mirror of
https://github.com/ceph/ceph-csi.git
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91774fc936
Uses github.com/libopenstorage/secrets to communicate with Vault. This removes the need for maintaining our own limited Vault APIs. By adding the new dependency, several other packages got updated in the process. Unused indirect dependencies have been removed from go.mod. Signed-off-by: Niels de Vos <ndevos@redhat.com>
99 lines
3.9 KiB
Go
99 lines
3.9 KiB
Go
// Copyright 2011 The Snappy-Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package snappy implements the Snappy compression format. It aims for very
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// high speeds and reasonable compression.
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//
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// There are actually two Snappy formats: block and stream. They are related,
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// but different: trying to decompress block-compressed data as a Snappy stream
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// will fail, and vice versa. The block format is the Decode and Encode
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// functions and the stream format is the Reader and Writer types.
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//
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// The block format, the more common case, is used when the complete size (the
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// number of bytes) of the original data is known upfront, at the time
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// compression starts. The stream format, also known as the framing format, is
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// for when that isn't always true.
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//
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// The canonical, C++ implementation is at https://github.com/google/snappy and
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// it only implements the block format.
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package snappy // import "github.com/golang/snappy"
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import (
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"hash/crc32"
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)
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/*
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Each encoded block begins with the varint-encoded length of the decoded data,
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followed by a sequence of chunks. Chunks begin and end on byte boundaries. The
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first byte of each chunk is broken into its 2 least and 6 most significant bits
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called l and m: l ranges in [0, 4) and m ranges in [0, 64). l is the chunk tag.
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Zero means a literal tag. All other values mean a copy tag.
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For literal tags:
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- If m < 60, the next 1 + m bytes are literal bytes.
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- Otherwise, let n be the little-endian unsigned integer denoted by the next
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m - 59 bytes. The next 1 + n bytes after that are literal bytes.
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For copy tags, length bytes are copied from offset bytes ago, in the style of
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Lempel-Ziv compression algorithms. In particular:
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- For l == 1, the offset ranges in [0, 1<<11) and the length in [4, 12).
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The length is 4 + the low 3 bits of m. The high 3 bits of m form bits 8-10
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of the offset. The next byte is bits 0-7 of the offset.
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- For l == 2, the offset ranges in [0, 1<<16) and the length in [1, 65).
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The length is 1 + m. The offset is the little-endian unsigned integer
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denoted by the next 2 bytes.
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- For l == 3, this tag is a legacy format that is no longer issued by most
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encoders. Nonetheless, the offset ranges in [0, 1<<32) and the length in
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[1, 65). The length is 1 + m. The offset is the little-endian unsigned
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integer denoted by the next 4 bytes.
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*/
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const (
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tagLiteral = 0x00
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tagCopy1 = 0x01
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tagCopy2 = 0x02
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tagCopy4 = 0x03
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)
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const (
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checksumSize = 4
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chunkHeaderSize = 4
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magicChunk = "\xff\x06\x00\x00" + magicBody
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magicBody = "sNaPpY"
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// maxBlockSize is the maximum size of the input to encodeBlock. It is not
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// part of the wire format per se, but some parts of the encoder assume
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// that an offset fits into a uint16.
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//
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// Also, for the framing format (Writer type instead of Encode function),
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// https://github.com/google/snappy/blob/master/framing_format.txt says
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// that "the uncompressed data in a chunk must be no longer than 65536
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// bytes".
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maxBlockSize = 65536
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// maxEncodedLenOfMaxBlockSize equals MaxEncodedLen(maxBlockSize), but is
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// hard coded to be a const instead of a variable, so that obufLen can also
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// be a const. Their equivalence is confirmed by
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// TestMaxEncodedLenOfMaxBlockSize.
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maxEncodedLenOfMaxBlockSize = 76490
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obufHeaderLen = len(magicChunk) + checksumSize + chunkHeaderSize
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obufLen = obufHeaderLen + maxEncodedLenOfMaxBlockSize
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)
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const (
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chunkTypeCompressedData = 0x00
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chunkTypeUncompressedData = 0x01
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chunkTypePadding = 0xfe
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chunkTypeStreamIdentifier = 0xff
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)
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var crcTable = crc32.MakeTable(crc32.Castagnoli)
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// crc implements the checksum specified in section 3 of
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// https://github.com/google/snappy/blob/master/framing_format.txt
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func crc(b []byte) uint32 {
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c := crc32.Update(0, crcTable, b)
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return uint32(c>>15|c<<17) + 0xa282ead8
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}
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