source: MondoRescue/branches/stable/mindi-busybox/archival/libunarchive/decompress_bunzip2.c @ 821

Last change on this file since 821 was 821, checked in by Bruno Cornec, 14 years ago

Addition of busybox 1.2.1 as a mindi-busybox new package
This should avoid delivering binary files in mindi not built there (Fedora and Debian are quite serious about that)

File size: 21.9 KB
Line 
1/* vi: set sw=4 ts=4: */
2/* Small bzip2 deflate implementation, by Rob Landley (rob@landley.net).
3
4   Based on bzip2 decompression code by Julian R Seward (jseward@acm.org),
5   which also acknowledges contributions by Mike Burrows, David Wheeler,
6   Peter Fenwick, Alistair Moffat, Radford Neal, Ian H. Witten,
7   Robert Sedgewick, and Jon L. Bentley.
8
9   Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
10*/
11
12/*
13    Size and speed optimizations by Manuel Novoa III  (mjn3@codepoet.org).
14
15    More efficient reading of Huffman codes, a streamlined read_bunzip()
16    function, and various other tweaks.  In (limited) tests, approximately
17    20% faster than bzcat on x86 and about 10% faster on arm.
18
19    Note that about 2/3 of the time is spent in read_unzip() reversing
20    the Burrows-Wheeler transformation.  Much of that time is delay
21    resulting from cache misses.
22
23    I would ask that anyone benefiting from this work, especially those
24    using it in commercial products, consider making a donation to my local
25    non-profit hospice organization (www.hospiceacadiana.com) in the name of
26    the woman I loved, Toni W. Hagan, who passed away Feb. 12, 2003.
27
28    Manuel
29 */
30
31#include <setjmp.h>
32#include <stdio.h>
33#include <stdlib.h>
34#include <string.h>
35#include <unistd.h>
36#include <limits.h>
37
38#include "libbb.h"
39
40#include "unarchive.h"
41
42/* Constants for Huffman coding */
43#define MAX_GROUPS          6
44#define GROUP_SIZE          50      /* 64 would have been more efficient */
45#define MAX_HUFCODE_BITS    20      /* Longest Huffman code allowed */
46#define MAX_SYMBOLS         258     /* 256 literals + RUNA + RUNB */
47#define SYMBOL_RUNA         0
48#define SYMBOL_RUNB         1
49
50/* Status return values */
51#define RETVAL_OK                       0
52#define RETVAL_LAST_BLOCK               (-1)
53#define RETVAL_NOT_BZIP_DATA            (-2)
54#define RETVAL_UNEXPECTED_INPUT_EOF     (-3)
55#define RETVAL_UNEXPECTED_OUTPUT_EOF    (-4)
56#define RETVAL_DATA_ERROR               (-5)
57#define RETVAL_OUT_OF_MEMORY            (-6)
58#define RETVAL_OBSOLETE_INPUT           (-7)
59
60/* Other housekeeping constants */
61#define IOBUF_SIZE          4096
62
63/* This is what we know about each Huffman coding group */
64struct group_data {
65    /* We have an extra slot at the end of limit[] for a sentinal value. */
66    int limit[MAX_HUFCODE_BITS+1],base[MAX_HUFCODE_BITS],permute[MAX_SYMBOLS];
67    int minLen, maxLen;
68};
69
70/* Structure holding all the housekeeping data, including IO buffers and
71   memory that persists between calls to bunzip */
72
73typedef struct {
74    /* State for interrupting output loop */
75
76    int writeCopies,writePos,writeRunCountdown,writeCount,writeCurrent;
77
78    /* I/O tracking data (file handles, buffers, positions, etc.) */
79
80    int in_fd,out_fd,inbufCount,inbufPos /*,outbufPos*/;
81    unsigned char *inbuf /*,*outbuf*/;
82    unsigned int inbufBitCount, inbufBits;
83
84    /* The CRC values stored in the block header and calculated from the data */
85
86    uint32_t headerCRC, totalCRC, writeCRC;
87    uint32_t *crc32Table;
88    /* Intermediate buffer and its size (in bytes) */
89
