jochen
be92762969
The live tests reached one shared bus and assert, read and remove the mesh's own objects by their fixed names, so packages run in parallel deleted what each other read and the suite passed only one package at a time; a red suite read as noise. internal/testbus starts a server per test, linked in at the nats-server release go.mod pins, and a test holds that pin to the catalogue's bus image and to the facts snapshot's bus when there is one, so the tests never run a bus the mesh does not. The waiter test read a timing (the most connections held at one look) and now reads the state it means (the fewest held across the wait). make check runs the packages in parallel under the race detector, with a timeout.
353 lines
9.6 KiB
Go
353 lines
9.6 KiB
Go
// Copyright (c) 2022+ Klaus Post. 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 s2
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import (
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"bytes"
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"encoding/binary"
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"sync"
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)
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const (
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// MinDictSize is the minimum dictionary size when repeat has been read.
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MinDictSize = 16
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// MaxDictSize is the maximum dictionary size when repeat has been read.
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MaxDictSize = 65536
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// MaxDictSrcOffset is the maximum offset where a dictionary entry can start.
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MaxDictSrcOffset = 65535
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)
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// Dict contains a dictionary that can be used for encoding and decoding s2
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type Dict struct {
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dict []byte
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repeat int // Repeat as index of dict
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fast, better, best sync.Once
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fastTable *[1 << 14]uint16
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betterTableShort *[1 << 14]uint16
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betterTableLong *[1 << 17]uint16
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bestTableShort *[1 << 16]uint32
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bestTableLong *[1 << 19]uint32
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}
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// NewDict will read a dictionary.
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// It will return nil if the dictionary is invalid.
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func NewDict(dict []byte) *Dict {
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if len(dict) == 0 {
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return nil
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}
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var d Dict
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// Repeat is the first value of the dict
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r, n := binary.Uvarint(dict)
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if n <= 0 {
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return nil
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}
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dict = dict[n:]
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d.dict = dict
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if cap(d.dict) < len(d.dict)+16 {
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d.dict = append(make([]byte, 0, len(d.dict)+16), d.dict...)
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}
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if len(dict) < MinDictSize || len(dict) > MaxDictSize {
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return nil
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}
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// Compare as uint64: int(r) would wrap negative for r > MaxInt64,
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// slipping past the bounds check and causing an OOB read in encode.
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if r > uint64(len(dict)) {
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return nil
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}
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d.repeat = int(r)
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return &d
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}
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// Bytes will return a serialized version of the dictionary.
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// The output can be sent to NewDict.
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func (d *Dict) Bytes() []byte {
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dst := make([]byte, binary.MaxVarintLen16+len(d.dict))
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return append(dst[:binary.PutUvarint(dst, uint64(d.repeat))], d.dict...)
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}
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// MakeDict will create a dictionary.
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// 'data' must be at least MinDictSize.
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// If data is longer than MaxDictSize only the last MaxDictSize bytes will be used.
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// If searchStart is set the start repeat value will be set to the last
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// match of this content.
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// If no matches are found, it will attempt to find shorter matches.
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// This content should match the typical start of a block.
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// If at least 4 bytes cannot be matched, repeat is set to start of block.
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func MakeDict(data []byte, searchStart []byte) *Dict {
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if len(data) == 0 {
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return nil
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}
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if len(data) > MaxDictSize {
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data = data[len(data)-MaxDictSize:]
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}
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var d Dict
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dict := data
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d.dict = dict
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if cap(d.dict) < len(d.dict)+16 {
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d.dict = append(make([]byte, 0, len(d.dict)+16), d.dict...)
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}
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if len(dict) < MinDictSize {
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return nil
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}
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// Find the longest match possible, last entry if multiple.
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for s := len(searchStart); s > 4; s-- {
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if idx := bytes.LastIndex(data, searchStart[:s]); idx >= 0 && idx <= len(data)-8 {
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d.repeat = idx
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break
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}
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}
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return &d
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}
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// MakeDictManual will create a dictionary.
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// 'data' must be at least MinDictSize and less than or equal to MaxDictSize.
