You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
374 lines
10 KiB
374 lines
10 KiB
// Copyright 2015, Joe Tsai. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE.md file.
|
|
|
|
package bzip2
|
|
|
|
import (
|
|
"io"
|
|
|
|
"github.com/dsnet/compress/internal"
|
|
"github.com/dsnet/compress/internal/errors"
|
|
"github.com/dsnet/compress/internal/prefix"
|
|
)
|
|
|
|
const (
|
|
minNumTrees = 2
|
|
maxNumTrees = 6
|
|
|
|
maxPrefixBits = 20 // Maximum bit-width of a prefix code
|
|
maxNumSyms = 256 + 2 // Maximum number of symbols in the alphabet
|
|
numBlockSyms = 50 // Number of bytes in a block
|
|
)
|
|
|
|
// encSel and decSel are used to handle the prefix encoding for tree selectors.
|
|
// The prefix encoding is as follows:
|
|
//
|
|
// Code TreeIdx
|
|
// 0 <=> 0
|
|
// 10 <=> 1
|
|
// 110 <=> 2
|
|
// 1110 <=> 3
|
|
// 11110 <=> 4
|
|
// 111110 <=> 5
|
|
// 111111 <=> 6 Invalid tree index, so should fail
|
|
//
|
|
var encSel, decSel = func() (e prefix.Encoder, d prefix.Decoder) {
|
|
var selCodes [maxNumTrees + 1]prefix.PrefixCode
|
|
for i := range selCodes {
|
|
selCodes[i] = prefix.PrefixCode{Sym: uint32(i), Len: uint32(i + 1)}
|
|
}
|
|
selCodes[maxNumTrees] = prefix.PrefixCode{Sym: maxNumTrees, Len: maxNumTrees}
|
|
prefix.GeneratePrefixes(selCodes[:])
|
|
e.Init(selCodes[:])
|
|
d.Init(selCodes[:])
|
|
return
|
|
}()
|
|
|
|
type prefixReader struct{ prefix.Reader }
|
|
|
|
func (pr *prefixReader) Init(r io.Reader) {
|
|
pr.Reader.Init(r, true)
|
|
}
|
|
|
|
func (pr *prefixReader) ReadBitsBE64(nb uint) uint64 {
|
|
if nb <= 32 {
|
|
v := uint32(pr.ReadBits(nb))
|
|
return uint64(internal.ReverseUint32N(v, nb))
|
|
}
|
|
v0 := internal.ReverseUint32(uint32(pr.ReadBits(32)))
|
|
v1 := internal.ReverseUint32(uint32(pr.ReadBits(nb - 32)))
|
|
v := uint64(v0)<<32 | uint64(v1)
|
|
return v >> (64 - nb)
|
|
}
|
|
|
|
func (pr *prefixReader) ReadPrefixCodes(codes []prefix.PrefixCodes, trees []prefix.Decoder) {
|
|
for i, pc := range codes {
|
|
clen := int(pr.ReadBitsBE64(5))
|
|
sum := 1 << maxPrefixBits
|
|
for sym := range pc {
|
|
for {
|
|
if clen < 1 || clen > maxPrefixBits {
|
|
panicf(errors.Corrupted, "invalid prefix bit-length: %d", clen)
|
|
}
|
|
|
|
b, ok := pr.TryReadBits(1)
|
|
if !ok {
|
|
b = pr.ReadBits(1)
|
|
}
|
|
if b == 0 {
|
|
break
|
|
}
|
|
|
|
b, ok = pr.TryReadBits(1)
|
|
if !ok {
|
|
b = pr.ReadBits(1)
|
|
}
|
|
clen -= int(b*2) - 1 // +1 or -1
|
|
}
|
|
pc[sym] = prefix.PrefixCode{Sym: uint32(sym), Len: uint32(clen)}
|
|
sum -= (1 << maxPrefixBits) >> uint(clen)
|
|
}
|
|
|
|
if sum == 0 {
|
|
// Fast path, but only handles complete trees.
|
|
if err := prefix.GeneratePrefixes(pc); err != nil {
|
|
errors.Panic(err) // Using complete trees; should never fail
|
|
}
|
|
} else {
|
|
// Slow path, but handles anything.
