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extract.h
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extract.h
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/*
* Copyright (c) 1992, 1993, 1994, 1995, 1996
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that: (1) source code distributions
* retain the above copyright notice and this paragraph in its entirety, (2)
* distributions including binary code include the above copyright notice and
* this paragraph in its entirety in the documentation or other materials
* provided with the distribution, and (3) all advertising materials mentioning
* features or use of this software display the following acknowledgement:
* ``This product includes software developed by the University of California,
* Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
* the University nor the names of its contributors may be used to endorse
* or promote products derived from this software without specific prior
* written permission.
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*
* @(#) $Header: /tcpdump/master/tcpdump/extract.h,v 1.25 2006-01-30 16:20:07 hannes Exp $ (LBL)
*/
/*
* Macros to extract possibly-unaligned big-endian integral values.
*/
#ifdef LBL_ALIGN
/*
* The processor doesn't natively handle unaligned loads.
*/
#ifdef HAVE___ATTRIBUTE__
/*
* We have __attribute__; we assume that means we have __attribute__((packed)).
* Declare packed structures containing a u_int16_t and a u_int32_t,
* cast the pointer to point to one of those, and fetch through it;
* the GCC manual doesn't appear to explicitly say that
* __attribute__((packed)) causes the compiler to generate unaligned-safe
* code, but it apppears to do so.
*
* We do this in case the compiler can generate, for this instruction set,
* better code to do an unaligned load and pass stuff to "ntohs()" or
* "ntohl()" than the code to fetch the bytes one at a time and
* assemble them. (That might not be the case on a little-endian platform,
* where "ntohs()" and "ntohl()" might not be done inline.)
*/
typedef struct {
u_int16_t val;
} __attribute__((packed)) unaligned_u_int16_t;
typedef struct {
u_int32_t val;
} __attribute__((packed)) unaligned_u_int32_t;
#define EXTRACT_16BITS(p) \
((u_int16_t)ntohs(((const unaligned_u_int16_t *)(p))->val))
#define EXTRACT_32BITS(p) \
((u_int32_t)ntohl(((const unaligned_u_int32_t *)(p))->val))
#define EXTRACT_64BITS(p) \
((u_int64_t)(((u_int64_t)ntohl(((const unaligned_u_int32_t *)(p) + 0)->val)) << 32 | \
((u_int64_t)ntohl(((const unaligned_u_int32_t *)(p) + 1)->val)) << 0))
#else /* HAVE___ATTRIBUTE__ */
/*
* We don't have __attribute__, so do unaligned loads of big-endian
* quantities the hard way - fetch the bytes one at a time and
* assemble them.
*/
#define EXTRACT_16BITS(p) \
((u_int16_t)((u_int16_t)*((const u_int8_t *)(p) + 0) << 8 | \
(u_int16_t)*((const u_int8_t *)(p) + 1)))
#define EXTRACT_32BITS(p) \
((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 0) << 24 | \
(u_int32_t)*((const u_int8_t *)(p) + 1) << 16 | \
(u_int32_t)*((const u_int8_t *)(p) + 2) << 8 | \
(u_int32_t)*((const u_int8_t *)(p) + 3)))
#define EXTRACT_64BITS(p) \
((u_int64_t)((u_int64_t)*((const u_int8_t *)(p) + 0) << 56 | \
(u_int64_t)*((const u_int8_t *)(p) + 1) << 48 | \
(u_int64_t)*((const u_int8_t *)(p) + 2) << 40 | \
(u_int64_t)*((const u_int8_t *)(p) + 3) << 32 | \
(u_int64_t)*((const u_int8_t *)(p) + 4) << 24 | \
(u_int64_t)*((const u_int8_t *)(p) + 5) << 16 | \
(u_int64_t)*((const u_int8_t *)(p) + 6) << 8 | \
(u_int64_t)*((const u_int8_t *)(p) + 7)))
#endif /* HAVE___ATTRIBUTE__ */
#else /* LBL_ALIGN */
/*
* The processor natively handles unaligned loads, so we can just
* cast the pointer and fetch through it.
*/
#define EXTRACT_16BITS(p) \
((u_int16_t)ntohs(*(const u_int16_t *)(p)))
#define EXTRACT_32BITS(p) \
((u_int32_t)ntohl(*(const u_int32_t *)(p)))
#define EXTRACT_64BITS(p) \
((u_int64_t)(((u_int64_t)ntohl(*((const u_int32_t *)(p) + 0))) << 32 | \
((u_int64_t)ntohl(*((const u_int32_t *)(p) + 1))) << 0))
#endif /* LBL_ALIGN */
#define EXTRACT_24BITS(p) \
((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 0) << 16 | \
(u_int32_t)*((const u_int8_t *)(p) + 1) << 8 | \
(u_int32_t)*((const u_int8_t *)(p) + 2)))
/*
* Macros to extract possibly-unaligned little-endian integral values.
* XXX - do loads on little-endian machines that support unaligned loads?
*/
#define EXTRACT_LE_8BITS(p) (*(p))
#define EXTRACT_LE_16BITS(p) \
((u_int16_t)((u_int16_t)*((const u_int8_t *)(p) + 1) << 8 | \
(u_int16_t)*((const u_int8_t *)(p) + 0)))
#define EXTRACT_LE_32BITS(p) \
((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 3) << 24 | \
(u_int32_t)*((const u_int8_t *)(p) + 2) << 16 | \
(u_int32_t)*((const u_int8_t *)(p) + 1) << 8 | \
(u_int32_t)*((const u_int8_t *)(p) + 0)))
#define EXTRACT_LE_24BITS(p) \
((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 2) << 16 | \
(u_int32_t)*((const u_int8_t *)(p) + 1) << 8 | \
(u_int32_t)*((const u_int8_t *)(p) + 0)))
#define EXTRACT_LE_64BITS(p) \
((u_int64_t)((u_int64_t)*((const u_int8_t *)(p) + 7) << 56 | \
(u_int64_t)*((const u_int8_t *)(p) + 6) << 48 | \
(u_int64_t)*((const u_int8_t *)(p) + 5) << 40 | \
(u_int64_t)*((const u_int8_t *)(p) + 4) << 32 | \
(u_int64_t)*((const u_int8_t *)(p) + 3) << 24 | \
(u_int64_t)*((const u_int8_t *)(p) + 2) << 16 | \
(u_int64_t)*((const u_int8_t *)(p) + 1) << 8 | \
(u_int64_t)*((const u_int8_t *)(p) + 0)))