90    unsigned int *dbuf, dbufSize;
91
92    /* These things are a bit too big to go on the stack */
93
94    unsigned char selectors[32768];         /* nSelectors=15 bits */
95    struct group_data groups[MAX_GROUPS];   /* Huffman coding tables */
96
97    /* For I/O error handling */
98
99    jmp_buf jmpbuf;
100} bunzip_data;
101
102/* Return the next nnn bits of input.  All reads from the compressed input
103   are done through this function.  All reads are big endian */
104
105static unsigned int get_bits(bunzip_data *bd, char bits_wanted)
106{
107    unsigned int bits=0;
108
109    /* If we need to get more data from the byte buffer, do so.  (Loop getting
110       one byte at a time to enforce endianness and avoid unaligned access.) */
111
112    while (bd->inbufBitCount<bits_wanted) {
113
114        /* If we need to read more data from file into byte buffer, do so */
115
116        if(bd->inbufPos==bd->inbufCount) {
117            if((bd->inbufCount = read(bd->in_fd, bd->inbuf, IOBUF_SIZE)) <= 0)
118                longjmp(bd->jmpbuf,RETVAL_UNEXPECTED_INPUT_EOF);
119            bd->inbufPos=0;
120        }
121
122        /* Avoid 32-bit overflow (dump bit buffer to top of output) */
123
124        if(bd->inbufBitCount>=24) {
125            bits=bd->inbufBits&((1<<bd->inbufBitCount)-1);
126            bits_wanted-=bd->inbufBitCount;
127            bits<<=bits_wanted;
128            bd->inbufBitCount=0;
129        }
130
131        /* Grab next 8 bits of input from buffer. */
132
133        bd->inbufBits=(bd->inbufBits<<8)|bd->inbuf[bd->inbufPos++];
134        bd->inbufBitCount+=8;
135    }
136
137    /* Calculate result */
138
139    bd->inbufBitCount-=bits_wanted;
140    bits|=(bd->inbufBits>>bd->inbufBitCount)&((1<<bits_wanted)-1);
141
142    return bits;
143}
144
145/* Unpacks the next block and sets up for the inverse burrows-wheeler step. */
146
147static int get_next_block(bunzip_data *bd)
148{
149    struct group_data *hufGroup;
150    int dbufCount,nextSym,dbufSize,groupCount,*base,*limit,selector,
151        i,j,k,t,runPos,symCount,symTotal,nSelectors,byteCount[256];
152    unsigned char uc, symToByte[256], mtfSymbol[256], *selectors;
153    unsigned int *dbuf,origPtr;
154
155    dbuf=bd->dbuf;
156    dbufSize=bd->dbufSize;
157    selectors=bd->selectors;
158
159    /* Reset longjmp I/O error handling */
160
161    i=setjmp(bd->jmpbuf);
162    if(i) return i;
163
164    /* Read in header signature and CRC, then validate signature.
165       (last block signature means CRC is for whole file, return now) */
166
167    i = get_bits(bd,24);
168    j = get_bits(bd,24);
169    bd->headerCRC=get_bits(bd,32);
170    if ((i == 0x177245) && (j == 0x385090)) return RETVAL_LAST_BLOCK;
171    if ((i != 0x314159) || (j != 0x265359)) return RETVAL_NOT_BZIP_DATA;
172
173    /* We can add support for blockRandomised if anybody complains.  There was
174       some code for this in busybox 1.0.0-pre3, but nobody ever noticed that
175       it didn't actually work. */
176
177    if(get_bits(bd,1)) return RETVAL_OBSOLETE_INPUT;
178    if((origPtr=get_bits(bd,24)) > dbufSize) return RETVAL_DATA_ERROR;
179
180    /* mapping table: if some byte values are never used (encoding things
181       like ascii text), the compression code removes the gaps to have fewer
182       symbols to deal with, and writes a sparse bitfield indicating which
183       values were present.  We make a translation table to convert the symbols
184       back to the corresponding bytes. */
185
186    t=get_bits(bd, 16);
187    symTotal=0;
188    for (i=0;i<16;i++) {
189        if(t&(1<<(15-i))) {
190            k=get_bits(bd,16);
