINT64 tmp;     //!<temporary buffer of read data
    OPJ_UINT32 bits;  //!<number of bits stored in tmp
    int size;         //!<number of bytes left
    OPJ_BOOL unstuff; //!<true if the last byte is more than 0x8F
    //!<then the current byte is unstuffed if it is 0x7F
} rev_struct_t;

//************************************************************************/
/** @brief Read and unstuff data from a backwardly-growing segment
  *
  *  This reader can read up to 8 bytes from before the VLC segment.
  *  Care must be taken not read from unreadable memory, causing a
  *  segmentation fault.
  *
  *  Note that there is another subroutine rev_read_mrp that is slightly
  *  different.  The other one fills zeros when the buffer is exhausted.
  *  This one basically does not care if the bytes are consumed, because
  *  any extra data should not be used in the actual decoding.
  *
  *  Unstuffing is needed to prevent sequences more than 0xFF8F from
  *  appearing in the bits stream; since we are reading backward, we keep
  *  watch when a value larger than 0x8F appears in the bitstream.
  *  If the byte following this is 0x7F, we unstuff this byte (ignore the
  *  MSB of that byte, which should be 0).
  *
  *  @param [in]  vlcp is a pointer to rev_struct_t structure
  */
static INLINE
void rev_read(rev_struct_t *vlcp)
{
    OPJ_UINT32 val;
    OPJ_UINT32 tmp;
    OPJ_UINT32 bits;
    OPJ_BOOL unstuff;

    //process 4 bytes at a time
    if (vlcp->bits > 32) { // if there are more than 32 bits in tmp, then
        return;    // reading 32 bits can overflow vlcp->tmp
    }
    val = 0;
    //the next line (the if statement) needs to be tested first
    if (vlcp->size > 3) { // if there are more than 3 bytes left in VLC
        // (vlcp->data - 3) move pointer back to read 32 bits at once
        val = read_le_uint32(vlcp->data - 3); // then read 32 bits
        vlcp->data -= 4;                // move data pointer back by 4
        vlcp->size -= 4;                // reduce available byte by 4
    } else if (vlcp->size > 0) { // 4 or less
        int i = 24;
        while (vlcp->size > 0) {
            OPJ_UINT32 v = *vlcp->data--; // read one byte at a time
            val |= (v << i);              // put byte in its correct location
            --vlcp->size;
            i -= 8;
        }
    }

    //accumulate in tmp, number of bits in tmp are stored in bits
    tmp = val >> 24;  //start with the MSB byte

    // test unstuff (previous byte is >0x8F), and this byte is 0x7F
    bits = 8u - ((vlcp->unstuff && (((val >> 24) & 0x7F) == 0x7F)) ? 1u : 0u);
    unstuff = (val >> 24) > 0x8F; //this is for the next byte

    tmp |= ((val >> 16) & 0xFF) << bits; //process the next byte
    bits += 8u - ((unstuff && (((val >> 16) & 0x7F) == 0x7F)) ? 1u : 0u);
    unstuff = ((val >> 16) & 0xFF) > 0x8F;

    tmp |= ((val >> 8) & 0xFF) << bits;
    bits += 8u - ((unstuff && (((val >> 8) & 0x7F) == 0x7F)) ? 1u : 0u);
    unstuff = ((val >> 8) & 0xFF) > 0x8F;

    tmp |= (val & 0xFF) << bits;
    bits += 8u - ((unstuff && ((val & 0x7F) == 0x7F)) ? 1u : 0u);
    unstuff = (val & 0xFF) > 0x8F;

    // now move the read and unstuffed bits into vlcp->tmp
    vlcp->tmp |= (OPJ_UINT64)tmp << vlcp->bits;
    vlcp->bits += bits;
    vlcp->unstuff = unstuff; // this for the next read
}

//************************************************************************/
/** @brief Initiates the rev_struct_t structure and reads a few bytes to
  *         move the read address to multiple of 4
  *
  *  There is another similar rev_init_mrp subroutine.  The difference is
  *  that this one, rev_init, discards the first 12 bits (they have the
  *  sum of the lengths of VLC and MEL segments), and first unstuff depends
  *  on first 4 bits.
  *
  *  @param [in]  vlcp is a pointer to rev_struct_t structure
  *  @param [in]  data is a pointer to byte at the start of the cleanup pass
  *  @param [in]  lcup is the length of MagSgn+MEL+VLC segments
  *  @param [in]  scup is the length of MEL+VLC segments
  */
static INLINE
void rev_init(rev_struct_t *vlcp, OPJ_UINT8* data, int lcup, int scup)
{
    OPJ_UINT32 d;
    int num, tnum, i;

    //first byte has only the upper 4 bits
    vlcp->data = data + lcup - 2;

    //size can not be larger than this, in fact it should be smaller
    vlcp->size = scup - 2;

    d = *vlcp->data--;            // read one byte (this is a half byte)
    vlcp->tmp = d >> 4;           // both initialize and set
    vlcp->bits = 4 - ((vlcp->tmp & 7) == 7); //check standard
    vlcp->unstuff = (d | 0xF) > 0x8F; //this is useful for the next byte

    //This code is designed for an architecture that read address should
    // align to the read size (address multiple of 4 if read size is 4)
    //These few lines take care of the case where data is not at a multiple
    // of 4 boundary. It reads 1,2,3 up to 4 bytes from the VLC bitstream.
    // To read 32 bits, read from (vlcp->data - 3)
    num = 1 + (int)((intptr_t)(vlcp->data) & 0x3);
    tnum = num < vlcp->size ? num : vlcp->size;
    for (i = 0; i < tnum; ++i) {
        OPJ_UINT64 d;
        OPJ_UINT32 d_bits;
        d = *vlcp->data--;  // read one byte and move read pointer
        //check if the last byte was >0x8F (unstuff == true) and this is 0x7F
        d_bits = 8u - ((vlcp->unstuff && ((d & 0x7F) == 0x7F)) ? 1u : 0u);
        vlcp->tmp |= d << vlcp->bits; // move data to vlcp->tmp
        vlcp->bits += d_bits;
        vlcp->unstuff = d > 0x8F; // for next byte
    }
    vlcp->size -= tnum;
    rev_read(vlcp);  // read another 32 buts
}

//************************************************************************/
/** @brief Retrieves 32 bits from the head of a rev_struct structure
  *
  *  By the end of this call, vlcp->tmp must have no less than 33 bits
  *
  *  @param [in]  vlcp is a pointer to rev_struct structure
  */
static INLINE
OPJ_UINT32 rev_fetch(rev_struct_t *vlcp)
{
    if (vlcp->bits < 32) { // if there are less then 32 bits, read more
        rev_read(vlcp);     // read 32 bits, but unstuffing might reduce this
        if (vlcp->bits < 32) { // if there is still space in vlcp->tmp for 32 bits
            rev_read(vlcp);    // read another 32
        }
    }
    return (OPJ_UINT32)vlcp->tmp; // return the head (bottom-most) of vlcp->tmp
}

//************************************************************************/
/** @brief Consumes num_bits from a rev_struct structure
  *
  *  @param [in]  vlcp is a pointer to rev_struct structure
  *  @param [in]  num_bits is the number of bits to be removed
  */
static INLINE
OPJ_UINT32 rev_advance(rev_struct_t *vlcp, OPJ_UINT32 num_bits)
{
    assert(num_bits <= vlcp->bits); // vlcp->tmp must have more than num_bits
    vlcp->tmp >>= num_bits;         // remove bits
    vlcp->bits -= num_bits;         // decrement the number of bits
    return (OPJ_UINT32)vlcp->tmp;
}

//************************************************************************/
/** @brief Reads and unstuffs from rev_struct
  *
  *  This is different than rev_read in that this fills in zeros when the
  *  the available data is consumed.  The other does not care about the
  *  values when all data is consumed.
  *
  *  See rev_read for more information about unstuffing
  *
  *  @param [in]  mrp is a pointer to rev_struct structure
  */
static INLINE
void rev_read_mrp(rev_struct_t *mrp)
{
    OPJ_UINT32 val;
    OPJ_UINT32 tmp;
    OPJ_UINT32 bits;
    OPJ_BOOL unstuff;

    //process 4 bytes at a time
    if (mrp->bits > 32) {
        return;
    }
    val = 0;
    if (mrp->size > 3) { // If there are 3 byte or more
        // (mrp->data - 3) move pointer back to read 32 bits at once
        val = read_le_uint32(mrp->data - 3); // read 32 bits
        mrp->data -= 4;                      // move back pointer
        mrp->size -= 4;                      // reduce count
    } else if (mrp->size > 0) {
        int i = 24;
        while (mrp->size > 0) {
            OPJ_UINT32 v = *mrp->data--; // read one byte at a time
            val |= (v << i);             // put byte in its correct location
            --mrp->size;
            i -= 8;
        }
    }


    //accumulate in tmp, and keep count in bits
    tmp = val >> 24;

    //test if the last byte > 0x8F (unstuff must be true) and this is 0x7F
    bits = 8u - ((mrp->unstuff && (((val >> 24) & 0x7F) == 0x7F)) ? 1u : 0u);
    unstuff = (val >> 24) > 0x8F;

    //process the next byte
    tmp |= ((val >> 16) & 0xFF) << bits;
    bits += 8u - ((unstuff && (((val >> 16) & 0x7F) == 0x7F)) ? 1u : 0u);
    unstuff = ((val >> 16) & 0xFF) > 0x8F;

    tmp |= ((val >> 8) & 0xFF) << bits;
    bits += 8u - ((unstuff && (((val >> 8) & 0x7F) == 0x7F)) ? 1u : 0u);
    unstuff = ((val >> 8) & 0xFF) > 0x8F;

    tmp |= (val & 0xFF) << bits;
    bits += 8u - ((unstuff && ((val & 0x7F) == 0x7F)) ? 1u : 0u);
    unstuff = (val & 0xFF) > 0x8F;

    mrp->tmp |= (OPJ_UINT64)tmp << mrp->bits; // move data to mrp pointer
    mrp->bits += bits;
    mrp->unstuff = unstuff;                   // next byte
}

//************************************************************************/
/** @brief Initialized rev_struct structure for MRP segment, and reads
  *         a number of bytes such that the next 32 bits read are from
  *         an address that is a multiple of 4. Note this is designed for
  *         an architecture that read size must be compatible with the
  *         alignment of the read address
  *
  *  There is another similar subroutine rev_init.  This subroutine does
  *  NOT skip the first 12 bits, and starts with unstuff set to true.
  *
  *  @param [in]  mrp is a pointer to rev_struct structure
  *  @param [in]  data is a pointer to byte at the start of the cleanup pass
  *  @param [in]  lcup is the length of MagSgn+MEL+VLC segments
  *  @param [in]  len2 is the length of SPP+MRP segments
  */
static INLINE
void rev_init_mrp(rev_struct_t *mrp, OPJ_UINT8* data, int lcup, int len2)
{
    int num, i;

    mrp->data = data + lcup + len2 - 1;
    mrp->size = len2;
    mrp->unstuff = OPJ_TRUE;
    mrp->bits = 0;
    mrp->tmp = 0;

    //This code is designed for an architecture that read address should
    // align to the read size (address multiple of 4 if read size is 4)
    //These few lines take care of the case where data is not at a multiple
    // of 4 boundary.  It reads 1,2,3 up to 4 bytes from the MRP stream
    num = 1 + (int)((intptr_t)(mrp->data) & 0x3);
    for (i = 0; i < num; ++i) {
        OPJ_UINT64 d;
        OPJ_UINT32 d_bits;

        //read a byte, 0 if no more data
        d = (mrp->size-- > 0) ? *mrp->data-- : 0;
        //check if unstuffing is needed
        d_bits = 8u - ((mrp->unstuff && ((d & 0x7F) == 0x7F)) ? 1u : 0u);
        mrp->tmp |= d << mrp->bits; // move data to vlcp->tmp
        mrp->bits += d_bits;
        mrp->unstuff = d > 0x8F; // for next byte
    }
    rev_read_mrp(mrp);
}

