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Diffstat (limited to 'Godeps/_workspace/src/code.google.com/p/snappy-go/snappy/snappy.go')
| -rw-r--r-- | Godeps/_workspace/src/code.google.com/p/snappy-go/snappy/snappy.go | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/Godeps/_workspace/src/code.google.com/p/snappy-go/snappy/snappy.go b/Godeps/_workspace/src/code.google.com/p/snappy-go/snappy/snappy.go new file mode 100644 index 000000000..2f1b790d0 --- /dev/null +++ b/Godeps/_workspace/src/code.google.com/p/snappy-go/snappy/snappy.go @@ -0,0 +1,38 @@ +// 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 block-based compression format. +// It aims for very high speeds and reasonable compression. +// +// The C++ snappy implementation is at http://code.google.com/p/snappy/ +package snappy + +/* +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 supported. +*/ +const ( + tagLiteral = 0x00 + tagCopy1 = 0x01 + tagCopy2 = 0x02 + tagCopy4 = 0x03 +) |