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gitea/vendor/github.com/xi2/xz/dec_stream.go

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/*
* .xz Stream decoder
*
* Author: Lasse Collin <lasse.collin@tukaani.org>
*
* Translation to Go: Michael Cross <https://github.com/xi2>
*
* This file has been put into the public domain.
* You can do whatever you want with this file.
*/
package xz
import (
"bytes"
"crypto/sha256"
"hash"
"hash/crc32"
"hash/crc64"
)
/* from linux/lib/xz/xz_stream.h **************************************/
/*
* See the .xz file format specification at
* http://tukaani.org/xz/xz-file-format.txt
* to understand the container format.
*/
const (
streamHeaderSize = 12
headerMagic = "\xfd7zXZ\x00"
footerMagic = "YZ"
)
/*
* Variable-length integer can hold a 63-bit unsigned integer or a special
* value indicating that the value is unknown.
*/
type vliType uint64
const (
vliUnknown vliType = ^vliType(0)
/* Maximum encoded size of a VLI */
vliBytesMax = 8 * 8 / 7 // (Sizeof(vliType) * 8 / 7)
)
/* from linux/lib/xz/xz_dec_stream.c **********************************/
/* Hash used to validate the Index field */
type xzDecHash struct {
unpadded vliType
uncompressed vliType
sha256 hash.Hash
}
// type of xzDec.sequence
type xzDecSeq int
const (
seqStreamHeader xzDecSeq = iota
seqBlockStart
seqBlockHeader
seqBlockUncompress
seqBlockPadding
seqBlockCheck
seqIndex
seqIndexPadding
seqIndexCRC32
seqStreamFooter
)
// type of xzDec.index.sequence
type xzDecIndexSeq int
const (
seqIndexCount xzDecIndexSeq = iota
seqIndexUnpadded
seqIndexUncompressed
)
/**
* xzDec - Opaque type to hold the XZ decoder state
*/
type xzDec struct {
/* Position in decMain */
sequence xzDecSeq
/* Position in variable-length integers and Check fields */
pos int
/* Variable-length integer decoded by decVLI */
vli vliType
/* Saved inPos and outPos */
inStart int
outStart int
/* CRC32 checksum hash used in Index */
crc32 hash.Hash
/* Hashes used in Blocks */
checkCRC32 hash.Hash
checkCRC64 hash.Hash
checkSHA256 hash.Hash
/* for checkTypes CRC32/CRC64/SHA256, check is one of the above 3 hashes */
check hash.Hash
/* Embedded stream header struct containing CheckType */
*Header
/*
* True if the next call to xzDecRun is allowed to return
* xzBufError.
*/
allowBufError bool
/* Information stored in Block Header */
blockHeader struct {
/*
* Value stored in the Compressed Size field, or
* vliUnknown if Compressed Size is not present.
*/
compressed vliType
/*
* Value stored in the Uncompressed Size field, or
* vliUnknown if Uncompressed Size is not present.
*/
uncompressed vliType
/* Size of the Block Header field */
size int
}
/* Information collected when decoding Blocks */
block struct {
/* Observed compressed size of the current Block */
compressed vliType
/* Observed uncompressed size of the current Block */
uncompressed vliType
/* Number of Blocks decoded so far */
count vliType
/*
* Hash calculated from the Block sizes. This is used to
* validate the Index field.
*/
hash xzDecHash
}
/* Variables needed when verifying the Index field */
index struct {
/* Position in decIndex */
sequence xzDecIndexSeq
/* Size of the Index in bytes */
size vliType
/* Number of Records (matches block.count in valid files) */
count vliType
/*
* Hash calculated from the Records (matches block.hash in
* valid files).
*/
hash xzDecHash
}
/*
* Temporary buffer needed to hold Stream Header, Block Header,
* and Stream Footer. The Block Header is the biggest (1 KiB)
* so we reserve space according to that. bufArray has to be aligned
* to a multiple of four bytes; the variables before it
* should guarantee this.