//************************************************************************/
/** @brief Retrieves 32 bits from the head of a rev_struct structure
  *
  *  By the end of this call, mrp->tmp must have no less than 33 bits
  *
  *  @param [in]  mrp is a pointer to rev_struct structure
  */
static INLINE
OPJ_UINT32 rev_fetch_mrp(rev_struct_t *mrp)
{
    if (mrp->bits < 32) { // if there are less than 32 bits in mrp->tmp
        rev_read_mrp(mrp);    // read 30-32 bits from mrp
        if (mrp->bits < 32) { // if there is a space of 32 bits
            rev_read_mrp(mrp);    // read more
        }
    }
    return (OPJ_UINT32)mrp->tmp;  // return the head of mrp->tmp
}

//************************************************************************/
/** @brief Consumes num_bits from a rev_struct structure
  *
  *  @param [in]  mrp is a pointer to rev_struct structure
  *  @param [in]  num_bits is the number of bits to be removed
  */
static INLINE
OPJ_UINT32 rev_advance_mrp(rev_struct_t *mrp, OPJ_UINT32 num_bits)
{
    assert(num_bits <= mrp->bits); // we must not consume more than mrp->bits
    mrp->tmp >>= num_bits;         // discard the lowest num_bits bits
    mrp->bits -= num_bits;
    return (OPJ_UINT32)mrp->tmp;   // return data after consumption
}

//************************************************************************/
/** @brief Decode initial UVLC to get the u value (or u_q)
  *
  *  @param [in]  vlc is the head of the VLC bitstream
  *  @param [in]  mode is 0, 1, 2, 3, or 4. Values in 0 to 3 are composed of
  *               u_off of 1st quad and 2nd quad of a quad pair.  The value
  *               4 occurs when both bits are 1, and the event decoded
  *               from MEL bitstream is also 1.
  *  @param [out] u is the u value (or u_q) + 1.  Note: we produce u + 1;
  *               this value is a partial calculation of u + kappa.
  */
static INLINE
OPJ_UINT32 decode_init_uvlc(OPJ_UINT32 vlc, OPJ_UINT32 mode, OPJ_UINT32 *u)
{
    //table stores possible decoding three bits from vlc
    // there are 8 entries for xx1, x10, 100, 000, where x means do not care
    // table value is made up of
    // 2 bits in the LSB for prefix length
    // 3 bits for suffix length
    // 3 bits in the MSB for prefix value (u_pfx in Table 3 of ITU T.814)
    static const OPJ_UINT8 dec[8] = { // the index is the prefix codeword
        3 | (5 << 2) | (5 << 5),        //000 == 000, prefix codeword "000"
        1 | (0 << 2) | (1 << 5),        //001 == xx1, prefix codeword "1"
        2 | (0 << 2) | (2 << 5),        //010 == x10, prefix codeword "01"
        1 | (0 << 2) | (1 << 5),        //011 == xx1, prefix codeword "1"
        3 | (1 << 2) | (3 << 5),        //100 == 100, prefix codeword "001"
        1 | (0 << 2) | (1 << 5),        //101 == xx1, prefix codeword "1"
        2 | (0 << 2) | (2 << 5),        //110 == x10, prefix codeword "01"
        1 | (0 << 2) | (1 << 5)         //111 == xx1, prefix codeword "1"
    };

    OPJ_UINT32 consumed_bits = 0;
    if (mode == 0) { // both u_off are 0
        u[0] = u[1] = 1; //Kappa is 1 for initial line
    } else if (mode <= 2) { // u_off are either 01 or 10
        OPJ_UINT32 d;
        OPJ_UINT32 suffix_len;

        d = dec[vlc & 0x7];   //look at the least significant 3 bits
        vlc >>= d & 0x3;                 //prefix length
        consumed_bits += d & 0x3;

        suffix_len = ((d >> 2) & 0x7);
        consumed_bits += suffix_len;

        d = (d >> 5) + (vlc & ((1U << suffix_len) - 1)); // u value
        u[0] = (mode == 1) ? d + 1 : 1; // kappa is 1 for initial line
        u[1] = (mode == 1) ? 1 : d + 1; // kappa is 1 for initial line
    } else if (mode == 3) { // both u_off are 1, and MEL event is 0
        OPJ_UINT32 d1 = dec[vlc & 0x7];  // LSBs of VLC are prefix codeword
        vlc >>= d1 & 0x3;                // Consume bits
        consumed_bits += d1 & 0x3;

        if ((d1 & 0x3) > 2) {
            OPJ_UINT32 suffix_len;

            //u_{q_2} prefix
            u[1] = (vlc & 1) + 1 + 1; //Kappa is 1 for initial line
            ++consumed_bits;
            vlc >>= 1;

            suffix_len = ((d1 >> 2) & 0x7);
            consumed_bits += suffix_len;
            d1 = (d1 >> 5) + (vlc & ((1U << suffix_len) - 1)); // u value
            u[0] = d1 + 1; //Kappa is 1 for initial line
        } else {
            OPJ_UINT32 d2;
            OPJ_UINT32 suffix_len;

            d2 = dec[vlc & 0x7];  // LSBs of VLC are prefix codeword
            vlc >>= d2 & 0x3;                // Consume bits
            consumed_bits += d2 & 0x3;

            suffix_len = ((d1 >> 2) & 0x7);
            consumed_bits += suffix_len;

            d1 = (d1 >> 5) + (vlc & ((1U << suffix_len) - 1)); // u value
            u[0] = d1 + 1; //Kappa is 1 for initial line
            vlc >>= suffix_len;

            suffix_len = ((d2 >> 2) & 0x7);
            consumed_bits += suffix_len;

            d2 = (d2 >> 5) + (vlc & ((1U << suffix_len) - 1)); // u value
            u[1] = d2 + 1; //Kappa is 1 for initial line
        }
    } else if (mode == 4) { // both u_off are 1, and MEL event is 1
        OPJ_UINT32 d1;
        OPJ_UINT32 d2;
        OPJ_UINT32 suffix_len;

        d1 = dec[vlc & 0x7];  // LSBs of VLC are prefix codeword
        vlc >>= d1 & 0x3;                // Consume bits
        consumed_bits += d1 & 0x3;

        d2 = dec[vlc & 0x7];  // LSBs of VLC are prefix codeword
        vlc >>= d2 & 0x3;                // Consume bits
        consumed_bits += d2 & 0x3;

        suffix_len = ((d1 >> 2) & 0x7);
        consumed_bits += suffix_len;

        d1 = (d1 >> 5) + (vlc & ((1U << suffix_len) - 1)); // u value
        u[0] = d1 + 3; // add 2+kappa
        vlc >>= suffix_len;

        suffix_len = ((d2 >> 2) & 0x7);
        consumed_bits += suffix_len;

        d2 = (d2 >> 5) + (vlc & ((1U << suffix_len) - 1)); // u value
        u[1] = d2 + 3; // add 2+kappa
    }
    return consumed_bits;
}

//************************************************************************/
/** @brief Decode non-initial UVLC to get the u value (or u_q)
  *
  *  @param [in]  vlc is the head of the VLC bitstream
  *  @param [in]  mode is 0, 1, 2, or 3. The 1st bit is u_off of 1st quad
  *               and 2nd for 2nd quad of a quad pair
  *  @param [out] u is the u value (or u_q) + 1.  Note: we produce u + 1;
  *               this value is a partial calculation of u + kappa.
  */
static INLINE
OPJ_UINT32 decode_noninit_uvlc(OPJ_UINT32 vlc, OPJ_UINT32 mode, OPJ_UINT32 *u)
{
    //table stores possible decoding three bits from vlc
    // there are 8 entries for xx1, x10, 100, 000, where x means do not care
    // table value is made up of
    // 2 bits in the LSB for prefix length
    // 3 bits for suffix length
    // 3 bits in the MSB for prefix value (u_pfx in Table 3 of ITU T.814)
    static const OPJ_UINT8 dec[8] = {
        3 | (5 << 2) | (5 << 5), //000 == 000, prefix codeword "000"
        1 | (0 << 2) | (1 << 5), //001 == xx1, prefix codeword "1"
        2 | (0 << 2) | (2 << 5), //010 == x10, prefix codeword "01"
        1 | (0 << 2) | (1 << 5), //011 == xx1, prefix codeword "1"
        3 | (1 << 2) | (3 << 5), //100 == 100, prefix codeword "001"
        1 | (0 << 2) | (1 << 5), //101 == xx1, prefix codeword "1"
        2 | (0 << 2) | (2 << 5), //110 == x10, prefix codeword "01"
        1 | (0 << 2) | (1 << 5)  //111 == xx1, prefix codeword "1"
    };

    OPJ_UINT32 consumed_bits = 0;
    if (mode == 0) {
        u[0] = u[1] = 1; //for kappa
    } else if (mode <= 2) { //u_off are either 01 or 10
        OPJ_UINT32 d;
        OPJ_UINT32 suffix_len;

        d = dec[vlc & 0x7];  //look at the least significant 3 bits
        vlc >>= d & 0x3;                //prefix length
        consumed_bits += d & 0x3;

        suffix_len = ((d >> 2) & 0x7);
        consumed_bits += suffix_len;

        d = (d >> 5) + (vlc & ((1U << suffix_len) - 1)); // u value
        u[0] = (mode == 1) ? d + 1 : 1; //for kappa
        u[1] = (mode == 1) ? 1 : d + 1; //for kappa
    } else if (mode == 3) { // both u_off are 1
        OPJ_UINT32 d1;
        OPJ_UINT32 d2;
        OPJ_UINT32 suffix_len;

        d1 = dec[vlc & 0x7];  // LSBs of VLC are prefix codeword
        vlc >>= d1 & 0x3;                // Consume bits
        consumed_bits += d1 & 0x3;

        d2 = dec[vlc & 0x7];  // LSBs of VLC are prefix codeword
        vlc >>= d2 & 0x3;                // Consume bits
        consumed_bits += d2 & 0x3;

        suffix_len = ((d1 >> 2) & 0x7);
        consumed_bits += suffix_len;

        d1 = (d1 >> 5) + (vlc & ((1U << suffix_len) - 1)); // u value
        u[0] = d1 + 1;  //1 for kappa
        vlc >>= suffix_len;

        suffix_len = ((d2 >> 2) & 0x7);
        consumed_bits += suffix_len;

        d2 = (d2 >> 5) + (vlc & ((1U << suffix_len) - 1)); // u value
        u[1] = d2 + 1;  //1 for kappa
    }
    return consumed_bits;
}

//************************************************************************/
/** @brief State structure for reading and unstuffing of forward-growing
  *         bitstreams; these are: MagSgn and SPP bitstreams
  */
typedef struct frwd_struct {
    const OPJ_UINT8* data; //!<pointer to bitstream
    OPJ_UINT64 tmp;        //!<temporary buffer of read data
    OPJ_UINT32 bits;       //!<number of bits stored in tmp
    OPJ_BOOL unstuff;      //!<true if a bit needs to be unstuffed from next byte
    int size;              //!<size of data
    OPJ_UINT32 X;          //!<0 or 0xFF, X's are inserted at end of bitstream
} frwd_struct_t;

