mirror of
https://github.com/genuinetools/reg.git
synced 2024-08-22 06:30:23 -04:00
607 lines
14 KiB
Go
607 lines
14 KiB
Go
![]() |
// Package lzx implements a decompressor for the the WIM variant of the
|
||
|
// LZX compression algorithm.
|
||
|
//
|
||
|
// The LZX algorithm is an earlier variant of LZX DELTA, which is documented
|
||
|
// at https://msdn.microsoft.com/en-us/library/cc483133(v=exchg.80).aspx.
|
||
|
package lzx
|
||
|
|
||
|
import (
|
||
|
"bytes"
|
||
|
"encoding/binary"
|
||
|
"errors"
|
||
|
"io"
|
||
|
)
|
||
|
|
||
|
const (
|
||
|
maincodecount = 496
|
||
|
maincodesplit = 256
|
||
|
lencodecount = 249
|
||
|
lenshift = 9
|
||
|
codemask = 0x1ff
|
||
|
tablebits = 9
|
||
|
tablesize = 1 << tablebits
|
||
|
|
||
|
maxBlockSize = 32768
|
||
|
windowSize = 32768
|
||
|
|
||
|
maxTreePathLen = 16
|
||
|
|
||
|
e8filesize = 12000000
|
||
|
maxe8offset = 0x3fffffff
|
||
|
|
||
|
verbatimBlock = 1
|
||
|
alignedOffsetBlock = 2
|
||
|
uncompressedBlock = 3
|
||
|
)
|
||
|
|
||
|
var footerBits = [...]byte{
|
||
|
0, 0, 0, 0, 1, 1, 2, 2,
|
||
|
3, 3, 4, 4, 5, 5, 6, 6,
|
||
|
7, 7, 8, 8, 9, 9, 10, 10,
|
||
|
11, 11, 12, 12, 13, 13, 14,
|
||
|
}
|
||
|
|
||
|
var basePosition = [...]uint16{
|
||
|
0, 1, 2, 3, 4, 6, 8, 12,
|
||
|
16, 24, 32, 48, 64, 96, 128, 192,
|
||
|
256, 384, 512, 768, 1024, 1536, 2048, 3072,
|
||
|
4096, 6144, 8192, 12288, 16384, 24576, 32768,
|
||
|
}
|
||
|
|
||
|
var (
|
||
|
errCorrupt = errors.New("LZX data corrupt")
|
||
|
)
|
||
|
|
||
|
// Reader is an interface used by the decompressor to access
|
||
|
// the input stream. If the provided io.Reader does not implement
|
||
|
// Reader, then a bufio.Reader is used.
|
||
|
type Reader interface {
|
||
|
io.Reader
|
||
|
io.ByteReader
|
||
|
}
|
||
|
|
||
|
type decompressor struct {
|
||
|
r io.Reader
|
||
|
err error
|
||
|
unaligned bool
|
||
|
nbits byte
|
||
|
c uint32
|
||
|
lru [3]uint16
|
||
|
uncompressed int
|
||
|
windowReader *bytes.Reader
|
||
|
mainlens [maincodecount]byte
|
||
|
lenlens [lencodecount]byte
|
||
|
window [windowSize]byte
|
||
|
b []byte
|
||
|
bv int
|
||
|
bo int
|
||
|
}
|
||
|
|
||
|
//go:noinline
|
||
|
func (f *decompressor) fail(err error) {
|
||
|
if f.err == nil {
|
||
|
f.err = err
|
||
|
}
|
||
|
f.bo = 0
|
||
|
f.bv = 0
|
||
|
}
|
||
|
|
||
|
func (f *decompressor) ensureAtLeast(n int) error {
|
||
|
if f.bv-f.bo >= n {
|
||
|
return nil
|
||
|
}
|
||
|
|
||
|
if f.err != nil {
|
||
|
return f.err
|
||
|
}
|
||
|
|
||
|
if f.bv != f.bo {
|
||
|
copy(f.b[:f.bv-f.bo], f.b[f.bo:f.bv])
|
||
|
}
|
||
|
n, err := io.ReadAtLeast(f.r, f.b[f.bv-f.bo:], n)
|
||
|
if err != nil {
|
||
|
if err == io.EOF {
|
||
|
err = io.ErrUnexpectedEOF
|
||
|
} else {
|
||
|
f.fail(err)
|
||
|
}
|
||
|
return err
|
||
|
}
|
||
|
f.bv = f.bv - f.bo + n
|
||
|
f.bo = 0
|
||
|
return nil
|
||
|
}
|
||
|
|
||
|
// feed retrieves another 16-bit word from the stream and consumes
|
||
|
// it into f.c. It returns false if there are no more bytes available.
