aboutsummaryrefslogtreecommitdiffstats
path: root/Godeps/_workspace/src/github.com/golang/snappy/decode.go
diff options
context:
space:
mode:
Diffstat (limited to 'Godeps/_workspace/src/github.com/golang/snappy/decode.go')
-rw-r--r--Godeps/_workspace/src/github.com/golang/snappy/decode.go294
1 files changed, 294 insertions, 0 deletions
diff --git a/Godeps/_workspace/src/github.com/golang/snappy/decode.go b/Godeps/_workspace/src/github.com/golang/snappy/decode.go
new file mode 100644
index 000000000..8bab5bdd0
--- /dev/null
+++ b/Godeps/_workspace/src/github.com/golang/snappy/decode.go
@@ -0,0 +1,294 @@
+// 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")
+)
+
+// 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
+}
+
+// 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.
+// 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 len(dst) < dLen {
+ dst = make([]byte, dLen)
+ }
+
+ var d, offset, length int
+ for s < len(src) {
+ switch src[s] & 0x03 {
+ case tagLiteral:
+ x := uint(src[s] >> 2)
+ switch {
+ case x < 60:
+ s++
+ case x == 60:
+ s += 2
+ if s > len(src) {
+ return nil, ErrCorrupt
+ }
+ x = uint(src[s-1])
+ case x == 61:
+ s += 3
+ if s > len(src) {
+ return nil, ErrCorrupt
+ }
+ x = uint(src[s-2]) | uint(src[s-1])<<8
+ case x == 62:
+ s += 4
+ if s > len(src) {
+ return nil, ErrCorrupt
+ }
+ x = uint(src[s-3]) | uint(src[s-2])<<8 | uint(src[s-1])<<16
+ case x == 63:
+ s += 5
+ if s > len(src) {
+ return nil, ErrCorrupt
+ }
+ x = uint(src[s-4]) | uint(src[s-3])<<8 | uint(src[s-2])<<16 | uint(src[s-1])<<24
+ }
+ length = int(x + 1)
+ if length <= 0 {
+ return nil, errors.New("snappy: unsupported literal length")
+ }
+ if length > len(dst)-d || length > len(src)-s {
+ return nil, ErrCorrupt
+ }
+ copy(dst[d:], src[s:s+length])
+ d += length
+ s += length
+ continue
+
+ case tagCopy1:
+ s += 2
+ if s > len(src) {
+ return nil, ErrCorrupt
+ }
+ length = 4 + int(src[s-2])>>2&0x7
+ offset = int(src[s-2])&0xe0<<3 | int(src[s-1])
+
+ case tagCopy2:
+ s += 3
+ if s > len(src) {
+ return nil, ErrCorrupt
+ }
+ length = 1 + int(src[s-3])>>2
+ offset = int(src[s-2]) | int(src[s-1])<<8
+
+ case tagCopy4:
+ return nil, errors.New("snappy: unsupported COPY_4 tag")
+ }
+
+ end := d + length
+ if offset > d || end > len(dst) {
+ return nil, ErrCorrupt
+ }
+ for ; d < end; d++ {
+ dst[d] = dst[d-offset]
+ }
+ }
+ if d != dLen {
+ return nil, ErrCorrupt
+ }
+ return dst[:d], nil
+}
+
+// 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, maxUncompressedChunkLen),
+ buf: make([]byte, MaxEncodedLen(maxUncompressedChunkLen)+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
+ }
+ }
+}
generated by cgit v1.2.3 (git 2.25.1) at 2024-08-22 01:54:51 +0800