191            for(j=0;j<16;j++)
192                if(k&(1<<(15-j))) symToByte[symTotal++]=(16*i)+j;
193        }
194    }
195
196    /* How many different Huffman coding groups does this block use? */
197
198    groupCount=get_bits(bd,3);
199    if (groupCount<2 || groupCount>MAX_GROUPS) return RETVAL_DATA_ERROR;
200
201    /* nSelectors: Every GROUP_SIZE many symbols we select a new Huffman coding
202       group.  Read in the group selector list, which is stored as MTF encoded
203       bit runs.  (MTF=Move To Front, as each value is used it's moved to the
204       start of the list.) */
205
206    if(!(nSelectors=get_bits(bd, 15))) return RETVAL_DATA_ERROR;
207    for(i=0; i<groupCount; i++) mtfSymbol[i] = i;
208    for(i=0; i<nSelectors; i++) {
209
210        /* Get next value */
211
212        for(j=0;get_bits(bd,1);j++) if (j>=groupCount) return RETVAL_DATA_ERROR;
213
214        /* Decode MTF to get the next selector */
215
216        uc = mtfSymbol[j];
217        for(;j;j--) mtfSymbol[j] = mtfSymbol[j-1];
218        mtfSymbol[0]=selectors[i]=uc;
219    }
220
221    /* Read the Huffman coding tables for each group, which code for symTotal
222       literal symbols, plus two run symbols (RUNA, RUNB) */
223
224    symCount=symTotal+2;
225    for (j=0; j<groupCount; j++) {
226        unsigned char length[MAX_SYMBOLS],temp[MAX_HUFCODE_BITS+1];
227        int minLen, maxLen, pp;
228
229        /* Read Huffman code lengths for each symbol.  They're stored in
230           a way similar to mtf; record a starting value for the first symbol,
231           and an offset from the previous value for everys symbol after that.
232           (Subtracting 1 before the loop and then adding it back at the end is
233           an optimization that makes the test inside the loop simpler: symbol
234           length 0 becomes negative, so an unsigned inequality catches it.) */
235
236        t=get_bits(bd, 5)-1;
237        for (i = 0; i < symCount; i++) {
238            for(;;) {
239                if (((unsigned)t) > (MAX_HUFCODE_BITS-1))
240                    return RETVAL_DATA_ERROR;
241
242                /* If first bit is 0, stop.  Else second bit indicates whether
243                   to increment or decrement the value.  Optimization: grab 2
244                   bits and unget the second if the first was 0. */
245
246                k = get_bits(bd,2);
247                if (k < 2) {
248                    bd->inbufBitCount++;
249                    break;
250                }
251
252                /* Add one if second bit 1, else subtract 1.  Avoids if/else */
253
254                t+=(((k+1)&2)-1);
255            }
256
257            /* Correct for the initial -1, to get the final symbol length */
258
259            length[i]=t+1;
260        }
261
262        /* Find largest and smallest lengths in this group */
263
264        minLen=maxLen=length[0];
265        for(i = 1; i < symCount; i++) {
266            if(length[i] > maxLen) maxLen = length[i];
267            else if(length[i] < minLen) minLen = length[i];
268        }
269
270        /* Calculate permute[], base[], and limit[] tables from length[].
271         *
272         * permute[] is the lookup table for converting Huffman coded symbols
273         * into decoded symbols.  base[] is the amount to subtract from the
274         * value of a Huffman symbol of a given length when using permute[].
275         *
276         * limit[] indicates the largest numerical value a symbol with a given
277         * number of bits can have.  This is how the Huffman codes can vary in
278         * length: each code with a value>limit[length] needs another bit.