|
||
|
// Otherwise, on error, it sets f.err.
|
||
|
func (f *decompressor) feed() bool {
|
||
|
err := f.ensureAtLeast(2)
|
||
|
if err != nil {
|
||
|
if err == io.ErrUnexpectedEOF {
|
||
|
return false
|
||
|
}
|
||
|
}
|
||
|
f.c |= (uint32(f.b[f.bo+1])<<8 | uint32(f.b[f.bo])) << (16 - f.nbits)
|
||
|
f.nbits += 16
|
||
|
f.bo += 2
|
||
|
return true
|
||
|
}
|
||
|
|
||
|
// getBits retrieves the next n bits from the byte stream. n
|
||
|
// must be <= 16. It sets f.err on error.
|
||
|
func (f *decompressor) getBits(n byte) uint16 {
|
||
|
if f.nbits < n {
|
||
|
if !f.feed() {
|
||
|
f.fail(io.ErrUnexpectedEOF)
|
||
|
}
|
||
|
}
|
||
|
c := uint16(f.c >> (32 - n))
|
||
|
f.c <<= n
|
||
|
f.nbits -= n
|
||
|
return c
|
||
|
}
|
||
|
|
||
|
type huffman struct {
|
||
|
extra [][]uint16
|
||
|
maxbits byte
|
||
|
table [tablesize]uint16
|
||
|
}
|
||
|
|
||
|
// buildTable builds a huffman decoding table from a slice of code lengths,
|
||
|
// one per code, in order. Each code length must be <= maxTreePathLen.
|
||
|
// See https://en.wikipedia.org/wiki/Canonical_Huffman_code.
|
||
|
func buildTable(codelens []byte) *huffman {
|
||
|
// Determine the number of codes of each length, and the
|
||
|
// maximum length.
|
||
|
var count [maxTreePathLen + 1]uint
|
||
|
var max byte
|
||
|
for _, cl := range codelens {
|
||
|
count[cl]++
|
||
|
if max < cl {
|
||
|
max = cl
|
||
|
}
|
||
|
}
|
||
|
|
||
|
if max == 0 {
|
||
|
return &huffman{}
|
||
|
}
|
||
|
|
||
|
// Determine the first code of each length.
|
||
|
var first [maxTreePathLen + 1]uint
|
||
|
code := uint(0)
|
||
|
for i := byte(1); i <= max; i++ {
|
||
|
code <<= 1
|
||
|
first[i] = code
|
||
|
code += count[i]
|
||
|
}
|
||
|
|
||
|
if code != 1<<max {
|
||
|
return nil
|
||
|
}
|
||
|
|
||
|
// Build a table for code lookup. For code sizes < max,
|
||
|
// put all possible suffixes for the code into the table, too.
|
||
|
// For max > tablebits, split long codes into additional tables
|
||
|
// of suffixes of max-tablebits length.
