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inflate.go
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inflate.go
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// Copyright (c) 2024, Intel Corporation.
// SPDX-License-Identifier: BSD-3-Clause
package flate
import (
"encoding/binary"
)
type inflate struct {
input []byte
bits uint64 // Bits buffered to handle unaligned streams
bitsLen int32 // Bits in readIn
writeOverflowLits int32
writeOverflowLen int32
copyOverflowLength int32
copyOverflowDistance int32
litLenTable largeHuffCodeTable
distTable smallHuffCodeTable
phase int32 // Current decompression state
bfinal uint32 // Flag identifying final block
litBlockLength int
headerBuffered int16 // Number of bytes in tmpInBuffer
headerBuffer [328]uint8 // Temporary buffer to accumulate data for decoding the header
dynHdr dynamicHeaderReader // temp objects for processing header
roffset int64
}
type dynamicHeaderReader struct {
litAndDistHuff [litLenElems]huffCode
clcTable smallHuffCodeTable // Table for decoding codelencode symbols
codeList [litLenElems + 2]uint32
litCount [maxLitLenCount]uint16
distCount [maxHuffTreeDepth + 1]uint16
litExpandCount [maxLitLenCount]uint16
nextCode [maxHuffTreeDepth + 1]uint32
lenHuffCodes [litLen - litSymbolsSize]huffCode
}
func (s *inflate) reset() {
s.input = nil
s.bits = 0 // Bits buffered to handle unaligned streams
s.bitsLen = 0 // Bits in readIn
s.phase = 0
s.bfinal = 0
s.litBlockLength = 0
s.writeOverflowLits = 0
s.writeOverflowLen = 0
s.copyOverflowLength = 0
s.copyOverflowDistance = 0
s.headerBuffered = 0
s.roffset = 0
}
const (
phaseNewBlock = iota
phaseDecodingHeader
phaseLitBlock
phaseHeaderDecoded
phaseStreamEnd
phaseFinish
)
func (state *inflate) nextBits(bitCount uint8) uint64 {
ret := (state.bits) & ((1 << bitCount) - 1)
state.bits = state.bits >> bitCount
state.bitsLen -= int32(bitCount)
return ret
}
func (state *inflate) readBits(bitCount uint8) uint64 {
state.loadBits()
return state.nextBits(bitCount)
}
func (state *inflate) loadBits() {
if state.bitsLen < 57 {
if len(state.input) >= 8 {
/* If there is enough space to load a 64 bits, load the data and use
* that to fill readIn */
consumed := 8 - uint8(state.bitsLen+7)/8
temp := binary.LittleEndian.Uint64(state.input)
state.bits |= temp << state.bitsLen
state.input = state.input[consumed:]
state.bitsLen += int32(consumed) * 8
} else {
size := int(64-state.bitsLen) / 8
if len(state.input) < size {
size = len(state.input)
}
for _, b := range state.input[:size] {
state.bits |= uint64(b) << state.bitsLen
state.bitsLen += 8
}
state.input = state.input[size:]
}
}
}
func (state *inflate) tryDecodeHeader() (err error) {
state.bfinal = uint32(state.readBits(1))
btype := uint32(state.readBits(2))
if state.bitsLen < 0 {
return errEndInput
}
switch btype {
case 0:
return state.prepareForLitBlock()
case 1:
state.setupStaticHeader()
return nil
case 2:
return state.setupDynamicHeader()
default:
return errInvalidBlock
}
}
func (state *inflate) prepareForLitBlock() error {
state.loadBits()
bytes := uint8(state.bitsLen / 8)
if bytes < 4 {
return errEndInput
}
state.bits >>= state.bitsLen % 8
state.bitsLen = int32(bytes * 8)