*/
temp struct {
pos int
buf []byte // slice buf will be backed by bufArray
bufArray [1024]byte
}
// chain is the function (or to be more precise, closure) which
// does the decompression and will call into the lzma2 and other
// filter code as needed. It is constructed by decBlockHeader
chain func(b *xzBuf) xzRet
// lzma2 holds the state of the last filter (which must be LZMA2)
lzma2 *xzDecLZMA2
// pointers to allocated BCJ/Delta filters
bcjs []*xzDecBCJ
deltas []*xzDecDelta
// number of currently in use BCJ/Delta filters from the above
bcjsUsed int
deltasUsed int
}
/* Sizes of the Check field with different Check IDs */
var checkSizes = [...]byte{
0,
4, 4, 4,
8, 8, 8,
16, 16, 16,
32, 32, 32,
64, 64, 64,
}
/*
* Fill s.temp by copying data starting from b.in[b.inPos]. Caller
* must have set s.temp.pos to indicate how much data we are supposed
* to copy into s.temp.buf. Return true once s.temp.pos has reached
* len(s.temp.buf).
*/
func fillTemp(s *xzDec, b *xzBuf) bool {
copySize := len(b.in) - b.inPos
tempRemaining := len(s.temp.buf) - s.temp.pos
if copySize > tempRemaining {
copySize = tempRemaining
}
copy(s.temp.buf[s.temp.pos:], b.in[b.inPos:])
b.inPos += copySize
s.temp.pos += copySize
if s.temp.pos == len(s.temp.buf) {
s.temp.pos = 0
return true
}
return false
}
/* Decode a variable-length integer (little-endian base-128 encoding) */
func decVLI(s *xzDec, in []byte, inPos *int) xzRet {
var byte byte
if s.pos == 0 {
s.vli = 0
}
for *inPos < len(in) {
byte = in[*inPos]
*inPos++
s.vli |= vliType(byte&0x7f) << uint(s.pos)
if byte&0x80 == 0 {
/* Don't allow non-minimal encodings. */
if byte == 0 && s.pos != 0 {
return xzDataError
}
s.pos = 0
return xzStreamEnd
}
s.pos += 7
if s.pos == 7*vliBytesMax {
return xzDataError
}
}
return xzOK
}
/*
* Decode the Compressed Data field from a Block. Update and validate
* the observed compressed and uncompressed sizes of the Block so that
* they don't exceed the values possibly stored in the Block Header
* (validation assumes that no integer overflow occurs, since vliType
* is uint64). Update s.check if presence of the CRC32/CRC64/SHA256
* field was indicated in Stream Header.
*
* Once the decoding is finished, validate that the observed sizes match
* the sizes possibly stored in the Block Header. Update the hash and
* Block count, which are later used to validate the Index field.
*/
func decBlock(s *xzDec, b *xzBuf) xzRet {
var ret xzRet
s.inStart = b.inPos
s.outStart = b.outPos
ret = s.chain(b)
s.block.compressed += vliType(b.inPos - s.inStart)
s.block.uncompressed += vliType(b.outPos - s.outStart)
/*
* There is no need to separately check for vliUnknown since
* the observed sizes are always smaller than vliUnknown.