|
||
|
h := &huffman{maxbits: max}
|
||
|
if max > tablebits {
|
||
|
core := first[tablebits+1] / 2 // Number of codes that fit without extra tables
|
||
|
nextra := 1<<tablebits - core // Number of extra entries
|
||
|
h.extra = make([][]uint16, nextra)
|
||
|
for code := core; code < 1<<tablebits; code++ {
|
||
|
h.table[code] = uint16(code - core)
|
||
|
h.extra[code-core] = make([]uint16, 1<<(max-tablebits))
|
||
|
}
|
||
|
}
|
||
|
|
||
|
for i, cl := range codelens {
|
||
|
if cl != 0 {
|
||
|
code := first[cl]
|
||
|
first[cl]++
|
||
|
v := uint16(cl)<<lenshift | uint16(i)
|
||
|
if cl <= tablebits {
|
||
|
extendedCode := code << (tablebits - cl)
|
||
|
for j := uint(0); j < 1<<(tablebits-cl); j++ {
|
||
|
h.table[extendedCode+j] = v
|
||
|
}
|
||
|
} else {
|
||
|
prefix := code >> (cl - tablebits)
|
||
|
suffix := code & (1<<(cl-tablebits) - 1)
|
||
|
extendedCode := suffix << (max - cl)
|
||
|
for j := uint(0); j < 1<<(max-cl); j++ {
|
||
|
h.extra[h.table[prefix]][extendedCode+j] = v
|
||
|
}
|
||
|
}
|
||
|
}
|
||
|
}
|
||
|
|
||
|
return h
|
||
|
}
|
||
|
|
||
|
// getCode retrieves the next code using the provided
|
||
|
// huffman tree. It sets f.err on error.
|
||
|
func (f *decompressor) getCode(h *huffman) uint16 {
|
||
|
if h.maxbits > 0 {
|
||
|
if f.nbits < maxTreePathLen {
|
||
|
f.feed()
|
||
|
}
|
||
|
|
||
|
// For codes with length < tablebits, it doesn't matter
|
||
|
// what the remainder of the bits used for table lookup
|
||
|
// are, since entries with all possible suffixes were
|
||
|
// added to the table.
|
||
|
c := h.table[f.c>>(32-tablebits)]
|
||
|
if c >= 1<<lenshift {
|
||
|
// The code is already in c.
|
||
|
} else {
|
||
|
c = h.extra[c][f.c<<tablebits>>(32-(h.maxbits-tablebits))]
|
||
|
}
|
||
|
|
||
|
n := byte(c >> lenshift)
|
||
|
if f.nbits >= n {
|
||
|
// Only consume the length of the code, not the maximum
|
||
|
// code length.
|
||
|
f.c <<= n
|
||
|
f.nbits -= n
|
||
|
return c & codemask
|
||
|
}
|
||
|
|
||
|
f.fail(io.ErrUnexpectedEOF)
|
||
|
return 0
|
||
|
}
|
||
|
|
||
|
// This is an empty tree. It should not be used.
|
||
|
f.fail(errCorrupt)
|
||
|
return 0
|
||
|
}
|
||
|
|
||
|
// readTree updates the huffman tree path lengths in lens by
|
||
|
// reading and decoding lengths from the byte stream. lens
|
||
|
// should be prepopulated with the previous block's tree's path
|
||
|
// lengths. For the first block, lens should be zero.
|
||
|
func (f *decompressor) readTree(lens []byte) error {
|
||
|
// Get the pre-tree for the main tree.
|
||
|
var pretreeLen [20]byte
|
||
|
for i := range pretreeLen {
|
||
|
pretreeLen[i] = byte(f.getBits(4))
|
||
|
}
|
||
|
if f.err != nil {
|
||
|
return f.err
|
||
|
}
|
||
|
h := buildTable(pretreeLen[:])
|
||
|
|
||
|
// The lengths are encoded as a series of huffman codes
|
||
|
// encoded by the pre-tree.
