mirror of
https://github.com/42wim/matterbridge.git
synced 2024-11-24 03:32:02 -08:00
293 lines
7.8 KiB
Go
293 lines
7.8 KiB
Go
// Copyright 2016 The Snappy-Go Authors. All rights reserved.
|
|
// Copyright (c) 2019 Klaus Post. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
//go:build (!amd64 && !arm64) || appengine || !gc || noasm
|
|
// +build !amd64,!arm64 appengine !gc noasm
|
|
|
|
package s2
|
|
|
|
import (
|
|
"fmt"
|
|
"strconv"
|
|
)
|
|
|
|
// decode writes the decoding of src to dst. It assumes that the varint-encoded
|
|
// length of the decompressed bytes has already been read, and that len(dst)
|
|
// equals that length.
|
|
//
|
|
// It returns 0 on success or a decodeErrCodeXxx error code on failure.
|
|
func s2Decode(dst, src []byte) int {
|
|
const debug = false
|
|
if debug {
|
|
fmt.Println("Starting decode, dst len:", len(dst))
|
|
}
|
|
var d, s, length int
|
|
offset := 0
|
|
|
|
// As long as we can read at least 5 bytes...
|
|
for s < len(src)-5 {
|
|
// Removing bounds checks is SLOWER, when if doing
|
|
// in := src[s:s+5]
|
|
// Checked on Go 1.18
|
|
switch src[s] & 0x03 {
|
|
case tagLiteral:
|
|
x := uint32(src[s] >> 2)
|
|
switch {
|
|
case x < 60:
|
|
s++
|
|
case x == 60:
|
|
s += 2
|
|
x = uint32(src[s-1])
|
|
case x == 61:
|
|
in := src[s : s+3]
|
|
x = uint32(in[1]) | uint32(in[2])<<8
|
|
s += 3
|
|
case x == 62:
|
|
in := src[s : s+4]
|
|
// Load as 32 bit and shift down.
|
|
x = uint32(in[0]) | uint32(in[1])<<8 | uint32(in[2])<<16 | uint32(in[3])<<24
|
|
x >>= 8
|
|
s += 4
|
|
case x == 63:
|
|
in := src[s : s+5]
|
|
x = uint32(in[1]) | uint32(in[2])<<8 | uint32(in[3])<<16 | uint32(in[4])<<24
|
|
s += 5
|
|
}
|
|
length = int(x) + 1
|
|
if length > len(dst)-d || length > len(src)-s || (strconv.IntSize == 32 && length <= 0) {
|
|
if debug {
|
|
fmt.Println("corrupt: lit size", length)
|
|
}
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
if debug {
|
|
fmt.Println("literals, length:", length, "d-after:", d+length)
|
|
}
|
|
|
|
copy(dst[d:], src[s:s+length])
|
|
d += length
|
|
s += length
|
|
continue
|
|
|
|
case tagCopy1:
|
|
s += 2
|
|
toffset := int(uint32(src[s-2])&0xe0<<3 | uint32(src[s-1]))
|
|
length = int(src[s-2]) >> 2 & 0x7
|
|
if toffset == 0 {
|
|
if debug {
|
|
fmt.Print("(repeat) ")
|
|
}
|
|
// keep last offset
|
|
switch length {
|
|
case 5:
|
|
length = int(src[s]) + 4
|
|
s += 1
|
|
case 6:
|
|
in := src[s : s+2]
|
|
length = int(uint32(in[0])|(uint32(in[1])<<8)) + (1 << 8)
|
|
s += 2
|
|
case 7:
|
|
in := src[s : s+3]
|
|
length = int((uint32(in[2])<<16)|(uint32(in[1])<<8)|uint32(in[0])) + (1 << 16)
|
|
s += 3
|
|
default: // 0-> 4
|
|
}
|
|
} else {
|
|
offset = toffset
|
|
}
|
|
length += 4
|
|
case tagCopy2:
|
|
in := src[s : s+3]
|
|
offset = int(uint32(in[1]) | uint32(in[2])<<8)
|
|
length = 1 + int(in[0])>>2
|
|
s += 3
|
|
|
|
case tagCopy4:
|
|
in := src[s : s+5]
|
|
offset = int(uint32(in[1]) | uint32(in[2])<<8 | uint32(in[3])<<16 | uint32(in[4])<<24)
|
|
length = 1 + int(in[0])>>2
|
|
s += 5
|
|
}
|
|
|
|
if offset <= 0 || d < offset || length > len(dst)-d {
|
|
if debug {
|
|
fmt.Println("corrupt: match, length", length, "offset:", offset, "dst avail:", len(dst)-d, "dst pos:", d)
|
|
}
|
|
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
|
|
if debug {
|
|
fmt.Println("copy, length:", length, "offset:", offset, "d-after:", d+length)
|
|
}
|
|
|
|
// Copy from an earlier sub-slice of dst to a later sub-slice.
