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https://github.com/letic/terraform-provider-google.git
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961c878e0d
Switch to using Go modules. This migrates our vendor.json to use Go 1.11's modules system, and replaces the vendor folder with the output of go mod vendor. The vendored code should remain basically the same; I believe some tree shaking of packages and support scripts/licenses/READMEs/etc. happened. This also fixes Travis and our Makefile to no longer use govendor.
69 lines
2.9 KiB
Go
69 lines
2.9 KiB
Go
// Package lz4 implements reading and writing lz4 compressed data (a frame),
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// as specified in http://fastcompression.blogspot.fr/2013/04/lz4-streaming-format-final.html.
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//
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// Although the block level compression and decompression functions are exposed and are fully compatible
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// with the lz4 block format definition, they are low level and should not be used directly.
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// For a complete description of an lz4 compressed block, see:
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// http://fastcompression.blogspot.fr/2011/05/lz4-explained.html
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//
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// See https://github.com/Cyan4973/lz4 for the reference C implementation.
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//
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package lz4
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const (
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// Extension is the LZ4 frame file name extension
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Extension = ".lz4"
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// Version is the LZ4 frame format version
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Version = 1
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frameMagic uint32 = 0x184D2204
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frameSkipMagic uint32 = 0x184D2A50
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// The following constants are used to setup the compression algorithm.
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minMatch = 4 // the minimum size of the match sequence size (4 bytes)
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winSizeLog = 16 // LZ4 64Kb window size limit
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winSize = 1 << winSizeLog
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winMask = winSize - 1 // 64Kb window of previous data for dependent blocks
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compressedBlockFlag = 1 << 31
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compressedBlockMask = compressedBlockFlag - 1
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// hashLog determines the size of the hash table used to quickly find a previous match position.
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// Its value influences the compression speed and memory usage, the lower the faster,
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// but at the expense of the compression ratio.
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// 16 seems to be the best compromise.
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hashLog = 16
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hashTableSize = 1 << hashLog
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hashShift = uint((minMatch * 8) - hashLog)
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mfLimit = 8 + minMatch // The last match cannot start within the last 12 bytes.
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skipStrength = 6 // variable step for fast scan
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)
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// map the block max size id with its value in bytes: 64Kb, 256Kb, 1Mb and 4Mb.
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var (
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bsMapID = map[byte]int{4: 64 << 10, 5: 256 << 10, 6: 1 << 20, 7: 4 << 20}
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bsMapValue = make(map[int]byte, len(bsMapID))
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)
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// Reversed.
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func init() {
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for i, v := range bsMapID {
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bsMapValue[v] = i
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}
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}
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// Header describes the various flags that can be set on a Writer or obtained from a Reader.
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// The default values match those of the LZ4 frame format definition
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// (http://fastcompression.blogspot.com/2013/04/lz4-streaming-format-final.html).
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//
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// NB. in a Reader, in case of concatenated frames, the Header values may change between Read() calls.
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// It is the caller responsibility to check them if necessary.
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type Header struct {
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BlockChecksum bool // Compressed blocks checksum flag.
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NoChecksum bool // Frame checksum flag.
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BlockMaxSize int // Size of the uncompressed data block (one of [64KB, 256KB, 1MB, 4MB]). Default=4MB.
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Size uint64 // Frame total size. It is _not_ computed by the Writer.
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CompressionLevel int // Compression level (higher is better, use 0 for fastest compression).
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done bool // Header processed flag (Read or Write and checked).
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}
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