|
||
|
for i := 0; i < len(lens); {
|
||
|
c := byte(f.getCode(h))
|
||
|
if f.err != nil {
|
||
|
return f.err
|
||
|
}
|
||
|
switch {
|
||
|
case c <= 16: // length is delta from previous length
|
||
|
lens[i] = (lens[i] + 17 - c) % 17
|
||
|
i++
|
||
|
case c == 17: // next n + 4 lengths are zero
|
||
|
zeroes := int(f.getBits(4)) + 4
|
||
|
if i+zeroes > len(lens) {
|
||
|
return errCorrupt
|
||
|
}
|
||
|
for j := 0; j < zeroes; j++ {
|
||
|
lens[i+j] = 0
|
||
|
}
|
||
|
i += zeroes
|
||
|
case c == 18: // next n + 20 lengths are zero
|
||
|
zeroes := int(f.getBits(5)) + 20
|
||
|
if i+zeroes > len(lens) {
|
||
|
return errCorrupt
|
||
|
}
|
||
|
for j := 0; j < zeroes; j++ {
|
||
|
lens[i+j] = 0
|
||
|
}
|
||
|
i += zeroes
|
||
|
case c == 19: // next n + 4 lengths all have the same value
|
||
|
same := int(f.getBits(1)) + 4
|
||
|
if i+same > len(lens) {
|
||
|
return errCorrupt
|
||
|
}
|
||
|
c = byte(f.getCode(h))
|
||
|
if c > 16 {
|
||
|
return errCorrupt
|
||
|
}
|
||
|
l := (lens[i] + 17 - c) % 17
|
||
|
for j := 0; j < same; j++ {
|
||
|
lens[i+j] = l
|
||
|
}
|
||
|
i += same
|
||
|
default:
|
||
|
return errCorrupt
|
||
|
}
|
||
|
}
|
||
|
|
||
|
if f.err != nil {
|
||
|
return f.err
|
||
|
}
|
||
|
return nil
|
||
|
}
|
||
|
|
||
|
func (f *decompressor) readBlockHeader() (byte, uint16, error) {
|
||
|
// If the previous block was an unaligned uncompressed block, restore
|
||
|
// 2-byte alignment.
|
||
|
if f.unaligned {
|
||
|
err := f.ensureAtLeast(1)
|
||
|
if err != nil {
|
||
|
return 0, 0, err
|
||
|
}
|
||
|
f.bo++
|
||
|
f.unaligned = false
|
||
|
}
|
||
|
|
||
|
blockType := f.getBits(3)
|
||
|
full := f.getBits(1)
|
||
|
var blockSize uint16
|
||
|
if full != 0 {
|
||
|
blockSize = maxBlockSize
|
||
|
} else {
|
||
|
blockSize = f.getBits(16)
|
||
|
if blockSize > maxBlockSize {
|
||
|
return 0, 0, errCorrupt
|
||
|
}
|
||
|
}
|
||
|
|
||
|
if f.err != nil {
|
||
|
return 0, 0, f.err
|
||
|
}
|
||
|
|
||
|
switch blockType {
|
||
|
case verbatimBlock, alignedOffsetBlock:
|
||
|
// The caller will read the huffman trees.
|
||
|
case uncompressedBlock:
|
||
|
if f.nbits > 16 {
|
||
|
panic("impossible: more than one 16-bit word remains")
|
||
|
}
|
||
|
|
||
|
// Drop the remaining bits in the current 16-bit word
|
||
|
// If there are no bits left, discard a full 16-bit word.
|
||
|
n := f.nbits
|
||
|
if n == 0 {
|
||
|
n = 16
|
||
|
}
|
||
|
|
||
|
f.getBits(n)
|
||
|
|
||
|
// Read the LRU values for the next block.
|
||
|
err := f.ensureAtLeast(12)
|
||
|
if err != nil {
|
||
|
return 0, 0, err
|
||
|
}
|
||
|
|
||
|
f.lru[0] = uint16(binary.LittleEndian.Uint32(f.b[f.bo : f.bo+4]))
|
||
|
f.lru[1] = uint16(binary.LittleEndian.Uint32(f.b[f.bo+4 : f.bo+8]))
|
||
|
f.lru[2] = uint16(binary.LittleEndian.Uint32(f.b[f.bo+8 : f.bo+12]))
|
||
|
f.bo += 12
|
||
|
|
||
|
default:
|
||
|
return 0, 0, errCorrupt
|
||
|
}
|
||
|
|
||
|
return byte(blockType), blockSize, nil
|
||
|
}
|
||
|
|
||
|
// readTrees reads the two or three huffman trees for the current block.
|
||
|
// readAligned specifies whether to read the aligned offset tree.
|
||
|
func (f *decompressor) readTrees(readAligned bool) (main *huffman, length *huffman, aligned *huffman, err error) {
|
||
|
// Aligned offset blocks start with a small aligned offset tree.
|
||
|
if readAligned {
|
||
|
var alignedLen [8]byte
|
||
|
for i := range alignedLen {
|
||
|
alignedLen[i] = byte(f.getBits(3))
|
||
|
}
|
||
|
aligned = buildTable(alignedLen[:])
|
||
|
if aligned == nil {
|
||
|
err = errors.New("corrupt")
|
||
|
return
|
||
|
}
|
||
|
}
|
||
|
|
||
|
// The main tree is encoded in two parts.