*/
if s.block.compressed > s.blockHeader.compressed ||
s.block.uncompressed > s.blockHeader.uncompressed {
return xzDataError
}
switch s.CheckType {
case CheckCRC32, CheckCRC64, CheckSHA256:
_, _ = s.check.Write(b.out[s.outStart:b.outPos])
}
if ret == xzStreamEnd {
if s.blockHeader.compressed != vliUnknown &&
s.blockHeader.compressed != s.block.compressed {
return xzDataError
}
if s.blockHeader.uncompressed != vliUnknown &&
s.blockHeader.uncompressed != s.block.uncompressed {
return xzDataError
}
s.block.hash.unpadded +=
vliType(s.blockHeader.size) + s.block.compressed
s.block.hash.unpadded += vliType(checkSizes[s.CheckType])
s.block.hash.uncompressed += s.block.uncompressed
var buf [2 * 8]byte // 2*Sizeof(vliType)
putLE64(uint64(s.block.hash.unpadded), buf[:])
putLE64(uint64(s.block.hash.uncompressed), buf[8:])
_, _ = s.block.hash.sha256.Write(buf[:])
s.block.count++
}
return ret
}
/* Update the Index size and the CRC32 hash. */
func indexUpdate(s *xzDec, b *xzBuf) {
inUsed := b.inPos - s.inStart
s.index.size += vliType(inUsed)
_, _ = s.crc32.Write(b.in[s.inStart : s.inStart+inUsed])
}
/*
* Decode the Number of Records, Unpadded Size, and Uncompressed Size
* fields from the Index field. That is, Index Padding and CRC32 are not
* decoded by this function.
*
* This can return xzOK (more input needed), xzStreamEnd (everything
* successfully decoded), or xzDataError (input is corrupt).
*/
func decIndex(s *xzDec, b *xzBuf) xzRet {
var ret xzRet
for {
ret = decVLI(s, b.in, &b.inPos)
if ret != xzStreamEnd {
indexUpdate(s, b)
return ret
}
switch s.index.sequence {
case seqIndexCount:
s.index.count = s.vli
/*
* Validate that the Number of Records field
* indicates the same number of Records as
* there were Blocks in the Stream.
*/
if s.index.count != s.block.count {
return xzDataError
}
s.index.sequence = seqIndexUnpadded
case seqIndexUnpadded:
s.index.hash.unpadded += s.vli
s.index.sequence = seqIndexUncompressed
case seqIndexUncompressed:
s.index.hash.uncompressed += s.vli
var buf [2 * 8]byte // 2*Sizeof(vliType)
putLE64(uint64(s.index.hash.unpadded), buf[:])
putLE64(uint64(s.index.hash.uncompressed), buf[8:])
_, _ = s.index.hash.sha256.Write(buf[:])
s.index.count--
s.index.sequence = seqIndexUnpadded
}
if !(s.index.count > 0) {
break
}
}
return xzStreamEnd
}
/*
* Validate that the next 4 bytes match s.crc32.Sum(nil). s.pos must
* be zero when starting to validate the first byte.
*/
func crcValidate(s *xzDec, b *xzBuf) xzRet {
sum := s.crc32.Sum(nil)
// CRC32 - reverse slice
sum[0], sum[1], sum[2], sum[3] = sum[3], sum[2], sum[1], sum[0]
for {
if b.inPos == len(b.in) {
return xzOK
}
if sum[s.pos] != b.in[b.inPos] {
return xzDataError
}
b.inPos++
s.pos++
if !(s.pos < 4) {
break
}
}
s.crc32.Reset()
s.pos = 0
return xzStreamEnd
}
/*
* Validate that the next 4/8/32 bytes match s.check.Sum(nil). s.pos
* must be zero when starting to validate the first byte.
*/
func checkValidate(s *xzDec, b *xzBuf) xzRet {
sum := s.check.Sum(nil)
if s.CheckType == CheckCRC32 || s.CheckType == CheckCRC64 {
// CRC32/64 - reverse slice
for i, j := 0, len(sum)-1; i < j; i, j = i+1, j-1 {
sum[i], sum[j] = sum[j], sum[i]
}
}
for {
if b.inPos == len(b.in) {
return xzOK
}
if sum[s.pos] != b.in[b.inPos] {
return xzDataError
}
b.inPos++
s.pos++
if !(s.pos < len(sum)) {
break
}
}
s.check.Reset()
s.pos = 0
return xzStreamEnd
}
/*
* Skip over the Check field when the Check ID is not supported.
* Returns true once the whole Check field has been skipped over.