279         */
280
281        hufGroup=bd->groups+j;
282        hufGroup->minLen = minLen;
283        hufGroup->maxLen = maxLen;
284
285        /* Note that minLen can't be smaller than 1, so we adjust the base
286           and limit array pointers so we're not always wasting the first
287           entry.  We do this again when using them (during symbol decoding).*/
288
289        base=hufGroup->base-1;
290        limit=hufGroup->limit-1;
291
292        /* Calculate permute[].  Concurently, initialize temp[] and limit[]. */
293
294        pp=0;
295        for(i=minLen;i<=maxLen;i++) {
296            temp[i]=limit[i]=0;
297            for(t=0;t<symCount;t++)
298                if(length[t]==i) hufGroup->permute[pp++] = t;
299        }
300
301        /* Count symbols coded for at each bit length */
302
303        for (i=0;i<symCount;i++) temp[length[i]]++;
304
305        /* Calculate limit[] (the largest symbol-coding value at each bit
306         * length, which is (previous limit<<1)+symbols at this level), and
307         * base[] (number of symbols to ignore at each bit length, which is
308         * limit minus the cumulative count of symbols coded for already). */
309
310        pp=t=0;
311        for (i=minLen; i<maxLen; i++) {
312            pp+=temp[i];
313
314            /* We read the largest possible symbol size and then unget bits
315               after determining how many we need, and those extra bits could
316               be set to anything.  (They're noise from future symbols.)  At
317               each level we're really only interested in the first few bits,
318               so here we set all the trailing to-be-ignored bits to 1 so they
319               don't affect the value>limit[length] comparison. */
320
321            limit[i]= (pp << (maxLen - i)) - 1;
322            pp<<=1;
323            base[i+1]=pp-(t+=temp[i]);
324        }
325        limit[maxLen+1] = INT_MAX; /* Sentinal value for reading next sym. */
326        limit[maxLen]=pp+temp[maxLen]-1;
327        base[minLen]=0;
328    }
329
330    /* We've finished reading and digesting the block header.  Now read this
331       block's Huffman coded symbols from the file and undo the Huffman coding
332       and run length encoding, saving the result into dbuf[dbufCount++]=uc */
333
334    /* Initialize symbol occurrence counters and symbol Move To Front table */
335
336    for(i=0;i<256;i++) {
337        byteCount[i] = 0;
338        mtfSymbol[i]=(unsigned char)i;
339    }
340
341    /* Loop through compressed symbols. */
342
343    runPos=dbufCount=selector=0;
344    for(;;) {
345
346        /* fetch next Huffman coding group from list. */
347
348        symCount=GROUP_SIZE-1;
349        if(selector>=nSelectors) return RETVAL_DATA_ERROR;
350        hufGroup=bd->groups+selectors[selector++];
351        base=hufGroup->base-1;
352        limit=hufGroup->limit-1;
353continue_this_group:
354
355        /* Read next Huffman-coded symbol. */
356
357        /* Note: It is far cheaper to read maxLen bits and back up than it is
358           to read minLen bits and then an additional bit at a time, testing
359           as we go.  Because there is a trailing last block (with file CRC),
360           there is no danger of the overread causing an unexpected EOF for a
361           valid compressed file.  As a further optimization, we do the read
362           inline (falling back to a call to get_bits if the buffer runs
363           dry).  The following (up to got_huff_bits:) is equivalent to
364           j=get_bits(bd,hufGroup->maxLen);
365         */
366
367        while (bd->inbufBitCount<hufGroup->maxLen) {
368            if(bd->inbufPos==bd->inbufCount) {
369                j = get_bits(bd,hufGroup->maxLen);
370                goto got_huff_bits;
371            }
372            bd->inbufBits=(bd->inbufBits<<8)|bd->inbuf[bd->inbufPos++];
373            bd->inbufBitCount+=8;
374        };
375        bd->inbufBitCount-=hufGroup->maxLen;
376        j = (bd->inbufBits>>bd->inbufBitCount)&((1<<hufGroup->maxLen)-1);
377
378got_huff_bits:
379
380        /* Figure how how many bits are in next symbol and unget extras */
381
382        i=hufGroup->minLen;
383        while(j>limit[i]) ++i;
384        bd->inbufBitCount += (hufGroup->maxLen - i);
385
386        /* Huffman decode value to get nextSym (with bounds checking) */
387
388        if ((i > hufGroup->maxLen)
389            || (((unsigned)(j=(j>>(hufGroup->maxLen-i))-base[i]))
390                >= MAX_SYMBOLS))
391            return RETVAL_DATA_ERROR;
392        nextSym = hufGroup->permute[j];
393
394        /* We have now decoded the symbol, which indicates either a new literal
395           byte, or a repeated run of the most recent literal byte.  First,
396           check if nextSym indicates a repeated run, and if so loop collecting
397           how many times to repeat the last literal. */
398
399        if (((unsigned)nextSym) <= SYMBOL_RUNB) { /* RUNA or RUNB */
400
401            /* If this is the start of a new run, zero out counter */
402
403            if(!runPos) {
404                runPos = 1;
405                t = 0;
406            }
407
408            /* Neat trick that saves 1 symbol: instead of or-ing 0 or 1 at
409               each bit position, add 1 or 2 instead.  For example,
410               1011 is 1<<0 + 1<<1 + 2<<2.  1010 is 2<<0 + 2<<1 + 1<<2.
