/
reader.go
271 lines (241 loc) · 6.84 KB
/
reader.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
package bzip2
import (
"io"
"github.com/marco-spagnuolo/unisacompression/internal"
"github.com/marco-spagnuolo/unisacompression/internal/errors"
"github.com/marco-spagnuolo/unisacompression/internal/prefix"
)
type Reader struct {
InputOffset int64 // Total number of bytes read from underlying io.Reader
OutputOffset int64 // Total number of bytes emitted from Read
rd prefixReader
err error
level int // The current compression level
rdHdrFtr int // Number of times we read the stream header and footer
blkCRC uint32 // CRC-32 IEEE of each block (as stored)
endCRC uint32 // Checksum of all blocks using bzip2's custom method
crc crc
mtf moveToFront
bwt burrowsWheelerTransform
rle runLengthEncoding
// These fields are allocated with Reader and re-used later.
treeSels []uint8
codes2D [maxNumTrees][maxNumSyms]prefix.PrefixCode
codes1D [maxNumTrees]prefix.PrefixCodes
trees1D [maxNumTrees]prefix.Decoder
syms []uint16
fuzzReader // Exported functionality when fuzz testing
}
type ReaderConfig struct {
_ struct{} // Blank field to prevent unkeyed struct literals
}
func NewReader(r io.Reader, conf *ReaderConfig) (*Reader, error) {
zr := new(Reader)
zr.Reset(r)
return zr, nil
}
func (zr *Reader) Reset(r io.Reader) error {
*zr = Reader{
rd: zr.rd,
mtf: zr.mtf,
bwt: zr.bwt,
rle: zr.rle,
treeSels: zr.treeSels,
trees1D: zr.trees1D,
syms: zr.syms,
}
zr.rd.Init(r)
return nil
}
func (zr *Reader) Read(buf []byte) (int, error) {
for {
cnt, err := zr.rle.Read(buf)
if err != rleDone && zr.err == nil {
zr.err = err
}
if cnt > 0 {
zr.crc.update(buf[:cnt])
zr.OutputOffset += int64(cnt)
return cnt, nil
}
if zr.err != nil || len(buf) == 0 {
return 0, zr.err
}
// Read the next chunk.
zr.rd.Offset = zr.InputOffset
func() {
defer errors.Recover(&zr.err)
if zr.rdHdrFtr%2 == 0 {
// Check if we are already at EOF.
if err := zr.rd.PullBits(1); err != nil {
if err == io.ErrUnexpectedEOF && zr.rdHdrFtr > 0 {
err = io.EOF // EOF is okay if we read at least one stream
}
errors.Panic(err)
}
// Read stream header.
if zr.rd.ReadBitsBE64(16) != hdrMagic {
panicf(errors.Corrupted, "invalid stream magic")
}
if ver := zr.rd.ReadBitsBE64(8); ver != 'h' {
if ver == '0' {
panicf(errors.Deprecated, "bzip1 format is not supported")
}
panicf(errors.Corrupted, "invalid version: %q", ver)
}
lvl := int(zr.rd.ReadBitsBE64(8)) - '0'
if lvl < BestSpeed || lvl > BestCompression {
panicf(errors.Corrupted, "invalid block size: %d", lvl*blockSize)
}
zr.level = lvl
zr.rdHdrFtr++
} else {
// Check and update the CRC.
if internal.GoFuzz {
zr.updateChecksum(-1, zr.crc.val) // Update with value
zr.blkCRC = zr.crc.val // Suppress CRC failures
}
if zr.blkCRC != zr.crc.val {
panicf(errors.Corrupted, "mismatching block checksum")
}
zr.endCRC = (zr.endCRC<<1 | zr.endCRC>>31) ^ zr.blkCRC
}
buf := zr.decodeBlock()
zr.rle.Init(buf)
}()
if zr.InputOffset, err = zr.rd.Flush(); zr.err == nil {
zr.err = err
}
if zr.err != nil {
zr.err = errWrap(zr.err, errors.Corrupted)
return 0, zr.err
}
}
}
func (zr *Reader) Close() error {
if zr.err == io.EOF || zr.err == errClosed {
zr.rle.Init(nil) // Make sure future reads fail
zr.err = errClosed
return nil
}
return zr.err // Return the persistent error
}
func (zr *Reader) decodeBlock() []byte {
if magic := zr.rd.ReadBitsBE64(48); magic != blkMagic {
if magic == endMagic {
endCRC := uint32(zr.rd.ReadBitsBE64(32))
if internal.GoFuzz {
zr.updateChecksum(zr.rd.BitsRead()-32, zr.endCRC)
endCRC = zr.endCRC // Suppress CRC failures
}
if zr.endCRC != endCRC {
panicf(errors.Corrupted, "mismatching stream checksum")
}
zr.endCRC = 0
zr.rd.ReadPads()
zr.rdHdrFtr++
return nil
}
panicf(errors.Corrupted, "invalid block or footer magic")
}
zr.crc.val = 0
zr.blkCRC = uint32(zr.rd.ReadBitsBE64(32))
if internal.GoFuzz {
zr.updateChecksum(zr.rd.BitsRead()-32, 0) // Record offset only
}
if zr.rd.ReadBitsBE64(1) != 0 {
panicf(errors.Deprecated, "block randomization is not supported")
}
// Read BWT related fields.