//************************************************************************/
/** @brief Read and unstuffs 32 bits from forward-growing bitstream
  *
  *  A subroutine to read from both the MagSgn or SPP bitstreams;
  *  in particular, when MagSgn bitstream is consumed, 0xFF's are fed,
  *  while when SPP is exhausted 0's are fed in.
  *  X controls this value.
  *
  *  Unstuffing prevent sequences that are more than 0xFF7F from appearing
  *  in the conpressed sequence.  So whenever a value of 0xFF is coded, the
  *  MSB of the next byte is set 0 and must be ignored during decoding.
  *
  *  Reading can go beyond the end of buffer by up to 3 bytes.
  *
  *  @param  [in]  msp is a pointer to frwd_struct_t structure
  *
  */
static INLINE
void frwd_read(frwd_struct_t *msp)
{
    OPJ_UINT32 val;
    OPJ_UINT32 bits;
    OPJ_UINT32 t;
    OPJ_BOOL unstuff;

    assert(msp->bits <= 32); // assert that there is a space for 32 bits

    val = 0u;
    if (msp->size > 3) {
        val = read_le_uint32(msp->data);  // read 32 bits
        msp->data += 4;           // increment pointer
        msp->size -= 4;           // reduce size
    } else if (msp->size > 0) {
        int i = 0;
        val = msp->X != 0 ? 0xFFFFFFFFu : 0;
        while (msp->size > 0) {
            OPJ_UINT32 v = *msp->data++;  // read one byte at a time
            OPJ_UINT32 m = ~(0xFFu << i); // mask of location
            val = (val & m) | (v << i);   // put one byte in its correct location
            --msp->size;
            i += 8;
        }
    } else {
        val = msp->X != 0 ? 0xFFFFFFFFu : 0;
    }

    // we accumulate in t and keep a count of the number of bits in bits
    bits = 8u - (msp->unstuff ? 1u : 0u);
    t = val & 0xFF;
    unstuff = ((val & 0xFF) == 0xFF);  // Do we need unstuffing next?

    t |= ((val >> 8) & 0xFF) << bits;
    bits += 8u - (unstuff ? 1u : 0u);
    unstuff = (((val >> 8) & 0xFF) == 0xFF);

    t |= ((val >> 16) & 0xFF) << bits;
    bits += 8u - (unstuff ? 1u : 0u);
    unstuff = (((val >> 16) & 0xFF) == 0xFF);

    t |= ((val >> 24) & 0xFF) << bits;
    bits += 8u - (unstuff ? 1u : 0u);
    msp->unstuff = (((val >> 24) & 0xFF) == 0xFF); // for next byte

    msp->tmp |= ((OPJ_UINT64)t) << msp->bits;  // move data to msp->tmp
    msp->bits += bits;
}

//************************************************************************/
/** @brief Initialize frwd_struct_t struct and reads some bytes
  *
  *  @param [in]  msp is a pointer to frwd_struct_t
  *  @param [in]  data is a pointer to the start of data
  *  @param [in]  size is the number of byte in the bitstream
  *  @param [in]  X is the value fed in when the bitstream is exhausted.
  *               See frwd_read.
  */
static INLINE
void frwd_init(frwd_struct_t *msp, const OPJ_UINT8* data, int size,
               OPJ_UINT32 X)
{
    int num, i;

    msp->data = data;
    msp->tmp = 0;
    msp->bits = 0;
    msp->unstuff = OPJ_FALSE;
    msp->size = size;
    msp->X = X;
    assert(msp->X == 0 || msp->X == 0xFF);

    //This code is designed for an architecture that read address should
    // align to the read size (address multiple of 4 if read size is 4)
    //These few lines take care of the case where data is not at a multiple
    // of 4 boundary.  It reads 1,2,3 up to 4 bytes from the bitstream
    num = 4 - (int)((intptr_t)(msp->data) & 0x3);
    for (i = 0; i < num; ++i) {
        OPJ_UINT64 d;
        //read a byte if the buffer is not exhausted, otherwise set it to X
        d = msp->size-- > 0 ? *msp->data++ : msp->X;
        msp->tmp |= (d << msp->bits);      // store data in msp->tmp
        msp->bits += 8u - (msp->unstuff ? 1u : 0u); // number of bits added to msp->tmp
        msp->unstuff = ((d & 0xFF) == 0xFF); // unstuffing for next byte
    }
    frwd_read(msp); // read 32 bits more
}

//************************************************************************/
/** @brief Consume num_bits bits from the bitstream of frwd_struct_t
  *
  *  @param [in]  msp is a pointer to frwd_struct_t
  *  @param [in]  num_bits is the number of bit to consume
  */
static INLINE
void frwd_advance(frwd_struct_t *msp, OPJ_UINT32 num_bits)
{
    assert(num_bits <= msp->bits);
    msp->tmp >>= num_bits;  // consume num_bits
    msp->bits -= num_bits;
}

//************************************************************************/
/** @brief Fetches 32 bits from the frwd_struct_t bitstream
  *
  *  @param [in]  msp is a pointer to frwd_struct_t
  */
static INLINE
OPJ_UINT32 frwd_fetch(frwd_struct_t *msp)
{
    if (msp->bits < 32) {
        frwd_read(msp);
        if (msp->bits < 32) { //need to test
            frwd_read(msp);
        }
    }
    return (OPJ_UINT32)msp->tmp;
}

//************************************************************************/
/** @brief Allocates T1 buffers
  *
  *  @param [in, out]  t1 is codeblock cofficients storage
  *  @param [in]       w is codeblock width
  *  @param [in]       h is codeblock height
  */
static OPJ_BOOL opj_t1_allocate_buffers(
    opj_t1_t *t1,
    OPJ_UINT32 w,
    OPJ_UINT32 h)
{
    OPJ_UINT32 flagssize;

    /* No risk of overflow. Prior checks ensure those assert are met */
    /* They are per the specification */
    assert(w <= 1024);
    assert(h <= 1024);
    assert(w * h <= 4096);

    /* encoder uses tile buffer, so no need to allocate */
    {
        OPJ_UINT32 datasize = w * h;

        if (datasize > t1->datasize) {
            opj_aligned_free(t1->data);
            t1->data = (OPJ_INT32*)
                       opj_aligned_malloc(datasize * sizeof(OPJ_INT32));
            if (!t1->data) {
                /* FIXME event manager error callback */
                return OPJ_FALSE;
            }
            t1->datasize = datasize;
        }
        /* memset first arg is declared to never be null by gcc */
        if (t1->data != NULL) {
            memset(t1->data, 0, datasize * sizeof(OPJ_INT32));
        }
    }

    // We expand these buffers to multiples of 16 bytes.
    // We need 4 buffers of 129 integers each, expanded to 132 integers each
    // We also need 514 bytes of buffer, expanded to 528 bytes
    flagssize = 132U * sizeof(OPJ_UINT32) * 4U; // expanded to multiple of 16
    flagssize += 528U; // 514 expanded to multiples of 16

    {
        if (flagssize > t1->flagssize) {

            opj_aligned_free(t1->flags);
            t1->flags = (opj_flag_t*) opj_aligned_malloc(flagssize);
            if (!t1->flags) {
                /* FIXME event manager error callback */
                return OPJ_FALSE;
            }
        }
        t1->flagssize = flagssize;

        memset(t1->flags, 0, flagssize);
    }

    t1->w = w;
    t1->h = h;

    return OPJ_TRUE;
}

//************************************************************************/
/** @brief Decodes one codeblock, processing the cleanup, siginificance
  *         propagation, and magnitude refinement pass
  *
  *  @param [in, out]  t1 is codeblock cofficients storage
  *  @param [in]       cblk is codeblock properties
  *  @param [in]       orient is the subband to which the codeblock belongs (not needed)
  *  @param [in]       roishift is region of interest shift
  *  @param [in]       cblksty is codeblock style
  *  @param [in]       p_manager is events print manager
  *  @param [in]       p_manager_mutex a mutex to control access to p_manager
  *  @param [in]       check_pterm: check termination (not used)
  */
OPJ_BOOL opj_t1_ht_decode_cblk(opj_t1_t *t1,
                               opj_tcd_cblk_dec_t* cblk,
                               OPJ_UINT32 orient,
                               OPJ_UINT32 roishift,
                               OPJ_UINT32 cblksty,
                               opj_event_mgr_t *p_manager,
                               opj_mutex_t* p_manager_mutex,
                               OPJ_BOOL check_pterm)
{
    OPJ_BYTE* cblkdata = NULL;
    OPJ_UINT8* coded_data;
    OPJ_UINT32* decoded_data;
    OPJ_UINT32 zero_bplanes;
    OPJ_UINT32 num_passes;
    OPJ_UINT32 lengths1;
    OPJ_UINT32 lengths2;
    OPJ_INT32 width;
    OPJ_INT32 height;
    OPJ_INT32 stride;
    OPJ_UINT32 *pflags, *sigma1, *sigma2, *mbr1, *mbr2, *sip, sip_shift;
    OPJ_UINT32 p;
    OPJ_UINT32 zero_bplanes_p1;
    int lcup, scup;
    dec_mel_t mel;
    rev_struct_t vlc;
    frwd_struct_t magsgn;
    frwd_struct_t sigprop;
    rev_struct_t magref;
    OPJ_UINT8 *lsp, *line_state;
    int run;
    OPJ_UINT32 vlc_val;              // fetched data from VLC bitstream
    OPJ_UINT32 qinf[2];
    OPJ_UINT32 c_q;
    OPJ_UINT32* sp;
    OPJ_INT32 x, y; // loop indices
    OPJ_BOOL stripe_causal = (cblksty & J2K_CCP_CBLKSTY_VSC) != 0;
    OPJ_UINT32 cblk_len = 0;

    (void)(orient);      // stops unused parameter message
    (void)(check_pterm); // stops unused parameter message

    // We ignor orient, because the same decoder is used for all subbands
    // We also ignore check_pterm, because I am not sure how it applies
    if (roishift != 0) {
        if (p_manager_mutex) {
            opj_mutex_lock(p_manager_mutex);
        }
        opj_event_msg(p_manager, EVT_ERROR, "We do not support ROI in decoding "
                      "HT codeblocks\n");
        if (p_manager_mutex) {
            opj_mutex_unlock(p_manager_mutex);
        }
        return OPJ_FALSE;
    }

    if (!opj_t1_allocate_buffers(
                t1,
                (OPJ_UINT32)(cblk->x1 - cblk->x0),
                (OPJ_UINT32)(cblk->y1 - cblk->y0))) {
        return OPJ_FALSE;
    }

    if (cblk->Mb == 0) {
        return OPJ_TRUE;
    }

    /* numbps = Mb + 1 - zero_bplanes, Mb = Kmax, zero_bplanes = missing_msbs */
    zero_bplanes = (cblk->Mb + 1) - cblk->numbps;

    /* Compute whole codeblock length from chunk lengths */
    cblk_len = 0;
    {
        OPJ_UINT32 i;
        for (i = 0; i < cblk->numchunks; i++) {
            cblk_len += cblk->chunks[i].len;
        }
    }

    if (cblk->numchunks > 1 || t1->mustuse_cblkdatabuffer) {
        OPJ_UINT32 i;

        /* Allocate temporary memory if needed */
        if (cblk_len > t1->cblkdatabuffersize) {
            cblkdata = (OPJ_BYTE*)opj_realloc(
                           t1->cblkdatabuffer, cblk_len);
            if (cblkdata == NULL) {
                return OPJ_FALSE;
            }
            t1->cblkdatabuffer = cblkdata;
            t1->cblkdatabuffersize = cblk_len;
        }

        /* Concatenate all chunks */
        cblkdata = t1->cblkdatabuffer;
        cblk_len = 0;
        for (i = 0; i < cblk->numchunks; i++) {
            memcpy(cblkdata + cblk_len, cblk->chunks[i].data, cblk->chunks[i].len);
            cblk_len += cblk->chunks[i].len;
        }
    } else if (cblk->numchunks == 1) {
        cblkdata = cblk->chunks[0].data;
    } else {
        /* Not sure if that can happen in practice, but avoid Coverity to */
        /* think we will dereference a null cblkdta pointer */
        return OPJ_TRUE;
    }