*/
func checkSkip(s *xzDec, b *xzBuf) bool {
for s.pos < int(checkSizes[s.CheckType]) {
if b.inPos == len(b.in) {
return false
}
b.inPos++
s.pos++
}
s.pos = 0
return true
}
/* polynomial table used in decStreamHeader below */
var xzCRC64Table = crc64.MakeTable(crc64.ECMA)
/* Decode the Stream Header field (the first 12 bytes of the .xz Stream). */
func decStreamHeader(s *xzDec) xzRet {
if string(s.temp.buf[:len(headerMagic)]) != headerMagic {
return xzFormatError
}
if crc32.ChecksumIEEE(s.temp.buf[len(headerMagic):len(headerMagic)+2]) !=
getLE32(s.temp.buf[len(headerMagic)+2:]) {
return xzDataError
}
if s.temp.buf[len(headerMagic)] != 0 {
return xzOptionsError
}
/*
* Of integrity checks, we support none (Check ID = 0),
* CRC32 (Check ID = 1), CRC64 (Check ID = 4) and SHA256 (Check ID = 10)
* However, we will accept other check types too, but then the check
* won't be verified and a warning (xzUnsupportedCheck) will be given.
*/
s.CheckType = CheckID(s.temp.buf[len(headerMagic)+1])
if s.CheckType > checkMax {
return xzOptionsError
}
switch s.CheckType {
case CheckNone:
// CheckNone: no action needed
case CheckCRC32:
if s.checkCRC32 == nil {
s.checkCRC32 = crc32.NewIEEE()
} else {
s.checkCRC32.Reset()
}
s.check = s.checkCRC32
case CheckCRC64:
if s.checkCRC64 == nil {
s.checkCRC64 = crc64.New(xzCRC64Table)
} else {
s.checkCRC64.Reset()
}
s.check = s.checkCRC64
case CheckSHA256:
if s.checkSHA256 == nil {
s.checkSHA256 = sha256.New()
} else {
s.checkSHA256.Reset()
}
s.check = s.checkSHA256
default:
return xzUnsupportedCheck
}
return xzOK
}
/* Decode the Stream Footer field (the last 12 bytes of the .xz Stream) */
func decStreamFooter(s *xzDec) xzRet {
if string(s.temp.buf[10:10+len(footerMagic)]) != footerMagic {
return xzDataError
}
if crc32.ChecksumIEEE(s.temp.buf[4:10]) != getLE32(s.temp.buf) {
return xzDataError
}
/*
* Validate Backward Size. Note that we never added the size of the
* Index CRC32 field to s->index.size, thus we use s->index.size / 4
* instead of s->index.size / 4 - 1.
*/
if s.index.size>>2 != vliType(getLE32(s.temp.buf[4:])) {
return xzDataError
}
if s.temp.buf[8] != 0 || CheckID(s.temp.buf[9]) != s.CheckType {
return xzDataError
}
/*
* Use xzStreamEnd instead of xzOK to be more convenient
* for the caller.
*/
return xzStreamEnd
}
/* Decode the Block Header and initialize the filter chain. */
func decBlockHeader(s *xzDec) xzRet {
var ret xzRet
/*
* Validate the CRC32. We know that the temp buffer is at least
* eight bytes so this is safe.
*/
crc := getLE32(s.temp.buf[len(s.temp.buf)-4:])
s.temp.buf = s.temp.buf[:len(s.temp.buf)-4]
if crc32.ChecksumIEEE(s.temp.buf) != crc {
return xzDataError
}
s.temp.pos = 2
/*
* Catch unsupported Block Flags.
