/
fancy.go
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/
fancy.go
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// Copyright (c) 2009 Helmar Wodtke. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.
// The MIT License is an OSI approved license and can
// be found at
// http://www.opensource.org/licenses/mit-license.php
// Enhanced input.
package fancy
import (
"bufio"
"io"
"io/ioutil"
"os"
)
type Reader interface {
ReadAt(buf []byte, pos int64) (n int, err os.Error)
Read(b []byte) (n int, err os.Error)
Slice(n int) []byte
Seek(off int64, whence int) (ret int64, err os.Error)
ReadByte() (c byte, err os.Error)
UnreadByte() os.Error
Size() int64
}
// ------------------------------------------------------------------
const (
_SECTOR_SIZE = 512
_SECTOR_COUNT = 32
)
type SecReaderT struct {
cache map[int64][]byte
age map[int64]int
ticker int
pos, size int64
f io.ReaderAt
}
func min(a, b int64) int64 {
if a < b {
return a
}
return b
}
func (sr *SecReaderT) access(pos int64) (sl []byte, p int) {
p = int(pos % _SECTOR_SIZE)
pos /= _SECTOR_SIZE
if s, ok := sr.cache[pos]; ok {
if sr.age[pos] != sr.ticker {
sr.ticker++
sr.age[pos] = sr.ticker
}
return s, p
}
if len(sr.cache) >= _SECTOR_COUNT {
a := sr.ticker
old := int64(0)
for k := range sr.age {
if sr.age[k] < a {
old = k
a = sr.age[k]
}
}
sr.cache[old] = nil, false
sr.age[old] = 0, false
}
sr.ticker++
sl = make([]byte, min(sr.size-pos*_SECTOR_SIZE, _SECTOR_SIZE))
sr.f.ReadAt(sl, pos*_SECTOR_SIZE)
sr.cache[pos] = sl
sr.age[pos] = sr.ticker
return
}
func (sr *SecReaderT) ReadAt(buf []byte, pos int64) (n int, err os.Error) {
if pos >= sr.size {
return 0, os.EOF
}
b, p := sr.access(pos)
for ; p < _SECTOR_SIZE && n < len(buf); p++ {
buf[n] = b[p]
n++
}
if secs := (len(buf) - n) / _SECTOR_SIZE; secs > 0 {
sr.f.ReadAt(buf[n:n+secs*_SECTOR_SIZE], pos+int64(n))
n += secs * _SECTOR_SIZE
}
if len(buf)-n > 0 {
b, p = sr.access(pos + int64(n))
for ; n < len(buf); p++ {
buf[n] = b[p]
n++
}
}
if pos+int64(n) >= sr.size {
n -= int(pos + int64(n) - sr.size)
}
return
}
func (sr *SecReaderT) Read(b []byte) (n int, err os.Error) {
n, err = sr.ReadAt(b, sr.pos)
sr.pos += int64(n)
return
}
func (sr *SecReaderT) Seek(off int64, whence int) (ret int64, err os.Error) {
ret = sr.pos
switch whence {
case 0:
sr.pos = 0
case 2:
sr.pos = sr.size
}
sr.pos += off
return
}
func (sr *SecReaderT) ReadByte() (c byte, err os.Error) {
if sr.pos < sr.size {
b, p := sr.access(sr.pos)
c = b[p]
sr.pos++
} else {
err = os.EOF
}
return
}
func (sr *SecReaderT) UnreadByte() os.Error {
sr.pos--
return nil
}
func (sr *SecReaderT) Size() int64 { return sr.size }
func (sr *SecReaderT) Slice(n int) []byte {
r := make([]byte, n)
sr.Read(r)
return r
}
// grmpf: Next is for AUTOGENERATE!
// The thing here is only (!) for convenience.
func (sr *SecReaderT) ReadBytes(delim byte) ([]byte, os.Error) {
return bufio.NewReader(sr).ReadBytes(delim)
}
func SecReader(f io.ReaderAt, size int64) Reader {
sr := new(SecReaderT)
sr.f = f
sr.size = size
sr.cache = make(map[int64][]byte)
sr.age = make(map[int64]int)
return sr
}
// ------------------------------------------------------------------
type SliceReaderT struct {
bin []byte
pos int64
}
func (sl *SliceReaderT) ReadAt(b []byte, off int64) (n int, err os.Error) {
for n := 0; n < len(b); n++ {
if off >= int64(len(sl.bin)) {
if n > 0 {
break
}
return n, os.EOF
}
b[n] = sl.bin[off]
off++
}
return len(b), nil
}
func (sl *SliceReaderT) Read(b []byte) (n int, err os.Error) {
n, err = sl.ReadAt(b, sl.pos)
sl.pos += int64(n)
return
}
func (sl *SliceReaderT) Seek(off int64, whence int) (ret int64, err os.Error) {
ret = sl.pos
switch whence {
case 0:
sl.pos = 0
case 2:
sl.pos = int64(len(sl.bin))
}
sl.pos += off
return
}
func (sl *SliceReaderT) Size() int64 { return int64(len(sl.bin)) }
func (sl *SliceReaderT) ReadByte() (c byte, err os.Error) {
if sl.pos < int64(len(sl.bin)) {
c = sl.bin[sl.pos]
sl.pos++
} else {
err = os.EOF
}
return
}
func (sl *SliceReaderT) UnreadByte() os.Error {
sl.pos--
return nil
}
func (sl *SliceReaderT) Slice(n int) []byte {
sl.pos += int64(n)
return sl.bin[sl.pos-int64(n) : sl.pos]
}
// grmpf: Next is for AUTOGENERATE!
// The thing here is only (!) for convenience.
func (sl *SliceReaderT) ReadBytes(delim byte) ([]byte, os.Error) {
return bufio.NewReader(sl).ReadBytes(delim)
}
func SliceReader(bin []byte) Reader {
r := new(SliceReaderT)
r.bin = bin
return r
}
// ------------------------------------------------------------------
func ReadAndClose(f io.ReadCloser, err os.Error) []byte {
if err != nil {
return []byte{}
}
r, _ := ioutil.ReadAll(f)
f.Close()
return r
}
func FileReader(fn string) Reader {
dir, err := os.Stat(fn)
if err != nil {
return nil
}
fil, err := os.Open(fn, os.O_RDONLY, -1)
if err != nil {
return nil
}
return SecReader(fil, int64(dir.Size))
}
func ReadAll(f io.Reader) []byte {
r, _ := ioutil.ReadAll(f)
return r
}
// ------------------------------------------------------------------