    // OPJ_BYTE* coded_data is a pointer to bitstream
    coded_data = cblkdata;
    // OPJ_UINT32* decoded_data is a pointer to decoded codeblock data buf.
    decoded_data = (OPJ_UINT32*)t1->data;
    // OPJ_UINT32 num_passes is the number of passes: 1 if CUP only, 2 for
    // CUP+SPP, and 3 for CUP+SPP+MRP
    num_passes = cblk->numsegs > 0 ? cblk->segs[0].real_num_passes : 0;
    num_passes += cblk->numsegs > 1 ? cblk->segs[1].real_num_passes : 0;
    // OPJ_UINT32 lengths1 is the length of cleanup pass
    lengths1 = num_passes > 0 ? cblk->segs[0].len : 0;
    // OPJ_UINT32 lengths2 is the length of refinement passes (either SPP only or SPP+MRP)
    lengths2 = num_passes > 1 ? cblk->segs[1].len : 0;
    // OPJ_INT32 width is the decoded codeblock width
    width = cblk->x1 - cblk->x0;
    // OPJ_INT32 height is the decoded codeblock height
    height = cblk->y1 - cblk->y0;
    // OPJ_INT32 stride is the decoded codeblock buffer stride
    stride = width;

    /*  sigma1 and sigma2 contains significant (i.e., non-zero) pixel
     *  locations.  The buffers are used interchangeably, because we need
     *  more than 4 rows of significance information at a given time.
     *  Each 32 bits contain significance information for 4 rows of 8
     *  columns each.  If we denote 32 bits by 0xaaaaaaaa, the each "a" is
     *  called a nibble and has significance information for 4 rows.
     *  The least significant nibble has information for the first column,
     *  and so on. The nibble's LSB is for the first row, and so on.
     *  Since, at most, we can have 1024 columns in a quad, we need 128
     *  entries; we added 1 for convenience when propagation of signifcance
     *  goes outside the structure
     *  To work in OpenJPEG these buffers has been expanded to 132.
     */
    // OPJ_UINT32 *pflags, *sigma1, *sigma2, *mbr1, *mbr2, *sip, sip_shift;
    pflags = (OPJ_UINT32 *)t1->flags;
    sigma1 = pflags;
    sigma2 = sigma1 + 132;
    // mbr arrangement is similar to sigma; mbr contains locations
    // that become significant during significance propagation pass
    mbr1 = sigma2 + 132;
    mbr2 = mbr1 + 132;
    //a pointer to sigma
    sip = sigma1;  //pointers to arrays to be used interchangeably
    sip_shift = 0; //the amount of shift needed for sigma

    if (num_passes > 1 && lengths2 == 0) {
        if (p_manager_mutex) {
            opj_mutex_lock(p_manager_mutex);
        }
        opj_event_msg(p_manager, EVT_WARNING, "A malformed codeblock that has "
                      "more than one coding pass, but zero length for "
                      "2nd and potentially the 3rd pass in an HT codeblock.\n");
        if (p_manager_mutex) {
            opj_mutex_unlock(p_manager_mutex);
        }
        num_passes = 1;
    }
    if (num_passes > 3) {
        if (p_manager_mutex) {
            opj_mutex_lock(p_manager_mutex);
        }
        opj_event_msg(p_manager, EVT_ERROR, "We do not support more than 3 "
                      "coding passes in an HT codeblock; This codeblocks has "
                      "%d passes.\n", num_passes);
        if (p_manager_mutex) {
            opj_mutex_unlock(p_manager_mutex);
        }
        return OPJ_FALSE;
    }

    if (cblk->Mb > 30) {
        /* This check is better moved to opj_t2_read_packet_header() in t2.c
           We do not have enough precision to decode any passes
           The design of openjpeg assumes that the bits of a 32-bit integer are
           assigned as follows:
           bit 31 is for sign
           bits 30-1 are for magnitude
           bit 0 is for the center of the quantization bin
           Therefore we can only do values of cblk->Mb <= 30
         */
        if (p_manager_mutex) {
            opj_mutex_lock(p_manager_mutex);
        }
        opj_event_msg(p_manager, EVT_ERROR, "32 bits are not enough to "
                      "decode this codeblock, since the number of "
                      "bitplane, %d, is larger than 30.\n", cblk->Mb);
        if (p_manager_mutex) {
            opj_mutex_unlock(p_manager_mutex);
        }
        return OPJ_FALSE;
    }
    if (zero_bplanes > cblk->Mb) {
        /* This check is better moved to opj_t2_read_packet_header() in t2.c,
           in the line "l_cblk->numbps = (OPJ_UINT32)l_band->numbps + 1 - i;"
           where i is the zero bitplanes, and should be no larger than cblk->Mb
           We cannot have more zero bitplanes than there are planes. */
        if (p_manager_mutex) {
            opj_mutex_lock(p_manager_mutex);
        }
        opj_event_msg(p_manager, EVT_ERROR, "Malformed HT codeblock. "
                      "Decoding this codeblock is stopped. There are "
                      "%d zero bitplanes in %d bitplanes.\n",
                      zero_bplanes, cblk->Mb);

        if (p_manager_mutex) {
            opj_mutex_unlock(p_manager_mutex);
        }
        return OPJ_FALSE;
    } else if (zero_bplanes == cblk->Mb && num_passes > 1) {
        /* When the number of zero bitplanes is equal to the number of bitplanes,
           only the cleanup pass makes sense*/
        if (only_cleanup_pass_is_decoded == OPJ_FALSE) {
            if (p_manager_mutex) {
                opj_mutex_lock(p_manager_mutex);
            }
            /* We have a second check to prevent the possibility of an overrun condition,
               in the very unlikely event of a second thread discovering that
               only_cleanup_pass_is_decoded is false before the first thread changing
               the condition. */
            if (only_cleanup_pass_is_decoded == OPJ_FALSE) {
                only_cleanup_pass_is_decoded = OPJ_TRUE;
                opj_event_msg(p_manager, EVT_WARNING, "Malformed HT codeblock. "
                              "When the number of zero planes bitplanes is "
                              "equal to the number of bitplanes, only the cleanup "
                              "pass makes sense, but we have %d passes in this "
                              "codeblock. Therefore, only the cleanup pass will be "
                              "decoded. This message will not be displayed again.\n",
                              num_passes);
            }
            if (p_manager_mutex) {
                opj_mutex_unlock(p_manager_mutex);
            }
        }
        num_passes = 1;
    }

    /* OPJ_UINT32 */
    p = cblk->numbps;

    // OPJ_UINT32 zero planes plus 1
    zero_bplanes_p1 = zero_bplanes + 1;

    if (lengths1 < 2 || (OPJ_UINT32)lengths1 > cblk_len ||
            (OPJ_UINT32)(lengths1 + lengths2) > cblk_len) {
        if (p_manager_mutex) {
            opj_mutex_lock(p_manager_mutex);
        }
        opj_event_msg(p_manager, EVT_ERROR, "Malformed HT codeblock. "
                      "Invalid codeblock length values.\n");

        if (p_manager_mutex) {
            opj_mutex_unlock(p_manager_mutex);
        }
        return OPJ_FALSE;
    }
    // read scup and fix the bytes there
    lcup = (int)lengths1;  // length of CUP
    //scup is the length of MEL + VLC
    scup = (((int)coded_data[lcup - 1]) << 4) + (coded_data[lcup - 2] & 0xF);
    if (scup < 2 || scup > lcup || scup > 4079) { //something is wrong
        /* The standard stipulates 2 <= Scup <= min(Lcup, 4079) */
        if (p_manager_mutex) {
            opj_mutex_lock(p_manager_mutex);
        }
        opj_event_msg(p_manager, EVT_ERROR, "Malformed HT codeblock. "
                      "One of the following condition is not met: "
                      "2 <= Scup <= min(Lcup, 4079)\n");

        if (p_manager_mutex) {
            opj_mutex_unlock(p_manager_mutex);
        }
        return OPJ_FALSE;
    }

    // init structures
    mel_init(&mel, coded_data, lcup, scup);
    rev_init(&vlc, coded_data, lcup, scup);
    frwd_init(&magsgn, coded_data, lcup - scup, 0xFF);
    if (num_passes > 1) { // needs to be tested
        frwd_init(&sigprop, coded_data + lengths1, (int)lengths2, 0);
    }
    if (num_passes > 2) {
        rev_init_mrp(&magref, coded_data, (int)lengths1, (int)lengths2);
    }

    /** State storage
      *  One byte per quad; for 1024 columns, or 512 quads, we need
      *  512 bytes. We are using 2 extra bytes one on the left and one on
      *  the right for convenience.
      *
      *  The MSB bit in each byte is (\sigma^nw | \sigma^n), and the 7 LSBs
      *  contain max(E^nw | E^n)
      */

    // 514 is enough for a block width of 1024, +2 extra
    // here expanded to 528
    line_state = (OPJ_UINT8 *)(mbr2 + 132);

    //initial 2 lines
    /////////////////
    lsp = line_state;              // point to line state
    lsp[0] = 0;                    // for initial row of quad, we set to 0
    run = mel_get_run(&mel);    // decode runs of events from MEL bitstrm
    // data represented as runs of 0 events
    // See mel_decode description
    qinf[0] = qinf[1] = 0;      // quad info decoded from VLC bitstream
    c_q = 0;                    // context for quad q
    sp = decoded_data;          // decoded codeblock samples
    // vlc_val;                 // fetched data from VLC bitstream

    for (x = 0; x < width; x += 4) { // one iteration per quad pair
        OPJ_UINT32 U_q[2]; // u values for the quad pair
        OPJ_UINT32 uvlc_mode;
        OPJ_UINT32 consumed_bits;
        OPJ_UINT32 m_n, v_n;
        OPJ_UINT32 ms_val;
        OPJ_UINT32 locs;

        // decode VLC
        /////////////

        //first quad
        // Get the head of the VLC bitstream. One fetch is enough for two
        // quads, since the largest VLC code is 7 bits, and maximum number of
        // bits used for u is 8.  Therefore for two quads we need 30 bits
        // (if we include unstuffing, then 32 bits are enough, since we have
        // a maximum of one stuffing per two bytes)
        vlc_val = rev_fetch(&vlc);

        //decode VLC using the context c_q and the head of the VLC bitstream
        qinf[0] = vlc_tbl0[(c_q << 7) | (vlc_val & 0x7F) ];

        if (c_q == 0) { // if zero context, we need to use one MEL event
            run -= 2; //the number of 0 events is multiplied by 2, so subtract 2

            // Is the run terminated in 1? if so, use decoded VLC code,
            // otherwise, discard decoded data, since we will decoded again
            // using a different context
            qinf[0] = (run == -1) ? qinf[0] : 0;

            // is run -1 or -2? this means a run has been consumed
            if (run < 0) {
                run = mel_get_run(&mel);    // get another run
            }
        }

        // prepare context for the next quad; eqn. 1 in ITU T.814
        c_q = ((qinf[0] & 0x10) >> 4) | ((qinf[0] & 0xE0) >> 5);

        //remove data from vlc stream (0 bits are removed if qinf is not used)
        vlc_val = rev_advance(&vlc, qinf[0] & 0x7);

        //update sigma
        // The update depends on the value of x; consider one OPJ_UINT32
        // if x is 0, 8, 16 and so on, then this line update c locations
        //      nibble (4 bits) number   0 1 2 3 4 5 6 7
        //                         LSB   c c 0 0 0 0 0 0
        //                               c c 0 0 0 0 0 0
        //                               0 0 0 0 0 0 0 0
        //                               0 0 0 0 0 0 0 0
        // if x is 4, 12, 20, then this line update locations c
        //      nibble (4 bits) number   0 1 2 3 4 5 6 7
        //                         LSB   0 0 0 0 c c 0 0
        //                               0 0 0 0 c c 0 0
        //                               0 0 0 0 0 0 0 0
        //                               0 0 0 0 0 0 0 0
        *sip |= (((qinf[0] & 0x30) >> 4) | ((qinf[0] & 0xC0) >> 2)) << sip_shift;