*/
if s.temp.buf[1]&0x3C != 0 {
return xzOptionsError
}
/* Compressed Size */
if s.temp.buf[1]&0x40 != 0 {
if decVLI(s, s.temp.buf, &s.temp.pos) != xzStreamEnd {
return xzDataError
}
if s.vli >= 1<<63-8 {
// the whole block must stay smaller than 2^63 bytes
// the block header cannot be smaller than 8 bytes
return xzDataError
}
if s.vli == 0 {
// compressed size must be non-zero
return xzDataError
}
s.blockHeader.compressed = s.vli
} else {
s.blockHeader.compressed = vliUnknown
}
/* Uncompressed Size */
if s.temp.buf[1]&0x80 != 0 {
if decVLI(s, s.temp.buf, &s.temp.pos) != xzStreamEnd {
return xzDataError
}
s.blockHeader.uncompressed = s.vli
} else {
s.blockHeader.uncompressed = vliUnknown
}
// get total number of filters (1-4)
filterTotal := int(s.temp.buf[1]&0x03) + 1
// slice to hold decoded filters
filterList := make([]struct {
id xzFilterID
props uint32
}, filterTotal)
// decode the non-last filters which cannot be LZMA2
for i := 0; i < filterTotal-1; i++ {
/* Valid Filter Flags always take at least two bytes. */
if len(s.temp.buf)-s.temp.pos < 2 {
return xzDataError
}
s.temp.pos += 2
switch id := xzFilterID(s.temp.buf[s.temp.pos-2]); id {
case idDelta:
// delta filter
if s.temp.buf[s.temp.pos-1] != 0x01 {
return xzOptionsError
}
/* Filter Properties contains distance - 1 */
if len(s.temp.buf)-s.temp.pos < 1 {
return xzDataError
}
props := uint32(s.temp.buf[s.temp.pos])
s.temp.pos++
filterList[i] = struct {
id xzFilterID
props uint32
}{id: id, props: props}
case idBCJX86, idBCJPowerPC, idBCJIA64,
idBCJARM, idBCJARMThumb, idBCJSPARC:
// bcj filter
var props uint32
switch s.temp.buf[s.temp.pos-1] {
case 0x00:
props = 0
case 0x04:
if len(s.temp.buf)-s.temp.pos < 4 {
return xzDataError
}
props = getLE32(s.temp.buf[s.temp.pos:])
s.temp.pos += 4
default:
return xzOptionsError
}
filterList[i] = struct {
id xzFilterID
props uint32
}{id: id, props: props}
default:
return xzOptionsError
}
}
/*
* decode the last filter which must be LZMA2
*/
if len(s.temp.buf)-s.temp.pos < 2 {
return xzDataError
}
/* Filter ID = LZMA2 */
if xzFilterID(s.temp.buf[s.temp.pos]) != idLZMA2 {
return xzOptionsError
}
s.temp.pos++
/* Size of Properties = 1-byte Filter Properties */
if s.temp.buf[s.temp.pos] != 0x01 {
return xzOptionsError
}
s.temp.pos++
/* Filter Properties contains LZMA2 dictionary size. */
if len(s.temp.buf)-s.temp.pos < 1 {
return xzDataError
}
props := uint32(s.temp.buf[s.temp.pos])
s.temp.pos++
filterList[filterTotal-1] = struct {
id xzFilterID
props uint32
}{id: idLZMA2, props: props}
/*
* Process the filter list and create s.chain, going from last
* filter (LZMA2) to first filter
*
* First, LZMA2.