|
||
|
err = f.readTree(f.mainlens[:maincodesplit])
|
||
|
if err != nil {
|
||
|
return
|
||
|
}
|
||
|
err = f.readTree(f.mainlens[maincodesplit:])
|
||
|
if err != nil {
|
||
|
return
|
||
|
}
|
||
|
|
||
|
main = buildTable(f.mainlens[:])
|
||
|
if main == nil {
|
||
|
err = errors.New("corrupt")
|
||
|
return
|
||
|
}
|
||
|
|
||
|
// The length tree is encoding in a single part.
|
||
|
err = f.readTree(f.lenlens[:])
|
||
|
if err != nil {
|
||
|
return
|
||
|
}
|
||
|
|
||
|
length = buildTable(f.lenlens[:])
|
||
|
if length == nil {
|
||
|
err = errors.New("corrupt")
|
||
|
return
|
||
|
}
|
||
|
|
||
|
err = f.err
|
||
|
return
|
||
|
}
|
||
|
|
||
|
// readCompressedBlock decodes a compressed block, writing into the window
|
||
|
// starting at start and ending at end, and using the provided huffman trees.
|
||
|
func (f *decompressor) readCompressedBlock(start, end uint16, hmain, hlength, haligned *huffman) (int, error) {
|
||
|
i := start
|
||
|
for i < end {
|
||
|
main := f.getCode(hmain)
|
||
|
if f.err != nil {
|
||
|
break
|
||
|
}
|
||
|
if main < 256 {
|
||
|
// Literal byte.
|
||
|
f.window[i] = byte(main)
|
||
|
i++
|
||
|
continue
|
||
|
}
|
||
|
|
||
|
// This is a match backward in the window. Determine
|
||
|
// the offset and dlength.
|
||
|
matchlen := (main - 256) % 8
|
||
|
slot := (main - 256) / 8
|
||
|
|
||
|
// The length is either the low bits of the code,
|
||
|
// or if this is 7, is encoded with the length tree.
|
||
|
if matchlen == 7 {
|
||
|
matchlen += f.getCode(hlength)
|
||
|
}
|
||
|
matchlen += 2
|
||
|
|
||
|
var matchoffset uint16
|
||
|
if slot < 3 {
|
||
|
// The offset is one of the LRU values.
|
||
|
matchoffset = f.lru[slot]
|
||
|
f.lru[slot] = f.lru[0]
|
||
|
f.lru[0] = matchoffset
|
||
|
} else {
|
||
|
// The offset is encoded as a combination of the
|
||
|
// slot and more bits from the bit stream.
|
||
|
offsetbits := footerBits[slot]
|
||
|
var verbatimbits, alignedbits uint16
|
||
|
if offsetbits > 0 {
|
||
|
if haligned != nil && offsetbits >= 3 {
|
||
|
// This is an aligned offset block. Combine
|
||
|
// the bits written verbatim with the aligned
|
||
|
// offset tree code.
|
||
|
verbatimbits = f.getBits(offsetbits-3) * 8
|
||
|
alignedbits = f.getCode(haligned)
|
||
|
} else {
|
||
|
// There are no aligned offset bits to read,
|
||
|
// only verbatim bits.
|
||
|
verbatimbits = f.getBits(offsetbits)
|
||
|
alignedbits = 0
|
||
|
}
|
||
|
}
|
||
|
matchoffset = basePosition[slot] + verbatimbits + alignedbits - 2
|
||
|
// Update the LRU cache.
|
||
|
f.lru[2] = f.lru[1]
|
||
|
f.lru[1] = f.lru[0]
|
||
|
f.lru[0] = matchoffset
|
||
|
}
|
||
|
|
||
|
if matchoffset <= i && matchlen <= end-i {
|
||
|
copyend := i + matchlen
|
||
|
for ; i < copyend; i++ {
|
||
|
f.window[i] = f.window[i-matchoffset]
|
||
|
}
|
||
|
} else {
|
||
|
f.fail(errCorrupt)
|
||
|
break
|
||
|
}
|
||
|
}
|
||
|
return int(i - start), f.err
|
||
|
}
|
||
|
|
||
|
// readBlock decodes the current block and returns the number of uncompressed bytes.