        //second quad
        qinf[1] = 0;
        if (x + 2 < width) { // do not run if codeblock is narrower
            //decode VLC using the context c_q and the head of the VLC bitstream
            qinf[1] = vlc_tbl0[(c_q << 7) | (vlc_val & 0x7F)];

            // if context is zero, use one MEL event
            if (c_q == 0) { //zero context
                run -= 2; //subtract 2, since events number if multiplied by 2

                // if event is 0, discard decoded qinf
                qinf[1] = (run == -1) ? qinf[1] : 0;

                if (run < 0) { // have we consumed all events in a run
                    run = mel_get_run(&mel);    // if yes, then get another run
                }
            }

            //prepare context for the next quad, eqn. 1 in ITU T.814
            c_q = ((qinf[1] & 0x10) >> 4) | ((qinf[1] & 0xE0) >> 5);

            //remove data from vlc stream, if qinf is not used, cwdlen is 0
            vlc_val = rev_advance(&vlc, qinf[1] & 0x7);
        }

        //update sigma
        // The update depends on the value of x; consider one OPJ_UINT32
        // if x is 0, 8, 16 and so on, then this line update c locations
        //      nibble (4 bits) number   0 1 2 3 4 5 6 7
        //                         LSB   0 0 c c 0 0 0 0
        //                               0 0 c c 0 0 0 0
        //                               0 0 0 0 0 0 0 0
        //                               0 0 0 0 0 0 0 0
        // if x is 4, 12, 20, then this line update locations c
        //      nibble (4 bits) number   0 1 2 3 4 5 6 7
        //                         LSB   0 0 0 0 0 0 c c
        //                               0 0 0 0 0 0 c c
        //                               0 0 0 0 0 0 0 0
        //                               0 0 0 0 0 0 0 0
        *sip |= (((qinf[1] & 0x30) | ((qinf[1] & 0xC0) << 2))) << (4 + sip_shift);

        sip += x & 0x7 ? 1 : 0; // move sigma pointer to next entry
        sip_shift ^= 0x10;      // increment/decrement sip_shift by 16

        // retrieve u
        /////////////

        // uvlc_mode is made up of u_offset bits from the quad pair
        uvlc_mode = ((qinf[0] & 0x8) >> 3) | ((qinf[1] & 0x8) >> 2);
        if (uvlc_mode == 3) { // if both u_offset are set, get an event from
            // the MEL run of events
            run -= 2; //subtract 2, since events number if multiplied by 2
            uvlc_mode += (run == -1) ? 1 : 0; //increment uvlc_mode if event is 1
            if (run < 0) { // if run is consumed (run is -1 or -2), get another run
                run = mel_get_run(&mel);
            }
        }
        //decode uvlc_mode to get u for both quads
        consumed_bits = decode_init_uvlc(vlc_val, uvlc_mode, U_q);
        if (U_q[0] > zero_bplanes_p1 || U_q[1] > zero_bplanes_p1) {
            if (p_manager_mutex) {
                opj_mutex_lock(p_manager_mutex);
            }
            opj_event_msg(p_manager, EVT_ERROR, "Malformed HT codeblock. Decoding "
                          "this codeblock is stopped. U_q is larger than zero "
                          "bitplanes + 1 \n");
            if (p_manager_mutex) {
                opj_mutex_unlock(p_manager_mutex);
            }
            return OPJ_FALSE;
        }

        //consume u bits in the VLC code
        vlc_val = rev_advance(&vlc, consumed_bits);

        //decode magsgn and update line_state
        /////////////////////////////////////

        //We obtain a mask for the samples locations that needs evaluation
        locs = 0xFF;
        if (x + 4 > width) {
            locs >>= (x + 4 - width) << 1;    // limits width
        }
        locs = height > 1 ? locs : (locs & 0x55);         // limits height

        if ((((qinf[0] & 0xF0) >> 4) | (qinf[1] & 0xF0)) & ~locs) {
            if (p_manager_mutex) {
                opj_mutex_lock(p_manager_mutex);
            }
            opj_event_msg(p_manager, EVT_ERROR, "Malformed HT codeblock. "
                          "VLC code produces significant samples outside "
                          "the codeblock area.\n");
            if (p_manager_mutex) {
                opj_mutex_unlock(p_manager_mutex);
            }
            return OPJ_FALSE;
        }

        //first quad, starting at first sample in quad and moving on
        if (qinf[0] & 0x10) { //is it significant? (sigma_n)
            OPJ_UINT32 val;

            ms_val = frwd_fetch(&magsgn);         //get 32 bits of magsgn data
            m_n = U_q[0] - ((qinf[0] >> 12) & 1); //evaluate m_n (number of bits
            // to read from bitstream), using EMB e_k
            frwd_advance(&magsgn, m_n);         //consume m_n
            val = ms_val << 31;                 //get sign bit
            v_n = ms_val & ((1U << m_n) - 1);   //keep only m_n bits
            v_n |= ((qinf[0] & 0x100) >> 8) << m_n;  //add EMB e_1 as MSB
            v_n |= 1;                                //add center of bin
            //v_n now has 2 * (\mu - 1) + 0.5 with correct sign bit
            //add 2 to make it 2*\mu+0.5, shift it up to missing MSBs
            sp[0] = val | ((v_n + 2) << (p - 1));
        } else if (locs & 0x1) { // if this is inside the codeblock, set the
            sp[0] = 0;           // sample to zero
        }

        if (qinf[0] & 0x20) { //sigma_n
            OPJ_UINT32 val, t;

            ms_val = frwd_fetch(&magsgn);         //get 32 bits
            m_n = U_q[0] - ((qinf[0] >> 13) & 1); //m_n, uses EMB e_k
            frwd_advance(&magsgn, m_n);           //consume m_n
            val = ms_val << 31;                   //get sign bit
            v_n = ms_val & ((1U << m_n) - 1);     //keep only m_n bits
            v_n |= ((qinf[0] & 0x200) >> 9) << m_n; //add EMB e_1
            v_n |= 1;                               //bin center
            //v_n now has 2 * (\mu - 1) + 0.5 with correct sign bit
            //add 2 to make it 2*\mu+0.5, shift it up to missing MSBs
            sp[stride] = val | ((v_n + 2) << (p - 1));

            //update line_state: bit 7 (\sigma^N), and E^N
            t = lsp[0] & 0x7F;       // keep E^NW
            v_n = 32 - count_leading_zeros(v_n);
            lsp[0] = (OPJ_UINT8)(0x80 | (t > v_n ? t : v_n)); //max(E^NW, E^N) | s
        } else if (locs & 0x2) { // if this is inside the codeblock, set the
            sp[stride] = 0;      // sample to zero
        }

        ++lsp; // move to next quad information
        ++sp;  // move to next column of samples

        //this is similar to the above two samples
        if (qinf[0] & 0x40) {
            OPJ_UINT32 val;

            ms_val = frwd_fetch(&magsgn);
            m_n = U_q[0] - ((qinf[0] >> 14) & 1);
            frwd_advance(&magsgn, m_n);
            val = ms_val << 31;
            v_n = ms_val & ((1U << m_n) - 1);
            v_n |= (((qinf[0] & 0x400) >> 10) << m_n);
            v_n |= 1;
            sp[0] = val | ((v_n + 2) << (p - 1));
        } else if (locs & 0x4) {
            sp[0] = 0;
        }

        lsp[0] = 0;
        if (qinf[0] & 0x80) {
            OPJ_UINT32 val;
            ms_val = frwd_fetch(&magsgn);
            m_n = U_q[0] - ((qinf[0] >> 15) & 1); //m_n
            frwd_advance(&magsgn, m_n);
            val = ms_val << 31;
            v_n = ms_val & ((1U << m_n) - 1);
            v_n |= ((qinf[0] & 0x800) >> 11) << m_n;
            v_n |= 1; //center of bin
            sp[stride] = val | ((v_n + 2) << (p - 1));

            //line_state: bit 7 (\sigma^NW), and E^NW for next quad
            lsp[0] = (OPJ_UINT8)(0x80 | (32 - count_leading_zeros(v_n)));
        } else if (locs & 0x8) { //if outside set to 0
            sp[stride] = 0;
        }

        ++sp; //move to next column

        //second quad
        if (qinf[1] & 0x10) {
            OPJ_UINT32 val;

            ms_val = frwd_fetch(&magsgn);
            m_n = U_q[1] - ((qinf[1] >> 12) & 1); //m_n
            frwd_advance(&magsgn, m_n);
            val = ms_val << 31;
            v_n = ms_val & ((1U << m_n) - 1);
            v_n |= (((qinf[1] & 0x100) >> 8) << m_n);
            v_n |= 1;
            sp[0] = val | ((v_n + 2) << (p - 1));
        } else if (locs & 0x10) {
            sp[0] = 0;
        }

        if (qinf[1] & 0x20) {
            OPJ_UINT32 val, t;

            ms_val = frwd_fetch(&magsgn);
            m_n = U_q[1] - ((qinf[1] >> 13) & 1); //m_n
            frwd_advance(&magsgn, m_n);
            val = ms_val << 31;
            v_n = ms_val & ((1U << m_n) - 1);
            v_n |= (((qinf[1] & 0x200) >> 9) << m_n);
            v_n |= 1;
            sp[stride] = val | ((v_n + 2) << (p - 1));

            //update line_state: bit 7 (\sigma^N), and E^N
            t = lsp[0] & 0x7F;            //E^NW
            v_n = 32 - count_leading_zeros(v_n);     //E^N
            lsp[0] = (OPJ_UINT8)(0x80 | (t > v_n ? t : v_n)); //max(E^NW, E^N) | s
        } else if (locs & 0x20) {
            sp[stride] = 0;    //no need to update line_state
        }

        ++lsp; //move line state to next quad
        ++sp;  //move to next sample

        if (qinf[1] & 0x40) {
            OPJ_UINT32 val;

            ms_val = frwd_fetch(&magsgn);
            m_n = U_q[1] - ((qinf[1] >> 14) & 1); //m_n
            frwd_advance(&magsgn, m_n);
            val = ms_val << 31;
            v_n = ms_val & ((1U << m_n) - 1);
            v_n |= (((qinf[1] & 0x400) >> 10) << m_n);
            v_n |= 1;
            sp[0] = val | ((v_n + 2) << (p - 1));
        } else if (locs & 0x40) {
            sp[0] = 0;
        }

        lsp[0] = 0;
        if (qinf[1] & 0x80) {
            OPJ_UINT32 val;

            ms_val = frwd_fetch(&magsgn);
            m_n = U_q[1] - ((qinf[1] >> 15) & 1); //m_n
            frwd_advance(&magsgn, m_n);
            val = ms_val << 31;
            v_n = ms_val & ((1U << m_n) - 1);
            v_n |= (((qinf[1] & 0x800) >> 11) << m_n);
            v_n |= 1; //center of bin
            sp[stride] = val | ((v_n + 2) << (p - 1));

            //line_state: bit 7 (\sigma^NW), and E^NW for next quad
            lsp[0] = (OPJ_UINT8)(0x80 | (32 - count_leading_zeros(v_n)));
        } else if (locs & 0x80) {
            sp[stride] = 0;
        }

        ++sp;
    }

    //non-initial lines
    //////////////////////////
    for (y = 2; y < height; /*done at the end of loop*/) {
        OPJ_UINT32 *sip;
        OPJ_UINT8 ls0;
        OPJ_INT32 x;

        sip_shift ^= 0x2;  // shift sigma to the upper half od the nibble
        sip_shift &= 0xFFFFFFEFU; //move back to 0 (it might have been at 0x10)
        sip = y & 0x4 ? sigma2 : sigma1; //choose sigma array

        lsp = line_state;
        ls0 = lsp[0];                   // read the line state value
        lsp[0] = 0;                     // and set it to zero
        sp = decoded_data + y * stride; // generated samples
        c_q = 0;                        // context
        for (x = 0; x < width; x += 4) {
            OPJ_UINT32 U_q[2];
            OPJ_UINT32 uvlc_mode, consumed_bits;
            OPJ_UINT32 m_n, v_n;
            OPJ_UINT32 ms_val;
            OPJ_UINT32 locs;