*/
ret = xzDecLZMA2Reset(s.lzma2, byte(filterList[filterTotal-1].props))
if ret != xzOK {
return ret
}
s.chain = func(b *xzBuf) xzRet {
return xzDecLZMA2Run(s.lzma2, b)
}
/*
* Now the non-last filters
*/
for i := filterTotal - 2; i >= 0; i-- {
switch id := filterList[i].id; id {
case idDelta:
// delta filter
var delta *xzDecDelta
if s.deltasUsed < len(s.deltas) {
delta = s.deltas[s.deltasUsed]
} else {
delta = xzDecDeltaCreate()
s.deltas = append(s.deltas, delta)
}
s.deltasUsed++
ret = xzDecDeltaReset(delta, int(filterList[i].props)+1)
if ret != xzOK {
return ret
}
chain := s.chain
s.chain = func(b *xzBuf) xzRet {
return xzDecDeltaRun(delta, b, chain)
}
case idBCJX86, idBCJPowerPC, idBCJIA64,
idBCJARM, idBCJARMThumb, idBCJSPARC:
// bcj filter
var bcj *xzDecBCJ
if s.bcjsUsed < len(s.bcjs) {
bcj = s.bcjs[s.bcjsUsed]
} else {
bcj = xzDecBCJCreate()
s.bcjs = append(s.bcjs, bcj)
}
s.bcjsUsed++
ret = xzDecBCJReset(bcj, id, int(filterList[i].props))
if ret != xzOK {
return ret
}
chain := s.chain
s.chain = func(b *xzBuf) xzRet {
return xzDecBCJRun(bcj, b, chain)
}
}
}
/* The rest must be Header Padding. */
for s.temp.pos < len(s.temp.buf) {
if s.temp.buf[s.temp.pos] != 0x00 {
return xzOptionsError
}
s.temp.pos++
}
s.temp.pos = 0
s.block.compressed = 0
s.block.uncompressed = 0
return xzOK
}
func decMain(s *xzDec, b *xzBuf) xzRet {
var ret xzRet
/*
* Store the start position for the case when we are in the middle
* of the Index field.
*/
s.inStart = b.inPos
for {
switch s.sequence {
case seqStreamHeader:
/*
* Stream Header is copied to s.temp, and then
* decoded from there. This way if the caller
* gives us only little input at a time, we can
* still keep the Stream Header decoding code
* simple. Similar approach is used in many places
* in this file.
*/
if !fillTemp(s, b) {
return xzOK
}
/*
* If decStreamHeader returns
* xzUnsupportedCheck, it is still possible
* to continue decoding. Thus, update s.sequence
* before calling decStreamHeader.
*/
s.sequence = seqBlockStart
ret = decStreamHeader(s)
if ret != xzOK {
return ret
}
fallthrough
case seqBlockStart:
/* We need one byte of input to continue. */
if b.inPos == len(b.in) {
return xzOK
}
/* See if this is the beginning of the Index field. */
if b.in[b.inPos] == 0 {
s.inStart = b.inPos
b.inPos++
s.sequence = seqIndex
break
}
/*
* Calculate the size of the Block Header and
* prepare to decode it.
*/
s.blockHeader.size = (int(b.in[b.inPos]) + 1) * 4
s.temp.buf = s.temp.bufArray[:s.blockHeader.size]
s.temp.pos = 0
s.sequence = seqBlockHeader
fallthrough
case seqBlockHeader:
if !fillTemp(s, b) {
return xzOK
}
ret = decBlockHeader(s)
if ret != xzOK {
return ret
}
s.sequence = seqBlockUncompress
fallthrough
case seqBlockUncompress:
ret = decBlock(s, b)
if ret != xzStreamEnd {
return ret
}
s.sequence = seqBlockPadding
fallthrough
case seqBlockPadding:
/*
* Size of Compressed Data + Block Padding
* must be a multiple of four. We don't need
* s->block.compressed for anything else
* anymore, so we use it here to test the size
* of the Block Padding field.
