mirror of
https://github.com/go-gitea/gitea
synced 2024-07-07 10:35:48 +00:00
238 lines
5.9 KiB
Go
238 lines
5.9 KiB
Go
|
// 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 LICENSE file.
|
||
|
|
||
|
package snappy
|
||
|
|
||
|
import (
|
||
|
"encoding/binary"
|
||
|
"errors"
|
||
|
"io"
|
||
|
)
|
||
|
|
||
|
var (
|
||
|
// ErrCorrupt reports that the input is invalid.
|
||
|
ErrCorrupt = errors.New("snappy: corrupt input")
|
||
|
// ErrTooLarge reports that the uncompressed length is too large.
|
||
|
ErrTooLarge = errors.New("snappy: decoded block is too large")
|
||
|
// ErrUnsupported reports that the input isn't supported.
|
||
|
ErrUnsupported = errors.New("snappy: unsupported input")
|
||
|
|
||
|
errUnsupportedCopy4Tag = errors.New("snappy: unsupported COPY_4 tag")
|
||
|
errUnsupportedLiteralLength = errors.New("snappy: unsupported literal length")
|
||
|
)
|
||
|
|
||
|
// DecodedLen returns the length of the decoded block.
|
||
|
func DecodedLen(src []byte) (int, error) {
|
||
|
v, _, err := decodedLen(src)
|
||
|
return v, err
|
||
|
}
|
||
|
|
||
|
// decodedLen returns the length of the decoded block and the number of bytes
|
||
|
// that the length header occupied.
|
||
|
func decodedLen(src []byte) (blockLen, headerLen int, err error) {
|
||
|
v, n := binary.Uvarint(src)
|
||
|
if n <= 0 || v > 0xffffffff {
|
||
|
return 0, 0, ErrCorrupt
|
||
|
}
|
||
|
|
||
|
const wordSize = 32 << (^uint(0) >> 32 & 1)
|
||
|
if wordSize == 32 && v > 0x7fffffff {
|
||
|
return 0, 0, ErrTooLarge
|
||
|
}
|
||
|
return int(v), n, nil
|
||
|
}
|
||
|
|
||
|
const (
|
||
|
decodeErrCodeCorrupt = 1
|
||
|
decodeErrCodeUnsupportedLiteralLength = 2
|
||
|
decodeErrCodeUnsupportedCopy4Tag = 3
|
||
|
)
|
||
|
|
||
|
// Decode returns the decoded form of src. The returned slice may be a sub-
|
||
|
// slice of dst if dst was large enough to hold the entire decoded block.
|
||
|
// Otherwise, a newly allocated slice will be returned.
|
||
|
//
|
||
|
// The dst and src must not overlap. It is valid to pass a nil dst.
|
||
|
func Decode(dst, src []byte) ([]byte, error) {
|
||
|
dLen, s, err := decodedLen(src)
|
||
|
if err != nil {
|
||
|
return nil, err
|
||
|
}
|
||
|
if dLen <= len(dst) {
|
||
|
dst = dst[:dLen]
|
||
|
} else {
|
||
|
dst = make([]byte, dLen)
|
||
|
}
|
||
|
switch decode(dst, src[s:]) {
|
||
|
case 0:
|
||
|
return dst, nil
|
||
|
case decodeErrCodeUnsupportedLiteralLength:
|
||
|
return nil, errUnsupportedLiteralLength
|
||
|
case decodeErrCodeUnsupportedCopy4Tag:
|
||
|
return nil, errUnsupportedCopy4Tag
|
||
|
}
|
||
|
return nil, ErrCorrupt
|
||
|
}
|
||
|
|
||
|
// NewReader returns a new Reader that decompresses from r, using the framing
|
||
|
// format described at
|
||
|
// https://github.com/google/snappy/blob/master/framing_format.txt
|
||
|
func NewReader(r io.Reader) *Reader {
|
||
|
return &Reader{
|
||
|
r: r,
|
||
|
decoded: make([]byte, maxBlockSize),
|
||
|
buf: make([]byte, maxEncodedLenOfMaxBlockSize+checksumSize),
|
||
|
}
|
||
|
}
|
||
|
|
||
|
// Reader is an io.Reader that can read Snappy-compressed bytes.
|
||
|
type Reader struct {
|
||
|
r io.Reader
|
||
|
err error
|
||
|
decoded []byte
|
||
|
buf []byte
|
||
|
// decoded[i:j] contains decoded bytes that have not yet been passed on.
|
||
|
i, j int
|
||
|
readHeader bool
|
||
|
}
|
||
|
|
||
|
// Reset discards any buffered data, resets all state, and switches the Snappy
|
||
|
// reader to read from r. This permits reusing a Reader rather than allocating
|
||
|
// a new one.
|
||
|
func (r *Reader) Reset(reader io.Reader) {
|
||
|
r.r = reader
|
||
|
r.err = nil
|
||
|
r.i = 0
|
||
|
r.j = 0
|
||
|
r.readHeader = false
|
||
|
}
|
||
|
|
||
|
func (r *Reader) readFull(p []byte) (ok bool) {
|
||
|
if _, r.err = io.ReadFull(r.r, p); r.err != nil {
|
||
|
if r.err == io.ErrUnexpectedEOF {
|
||
|
r.err = ErrCorrupt
|
||
|
}
|
||
|
return false
|
||
|
}
|
||
|
return true
|
||
|
}
|
||
|
|
||
|
// Read satisfies the io.Reader interface.