|
|
// If no overlap, use the built-in copy:
|
|
if offset > length {
|
|
copy(dst[d:d+length], dst[d-offset:])
|
|
d += length
|
|
continue
|
|
}
|
|
|
|
// Unlike the built-in copy function, this byte-by-byte copy always runs
|
|
// forwards, even if the slices overlap. Conceptually, this is:
|
|
//
|
|
// d += forwardCopy(dst[d:d+length], dst[d-offset:])
|
|
//
|
|
// We align the slices into a and b and show the compiler they are the same size.
|
|
// This allows the loop to run without bounds checks.
|
|
a := dst[d : d+length]
|
|
b := dst[d-offset:]
|
|
b = b[:len(a)]
|
|
for i := range a {
|
|
a[i] = b[i]
|
|
}
|
|
d += length
|
|
}
|
|
|
|
// Remaining with extra checks...
|
|
for s < len(src) {
|
|
switch src[s] & 0x03 {
|
|
case tagLiteral:
|
|
x := uint32(src[s] >> 2)
|
|
switch {
|
|
case x < 60:
|
|
s++
|
|
case x == 60:
|
|
s += 2
|
|
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
x = uint32(src[s-1])
|
|
case x == 61:
|
|
s += 3
|
|
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
x = uint32(src[s-2]) | uint32(src[s-1])<<8
|
|
case x == 62:
|
|
s += 4
|
|
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
x = uint32(src[s-3]) | uint32(src[s-2])<<8 | uint32(src[s-1])<<16
|
|
case x == 63:
|
|
s += 5
|
|
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
x = uint32(src[s-4]) | uint32(src[s-3])<<8 | uint32(src[s-2])<<16 | uint32(src[s-1])<<24
|
|
}
|
|
length = int(x) + 1
|
|
if length > len(dst)-d || length > len(src)-s || (strconv.IntSize == 32 && length <= 0) {
|
|
if debug {
|
|
fmt.Println("corrupt: lit size", length)
|
|
}
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
if debug {
|
|
fmt.Println("literals, length:", length, "d-after:", d+length)
|
|
}
|
|
|
|
copy(dst[d:], src[s:s+length])
|
|
d += length
|
|
s += length
|
|
continue
|
|
|
|
case tagCopy1:
|
|
s += 2
|
|
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
length = int(src[s-2]) >> 2 & 0x7
|
|
toffset := int(uint32(src[s-2])&0xe0<<3 | uint32(src[s-1]))
|
|
if toffset == 0 {
|
|
if debug {
|
|
fmt.Print("(repeat) ")
|
|
}
|
|
// keep last offset
|
|
switch length {
|
|
case 5:
|
|
s += 1
|
|
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
length = int(uint32(src[s-1])) + 4
|
|
case 6:
|
|
s += 2
|
|
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
length = int(uint32(src[s-2])|(uint32(src[s-1])<<8)) + (1 << 8)
|
|
case 7:
|
|
s += 3
|
|
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
length = int(uint32(src[s-3])|(uint32(src[s-2])<<8)|(uint32(src[s-1])<<16)) + (1 << 16)
|
|
default: // 0-> 4
|
|
}
|
|
} else {
|
|
offset = toffset
|
|
}
|
|
length += 4
|
|
case tagCopy2:
|
|
s += 3
|
|
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
length = 1 + int(src[s-3])>>2
|
|
offset = int(uint32(src[s-2]) | uint32(src[s-1])<<8)
|
|
|
|
case tagCopy4:
|
|
s += 5
|
|
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
length = 1 + int(src[s-5])>>2
|
|
offset = int(uint32(src[s-4]) | uint32(src[s-3])<<8 | uint32(src[s-2])<<16 | uint32(src[s-1])<<24)
|
|
}
|
|
|
|
if offset <= 0 || d < offset || length > len(dst)-d {
|
|
if debug {
|
|
fmt.Println("corrupt: match, length", length, "offset:", offset, "dst avail:", len(dst)-d, "dst pos:", d)
|
|
}
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
|
|
if debug {
|
|
fmt.Println("copy, length:", length, "offset:", offset, "d-after:", d+length)
|
|
}
|
|
|
|
// Copy from an earlier sub-slice of dst to a later sub-slice.
|
|
// If no overlap, use the built-in copy:
|
|
if offset > length {
|
|
copy(dst[d:d+length], dst[d-offset:])
|
|
d += length
|
|
continue
|
|
}
|
|
|
|
// Unlike the built-in copy function, this byte-by-byte copy always runs
|
|
// forwards, even if the slices overlap. Conceptually, this is:
|
|
//
|
|
// d += forwardCopy(dst[d:d+length], dst[d-offset:])
|
|
//
|
|
// We align the slices into a and b and show the compiler they are the same size.
|
|
// This allows the loop to run without bounds checks.
|
|
a := dst[d : d+length]
|
|
b := dst[d-offset:]
|
|
b = b[:len(a)]
|
|
for i := range a {
|
|
a[i] = b[i]
|
|
}
|
|
d += length
|
|
}
|
|
|
|
if d != len(dst) {
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
return 0
|
|
}
|