*/
for s.block.compressed&3 != 0 {
if b.inPos == len(b.in) {
return xzOK
}
if b.in[b.inPos] != 0 {
return xzDataError
}
b.inPos++
s.block.compressed++
}
s.sequence = seqBlockCheck
fallthrough
case seqBlockCheck:
switch s.CheckType {
case CheckCRC32, CheckCRC64, CheckSHA256:
ret = checkValidate(s, b)
if ret != xzStreamEnd {
return ret
}
default:
if !checkSkip(s, b) {
return xzOK
}
}
s.sequence = seqBlockStart
case seqIndex:
ret = decIndex(s, b)
if ret != xzStreamEnd {
return ret
}
s.sequence = seqIndexPadding
fallthrough
case seqIndexPadding:
for (s.index.size+vliType(b.inPos-s.inStart))&3 != 0 {
if b.inPos == len(b.in) {
indexUpdate(s, b)
return xzOK
}
if b.in[b.inPos] != 0 {
return xzDataError
}
b.inPos++
}
/* Finish the CRC32 value and Index size. */
indexUpdate(s, b)
/* Compare the hashes to validate the Index field. */
if !bytes.Equal(
s.block.hash.sha256.Sum(nil), s.index.hash.sha256.Sum(nil)) {
return xzDataError
}
s.sequence = seqIndexCRC32
fallthrough
case seqIndexCRC32:
ret = crcValidate(s, b)
if ret != xzStreamEnd {
return ret
}
s.temp.buf = s.temp.bufArray[:streamHeaderSize]
s.sequence = seqStreamFooter
fallthrough
case seqStreamFooter:
if !fillTemp(s, b) {
return xzOK
}
return decStreamFooter(s)
}
}
/* Never reached */
}
/**
* xzDecRun - Run the XZ decoder
* @s: Decoder state allocated using xzDecInit
* @b: Input and output buffers
*
* See xzRet for details of return values.
*
* xzDecRun is a wrapper for decMain to handle some special cases.
*
* We must return xzBufError when it seems clear that we are not
* going to make any progress anymore. This is to prevent the caller
* from calling us infinitely when the input file is truncated or
* otherwise corrupt. Since zlib-style API allows that the caller
* fills the input buffer only when the decoder doesn't produce any
* new output, we have to be careful to avoid returning xzBufError
* too easily: xzBufError is returned only after the second
* consecutive call to xzDecRun that makes no progress.
*/
func xzDecRun(s *xzDec, b *xzBuf) xzRet {
inStart := b.inPos
outStart := b.outPos
ret := decMain(s, b)
if ret == xzOK && inStart == b.inPos && outStart == b.outPos {
if s.allowBufError {
ret = xzBufError
}
s.allowBufError = true
} else {
s.allowBufError = false
}
return ret
}
/**
* xzDecInit - Allocate and initialize a XZ decoder state
* @dictMax: Maximum size of the LZMA2 dictionary (history buffer) for
* decoding. LZMA2 dictionary is always 2^n bytes
* or 2^n + 2^(n-1) bytes (the latter sizes are less common
* in practice), so other values for dictMax don't make sense.
*
* dictMax specifies the maximum allowed dictionary size that xzDecRun
* may allocate once it has parsed the dictionary size from the stream
* headers. This way excessive allocations can be avoided while still
* limiting the maximum memory usage to a sane value to prevent running the
* system out of memory when decompressing streams from untrusted sources.
*
* xzDecInit returns a pointer to an xzDec, which is ready to be used with
* xzDecRun.
*/
func xzDecInit(dictMax uint32, header *Header) *xzDec {
s := new(xzDec)
s.crc32 = crc32.NewIEEE()
s.Header = header
s.block.hash.sha256 = sha256.New()
s.index.hash.sha256 = sha256.New()
s.lzma2 = xzDecLZMA2Create(dictMax)
xzDecReset(s)
return s
}
/**
* xzDecReset - Reset an already allocated decoder state
* @s: Decoder state allocated using xzDecInit
*
* This function can be used to reset the decoder state without
* reallocating memory with xzDecInit.
*/
func xzDecReset(s *xzDec) {
s.sequence = seqStreamHeader
s.allowBufError = false
s.pos = 0
s.crc32.Reset()
s.check = nil
s.CheckType = checkUnset
s.block.compressed = 0
s.block.uncompressed = 0
s.block.count = 0
s.block.hash.unpadded = 0
s.block.hash.uncompressed = 0
s.block.hash.sha256.Reset()
s.index.sequence = seqIndexCount
s.index.size = 0
s.index.count = 0
s.index.hash.unpadded = 0
s.index.hash.uncompressed = 0
s.index.hash.sha256.Reset()
s.temp.pos = 0
s.temp.buf = s.temp.bufArray[:streamHeaderSize]
s.chain = nil
s.bcjsUsed = 0
s.deltasUsed = 0
}
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