|
|
pc = handleDegenerateCodes(pc) // Never fails, but may fail later
|
|
codes[i] = pc
|
|
}
|
|
trees[i].Init(pc)
|
|
}
|
|
}
|
|
|
|
type prefixWriter struct{ prefix.Writer }
|
|
|
|
func (pw *prefixWriter) Init(w io.Writer) {
|
|
pw.Writer.Init(w, true)
|
|
}
|
|
|
|
func (pw *prefixWriter) WriteBitsBE64(v uint64, nb uint) {
|
|
if nb <= 32 {
|
|
v := internal.ReverseUint32N(uint32(v), nb)
|
|
pw.WriteBits(uint(v), nb)
|
|
return
|
|
}
|
|
v <<= (64 - nb)
|
|
v0 := internal.ReverseUint32(uint32(v >> 32))
|
|
v1 := internal.ReverseUint32(uint32(v))
|
|
pw.WriteBits(uint(v0), 32)
|
|
pw.WriteBits(uint(v1), nb-32)
|
|
return
|
|
}
|
|
|
|
func (pw *prefixWriter) WritePrefixCodes(codes []prefix.PrefixCodes, trees []prefix.Encoder) {
|
|
for i, pc := range codes {
|
|
if err := prefix.GeneratePrefixes(pc); err != nil {
|
|
errors.Panic(err) // Using complete trees; should never fail
|
|
}
|
|
trees[i].Init(pc)
|
|
|
|
clen := int(pc[0].Len)
|
|
pw.WriteBitsBE64(uint64(clen), 5)
|
|
for _, c := range pc {
|
|
for int(c.Len) < clen {
|
|
pw.WriteBits(3, 2) // 11
|
|
clen--
|
|
}
|
|
for int(c.Len) > clen {
|
|
pw.WriteBits(1, 2) // 10
|
|
clen++
|
|
}
|
|
pw.WriteBits(0, 1)
|
|
}
|
|
}
|
|
}
|
|
|
|
// handleDegenerateCodes converts a degenerate tree into a canonical tree.
|
|
//
|
|
// For example, when the input is an under-subscribed tree:
|
|
// input: []PrefixCode{
|
|
// {Sym: 0, Len: 3},
|
|
// {Sym: 1, Len: 4},
|
|
// {Sym: 2, Len: 3},
|
|
// }
|
|
// output: []PrefixCode{
|
|
// {Sym: 0, Len: 3, Val: 0}, // 000
|
|
// {Sym: 1, Len: 4, Val: 2}, // 0010
|
|
// {Sym: 2, Len: 3, Val: 4}, // 100
|
|
// {Sym: 258, Len: 4, Val: 10}, // 1010
|
|
// {Sym: 259, Len: 3, Val: 6}, // 110
|
|
// {Sym: 260, Len: 1, Val: 1}, // 1
|
|
// }
|
|
//
|
|
// For example, when the input is an over-subscribed tree:
|
|
// input: []PrefixCode{
|
|
// {Sym: 0, Len: 1},
|
|
// {Sym: 1, Len: 3},
|
|
// {Sym: 2, Len: 4},
|
|
// {Sym: 3, Len: 3},
|
|
// {Sym: 4, Len: 2},
|
|
// }
|
|
// output: []PrefixCode{
|
|
// {Sym: 0, Len: 1, Val: 0}, // 0
|
|
// {Sym: 1, Len: 3, Val: 3}, // 011
|
|
// {Sym: 3, Len: 3, Val: 7}, // 111
|
|
// {Sym: 4, Len: 2, Val: 1}, // 01
|
|
// }
|
|
func handleDegenerateCodes(codes prefix.PrefixCodes) prefix.PrefixCodes {
|
|
// Since there is no formal definition for the BZip2 format, there is no
|
|
// specification that says that the code lengths must form a complete
|
|
// prefix tree (IE: it is neither over-subscribed nor under-subscribed).
|
|
// Thus, the original C implementation becomes the reference for how prefix
|
|
// decoding is done in these edge cases. Unfortunately, the C version does
|
|
// not error when an invalid tree is used, but rather allows decoding to
|
|
// continue and only errors if some bit pattern happens to cause an error.
|
|
// Thus, it is possible for an invalid tree to end up decoding an input
|
|
// "properly" so long as invalid bit patterns are not present. In order to
|
|
// replicate this non-specified behavior, we use a ported version of the
|
|
// C code to generate the codes as a valid canonical tree by substituting
|
|
// invalid nodes with invalid symbols.
|
|
//
|
|
// ====================================================
|
|
// This program, "bzip2", the associated library "libbzip2", and all
|
|
// documentation, are copyright (C) 1996-2010 Julian R Seward. All
|
|
// rights reserved.
|
|
//
|
|
// Redistribution and use in source and binary forms, with or without
|
|
// modification, are permitted provided that the following conditions
|
|
// are met:
|
|
//
|
|
// 1. Redistributions of source code must retain the above copyright
|
|
// notice, this list of conditions and the following disclaimer.
|
|
//
|
|
// 2. The origin of this software must not be misrepresented; you must
|
|
// not claim that you wrote the original software. If you use this
|
|
// software in a product, an acknowledgment in the product
|
|
// documentation would be appreciated but is not required.
|
|
//
|
|
// 3. Altered source versions must be plainly marked as such, and must
|
|
// not be misrepresented as being the original software.
|
|
//
|
|
// 4. The name of the author may not be used to endorse or promote
|
|
// products derived from this software without specific prior written
|
|
// permission.
