diff options
Diffstat (limited to 'vendor/github.com/klauspost/compress/s2/s2.go')
| -rw-r--r-- | vendor/github.com/klauspost/compress/s2/s2.go | 151 |
1 files changed, 0 insertions, 151 deletions
diff --git a/vendor/github.com/klauspost/compress/s2/s2.go b/vendor/github.com/klauspost/compress/s2/s2.go deleted file mode 100644 index cbd1ed64d..000000000 --- a/vendor/github.com/klauspost/compress/s2/s2.go +++ /dev/null @@ -1,151 +0,0 @@ -// Copyright 2011 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. - -// Package s2 implements the S2 compression format. -// -// S2 is an extension of Snappy. Similar to Snappy S2 is aimed for high throughput, -// which is why it features concurrent compression for bigger payloads. -// -// Decoding is compatible with Snappy compressed content, -// but content compressed with S2 cannot be decompressed by Snappy. -// -// For more information on Snappy/S2 differences see README in: https://github.com/klauspost/compress/tree/master/s2 -// -// There are actually two S2 formats: block and stream. They are related, -// but different: trying to decompress block-compressed data as a S2 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. -// -// A "better" compression option is available. This will trade some compression -// speed -// -// 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. -// -// Blocks to not offer much data protection, so it is up to you to -// add data validation of decompressed blocks. -// -// Streams perform CRC validation of the decompressed data. -// Stream compression will also be performed on multiple CPU cores concurrently -// significantly improving throughput. -package s2 - -import ( - "bytes" - "hash/crc32" - - "github.com/klauspost/compress/internal/race" -) - -/* -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, 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 - magicChunkSnappy = "\xff\x06\x00\x00" + magicBodySnappy - magicBodySnappy = "sNaPpY" - magicBody = "S2sTwO" - - // maxBlockSize is the maximum size of the input to encodeBlock. - // - // For the framing format (Writer type instead of Encode function), - // this is the maximum uncompressed size of a block. - maxBlockSize = 4 << 20 - - // minBlockSize is the minimum size of block setting when creating a writer. - minBlockSize = 4 << 10 - - skippableFrameHeader = 4 - maxChunkSize = 1<<24 - 1 // 16777215 - - // Default block size - defaultBlockSize = 1 << 20 - - // maxSnappyBlockSize is the maximum snappy block size. - maxSnappyBlockSize = 1 << 16 - - obufHeaderLen = checksumSize + chunkHeaderSize -) - -const ( - chunkTypeCompressedData = 0x00 - chunkTypeUncompressedData = 0x01 - ChunkTypeIndex = 0x99 - chunkTypePadding = 0xfe - chunkTypeStreamIdentifier = 0xff -) - -var ( - crcTable = crc32.MakeTable(crc32.Castagnoli) - magicChunkSnappyBytes = []byte(magicChunkSnappy) // Can be passed to functions where it escapes. - magicChunkBytes = []byte(magicChunk) // Can be passed to functions where it escapes. -) - -// crc implements the checksum specified in section 3 of -// https://github.com/google/snappy/blob/master/framing_format.txt -func crc(b []byte) uint32 { - race.ReadSlice(b) - - c := crc32.Update(0, crcTable, b) - return c>>15 | c<<17 + 0xa282ead8 -} - -// literalExtraSize returns the extra size of encoding n literals. -// n should be >= 0 and <= math.MaxUint32. -func literalExtraSize(n int64) int64 { - if n == 0 { - return 0 - } - switch { - case n < 60: - return 1 - case n < 1<<8: - return 2 - case n < 1<<16: - return 3 - case n < 1<<24: - return 4 - default: - return 5 - } -} - -type byter interface { - Bytes() []byte -} - -var _ byter = &bytes.Buffer{} |