            // decode vlc
            /////////////

            //first quad
            // get context, eqn. 2 ITU T.814
            // c_q has \sigma^W | \sigma^SW
            c_q |= (ls0 >> 7);          //\sigma^NW | \sigma^N
            c_q |= (lsp[1] >> 5) & 0x4; //\sigma^NE | \sigma^NF

            //the following is very similar to previous code, so please refer to
            // that
            vlc_val = rev_fetch(&vlc);
            qinf[0] = vlc_tbl1[(c_q << 7) | (vlc_val & 0x7F)];
            if (c_q == 0) { //zero context
                run -= 2;
                qinf[0] = (run == -1) ? qinf[0] : 0;
                if (run < 0) {
                    run = mel_get_run(&mel);
                }
            }
            //prepare context for the next quad, \sigma^W | \sigma^SW
            c_q = ((qinf[0] & 0x40) >> 5) | ((qinf[0] & 0x80) >> 6);

            //remove data from vlc stream
            vlc_val = rev_advance(&vlc, qinf[0] & 0x7);

            //update sigma
            // The update depends on the value of x and y; consider one OPJ_UINT32
            // if x is 0, 8, 16 and so on, and y is 2, 6, etc., then this
            // line update c locations
            //      nibble (4 bits) number   0 1 2 3 4 5 6 7
            //                         LSB   0 0 0 0 0 0 0 0
            //                               0 0 0 0 0 0 0 0
            //                               c c 0 0 0 0 0 0
            //                               c c 0 0 0 0 0 0
            *sip |= (((qinf[0] & 0x30) >> 4) | ((qinf[0] & 0xC0) >> 2)) << sip_shift;

            //second quad
            qinf[1] = 0;
            if (x + 2 < width) {
                c_q |= (lsp[1] >> 7);
                c_q |= (lsp[2] >> 5) & 0x4;
                qinf[1] = vlc_tbl1[(c_q << 7) | (vlc_val & 0x7F)];
                if (c_q == 0) { //zero context
                    run -= 2;
                    qinf[1] = (run == -1) ? qinf[1] : 0;
                    if (run < 0) {
                        run = mel_get_run(&mel);
                    }
                }
                //prepare context for the next quad
                c_q = ((qinf[1] & 0x40) >> 5) | ((qinf[1] & 0x80) >> 6);
                //remove data from vlc stream
                vlc_val = rev_advance(&vlc, qinf[1] & 0x7);
            }

            //update sigma
            *sip |= (((qinf[1] & 0x30) | ((qinf[1] & 0xC0) << 2))) << (4 + sip_shift);

            sip += x & 0x7 ? 1 : 0;
            sip_shift ^= 0x10;

            //retrieve u
            ////////////
            uvlc_mode = ((qinf[0] & 0x8) >> 3) | ((qinf[1] & 0x8) >> 2);
            consumed_bits = decode_noninit_uvlc(vlc_val, uvlc_mode, U_q);
            vlc_val = rev_advance(&vlc, consumed_bits);

            //calculate E^max and add it to U_q, eqns 5 and 6 in ITU T.814
            if ((qinf[0] & 0xF0) & ((qinf[0] & 0xF0) - 1)) { // is \gamma_q 1?
                OPJ_UINT32 E = (ls0 & 0x7Fu);
                E = E > (lsp[1] & 0x7Fu) ? E : (lsp[1] & 0x7Fu); //max(E, E^NE, E^NF)
                //since U_q already has u_q + 1, we subtract 2 instead of 1
                U_q[0] += E > 2 ? E - 2 : 0;
            }

            if ((qinf[1] & 0xF0) & ((qinf[1] & 0xF0) - 1)) { //is \gamma_q 1?
                OPJ_UINT32 E = (lsp[1] & 0x7Fu);
                E = E > (lsp[2] & 0x7Fu) ? E : (lsp[2] & 0x7Fu); //max(E, E^NE, E^NF)
                //since U_q already has u_q + 1, we subtract 2 instead of 1
                U_q[1] += E > 2 ? E - 2 : 0;
            }

            if (U_q[0] > zero_bplanes_p1 || U_q[1] > zero_bplanes_p1) {
                if (p_manager_mutex) {
                    opj_mutex_lock(p_manager_mutex);
                }
                opj_event_msg(p_manager, EVT_ERROR, "Malformed HT codeblock. "
                              "Decoding this codeblock is stopped. U_q is"
                              "larger than bitplanes + 1 \n");
                if (p_manager_mutex) {
                    opj_mutex_unlock(p_manager_mutex);
                }
                return OPJ_FALSE;
            }

            ls0 = lsp[2]; //for next double quad
            lsp[1] = lsp[2] = 0;

            //decode magsgn and update line_state
            /////////////////////////////////////

            //locations where samples need update
            locs = 0xFF;
            if (x + 4 > width) {
                locs >>= (x + 4 - width) << 1;
            }
            locs = y + 2 <= height ? locs : (locs & 0x55);

            if ((((qinf[0] & 0xF0) >> 4) | (qinf[1] & 0xF0)) & ~locs) {
                if (p_manager_mutex) {
                    opj_mutex_lock(p_manager_mutex);
                }
                opj_event_msg(p_manager, EVT_ERROR, "Malformed HT codeblock. "
                              "VLC code produces significant samples outside "
                              "the codeblock area.\n");
                if (p_manager_mutex) {
                    opj_mutex_unlock(p_manager_mutex);
                }
                return OPJ_FALSE;
            }



            if (qinf[0] & 0x10) { //sigma_n
                OPJ_UINT32 val;

                ms_val = frwd_fetch(&magsgn);
                m_n = U_q[0] - ((qinf[0] >> 12) & 1); //m_n
                frwd_advance(&magsgn, m_n);
                val = ms_val << 31;
                v_n = ms_val & ((1U << m_n) - 1);
                v_n |= ((qinf[0] & 0x100) >> 8) << m_n;
                v_n |= 1; //center of bin
                sp[0] = val | ((v_n + 2) << (p - 1));
            } else if (locs & 0x1) {
                sp[0] = 0;
            }

            if (qinf[0] & 0x20) { //sigma_n
                OPJ_UINT32 val, t;

                ms_val = frwd_fetch(&magsgn);
                m_n = U_q[0] - ((qinf[0] >> 13) & 1); //m_n
                frwd_advance(&magsgn, m_n);
                val = ms_val << 31;
                v_n = ms_val & ((1U << m_n) - 1);
                v_n |= ((qinf[0] & 0x200) >> 9) << m_n;
                v_n |= 1; //center of bin
                sp[stride] = val | ((v_n + 2) << (p - 1));

                //update line_state: bit 7 (\sigma^N), and E^N
                t = lsp[0] & 0x7F;          //E^NW
                v_n = 32 - count_leading_zeros(v_n);
                lsp[0] = (OPJ_UINT8)(0x80 | (t > v_n ? t : v_n));
            } else if (locs & 0x2) {
                sp[stride] = 0;    //no need to update line_state
            }

            ++lsp;
            ++sp;

            if (qinf[0] & 0x40) { //sigma_n
                OPJ_UINT32 val;

                ms_val = frwd_fetch(&magsgn);
                m_n = U_q[0] - ((qinf[0] >> 14) & 1); //m_n
                frwd_advance(&magsgn, m_n);
                val = ms_val << 31;
                v_n = ms_val & ((1U << m_n) - 1);
                v_n |= (((qinf[0] & 0x400) >> 10) << m_n);
                v_n |= 1;                            //center of bin
                sp[0] = val | ((v_n + 2) << (p - 1));
            } else if (locs & 0x4) {
                sp[0] = 0;
            }

            if (qinf[0] & 0x80) { //sigma_n
                OPJ_UINT32 val;

                ms_val = frwd_fetch(&magsgn);
                m_n = U_q[0] - ((qinf[0] >> 15) & 1); //m_n
                frwd_advance(&magsgn, m_n);
                val = ms_val << 31;
                v_n = ms_val & ((1U << m_n) - 1);
                v_n |= ((qinf[0] & 0x800) >> 11) << m_n;
                v_n |= 1; //center of bin
                sp[stride] = val | ((v_n + 2) << (p - 1));

                //update line_state: bit 7 (\sigma^NW), and E^NW for next quad
                lsp[0] = (OPJ_UINT8)(0x80 | (32 - count_leading_zeros(v_n)));
            } else if (locs & 0x8) {
                sp[stride] = 0;
            }

            ++sp;

            if (qinf[1] & 0x10) { //sigma_n
                OPJ_UINT32 val;

                ms_val = frwd_fetch(&magsgn);
                m_n = U_q[1] - ((qinf[1] >> 12) & 1); //m_n
                frwd_advance(&magsgn, m_n);
                val = ms_val << 31;
                v_n = ms_val & ((1U << m_n) - 1);
                v_n |= (((qinf[1] & 0x100) >> 8) << m_n);
                v_n |= 1;                            //center of bin
                sp[0] = val | ((v_n + 2) << (p - 1));
            } else if (locs & 0x10) {
                sp[0] = 0;
            }

            if (qinf[1] & 0x20) { //sigma_n
                OPJ_UINT32 val, t;

                ms_val = frwd_fetch(&magsgn);
                m_n = U_q[1] - ((qinf[1] >> 13) & 1); //m_n
                frwd_advance(&magsgn, m_n);
                val = ms_val << 31;
                v_n = ms_val & ((1U << m_n) - 1);
                v_n |= (((qinf[1] & 0x200) >> 9) << m_n);
                v_n |= 1; //center of bin
                sp[stride] = val | ((v_n + 2) << (p - 1));

                //update line_state: bit 7 (\sigma^N), and E^N
                t = lsp[0] & 0x7F;          //E^NW
                v_n = 32 - count_leading_zeros(v_n);
                lsp[0] = (OPJ_UINT8)(0x80 | (t > v_n ? t : v_n));
            } else if (locs & 0x20) {
                sp[stride] = 0;    //no need to update line_state
            }

            ++lsp;
            ++sp;

            if (qinf[1] & 0x40) { //sigma_n
                OPJ_UINT32 val;

                ms_val = frwd_fetch(&magsgn);
                m_n = U_q[1] - ((qinf[1] >> 14) & 1); //m_n
                frwd_advance(&magsgn, m_n);
                val = ms_val << 31;
                v_n = ms_val & ((1U << m_n) - 1);
                v_n |= (((qinf[1] & 0x400) >> 10) << m_n);
                v_n |= 1;                            //center of bin
                sp[0] = val | ((v_n + 2) << (p - 1));
            } else if (locs & 0x40) {
                sp[0] = 0;
            }

            if (qinf[1] & 0x80) { //sigma_n
                OPJ_UINT32 val;

                ms_val = frwd_fetch(&magsgn);
                m_n = U_q[1] - ((qinf[1] >> 15) & 1); //m_n
                frwd_advance(&magsgn, m_n);
                val = ms_val << 31;
                v_n = ms_val & ((1U << m_n) - 1);
                v_n |= (((qinf[1] & 0x800) >> 11) << m_n);
                v_n |= 1; //center of bin
                sp[stride] = val | ((v_n + 2) << (p - 1));

                //update line_state: bit 7 (\sigma^NW), and E^NW for next quad
                lsp[0] = (OPJ_UINT8)(0x80 | (32 - count_leading_zeros(v_n)));
            } else if (locs & 0x80) {
                sp[stride] = 0;
            }