|
||
|
func (f *decompressor) readBlock(start uint16) (int, error) {
|
||
|
blockType, size, err := f.readBlockHeader()
|
||
|
if err != nil {
|
||
|
return 0, err
|
||
|
}
|
||
|
|
||
|
if blockType == uncompressedBlock {
|
||
|
if size%2 == 1 {
|
||
|
// Remember to realign the byte stream at the next block.
|
||
|
f.unaligned = true
|
||
|
}
|
||
|
copied := 0
|
||
|
if f.bo < f.bv {
|
||
|
copied = int(size)
|
||
|
s := int(start)
|
||
|
if copied > f.bv-f.bo {
|
||
|
copied = f.bv - f.bo
|
||
|
}
|
||
|
copy(f.window[s:s+copied], f.b[f.bo:f.bo+copied])
|
||
|
f.bo += copied
|
||
|
}
|
||
|
n, err := io.ReadFull(f.r, f.window[start+uint16(copied):start+size])
|
||
|
return copied + n, err
|
||
|
}
|
||
|
|
||
|
hmain, hlength, haligned, err := f.readTrees(blockType == alignedOffsetBlock)
|
||
|
if err != nil {
|
||
|
return 0, err
|
||
|
}
|
||
|
|
||
|
return f.readCompressedBlock(start, start+size, hmain, hlength, haligned)
|
||
|
}
|
||
|
|
||
|
// decodeE8 reverses the 0xe8 x86 instruction encoding that was performed
|
||
|
// to the uncompressed data before it was compressed.
|
||
|
func decodeE8(b []byte, off int64) {
|
||
|
if off > maxe8offset || len(b) < 10 {
|
||
|
return
|
||
|
}
|
||
|
for i := 0; i < len(b)-10; i++ {
|
||
|
if b[i] == 0xe8 {
|
||
|
currentPtr := int32(off) + int32(i)
|
||
|
abs := int32(binary.LittleEndian.Uint32(b[i+1 : i+5]))
|
||
|
if abs >= -currentPtr && abs < e8filesize {
|
||
|
var rel int32
|
||
|
if abs >= 0 {
|
||
|
rel = abs - currentPtr
|
||
|
} else {
|
||
|
rel = abs + e8filesize
|
||
|
}
|
||
|
binary.LittleEndian.PutUint32(b[i+1:i+5], uint32(rel))
|
||
|
}
|
||
|
i += 4
|
||
|
}
|
||
|
}
|
||
|
}
|
||
|
|
||
|
func (f *decompressor) Read(b []byte) (int, error) {
|
||
|
// Read and uncompress everything.
|
||
|
if f.windowReader == nil {
|
||
|
n := 0
|
||
|
for n < f.uncompressed {
|
||
|
k, err := f.readBlock(uint16(n))
|
||
|
if err != nil {
|
||
|
return 0, err
|
||
|
}
|
||
|
n += k
|
||
|
}
|
||
|
decodeE8(f.window[:f.uncompressed], 0)
|
||
|
f.windowReader = bytes.NewReader(f.window[:f.uncompressed])
|
||
|
}
|
||
|
|
||
|
// Just read directly from the window.
|
||
|
return f.windowReader.Read(b)
|
||
|
}
|
||
|
|
||
|
func (f *decompressor) Close() error {
|
||
|
return nil
|
||
|
}
|
||
|
|
||
|
// NewReader returns a new io.ReadCloser that decompresses a
|
||
|
// WIM LZX stream until uncompressedSize bytes have been returned.
|
||
|
func NewReader(r io.Reader, uncompressedSize int) (io.ReadCloser, error) {
|
||
|
if uncompressedSize > windowSize {
|
||
|
return nil, errors.New("uncompressed size is limited to 32KB")
|
||
|
}
|
||
|
f := &decompressor{
|
||
|
lru: [3]uint16{1, 1, 1},
|
||
|
uncompressed: uncompressedSize,
|
||
|
b: make([]byte, 4096),
|
||
|
r: r,
|
||
|
}
|
||
|
return f, nil
|
||
|
}
|