|
|
//
|
|
// THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
|
|
// OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
|
|
// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
// ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
|
|
// DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
|
|
// GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
|
|
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
|
|
// WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
|
|
// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
|
|
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
//
|
|
// Julian Seward, jseward@bzip.org
|
|
// bzip2/libbzip2 version 1.0.6 of 6 September 2010
|
|
// ====================================================
|
|
var (
|
|
limits [maxPrefixBits + 2]int32
|
|
bases [maxPrefixBits + 2]int32
|
|
perms [maxNumSyms]int32
|
|
|
|
minLen = uint32(maxPrefixBits)
|
|
maxLen = uint32(0)
|
|
)
|
|
|
|
const (
|
|
statusOkay = iota
|
|
statusInvalid
|
|
statusNeedBits
|
|
statusMaxBits
|
|
)
|
|
|
|
// createTables is the BZ2_hbCreateDecodeTables function from the C code.
|
|
createTables := func(codes []prefix.PrefixCode) {
|
|
for _, c := range codes {
|
|
if c.Len > maxLen {
|
|
maxLen = c.Len
|
|
}
|
|
if c.Len < minLen {
|
|
minLen = c.Len
|
|
}
|
|
}
|
|
|
|
var pp int
|
|
for i := minLen; i <= maxLen; i++ {
|
|
for j, c := range codes {
|
|
if c.Len == i {
|
|
perms[pp] = int32(j)
|
|
pp++
|
|
}
|
|
}
|
|
}
|
|
|
|
var vec int32
|
|
for _, c := range codes {
|
|
bases[c.Len+1]++
|
|
}
|
|
for i := 1; i < len(bases); i++ {
|
|
bases[i] += bases[i-1]
|
|
}
|
|
for i := minLen; i <= maxLen; i++ {
|
|
vec += bases[i+1] - bases[i]
|
|
limits[i] = vec - 1
|
|
vec <<= 1
|
|
}
|
|
for i := minLen + 1; i <= maxLen; i++ {
|
|
bases[i] = ((limits[i-1] + 1) << 1) - bases[i]
|
|
}
|
|
}
|
|
|
|
// getSymbol is the GET_MTF_VAL macro from the C code.
|
|
getSymbol := func(c prefix.PrefixCode) (uint32, int) {
|
|
v := internal.ReverseUint32(c.Val)
|
|
n := c.Len
|
|
|
|
zn := minLen
|
|
if zn > n {
|
|
return 0, statusNeedBits
|
|
}
|
|
zvec := int32(v >> (32 - zn))
|
|
v <<= zn
|
|
for {
|
|
if zn > maxLen {
|
|
return 0, statusMaxBits
|
|
}
|
|
if zvec <= limits[zn] {
|
|
break
|
|
}
|
|
zn++
|
|
if zn > n {
|
|
return 0, statusNeedBits
|
|
}
|
|
zvec = (zvec << 1) | int32(v>>31)
|
|
v <<= 1
|
|
}
|
|
if zvec-bases[zn] < 0 || zvec-bases[zn] >= maxNumSyms {
|
|
return 0, statusInvalid
|
|
}
|
|
return uint32(perms[zvec-bases[zn]]), statusOkay
|
|
}
|
|
|
|
// Step 1: Create the prefix trees using the C algorithm.
|
|
createTables(codes)
|
|
|
|
// Step 2: Starting with the shortest bit pattern, explore the whole tree.
|
|
// If tree is under-subscribed, the worst-case runtime is O(1<<maxLen).
|
|
// If tree is over-subscribed, the worst-case runtime is O(maxNumSyms).
|
|
var pcodesArr [2 * maxNumSyms]prefix.PrefixCode
|
|
pcodes := pcodesArr[:maxNumSyms]
|
|
var exploreCode func(prefix.PrefixCode) bool
|
|
exploreCode = func(c prefix.PrefixCode) (term bool) {
|
|
sym, status := getSymbol(c)
|
|
switch status {
|
|
case statusOkay:
|
|
// This code is valid, so insert it.
|
|
c.Sym = sym
|
|
pcodes[sym] = c
|
|
term = true
|
|
case statusInvalid:
|
|
// This code is invalid, so insert an invalid symbol.
|
|
c.Sym = uint32(len(pcodes))
|
|
pcodes = append(pcodes, c)
|
|
term = true
|
|
case statusNeedBits:
|
|
// This code is too short, so explore both children.
|
|
c.Len++
|
|
c0, c1 := c, c
|
|
c1.Val |= 1 << (c.Len - 1)
|
|
|
|
b0 := exploreCode(c0)
|
|
b1 := exploreCode(c1)
|
|
switch {
|
|
case !b0 && b1:
|
|
c0.Sym = uint32(len(pcodes))
|
|
pcodes = append(pcodes, c0)
|
|
case !b1 && b0:
|
|
c1.Sym = uint32(len(pcodes))
|
|
pcodes = append(pcodes, c1)
|
|
}
|
|
term = b0 || b1
|
|
case statusMaxBits:
|
|
// This code is too long, so report it upstream.
|
|
term = false
|
|
}
|
|
return term // Did this code terminate?
|
|
}
|
|
exploreCode(prefix.PrefixCode{})
|
|
|
|
// Step 3: Copy new sparse codes to old output codes.
|
|
codes = codes[:0]
|
|
for _, c := range pcodes {
|
|
if c.Len > 0 {
|
|
codes = append(codes, c)
|
|
}
|
|
}
|
|
return codes
|
|
}
|
|
|