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// A manual first repeat index into data must be provided.
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// It must be less than len(data)-8.
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func MakeDictManual(data []byte, firstIdx uint16) *Dict {
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if len(data) < MinDictSize || int(firstIdx) >= len(data)-8 || len(data) > MaxDictSize {
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return nil
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}
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var d Dict
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dict := data
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d.dict = dict
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if cap(d.dict) < len(d.dict)+16 {
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d.dict = append(make([]byte, 0, len(d.dict)+16), d.dict...)
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}
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d.repeat = int(firstIdx)
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return &d
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}
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// Encode returns the encoded form of src. The returned slice may be a sub-
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// slice of dst if dst was large enough to hold the entire encoded block.
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// Otherwise, a newly allocated slice will be returned.
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//
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// The dst and src must not overlap. It is valid to pass a nil dst.
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//
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// The blocks will require the same amount of memory to decode as encoding,
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// and does not make for concurrent decoding.
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// Also note that blocks do not contain CRC information, so corruption may be undetected.
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//
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// If you need to encode larger amounts of data, consider using
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// the streaming interface which gives all of these features.
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func (d *Dict) Encode(dst, src []byte) []byte {
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if n := MaxEncodedLen(len(src)); n < 0 {
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panic(ErrTooLarge)
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} else if cap(dst) < n {
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dst = make([]byte, n)
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} else {
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dst = dst[:n]
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}
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// The block starts with the varint-encoded length of the decompressed bytes.
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dstP := binary.PutUvarint(dst, uint64(len(src)))
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if len(src) == 0 {
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return dst[:dstP]
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}
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if len(src) < minNonLiteralBlockSize {
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dstP += emitLiteral(dst[dstP:], src)
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return dst[:dstP]
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}
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n := encodeBlockDictGo(dst[dstP:], src, d)
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if n > 0 {
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dstP += n
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return dst[:dstP]
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}
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// Not compressible
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dstP += emitLiteral(dst[dstP:], src)
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return dst[:dstP]
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}
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// EncodeBetter returns the encoded form of src. The returned slice may be a sub-
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// slice of dst if dst was large enough to hold the entire encoded block.
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// Otherwise, a newly allocated slice will be returned.
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//
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// EncodeBetter compresses better than Encode but typically with a
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// 10-40% speed decrease on both compression and decompression.
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//
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// The dst and src must not overlap. It is valid to pass a nil dst.
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//
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// The blocks will require the same amount of memory to decode as encoding,
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// and does not make for concurrent decoding.
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// Also note that blocks do not contain CRC information, so corruption may be undetected.
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//
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// If you need to encode larger amounts of data, consider using
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// the streaming interface which gives all of these features.
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func (d *Dict) EncodeBetter(dst, src []byte) []byte {
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if n := MaxEncodedLen(len(src)); n < 0 {
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panic(ErrTooLarge)
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} else if len(dst) < n {
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dst = make([]byte, n)
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}
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// The block starts with the varint-encoded length of the decompressed bytes.
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dstP := binary.PutUvarint(dst, uint64(len(src)))
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if len(src) == 0 {
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return dst[:dstP]
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}
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if len(src) < minNonLiteralBlockSize {
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dstP += emitLiteral(dst[dstP:], src)
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return dst[:dstP]
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}
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n := encodeBlockBetterDict(dst[dstP:], src, d)
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if n > 0 {
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dstP += n
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return dst[:dstP]
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}
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// Not compressible
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dstP += emitLiteral(dst[dstP:], src)
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return dst[:dstP]
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}
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// EncodeBest returns the encoded form of src. The returned slice may be a sub-
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// slice of dst if dst was large enough to hold the entire encoded block.
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// Otherwise, a newly allocated slice will be returned.
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//
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// EncodeBest compresses as good as reasonably possible but with a
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// big speed decrease.
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//
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// The dst and src must not overlap. It is valid to pass a nil dst.
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//
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// The blocks will require the same amount of memory to decode as encoding,
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// and does not make for concurrent decoding.