|
||
|
func (r *Reader) Read(p []byte) (int, error) {
|
||
|
if r.err != nil {
|
||
|
return 0, r.err
|
||
|
}
|
||
|
for {
|
||
|
if r.i < r.j {
|
||
|
n := copy(p, r.decoded[r.i:r.j])
|
||
|
r.i += n
|
||
|
return n, nil
|
||
|
}
|
||
|
if !r.readFull(r.buf[:4]) {
|
||
|
return 0, r.err
|
||
|
}
|
||
|
chunkType := r.buf[0]
|
||
|
if !r.readHeader {
|
||
|
if chunkType != chunkTypeStreamIdentifier {
|
||
|
r.err = ErrCorrupt
|
||
|
return 0, r.err
|
||
|
}
|
||
|
r.readHeader = true
|
||
|
}
|
||
|
chunkLen := int(r.buf[1]) | int(r.buf[2])<<8 | int(r.buf[3])<<16
|
||
|
if chunkLen > len(r.buf) {
|
||
|
r.err = ErrUnsupported
|
||
|
return 0, r.err
|
||
|
}
|
||
|
|
||
|
// The chunk types are specified at
|
||
|
// https://github.com/google/snappy/blob/master/framing_format.txt
|
||
|
switch chunkType {
|
||
|
case chunkTypeCompressedData:
|
||
|
// Section 4.2. Compressed data (chunk type 0x00).
|
||
|
if chunkLen < checksumSize {
|
||
|
r.err = ErrCorrupt
|
||
|
return 0, r.err
|
||
|
}
|
||
|
buf := r.buf[:chunkLen]
|
||
|
if !r.readFull(buf) {
|
||
|
return 0, r.err
|
||
|
}
|
||
|
checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
|
||
|
buf = buf[checksumSize:]
|
||
|
|
||
|
n, err := DecodedLen(buf)
|
||
|
if err != nil {
|
||
|
r.err = err
|
||
|
return 0, r.err
|
||
|
}
|
||
|
if n > len(r.decoded) {
|
||
|
r.err = ErrCorrupt
|
||
|
return 0, r.err
|
||
|
}
|
||
|
if _, err := Decode(r.decoded, buf); err != nil {
|
||
|
r.err = err
|
||
|
return 0, r.err
|
||
|
}
|
||
|
if crc(r.decoded[:n]) != checksum {
|
||
|
r.err = ErrCorrupt
|
||
|
return 0, r.err
|
||
|
}
|
||
|
r.i, r.j = 0, n
|
||
|
continue
|
||
|
|
||
|
case chunkTypeUncompressedData:
|
||
|
// Section 4.3. Uncompressed data (chunk type 0x01).
|
||
|
if chunkLen < checksumSize {
|
||
|
r.err = ErrCorrupt
|
||
|
return 0, r.err
|
||
|
}
|
||
|
buf := r.buf[:checksumSize]
|
||
|
if !r.readFull(buf) {
|
||
|
return 0, r.err
|
||
|
}
|
||
|
checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
|
||
|
// Read directly into r.decoded instead of via r.buf.
|
||
|
n := chunkLen - checksumSize
|
||
|
if !r.readFull(r.decoded[:n]) {
|
||
|
return 0, r.err
|
||
|
}
|
||
|
if crc(r.decoded[:n]) != checksum {
|
||
|
r.err = ErrCorrupt
|
||
|
return 0, r.err
|
||
|
}
|
||
|
r.i, r.j = 0, n
|
||
|
continue
|
||
|
|
||
|
case chunkTypeStreamIdentifier:
|
||
|
// Section 4.1. Stream identifier (chunk type 0xff).
|
||
|
if chunkLen != len(magicBody) {
|
||
|
r.err = ErrCorrupt
|
||
|
return 0, r.err
|
||
|
}
|
||
|
if !r.readFull(r.buf[:len(magicBody)]) {
|
||
|
return 0, r.err
|
||
|
}
|
||
|
for i := 0; i < len(magicBody); i++ {
|
||
|
if r.buf[i] != magicBody[i] {
|
||
|
r.err = ErrCorrupt
|
||
|
return 0, r.err
|
||
|
}
|
||
|
}
|
||
|
continue
|
||
|
}
|
||
|
|
||
|
if chunkType <= 0x7f {
|
||
|
// Section 4.5. Reserved unskippable chunks (chunk types 0x02-0x7f).
|
||
|
r.err = ErrUnsupported
|
||
|
return 0, r.err
|
||
|
}
|
||
|
// Section 4.4 Padding (chunk type 0xfe).
|
||
|
// Section 4.6. Reserved skippable chunks (chunk types 0x80-0xfd).
|
||
|
if !r.readFull(r.buf[:chunkLen]) {
|
||
|
return 0, r.err
|
||
|
}
|
||
|
}
|
||
|
}
|