            ++sp;
        }

        y += 2;
        if (num_passes > 1 && (y & 3) == 0) { //executed at multiples of 4
            // This is for SPP and potentially MRP

            if (num_passes > 2) { //do MRP
                // select the current stripe
                OPJ_UINT32 *cur_sig = y & 0x4 ? sigma1 : sigma2;
                // the address of the data that needs updating
                OPJ_UINT32 *dpp = decoded_data + (y - 4) * stride;
                OPJ_UINT32 half = 1u << (p - 2); // half the center of the bin
                OPJ_INT32 i;
                for (i = 0; i < width; i += 8) {
                    //Process one entry from sigma array at a time
                    // Each nibble (4 bits) in the sigma array represents 4 rows,
                    // and the 32 bits contain 8 columns
                    OPJ_UINT32 cwd = rev_fetch_mrp(&magref); // get 32 bit data
                    OPJ_UINT32 sig = *cur_sig++; // 32 bit that will be processed now
                    OPJ_UINT32 col_mask = 0xFu;  // a mask for a column in sig
                    OPJ_UINT32 *dp = dpp + i;    // next column in decode samples
                    if (sig) { // if any of the 32 bits are set
                        int j;
                        for (j = 0; j < 8; ++j, dp++) { //one column at a time
                            if (sig & col_mask) { // lowest nibble
                                OPJ_UINT32 sample_mask = 0x11111111u & col_mask; //LSB

                                if (sig & sample_mask) { //if LSB is set
                                    OPJ_UINT32 sym;

                                    assert(dp[0] != 0); // decoded value cannot be zero
                                    sym = cwd & 1; // get it value
                                    // remove center of bin if sym is 0
                                    dp[0] ^= (1 - sym) << (p - 1);
                                    dp[0] |= half;      // put half the center of bin
                                    cwd >>= 1;          //consume word
                                }
                                sample_mask += sample_mask; //next row

                                if (sig & sample_mask) {
                                    OPJ_UINT32 sym;

                                    assert(dp[stride] != 0);
                                    sym = cwd & 1;
                                    dp[stride] ^= (1 - sym) << (p - 1);
                                    dp[stride] |= half;
                                    cwd >>= 1;
                                }
                                sample_mask += sample_mask;

                                if (sig & sample_mask) {
                                    OPJ_UINT32 sym;

                                    assert(dp[2 * stride] != 0);
                                    sym = cwd & 1;
                                    dp[2 * stride] ^= (1 - sym) << (p - 1);
                                    dp[2 * stride] |= half;
                                    cwd >>= 1;
                                }
                                sample_mask += sample_mask;

                                if (sig & sample_mask) {
                                    OPJ_UINT32 sym;

                                    assert(dp[3 * stride] != 0);
                                    sym = cwd & 1;
                                    dp[3 * stride] ^= (1 - sym) << (p - 1);
                                    dp[3 * stride] |= half;
                                    cwd >>= 1;
                                }
                                sample_mask += sample_mask;
                            }
                            col_mask <<= 4; //next column
                        }
                    }
                    // consume data according to the number of bits set
                    rev_advance_mrp(&magref, population_count(sig));
                }
            }

            if (y >= 4) { // update mbr array at the end of each stripe
                //generate mbr corresponding to a stripe
                OPJ_UINT32 *sig = y & 0x4 ? sigma1 : sigma2;
                OPJ_UINT32 *mbr = y & 0x4 ? mbr1 : mbr2;

                //data is processed in patches of 8 columns, each
                // each 32 bits in sigma1 or mbr1 represent 4 rows

                //integrate horizontally
                OPJ_UINT32 prev = 0; // previous columns
                OPJ_INT32 i;
                for (i = 0; i < width; i += 8, mbr++, sig++) {
                    OPJ_UINT32 t, z;

                    mbr[0] = sig[0];         //start with significant samples
                    mbr[0] |= prev >> 28;    //for first column, left neighbors
                    mbr[0] |= sig[0] << 4;   //left neighbors
                    mbr[0] |= sig[0] >> 4;   //right neighbors
                    mbr[0] |= sig[1] << 28;  //for last column, right neighbors
                    prev = sig[0];           // for next group of columns

                    //integrate vertically
                    t = mbr[0], z = mbr[0];
                    z |= (t & 0x77777777) << 1; //above neighbors
                    z |= (t & 0xEEEEEEEE) >> 1; //below neighbors
                    mbr[0] = z & ~sig[0]; //remove already significance samples
                }
            }

            if (y >= 8) { //wait until 8 rows has been processed
                OPJ_UINT32 *cur_sig, *cur_mbr, *nxt_sig, *nxt_mbr;
                OPJ_UINT32 prev;
                OPJ_UINT32 val;
                OPJ_INT32 i;

                // add membership from the next stripe, obtained above
                cur_sig = y & 0x4 ? sigma2 : sigma1;
                cur_mbr = y & 0x4 ? mbr2 : mbr1;
                nxt_sig = y & 0x4 ? sigma1 : sigma2;  //future samples
                prev = 0; // the columns before these group of 8 columns
                for (i = 0; i < width; i += 8, cur_mbr++, cur_sig++, nxt_sig++) {
                    OPJ_UINT32 t = nxt_sig[0];
                    t |= prev >> 28;        //for first column, left neighbors
                    t |= nxt_sig[0] << 4;   //left neighbors
                    t |= nxt_sig[0] >> 4;   //right neighbors
                    t |= nxt_sig[1] << 28;  //for last column, right neighbors
                    prev = nxt_sig[0];      // for next group of columns

                    if (!stripe_causal) {
                        cur_mbr[0] |= (t & 0x11111111u) << 3; //propagate up to cur_mbr
                    }
                    cur_mbr[0] &= ~cur_sig[0]; //remove already significance samples
                }

                //find new locations and get signs
                cur_sig = y & 0x4 ? sigma2 : sigma1;
                cur_mbr = y & 0x4 ? mbr2 : mbr1;
                nxt_sig = y & 0x4 ? sigma1 : sigma2; //future samples
                nxt_mbr = y & 0x4 ? mbr1 : mbr2;     //future samples
                val = 3u << (p - 2); // sample values for newly discovered
                // significant samples including the bin center
                for (i = 0; i < width;
                        i += 8, cur_sig++, cur_mbr++, nxt_sig++, nxt_mbr++) {
                    OPJ_UINT32 ux, tx;
                    OPJ_UINT32 mbr = *cur_mbr;
                    OPJ_UINT32 new_sig = 0;
                    if (mbr) { //are there any samples that might be significant
                        OPJ_INT32 n;
                        for (n = 0; n < 8; n += 4) {
                            OPJ_UINT32 col_mask;
                            OPJ_UINT32 inv_sig;
                            OPJ_INT32 end;
                            OPJ_INT32 j;

                            OPJ_UINT32 cwd = frwd_fetch(&sigprop); //get 32 bits
                            OPJ_UINT32 cnt = 0;

                            OPJ_UINT32 *dp = decoded_data + (y - 8) * stride;
                            dp += i + n; //address for decoded samples

                            col_mask = 0xFu << (4 * n); //a mask to select a column

                            inv_sig = ~cur_sig[0]; // insignificant samples

                            //find the last sample we operate on
                            end = n + 4 + i < width ? n + 4 : width - i;

                            for (j = n; j < end; ++j, ++dp, col_mask <<= 4) {
                                OPJ_UINT32 sample_mask;

                                if ((col_mask & mbr) == 0) { //no samples need checking
                                    continue;
                                }

                                //scan mbr to find a new significant sample
                                sample_mask = 0x11111111u & col_mask; // LSB
                                if (mbr & sample_mask) {
                                    assert(dp[0] == 0); // the sample must have been 0
                                    if (cwd & 1) { //if this sample has become significant
                                        // must propagate it to nearby samples
                                        OPJ_UINT32 t;
                                        new_sig |= sample_mask;  // new significant samples
                                        t = 0x32u << (j * 4);// propagation to neighbors
                                        mbr |= t & inv_sig; //remove already significant samples
                                    }
                                    cwd >>= 1;
                                    ++cnt; //consume bit and increment number of
                                    //consumed bits
                                }

                                sample_mask += sample_mask;  // next row
                                if (mbr & sample_mask) {
                                    assert(dp[stride] == 0);
                                    if (cwd & 1) {
                                        OPJ_UINT32 t;
                                        new_sig |= sample_mask;
                                        t = 0x74u << (j * 4);
                                        mbr |= t & inv_sig;
                                    }
                                    cwd >>= 1;
                                    ++cnt;
                                }

                                sample_mask += sample_mask;
                                if (mbr & sample_mask) {
                                    assert(dp[2 * stride] == 0);
                                    if (cwd & 1) {
                                        OPJ_UINT32 t;
                                        new_sig |= sample_mask;
                                        t = 0xE8u << (j * 4);
                                        mbr |= t & inv_sig;
                                    }
                                    cwd >>= 1;
                                    ++cnt;
                                }

                                sample_mask += sample_mask;
                                if (mbr & sample_mask) {
                                    assert(dp[3 * stride] == 0);
                                    if (cwd & 1) {
                                        OPJ_UINT32 t;
                                        new_sig |= sample_mask;
                                        t = 0xC0u << (j * 4);
                                        mbr |= t & inv_sig;
                                    }
                                    cwd >>= 1;
                                    ++cnt;
                                }
                            }

                            //obtain signs here
                            if (new_sig & (0xFFFFu << (4 * n))) { //if any
                                OPJ_UINT32 col_mask;
                                OPJ_INT32 j;
                                OPJ_UINT32 *dp = decoded_data + (y - 8) * stride;
                                dp += i + n; // decoded samples address
                                col_mask = 0xFu << (4 * n); //mask to select a column

                                for (j = n; j < end; ++j, ++dp, col_mask <<= 4) {
                                    OPJ_UINT32 sample_mask;

                                    if ((col_mask & new_sig) == 0) { //if non is significant
                                        continue;
                                    }

                                    //scan 4 signs
                                    sample_mask = 0x11111111u & col_mask;
                                    if (new_sig & sample_mask) {
                                        assert(dp[0] == 0);
                                        dp[0] |= ((cwd & 1) << 31) | val; //put value and sign
                                        cwd >>= 1;
                                        ++cnt; //consume bit and increment number
                                        //of consumed bits
                                    }

                                    sample_mask += sample_mask;
                                    if (new_sig & sample_mask) {
                                        assert(dp[stride] == 0);
                                        dp[stride] |= ((cwd & 1) << 31) | val;
                                        cwd >>= 1;
                                        ++cnt;
                                    }

                                    sample_mask += sample_mask;
                                    if (new_sig & sample_mask) {
                                        assert(dp[2 * stride] == 0);
                                        dp[2 * stride] |= ((cwd & 1) << 31) | val;
                                        cwd >>= 1;
                                        ++cnt;
                                    }

                                    sample_mask += sample_mask;
                                    if (new_sig & sample_mask) {
                                        assert(dp[3 * stride] == 0);
                                        dp[3 * stride] |= ((cwd & 1) << 31) | val;
                                        cwd >>= 1;
                                        ++cnt;
                                    }
                                }

                            }
                            frwd_advance(&sigprop, cnt); //consume the bits from bitstrm
                            cnt = 0;

                            //update the next 8 columns
                            if (n == 4) {
                                //horizontally
                                OPJ_UINT32 t = new_sig >> 28;
                                t |= ((t & 0xE) >> 1) | ((t & 7) << 1);
                                cur_mbr[1] |= t & ~cur_sig[1];
                            }
                        }
                    }
                    //update the next stripe (vertically propagation)
                    new_sig |= cur_sig[0];
                    ux = (new_sig & 0x88888888) >> 3;
                    tx = ux | (ux << 4) | (ux >> 4); //left and right neighbors
                    if (i > 0) {
                        nxt_mbr[-1] |= (ux << 28) & ~nxt_sig[-1];
                    }
                    nxt_mbr[0] |= tx & ~nxt_sig[0];
                    nxt_mbr[1] |= (ux >> 28) & ~nxt_sig[1];
                }