ptr := int(zr.rd.ReadBitsBE64(24)) // BWT origin pointer
// Read MTF related fields.
var dictArr [256]uint8
dict := dictArr[:0]
bmapHi := uint16(zr.rd.ReadBits(16))
for i := 0; i < 256; i, bmapHi = i+16, bmapHi>>1 {
if bmapHi&1 > 0 {
bmapLo := uint16(zr.rd.ReadBits(16))
for j := 0; j < 16; j, bmapLo = j+1, bmapLo>>1 {
if bmapLo&1 > 0 {
dict = append(dict, uint8(i+j))
}
}
}
}
// Step 1: Prefix encoding.
syms := zr.decodePrefix(len(dict))
// Step 2: Move-to-front transform and run-length encoding.
zr.mtf.Init(dict, zr.level*blockSize)
buf := zr.mtf.Decode(syms)
// Step 3: Burrows-Wheeler transformation.
if ptr >= len(buf) {
panicf(errors.Corrupted, "origin pointer (0x%06x) exceeds block size: %d", ptr, len(buf))
}
zr.bwt.Decode(buf, ptr)
return buf
}
func (zr *Reader) decodePrefix(numSyms int) (syms []uint16) {
numSyms += 2 // Remove 0 symbol, add RUNA, RUNB, and EOF symbols
if numSyms < 3 {
panicf(errors.Corrupted, "not enough prefix symbols: %d", numSyms)
}
// Read information about the trees and tree selectors.
var mtf internal.MoveToFront
numTrees := int(zr.rd.ReadBitsBE64(3))
if numTrees < minNumTrees || numTrees > maxNumTrees {
panicf(errors.Corrupted, "invalid number of prefix trees: %d", numTrees)
}
numSels := int(zr.rd.ReadBitsBE64(15))
if cap(zr.treeSels) < numSels {
zr.treeSels = make([]uint8, numSels)
}
treeSels := zr.treeSels[:numSels]
for i := range treeSels {
sym, ok := zr.rd.TryReadSymbol(&decSel)
if !ok {
sym = zr.rd.ReadSymbol(&decSel)
}
if int(sym) >= numTrees {
panicf(errors.Corrupted, "invalid prefix tree selector: %d", sym)
}
treeSels[i] = uint8(sym)
}
mtf.Decode(treeSels)
zr.treeSels = treeSels
// Initialize prefix codes.
for i := range zr.codes2D[:numTrees] {
zr.codes1D[i] = zr.codes2D[i][:numSyms]
}
zr.rd.ReadPrefixCodes(zr.codes1D[:numTrees], zr.trees1D[:numTrees])
// Read prefix encoded symbols of compressed data.
var tree *prefix.Decoder
var blkLen, selIdx int
syms = zr.syms[:0]
for {
if blkLen == 0 {
blkLen = numBlockSyms
if selIdx >= len(treeSels) {
panicf(errors.Corrupted, "not enough prefix tree selectors")
}
tree = &zr.trees1D[treeSels[selIdx]]
selIdx++
}
blkLen--
sym, ok := zr.rd.TryReadSymbol(tree)
if !ok {
sym = zr.rd.ReadSymbol(tree)
}
if int(sym) == numSyms-1 {
break // EOF marker
}
if int(sym) >= numSyms {
panicf(errors.Corrupted, "invalid prefix symbol: %d", sym)
}
if len(syms) >= zr.level*blockSize {
panicf(errors.Corrupted, "number of prefix symbols exceeds block size")
}
syms = append(syms, uint16(sym))
}
zr.syms = syms
return syms
}