411               You can make any bit pattern that way using 1 less symbol than
412               the basic or 0/1 method (except all bits 0, which would use no
413               symbols, but a run of length 0 doesn't mean anything in this
414               context).  Thus space is saved. */
415
416            t += (runPos << nextSym); /* +runPos if RUNA; +2*runPos if RUNB */
417            if(runPos < dbufSize) runPos <<= 1;
418            goto end_of_huffman_loop;
419        }
420
421        /* When we hit the first non-run symbol after a run, we now know
422           how many times to repeat the last literal, so append that many
423           copies to our buffer of decoded symbols (dbuf) now.  (The last
424           literal used is the one at the head of the mtfSymbol array.) */
425
426        if(runPos) {
427            runPos=0;
428            if(dbufCount+t>=dbufSize) return RETVAL_DATA_ERROR;
429
430            uc = symToByte[mtfSymbol[0]];
431            byteCount[uc] += t;
432            while(t--) dbuf[dbufCount++]=uc;
433        }
434
435        /* Is this the terminating symbol? */
436
437        if(nextSym>symTotal) break;
438
439        /* At this point, nextSym indicates a new literal character.  Subtract
440           one to get the position in the MTF array at which this literal is
441           currently to be found.  (Note that the result can't be -1 or 0,
442           because 0 and 1 are RUNA and RUNB.  But another instance of the
443           first symbol in the mtf array, position 0, would have been handled
444           as part of a run above.  Therefore 1 unused mtf position minus
445           2 non-literal nextSym values equals -1.) */
446
447        if(dbufCount>=dbufSize) return RETVAL_DATA_ERROR;
448        i = nextSym - 1;
449        uc = mtfSymbol[i];
450
451        /* Adjust the MTF array.  Since we typically expect to move only a
452         * small number of symbols, and are bound by 256 in any case, using
453         * memmove here would typically be bigger and slower due to function
454         * call overhead and other assorted setup costs. */
455
456        do {
457            mtfSymbol[i] = mtfSymbol[i-1];
458        } while (--i);
459        mtfSymbol[0] = uc;
460        uc=symToByte[uc];
461
462        /* We have our literal byte.  Save it into dbuf. */
463
464        byteCount[uc]++;
465        dbuf[dbufCount++] = (unsigned int)uc;
466
467        /* Skip group initialization if we're not done with this group.  Done
468         * this way to avoid compiler warning. */
469
470end_of_huffman_loop:
471        if(symCount--) goto continue_this_group;
472    }
473
474    /* At this point, we've read all the Huffman-coded symbols (and repeated
475       runs) for this block from the input stream, and decoded them into the
476       intermediate buffer.  There are dbufCount many decoded bytes in dbuf[].
477       Now undo the Burrows-Wheeler transform on dbuf.
478       See http://dogma.net/markn/articles/bwt/bwt.htm
479     */
480
481    /* Turn byteCount into cumulative occurrence counts of 0 to n-1. */
482
483    j=0;
484    for(i=0;i<256;i++) {
485        k=j+byteCount[i];
486        byteCount[i] = j;
487        j=k;
488    }
489
490    /* Figure out what order dbuf would be in if we sorted it. */
491
492    for (i=0;i<dbufCount;i++) {
493        uc=(unsigned char)(dbuf[i] & 0xff);
494        dbuf[byteCount[uc]] |= (i << 8);
495        byteCount[uc]++;
496    }
497
498    /* Decode first byte by hand to initialize "previous" byte.  Note that it
499       doesn't get output, and if the first three characters are identical
500       it doesn't qualify as a run (hence writeRunCountdown=5). */
501
502    if(dbufCount) {
503        if(origPtr>=dbufCount) return RETVAL_DATA_ERROR;
504        bd->writePos=dbuf[origPtr];
505        bd->writeCurrent=(unsigned char)(bd->writePos&0xff);
506        bd->writePos>>=8;
507        bd->writeRunCountdown=5;
508    }
509    bd->writeCount=dbufCount;
510
511    return RETVAL_OK;
512}
513
514/* Undo burrows-wheeler transform on intermediate buffer to produce output.
