mirror of
https://github.com/octoleo/syncthing.git
synced 2024-11-10 07:11:08 +00:00
143 lines
3.2 KiB
Go
143 lines
3.2 KiB
Go
// Copyright 2014 The zappy Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
// Copyright 2011 The Snappy-Go Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the SNAPPY-GO-LICENSE file.
|
|
|
|
// +build cgo,!purego
|
|
|
|
package zappy
|
|
|
|
/*
|
|
|
|
#include <stdint.h>
|
|
#include <string.h>
|
|
|
|
#define MAXOFFSET 1<<20
|
|
|
|
int putUvarint(uint8_t* buf, unsigned int x) {
|
|
int i = 1;
|
|
for (; x >= 0x80; i++) {
|
|
*buf++ = x|0x80;
|
|
x >>= 7;
|
|
}
|
|
*buf = x;
|
|
return i;
|
|
}
|
|
|
|
int putVarint(uint8_t* buf, int x) {
|
|
unsigned int ux = x << 1;
|
|
if (x < 0)
|
|
ux = ~ux;
|
|
return putUvarint(buf, ux);
|
|
}
|
|
|
|
int emitLiteral(uint8_t* dst, uint8_t* lit, int len_lit) {
|
|
int n = putVarint(dst, len_lit-1);
|
|
memcpy(dst+n, lit, len_lit);
|
|
return n+len_lit;
|
|
}
|
|
|
|
int emitCopy(uint8_t* dst, int off, int len) {
|
|
int n = putVarint(dst, -len);
|
|
return n+putUvarint(dst+n, (unsigned int)off);
|
|
}
|
|
|
|
int encode(int d, uint8_t* dst, uint8_t* src, int len_src) {
|
|
int table[1<<12];
|
|
int s = 0;
|
|
int t = 0;
|
|
int lit = 0;
|
|
int lim = 0;
|
|
memset(table, 0, sizeof(table));
|
|
for (lim = len_src-3; s < lim; ) {
|
|
// Update the hash table.
|
|
uint32_t b0 = src[s];
|
|
uint32_t b1 = src[s+1];
|
|
uint32_t b2 = src[s+2];
|
|
uint32_t b3 = src[s+3];
|
|
uint32_t h = b0 | (b1<<8) | (b2<<16) | (b3<<24);
|
|
uint32_t i;
|
|
more:
|
|
i = (h*0x1e35a7bd)>>20;
|
|
t = table[i];
|
|
table[i] = s;
|
|
// If t is invalid or src[s:s+4] differs from src[t:t+4], accumulate a literal byte.
|
|
if ((t == 0) || (s-t >= MAXOFFSET) || (b0 != src[t]) || (b1 != src[t+1]) || (b2 != src[t+2]) || (b3 != src[t+3])) {
|
|
s++;
|
|
if (s >= lim)
|
|
break;
|
|
|
|
b0 = b1;
|
|
b1 = b2;
|
|
b2 = b3;
|
|
b3 = src[s+3];
|
|
h = (h>>8) | ((b3)<<24);
|
|
goto more;
|
|
}
|
|
|
|
// Otherwise, we have a match. First, emit any pending literal bytes.
|
|
if (lit != s) {
|
|
d += emitLiteral(dst+d, src+lit, s-lit);
|
|
}
|
|
// Extend the match to be as long as possible.
|
|
int s0 = s;
|
|
s += 4;
|
|
t += 4;
|
|
while ((s < len_src) && (src[s] == src[t])) {
|
|
s++;
|
|
t++;
|
|
}
|
|
d += emitCopy(dst+d, s-t, s-s0);
|
|
lit = s;
|
|
}
|
|
// Emit any final pending literal bytes and return.
|
|
if (lit != len_src) {
|
|
d += emitLiteral(dst+d, src+lit, len_src-lit);
|
|
}
|
|
return d;
|
|
}
|
|
|
|
*/
|
|
import "C"
|
|
|
|
import (
|
|
"encoding/binary"
|
|
"fmt"
|
|
"math"
|
|
|
|
"github.com/cznic/internal/buffer"
|
|
)
|
|
|
|
func puregoEncode() bool { return false }
|
|
|
|
// Encode returns the encoded form of src. The returned slice may be a sub-
|
|
// slice of buf if buf was large enough to hold the entire encoded block.
|
|
// Otherwise, a newly allocated slice will be returned.
|
|
// It is valid to pass a nil buf.
|
|
func Encode(buf, src []byte) ([]byte, error) {
|
|
if n := MaxEncodedLen(len(src)); len(buf) < n {
|
|
buf = *buffer.Get(n)
|
|
}
|
|
|
|
if len(src) > math.MaxInt32 {
|
|
return nil, fmt.Errorf("zappy.Encode: too long data: %d bytes", len(src))
|
|
}
|
|
|
|
// The block starts with the varint-encoded length of the decompressed bytes.
|
|
d := binary.PutUvarint(buf, uint64(len(src)))
|
|
|
|
// Return early if src is short.
|
|
if len(src) <= 4 {
|
|
if len(src) != 0 {
|
|
d += emitLiteral(buf[d:], src)
|
|
}
|
|
return buf[:d], nil
|
|
}
|
|
|
|
d = int(C.encode(C.int(d), (*C.uint8_t)(&buf[0]), (*C.uint8_t)(&src[0]), C.int(len(src))))
|
|
return buf[:d], nil
|
|
}
|