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Diffstat (limited to 'vendor/github.com/golang/snappy/snappy.go')
| -rw-r--r-- | vendor/github.com/golang/snappy/snappy.go | 98 |
1 files changed, 0 insertions, 98 deletions
diff --git a/vendor/github.com/golang/snappy/snappy.go b/vendor/github.com/golang/snappy/snappy.go deleted file mode 100644 index ece692e..0000000 --- a/vendor/github.com/golang/snappy/snappy.go +++ /dev/null @@ -1,98 +0,0 @@ -// 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 implements the Snappy compression format. It aims for very -// high speeds and reasonable compression. -// -// There are actually two Snappy formats: block and stream. They are related, -// but different: trying to decompress block-compressed data as a Snappy stream -// will fail, and vice versa. The block format is the Decode and Encode -// functions and the stream format is the Reader and Writer types. -// -// The block format, the more common case, is used when the complete size (the -// number of bytes) of the original data is known upfront, at the time -// compression starts. The stream format, also known as the framing format, is -// for when that isn't always true. -// -// The canonical, C++ implementation is at https://github.com/google/snappy and -// it only implements the block format. -package snappy // import "github.com/golang/snappy" - -import ( - "hash/crc32" -) - -/* -Each encoded block begins with the varint-encoded length of the decoded data, -followed by a sequence of chunks. Chunks begin and end on byte boundaries. The -first byte of each chunk is broken into its 2 least and 6 most significant bits -called l and m: l ranges in [0, 4) and m ranges in [0, 64). l is the chunk tag. -Zero means a literal tag. All other values mean a copy tag. - -For literal tags: - - If m < 60, the next 1 + m bytes are literal bytes. - - Otherwise, let n be the little-endian unsigned integer denoted by the next - m - 59 bytes. The next 1 + n bytes after that are literal bytes. - -For copy tags, length bytes are copied from offset bytes ago, in the style of -Lempel-Ziv compression algorithms. In particular: - - For l == 1, the offset ranges in [0, 1<<11) and the length in [4, 12). - The length is 4 + the low 3 bits of m. The high 3 bits of m form bits 8-10 - of the offset. The next byte is bits 0-7 of the offset. - - For l == 2, the offset ranges in [0, 1<<16) and the length in [1, 65). - The length is 1 + m. The offset is the little-endian unsigned integer - denoted by the next 2 bytes. - - For l == 3, this tag is a legacy format that is no longer issued by most - encoders. Nonetheless, the offset ranges in [0, 1<<32) and the length in - [1, 65). The length is 1 + m. The offset is the little-endian unsigned - integer denoted by the next 4 bytes. -*/ -const ( - tagLiteral = 0x00 - tagCopy1 = 0x01 - tagCopy2 = 0x02 - tagCopy4 = 0x03 -) - -const ( - checksumSize = 4 - chunkHeaderSize = 4 - magicChunk = "\xff\x06\x00\x00" + magicBody - magicBody = "sNaPpY" - - // maxBlockSize is the maximum size of the input to encodeBlock. It is not - // part of the wire format per se, but some parts of the encoder assume - // that an offset fits into a uint16. - // - // Also, for the framing format (Writer type instead of Encode function), - // https://github.com/google/snappy/blob/master/framing_format.txt says - // that "the uncompressed data in a chunk must be no longer than 65536 - // bytes". - maxBlockSize = 65536 - - // maxEncodedLenOfMaxBlockSize equals MaxEncodedLen(maxBlockSize), but is - // hard coded to be a const instead of a variable, so that obufLen can also - // be a const. Their equivalence is confirmed by - // TestMaxEncodedLenOfMaxBlockSize. - maxEncodedLenOfMaxBlockSize = 76490 - - obufHeaderLen = len(magicChunk) + checksumSize + chunkHeaderSize - obufLen = obufHeaderLen + maxEncodedLenOfMaxBlockSize -) - -const ( - chunkTypeCompressedData = 0x00 - chunkTypeUncompressedData = 0x01 - chunkTypePadding = 0xfe - chunkTypeStreamIdentifier = 0xff -) - -var crcTable = crc32.MakeTable(crc32.Castagnoli) - -// crc implements the checksum specified in section 3 of -// https://github.com/google/snappy/blob/master/framing_format.txt -func crc(b []byte) uint32 { - c := crc32.Update(0, crcTable, b) - return uint32(c>>15|c<<17) + 0xa282ead8 -} |