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// Also note that blocks do not contain CRC information, so corruption may be undetected.
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//
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// If you need to encode larger amounts of data, consider using
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// the streaming interface which gives all of these features.
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func (d *Dict) EncodeBest(dst, src []byte) []byte {
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if n := MaxEncodedLen(len(src)); n < 0 {
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panic(ErrTooLarge)
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} else if len(dst) < n {
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dst = make([]byte, n)
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}
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// The block starts with the varint-encoded length of the decompressed bytes.
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dstP := binary.PutUvarint(dst, uint64(len(src)))
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if len(src) == 0 {
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return dst[:dstP]
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}
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if len(src) < minNonLiteralBlockSize {
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dstP += emitLiteral(dst[dstP:], src)
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return dst[:dstP]
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}
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n := encodeBlockBest(dst[dstP:], src, d)
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if n > 0 {
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dstP += n
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return dst[:dstP]
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}
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// Not compressible
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dstP += emitLiteral(dst[dstP:], src)
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return dst[:dstP]
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}
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// Decode returns the decoded form of src. The returned slice may be a sub-
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// slice of dst if dst was large enough to hold the entire decoded block.
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// Otherwise, a newly allocated slice will be returned.
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//
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// The dst and src must not overlap. It is valid to pass a nil dst.
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func (d *Dict) Decode(dst, src []byte) ([]byte, error) {
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dLen, s, err := decodedLen(src)
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if err != nil {
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return nil, err
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}
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if dLen <= cap(dst) {
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dst = dst[:dLen]
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} else {
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dst = make([]byte, dLen)
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}
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if s2DecodeDict(dst, src[s:], d) != 0 {
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return nil, ErrCorrupt
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}
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return dst, nil
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}
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func (d *Dict) initFast() {
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d.fast.Do(func() {
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const (
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tableBits = 14
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maxTableSize = 1 << tableBits
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)
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var table [maxTableSize]uint16
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// We stop so any entry of length 8 can always be read.
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for i := 0; i < len(d.dict)-8-2; i += 3 {
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x0 := load64(d.dict, i)
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h0 := hash6(x0, tableBits)
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h1 := hash6(x0>>8, tableBits)
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h2 := hash6(x0>>16, tableBits)
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table[h0] = uint16(i)
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table[h1] = uint16(i + 1)
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table[h2] = uint16(i + 2)
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}
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d.fastTable = &table
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})
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}
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func (d *Dict) initBetter() {
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d.better.Do(func() {
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const (
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// Long hash matches.
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lTableBits = 17
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maxLTableSize = 1 << lTableBits
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// Short hash matches.
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sTableBits = 14
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maxSTableSize = 1 << sTableBits
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)
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var lTable [maxLTableSize]uint16
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var sTable [maxSTableSize]uint16
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// We stop so any entry of length 8 can always be read.
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for i := 0; i < len(d.dict)-8; i++ {
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cv := load64(d.dict, i)
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lTable[hash7(cv, lTableBits)] = uint16(i)
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sTable[hash4(cv, sTableBits)] = uint16(i)
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}
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d.betterTableShort = &sTable
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d.betterTableLong = &lTable
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})
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}
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func (d *Dict) initBest() {
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d.best.Do(func() {
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const (
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// Long hash matches.
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lTableBits = 19
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maxLTableSize = 1 << lTableBits
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// Short hash matches.
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sTableBits = 16
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maxSTableSize = 1 << sTableBits
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)
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var lTable [maxLTableSize]uint32
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var sTable [maxSTableSize]uint32
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// We stop so any entry of length 8 can always be read.
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for i := 0; i < len(d.dict)-8; i++ {
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cv := load64(d.dict, i)
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hashL := hash8(cv, lTableBits)
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hashS := hash4(cv, sTableBits)
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candidateL := lTable[hashL]
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candidateS := sTable[hashS]
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lTable[hashL] = uint32(i) | candidateL<<16
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sTable[hashS] = uint32(i) | candidateS<<16
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}
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d.bestTableShort = &sTable
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d.bestTableLong = &lTable
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})
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}
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