515   If start_bunzip was initialized with out_fd=-1, then up to len bytes of
516   data are written to outbuf.  Return value is number of bytes written or
517   error (all errors are negative numbers).  If out_fd!=-1, outbuf and len
518   are ignored, data is written to out_fd and return is RETVAL_OK or error.
519*/
520
521static int read_bunzip(bunzip_data *bd, char *outbuf, int len)
522{
523    const unsigned int *dbuf;
524    int pos,current,previous,gotcount;
525
526    /* If last read was short due to end of file, return last block now */
527    if(bd->writeCount<0) return bd->writeCount;
528
529    gotcount = 0;
530    dbuf=bd->dbuf;
531    pos=bd->writePos;
532    current=bd->writeCurrent;
533
534    /* We will always have pending decoded data to write into the output
535       buffer unless this is the very first call (in which case we haven't
536       Huffman-decoded a block into the intermediate buffer yet). */
537
538    if (bd->writeCopies) {
539
540        /* Inside the loop, writeCopies means extra copies (beyond 1) */
541
542        --bd->writeCopies;
543
544        /* Loop outputting bytes */
545
546        for(;;) {
547
548            /* If the output buffer is full, snapshot state and return */
549
550            if(gotcount >= len) {
551                bd->writePos=pos;
552                bd->writeCurrent=current;
553                bd->writeCopies++;
554                return len;
555            }
556
557            /* Write next byte into output buffer, updating CRC */
558
559            outbuf[gotcount++] = current;
560            bd->writeCRC=(((bd->writeCRC)<<8)
561                          ^bd->crc32Table[((bd->writeCRC)>>24)^current]);
562
563            /* Loop now if we're outputting multiple copies of this byte */
564
565            if (bd->writeCopies) {
566                --bd->writeCopies;
567                continue;
568            }
569decode_next_byte:
570            if (!bd->writeCount--) break;
571            /* Follow sequence vector to undo Burrows-Wheeler transform */
572            previous=current;
573            pos=dbuf[pos];
574            current=pos&0xff;
575            pos>>=8;
576
577            /* After 3 consecutive copies of the same byte, the 4th is a repeat
578               count.  We count down from 4 instead
579             * of counting up because testing for non-zero is faster */
580
581            if(--bd->writeRunCountdown) {
582                if(current!=previous) bd->writeRunCountdown=4;
583            } else {
584
585                /* We have a repeated run, this byte indicates the count */
586
587                bd->writeCopies=current;
588                current=previous;
589                bd->writeRunCountdown=5;
590
591                /* Sometimes there are just 3 bytes (run length 0) */
592
593                if(!bd->writeCopies) goto decode_next_byte;
594
595                /* Subtract the 1 copy we'd output anyway to get extras */
596
597                --bd->writeCopies;
598            }
599        }
600
601        /* Decompression of this block completed successfully */
602
603        bd->writeCRC=~bd->writeCRC;
604        bd->totalCRC=((bd->totalCRC<<1) | (bd->totalCRC>>31)) ^ bd->writeCRC;
605
606        /* If this block had a CRC error, force file level CRC error. */
607
608        if(bd->writeCRC!=bd->headerCRC) {
609            bd->totalCRC=bd->headerCRC+1;
610            return RETVAL_LAST_BLOCK;
611        }
612    }
613
614    /* Refill the intermediate buffer by Huffman-decoding next block of input */
615    /* (previous is just a convenient unused temp variable here) */
616
617    previous=get_next_block(bd);