                //clear current sigma
                //mbr need not be cleared because it is overwritten
                cur_sig = y & 0x4 ? sigma2 : sigma1;
                memset(cur_sig, 0, ((((OPJ_UINT32)width + 7u) >> 3) + 1u) << 2);
            }
        }
    }

    //terminating
    if (num_passes > 1) {
        OPJ_INT32 st, y;

        if (num_passes > 2 && ((height & 3) == 1 || (height & 3) == 2)) {
            //do magref
            OPJ_UINT32 *cur_sig = height & 0x4 ? sigma2 : sigma1; //reversed
            OPJ_UINT32 *dpp = decoded_data + (height & 0xFFFFFC) * stride;
            OPJ_UINT32 half = 1u << (p - 2);
            OPJ_INT32 i;
            for (i = 0; i < width; i += 8) {
                OPJ_UINT32 cwd = rev_fetch_mrp(&magref);
                OPJ_UINT32 sig = *cur_sig++;
                OPJ_UINT32 col_mask = 0xF;
                OPJ_UINT32 *dp = dpp + i;
                if (sig) {
                    int j;
                    for (j = 0; j < 8; ++j, dp++) {
                        if (sig & col_mask) {
                            OPJ_UINT32 sample_mask = 0x11111111 & col_mask;

                            if (sig & sample_mask) {
                                OPJ_UINT32 sym;
                                assert(dp[0] != 0);
                                sym = cwd & 1;
                                dp[0] ^= (1 - sym) << (p - 1);
                                dp[0] |= half;
                                cwd >>= 1;
                            }
                            sample_mask += sample_mask;

                            if (sig & sample_mask) {
                                OPJ_UINT32 sym;
                                assert(dp[stride] != 0);
                                sym = cwd & 1;
                                dp[stride] ^= (1 - sym) << (p - 1);
                                dp[stride] |= half;
                                cwd >>= 1;
                            }
                            sample_mask += sample_mask;

                            if (sig & sample_mask) {
                                OPJ_UINT32 sym;
                                assert(dp[2 * stride] != 0);
                                sym = cwd & 1;
                                dp[2 * stride] ^= (1 - sym) << (p - 1);
                                dp[2 * stride] |= half;
                                cwd >>= 1;
                            }
                            sample_mask += sample_mask;

                            if (sig & sample_mask) {
                                OPJ_UINT32 sym;
                                assert(dp[3 * stride] != 0);
                                sym = cwd & 1;
                                dp[3 * stride] ^= (1 - sym) << (p - 1);
                                dp[3 * stride] |= half;
                                cwd >>= 1;
                            }
                            sample_mask += sample_mask;
                        }
                        col_mask <<= 4;
                    }
                }
                rev_advance_mrp(&magref, population_count(sig));
            }
        }

        //do the last incomplete stripe
        // for cases of (height & 3) == 0 and 3
        // the should have been processed previously
        if ((height & 3) == 1 || (height & 3) == 2) {
            //generate mbr of first stripe
            OPJ_UINT32 *sig = height & 0x4 ? sigma2 : sigma1;
            OPJ_UINT32 *mbr = height & 0x4 ? mbr2 : mbr1;
            //integrate horizontally
            OPJ_UINT32 prev = 0;
            OPJ_INT32 i;
            for (i = 0; i < width; i += 8, mbr++, sig++) {
                OPJ_UINT32 t, z;

                mbr[0] = sig[0];
                mbr[0] |= prev >> 28;    //for first column, left neighbors
                mbr[0] |= sig[0] << 4;   //left neighbors
                mbr[0] |= sig[0] >> 4;   //left neighbors
                mbr[0] |= sig[1] << 28;  //for last column, right neighbors
                prev = sig[0];

                //integrate vertically
                t = mbr[0], z = mbr[0];
                z |= (t & 0x77777777) << 1; //above neighbors
                z |= (t & 0xEEEEEEEE) >> 1; //below neighbors
                mbr[0] = z & ~sig[0]; //remove already significance samples
            }
        }

        st = height;
        st -= height > 6 ? (((height + 1) & 3) + 3) : height;
        for (y = st; y < height; y += 4) {
            OPJ_UINT32 *cur_sig, *cur_mbr, *nxt_sig, *nxt_mbr;
            OPJ_UINT32 val;
            OPJ_INT32 i;

            OPJ_UINT32 pattern = 0xFFFFFFFFu; // a pattern needed samples
            if (height - y == 3) {
                pattern = 0x77777777u;
            } else if (height - y == 2) {
                pattern = 0x33333333u;
            } else if (height - y == 1) {
                pattern = 0x11111111u;
            }

            //add membership from the next stripe, obtained above
            if (height - y > 4) {
                OPJ_UINT32 prev = 0;
                OPJ_INT32 i;
                cur_sig = y & 0x4 ? sigma2 : sigma1;
                cur_mbr = y & 0x4 ? mbr2 : mbr1;
                nxt_sig = y & 0x4 ? sigma1 : sigma2;
                for (i = 0; i < width; i += 8, cur_mbr++, cur_sig++, nxt_sig++) {
                    OPJ_UINT32 t = nxt_sig[0];
                    t |= prev >> 28;     //for first column, left neighbors
                    t |= nxt_sig[0] << 4;   //left neighbors
                    t |= nxt_sig[0] >> 4;   //left neighbors
                    t |= nxt_sig[1] << 28;  //for last column, right neighbors
                    prev = nxt_sig[0];

                    if (!stripe_causal) {
                        cur_mbr[0] |= (t & 0x11111111u) << 3;
                    }
                    //remove already significance samples
                    cur_mbr[0] &= ~cur_sig[0];
                }
            }

            //find new locations and get signs
            cur_sig = y & 0x4 ? sigma2 : sigma1;
            cur_mbr = y & 0x4 ? mbr2 : mbr1;
            nxt_sig = y & 0x4 ? sigma1 : sigma2;
            nxt_mbr = y & 0x4 ? mbr1 : mbr2;
            val = 3u << (p - 2);
            for (i = 0; i < width; i += 8,
                    cur_sig++, cur_mbr++, nxt_sig++, nxt_mbr++) {
                OPJ_UINT32 mbr = *cur_mbr & pattern; //skip unneeded samples
                OPJ_UINT32 new_sig = 0;
                OPJ_UINT32 ux, tx;
                if (mbr) {
                    OPJ_INT32 n;
                    for (n = 0; n < 8; n += 4) {
                        OPJ_UINT32 col_mask;
                        OPJ_UINT32 inv_sig;
                        OPJ_INT32 end;
                        OPJ_INT32 j;

                        OPJ_UINT32 cwd = frwd_fetch(&sigprop);
                        OPJ_UINT32 cnt = 0;

                        OPJ_UINT32 *dp = decoded_data + y * stride;
                        dp += i + n;

                        col_mask = 0xFu << (4 * n);

                        inv_sig = ~cur_sig[0] & pattern;

                        end = n + 4 + i < width ? n + 4 : width - i;
                        for (j = n; j < end; ++j, ++dp, col_mask <<= 4) {
                            OPJ_UINT32 sample_mask;

                            if ((col_mask & mbr) == 0) {
                                continue;
                            }

                            //scan 4 mbr
                            sample_mask = 0x11111111u & col_mask;
                            if (mbr & sample_mask) {
                                assert(dp[0] == 0);
                                if (cwd & 1) {
                                    OPJ_UINT32 t;
                                    new_sig |= sample_mask;
                                    t = 0x32u << (j * 4);
                                    mbr |= t & inv_sig;
                                }
                                cwd >>= 1;
                                ++cnt;
                            }

                            sample_mask += sample_mask;
                            if (mbr & sample_mask) {
                                assert(dp[stride] == 0);
                                if (cwd & 1) {
                                    OPJ_UINT32 t;
                                    new_sig |= sample_mask;
                                    t = 0x74u << (j * 4);
                                    mbr |= t & inv_sig;
                                }
                                cwd >>= 1;
                                ++cnt;
                            }

                            sample_mask += sample_mask;
                            if (mbr & sample_mask) {
                                assert(dp[2 * stride] == 0);
                                if (cwd & 1) {
                                    OPJ_UINT32 t;
                                    new_sig |= sample_mask;
                                    t = 0xE8u << (j * 4);
                                    mbr |= t & inv_sig;
                                }
                                cwd >>= 1;
                                ++cnt;
                            }

                            sample_mask += sample_mask;
                            if (mbr & sample_mask) {
                                assert(dp[3 * stride] == 0);
                                if (cwd & 1) {
                                    OPJ_UINT32 t;
                                    new_sig |= sample_mask;
                                    t = 0xC0u << (j * 4);
                                    mbr |= t & inv_sig;
                                }
                                cwd >>= 1;
                                ++cnt;
                            }
                        }

                        //signs here
                        if (new_sig & (0xFFFFu << (4 * n))) {
                            OPJ_UINT32 col_mask;
                            OPJ_INT32 j;
                            OPJ_UINT32 *dp = decoded_data + y * stride;
                            dp += i + n;
                            col_mask = 0xFu << (4 * n);

                            for (j = n; j < end; ++j, ++dp, col_mask <<= 4) {
                                OPJ_UINT32 sample_mask;
                                if ((col_mask & new_sig) == 0) {
                                    continue;
                                }

                                //scan 4 signs
                                sample_mask = 0x11111111u & col_mask;
                                if (new_sig & sample_mask) {
                                    assert(dp[0] == 0);
                                    dp[0] |= ((cwd & 1) << 31) | val;
                                    cwd >>= 1;
                                    ++cnt;
                                }

                                sample_mask += sample_mask;
                                if (new_sig & sample_mask) {
                                    assert(dp[stride] == 0);
                                    dp[stride] |= ((cwd & 1) << 31) | val;
                                    cwd >>= 1;
                                    ++cnt;
                                }

                                sample_mask += sample_mask;
                                if (new_sig & sample_mask) {
                                    assert(dp[2 * stride] == 0);
                                    dp[2 * stride] |= ((cwd & 1) << 31) | val;
                                    cwd >>= 1;
                                    ++cnt;
                                }

                                sample_mask += sample_mask;
                                if (new_sig & sample_mask) {
                                    assert(dp[3 * stride] == 0);
                                    dp[3 * stride] |= ((cwd & 1) << 31) | val;
                                    cwd >>= 1;
                                    ++cnt;
                                }
                            }

                        }
                        frwd_advance(&sigprop, cnt);
                        cnt = 0;

                        //update next columns
                        if (n == 4) {
                            //horizontally
                            OPJ_UINT32 t = new_sig >> 28;
                            t |= ((t & 0xE) >> 1) | ((t & 7) << 1);
                            cur_mbr[1] |= t & ~cur_sig[1];
                        }
                    }
                }
                //propagate down (vertically propagation)
                new_sig |= cur_sig[0];
                ux = (new_sig & 0x88888888) >> 3;
                tx = ux | (ux << 4) | (ux >> 4);
                if (i > 0) {
                    nxt_mbr[-1] |= (ux << 28) & ~nxt_sig[-1];
                }
                nxt_mbr[0] |= tx & ~nxt_sig[0];
                nxt_mbr[1] |= (ux >> 28) & ~nxt_sig[1];
            }
        }
    }

    {
        OPJ_INT32 x, y;
        for (y = 0; y < height; ++y) {
            OPJ_INT32* sp = (OPJ_INT32*)decoded_data + y * stride;
            for (x = 0; x < width; ++x, ++sp) {
                OPJ_INT32 val = (*sp & 0x7FFFFFFF);
                *sp = ((OPJ_UINT32) * sp & 0x80000000) ? -val : val;
            }
        }
    }

    return OPJ_TRUE;
}