len := uint16(state.bits & 0xFFFF)
state.bits >>= 16
nlen := uint16(state.bits & 0xFFFF)
state.bits >>= 16
state.bitsLen -= 32
/* Check if len and nlen match */
if len != (^nlen & 0xffff) {
return errInvalidBlock
}
rest := state.bitsLen % 8
if rest != 0 {
state.bitsLen -= rest
state.bits >>= uint64(rest)
}
state.bits = (state.bits) & ((1 << state.bitsLen) - 1)
state.litBlockLength = int(len)
state.phase = phaseLitBlock
return nil
}
type huffCode struct {
codeAndLength uint32
}
func (h *huffCode) Set(code uint32, length uint32) {
h.codeAndLength = code | length<<24
}
const (
lengthMask = uint32(1<<24 - 1)
codeMask = ^lengthMask
)
func (h *huffCode) SetCode(code uint32) {
// clear code
h.codeAndLength = codeMask & h.codeAndLength
// set code
h.codeAndLength |= code & lengthMask
}
func (h *huffCode) Code() uint32 {
return h.codeAndLength & lengthMask
}
func (h *huffCode) Length() uint32 {
return h.codeAndLength >> 24
}
const (
codeLenCodes = 19
huffLen = 19
maxLitLenSym = 512
litLenElems = 514
maxLitLenCodeLen = 21
maxLitLenCount = (maxLitLenCodeLen + 2)
tripleSymFlag = 0
doubleSymFlag = tripleSymFlag + 1
singleSymFlag = doubleSymFlag + 1
defaultSymFlag = tripleSymFlag
distLen = 30
singleSymThresh = (2 * 1024)
doubleSymThresh = (4 * 1024)
maxHuffTreeDepth = 15
litLen = 257 + 29
litTableSize = 257
maxHdrSize = 328
maxCodeLen = 15
historySize = (32 * 1024)
maxHistoryBits = 15
maxMatch = 258
minMatch = 3
lookAhead = (maxMatch + 31) & ^31
)
func setCodes(table []huffCode, count []uint16) (ret int) {
var max, code, length uint32
var nextCode [maxHuffTreeDepth + 1]uint32
for i := 2; i < maxHuffTreeDepth+1; i++ {
nextCode[i] = (nextCode[i-1] + uint32(count[i-1])) << 1
}
max = nextCode[maxHuffTreeDepth] + uint32(count[maxHuffTreeDepth])
if max > (1 << maxHuffTreeDepth) {
return errorNoInvalidBlock
}
for i := 0; i < len(table); i++ {
length = table[i].Length()
if length == 0 {
continue
}
code = bitReverse2(uint16(nextCode[length]), uint8(length))
table[i].Set(code, length)
nextCode[length]++
}
return 0
}
func (state *inflate) rOffset(inputSize, bitsLen int) {
start := inputSize*8 + bitsLen
end := len(state.input)*8 + int(state.bitsLen)
size := (start - end) / 8
state.roffset += int64(size)
}
func (state *inflate) readHeader() (err error) {
bits := state.bits
bitsLen := state.bitsLen
input := state.input
phase := state.phase
var tempLen int
if phase == phaseDecodingHeader {
/* Setup so readHeader decodes data in tmpInBuffer */
copySize := int(maxHdrSize - state.headerBuffered)
if copySize > len(state.input) {
copySize = len(state.input)
}
copy(state.headerBuffer[state.headerBuffered:], state.input[:copySize])
tempLen = copySize + int(state.headerBuffered)
state.input = state.headerBuffer[:tempLen]
}
err = state.tryDecodeHeader()
if phase == phaseDecodingHeader {
read := tempLen - len(state.input) - int(state.headerBuffered)
state.input = input[read:]
}
if err == errEndInput {
state.bits = bits
state.bitsLen = bitsLen
size := copy(state.headerBuffer[state.headerBuffered:], input)
state.headerBuffered += int16(size)
state.input = state.input[:0]
state.phase = phaseDecodingHeader
} else {
state.headerBuffered = 0
}
return err
}