618    if(previous) {
619        bd->writeCount=previous;
620        return (previous!=RETVAL_LAST_BLOCK) ? previous : gotcount;
621    }
622    bd->writeCRC=~0;
623    pos=bd->writePos;
624    current=bd->writeCurrent;
625    goto decode_next_byte;
626}
627
628/* Allocate the structure, read file header.  If in_fd==-1, inbuf must contain
629   a complete bunzip file (len bytes long).  If in_fd!=-1, inbuf and len are
630   ignored, and data is read from file handle into temporary buffer. */
631
632static int start_bunzip(bunzip_data **bdp, int in_fd, unsigned char *inbuf,
633                        int len)
634{
635    bunzip_data *bd;
636    unsigned int i;
637    const unsigned int BZh0=(((unsigned int)'B')<<24)+(((unsigned int)'Z')<<16)
638                            +(((unsigned int)'h')<<8)+(unsigned int)'0';
639
640    /* Figure out how much data to allocate */
641
642    i=sizeof(bunzip_data);
643    if(in_fd!=-1) i+=IOBUF_SIZE;
644
645    /* Allocate bunzip_data.  Most fields initialize to zero. */
646
647    bd=*bdp=xzalloc(i);
648
649    /* Setup input buffer */
650
651    if(-1==(bd->in_fd=in_fd)) {
652        bd->inbuf=inbuf;
653        bd->inbufCount=len;
654    } else bd->inbuf=(unsigned char *)(bd+1);
655
656    /* Init the CRC32 table (big endian) */
657
658    bd->crc32Table = bb_crc32_filltable(1);
659
660    /* Setup for I/O error handling via longjmp */
661
662    i=setjmp(bd->jmpbuf);
663    if(i) return i;
664
665    /* Ensure that file starts with "BZh['1'-'9']." */
666
667    i = get_bits(bd,32);
668    if (((unsigned int)(i-BZh0-1)) >= 9) return RETVAL_NOT_BZIP_DATA;
669
670    /* Fourth byte (ascii '1'-'9'), indicates block size in units of 100k of
671       uncompressed data.  Allocate intermediate buffer for block. */
672
673    bd->dbufSize=100000*(i-BZh0);
674
675    bd->dbuf=xmalloc(bd->dbufSize * sizeof(int));
676    return RETVAL_OK;
677}
678
679/* Example usage: decompress src_fd to dst_fd.  (Stops at end of bzip data,
680   not end of file.) */
681
682int uncompressStream(int src_fd, int dst_fd)
683{
684    char *outbuf;
685    bunzip_data *bd;
686    int i;
687
688    outbuf=xmalloc(IOBUF_SIZE);
689    if(!(i=start_bunzip(&bd,src_fd,0,0))) {
690        for(;;) {
691            if((i=read_bunzip(bd,outbuf,IOBUF_SIZE)) <= 0) break;
692            if(i!=write(dst_fd,outbuf,i)) {
693                i=RETVAL_UNEXPECTED_OUTPUT_EOF;
694                break;
695            }
696        }
697    }
698
699    /* Check CRC and release memory */
700
701    if(i==RETVAL_LAST_BLOCK) {
702        if (bd->headerCRC!=bd->totalCRC) {
703            bb_error_msg("Data integrity error when decompressing.");
704        } else {
705            i=RETVAL_OK;
706        }
707    } else if (i==RETVAL_UNEXPECTED_OUTPUT_EOF) {
708        bb_error_msg("Compressed file ends unexpectedly");
709    } else {
710        bb_error_msg("Decompression failed");
711    }
712    free(bd->dbuf);
713    free(bd);
714    free(outbuf);
715
716    return i;
717}
718
719#ifdef TESTING
720
721static char * const bunzip_errors[]={NULL,"Bad file checksum","Not bzip data",
722        "Unexpected input EOF","Unexpected output EOF","Data error",
723         "Out of memory","Obsolete (pre 0.9.5) bzip format not supported."};
724
725/* Dumb little test thing, decompress stdin to stdout */
726int main(int argc, char *argv[])
727{
728    int i=uncompressStream(0,1);
729    char c;
730
731    if(i) fprintf(stderr,"%s\n", bunzip_errors[-i]);
732    else if(read(0,&c,1)) fprintf(stderr,"Trailing garbage ignored\n");
733    return -i;
734}
735#endif
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