diff options
Diffstat (limited to 'Godeps/_workspace/src/code.google.com/p/snappy-go/snappy/decode.go')
-rw-r--r-- | Godeps/_workspace/src/code.google.com/p/snappy-go/snappy/decode.go | 124 |
1 files changed, 124 insertions, 0 deletions
diff --git a/Godeps/_workspace/src/code.google.com/p/snappy-go/snappy/decode.go b/Godeps/_workspace/src/code.google.com/p/snappy-go/snappy/decode.go new file mode 100644 index 000000000..d93c1b9db --- /dev/null +++ b/Godeps/_workspace/src/code.google.com/p/snappy-go/snappy/decode.go @@ -0,0 +1,124 @@ +// 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" +) + +// ErrCorrupt reports that the input is invalid. +var ErrCorrupt = errors.New("snappy: corrupt 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 { + return 0, 0, ErrCorrupt + } + if uint64(int(v)) != v { + return 0, 0, errors.New("snappy: decoded block is too large") + } + 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 += 1 + 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 +} |