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Diffstat (limited to 'vendor/github.com/klauspost/compress/fse/fse.go')
-rw-r--r-- | vendor/github.com/klauspost/compress/fse/fse.go | 144 |
1 files changed, 0 insertions, 144 deletions
diff --git a/vendor/github.com/klauspost/compress/fse/fse.go b/vendor/github.com/klauspost/compress/fse/fse.go deleted file mode 100644 index 535cbadfd..000000000 --- a/vendor/github.com/klauspost/compress/fse/fse.go +++ /dev/null @@ -1,144 +0,0 @@ -// Copyright 2018 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. -// Based on work Copyright (c) 2013, Yann Collet, released under BSD License. - -// Package fse provides Finite State Entropy encoding and decoding. -// -// Finite State Entropy encoding provides a fast near-optimal symbol encoding/decoding -// for byte blocks as implemented in zstd. -// -// See https://github.com/klauspost/compress/tree/master/fse for more information. -package fse - -import ( - "errors" - "fmt" - "math/bits" -) - -const ( - /*!MEMORY_USAGE : - * Memory usage formula : N->2^N Bytes (examples : 10 -> 1KB; 12 -> 4KB ; 16 -> 64KB; 20 -> 1MB; etc.) - * Increasing memory usage improves compression ratio - * Reduced memory usage can improve speed, due to cache effect - * Recommended max value is 14, for 16KB, which nicely fits into Intel x86 L1 cache */ - maxMemoryUsage = 14 - defaultMemoryUsage = 13 - - maxTableLog = maxMemoryUsage - 2 - maxTablesize = 1 << maxTableLog - defaultTablelog = defaultMemoryUsage - 2 - minTablelog = 5 - maxSymbolValue = 255 -) - -var ( - // ErrIncompressible is returned when input is judged to be too hard to compress. - ErrIncompressible = errors.New("input is not compressible") - - // ErrUseRLE is returned from the compressor when the input is a single byte value repeated. - ErrUseRLE = errors.New("input is single value repeated") -) - -// Scratch provides temporary storage for compression and decompression. -type Scratch struct { - // Private - count [maxSymbolValue + 1]uint32 - norm [maxSymbolValue + 1]int16 - br byteReader - bits bitReader - bw bitWriter - ct cTable // Compression tables. - decTable []decSymbol // Decompression table. - maxCount int // count of the most probable symbol - - // Per block parameters. - // These can be used to override compression parameters of the block. - // Do not touch, unless you know what you are doing. - - // Out is output buffer. - // If the scratch is re-used before the caller is done processing the output, - // set this field to nil. - // Otherwise the output buffer will be re-used for next Compression/Decompression step - // and allocation will be avoided. - Out []byte - - // DecompressLimit limits the maximum decoded size acceptable. - // If > 0 decompression will stop when approximately this many bytes - // has been decoded. - // If 0, maximum size will be 2GB. - DecompressLimit int - - symbolLen uint16 // Length of active part of the symbol table. - actualTableLog uint8 // Selected tablelog. - zeroBits bool // no bits has prob > 50%. - clearCount bool // clear count - - // MaxSymbolValue will override the maximum symbol value of the next block. - MaxSymbolValue uint8 - - // TableLog will attempt to override the tablelog for the next block. - TableLog uint8 -} - -// Histogram allows to populate the histogram and skip that step in the compression, -// It otherwise allows to inspect the histogram when compression is done. -// To indicate that you have populated the histogram call HistogramFinished -// with the value of the highest populated symbol, as well as the number of entries -// in the most populated entry. These are accepted at face value. -// The returned slice will always be length 256. -func (s *Scratch) Histogram() []uint32 { - return s.count[:] -} - -// HistogramFinished can be called to indicate that the histogram has been populated. -// maxSymbol is the index of the highest set symbol of the next data segment. -// maxCount is the number of entries in the most populated entry. -// These are accepted at face value. -func (s *Scratch) HistogramFinished(maxSymbol uint8, maxCount int) { - s.maxCount = maxCount - s.symbolLen = uint16(maxSymbol) + 1 - s.clearCount = maxCount != 0 -} - -// prepare will prepare and allocate scratch tables used for both compression and decompression. -func (s *Scratch) prepare(in []byte) (*Scratch, error) { - if s == nil { - s = &Scratch{} - } - if s.MaxSymbolValue == 0 { - s.MaxSymbolValue = 255 - } - if s.TableLog == 0 { - s.TableLog = defaultTablelog - } - if s.TableLog > maxTableLog { - return nil, fmt.Errorf("tableLog (%d) > maxTableLog (%d)", s.TableLog, maxTableLog) - } - if cap(s.Out) == 0 { - s.Out = make([]byte, 0, len(in)) - } - if s.clearCount && s.maxCount == 0 { - for i := range s.count { - s.count[i] = 0 - } - s.clearCount = false - } - s.br.init(in) - if s.DecompressLimit == 0 { - // Max size 2GB. - s.DecompressLimit = (2 << 30) - 1 - } - - return s, nil -} - -// tableStep returns the next table index. -func tableStep(tableSize uint32) uint32 { - return (tableSize >> 1) + (tableSize >> 3) + 3 -} - -func highBits(val uint32) (n uint32) { - return uint32(bits.Len32(val) - 1) -} |