1 /* vi: set sw=4 ts=4: */
2 /* Small bzip2 deflate implementation, by Rob Landley (rob@landley.net).
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.
9 Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
13 Size and speed optimizations by Manuel Novoa III (mjn3@codepoet.org).
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.
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.
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.
32 #include "unarchive.h"
34 /* Constants for Huffman coding */
36 #define GROUP_SIZE 50 /* 64 would have been more efficient */
37 #define MAX_HUFCODE_BITS 20 /* Longest Huffman code allowed */
38 #define MAX_SYMBOLS 258 /* 256 literals + RUNA + RUNB */
42 /* Status return values */
44 #define RETVAL_LAST_BLOCK (-1)
45 #define RETVAL_NOT_BZIP_DATA (-2)
46 #define RETVAL_UNEXPECTED_INPUT_EOF (-3)
47 #define RETVAL_UNEXPECTED_OUTPUT_EOF (-4)
48 #define RETVAL_DATA_ERROR (-5)
49 #define RETVAL_OUT_OF_MEMORY (-6)
50 #define RETVAL_OBSOLETE_INPUT (-7)
52 /* Other housekeeping constants */
53 #define IOBUF_SIZE 4096
55 /* This is what we know about each Huffman coding group */
57 /* We have an extra slot at the end of limit[] for a sentinal value. */
58 int limit[MAX_HUFCODE_BITS+1], base[MAX_HUFCODE_BITS], permute[MAX_SYMBOLS];
62 /* Structure holding all the housekeeping data, including IO buffers and
63 memory that persists between calls to bunzip */
66 /* State for interrupting output loop */
67 int writeCopies, writePos, writeRunCountdown, writeCount, writeCurrent;
69 /* I/O tracking data (file handles, buffers, positions, etc.) */
70 int in_fd, out_fd, inbufCount, inbufPos /*, outbufPos*/;
71 unsigned char *inbuf /*,*outbuf*/;
72 unsigned inbufBitCount, inbufBits;
74 /* The CRC values stored in the block header and calculated from the data */
75 uint32_t headerCRC, totalCRC, writeCRC;
77 /* Intermediate buffer and its size (in bytes) */
78 unsigned *dbuf, dbufSize;
80 /* For I/O error handling */
83 /* Big things go last (register-relative addressing can be larger for big offsets */
84 uint32_t crc32Table[256];
85 unsigned char selectors[32768]; /* nSelectors=15 bits */
86 struct group_data groups[MAX_GROUPS]; /* Huffman coding tables */
88 /* typedef struct bunzip_data bunzip_data; -- done in .h file */
91 /* Return the next nnn bits of input. All reads from the compressed input
92 are done through this function. All reads are big endian */
94 static unsigned get_bits(bunzip_data *bd, char bits_wanted)
98 /* If we need to get more data from the byte buffer, do so. (Loop getting
99 one byte at a time to enforce endianness and avoid unaligned access.) */
101 while (bd->inbufBitCount < bits_wanted) {
103 /* If we need to read more data from file into byte buffer, do so */
105 if (bd->inbufPos == bd->inbufCount) {
106 /* if "no input fd" case: in_fd == -1, read fails, we jump */
107 bd->inbufCount = read(bd->in_fd, bd->inbuf, IOBUF_SIZE);
108 if (bd->inbufCount <= 0)
109 longjmp(bd->jmpbuf, RETVAL_UNEXPECTED_INPUT_EOF);
113 /* Avoid 32-bit overflow (dump bit buffer to top of output) */
115 if (bd->inbufBitCount >= 24) {
116 bits = bd->inbufBits & ((1 << bd->inbufBitCount) - 1);
117 bits_wanted -= bd->inbufBitCount;
118 bits <<= bits_wanted;
119 bd->inbufBitCount = 0;
122 /* Grab next 8 bits of input from buffer. */
124 bd->inbufBits = (bd->inbufBits<<8) | bd->inbuf[bd->inbufPos++];
125 bd->inbufBitCount += 8;
128 /* Calculate result */
130 bd->inbufBitCount -= bits_wanted;
131 bits |= (bd->inbufBits >> bd->inbufBitCount) & ((1 << bits_wanted) - 1);
136 /* Unpacks the next block and sets up for the inverse burrows-wheeler step. */
138 static int get_next_block(bunzip_data *bd)
140 struct group_data *hufGroup;
141 int dbufCount, nextSym, dbufSize, groupCount, *base, *limit, selector,
142 i, j, k, t, runPos, symCount, symTotal, nSelectors, byteCount[256];
143 unsigned char uc, symToByte[256], mtfSymbol[256], *selectors;
144 unsigned *dbuf, origPtr;
147 dbufSize = bd->dbufSize;
148 selectors = bd->selectors;
150 /* Reset longjmp I/O error handling */
152 i = setjmp(bd->jmpbuf);
155 /* Read in header signature and CRC, then validate signature.
156 (last block signature means CRC is for whole file, return now) */
158 i = get_bits(bd, 24);
159 j = get_bits(bd, 24);
160 bd->headerCRC = get_bits(bd, 32);
161 if ((i == 0x177245) && (j == 0x385090)) return RETVAL_LAST_BLOCK;
162 if ((i != 0x314159) || (j != 0x265359)) return RETVAL_NOT_BZIP_DATA;
164 /* We can add support for blockRandomised if anybody complains. There was
165 some code for this in busybox 1.0.0-pre3, but nobody ever noticed that
166 it didn't actually work. */
168 if (get_bits(bd, 1)) return RETVAL_OBSOLETE_INPUT;
169 origPtr = get_bits(bd, 24);
170 if (origPtr > dbufSize) return RETVAL_DATA_ERROR;
172 /* mapping table: if some byte values are never used (encoding things
173 like ascii text), the compression code removes the gaps to have fewer
174 symbols to deal with, and writes a sparse bitfield indicating which
175 values were present. We make a translation table to convert the symbols
176 back to the corresponding bytes. */
178 t = get_bits(bd, 16);
180 for (i = 0; i < 16; i++) {
181 if (t & (1 << (15-i))) {
182 k = get_bits(bd, 16);
183 for (j = 0; j < 16; j++)
184 if (k & (1 << (15-j)))
185 symToByte[symTotal++] = (16*i) + j;
189 /* How many different Huffman coding groups does this block use? */
191 groupCount = get_bits(bd, 3);
192 if (groupCount < 2 || groupCount > MAX_GROUPS)
193 return RETVAL_DATA_ERROR;
195 /* nSelectors: Every GROUP_SIZE many symbols we select a new Huffman coding
196 group. Read in the group selector list, which is stored as MTF encoded
197 bit runs. (MTF=Move To Front, as each value is used it's moved to the
198 start of the list.) */
200 nSelectors = get_bits(bd, 15);
201 if (!nSelectors) return RETVAL_DATA_ERROR;
202 for (i = 0; i < groupCount; i++) mtfSymbol[i] = i;
203 for (i = 0; i < nSelectors; i++) {
207 for (j = 0; get_bits(bd, 1); j++)
208 if (j>=groupCount) return RETVAL_DATA_ERROR;
210 /* Decode MTF to get the next selector */
213 for (;j;j--) mtfSymbol[j] = mtfSymbol[j-1];
214 mtfSymbol[0] = selectors[i] = uc;
217 /* Read the Huffman coding tables for each group, which code for symTotal
218 literal symbols, plus two run symbols (RUNA, RUNB) */
220 symCount = symTotal + 2;
221 for (j = 0; j < groupCount; j++) {
222 unsigned char length[MAX_SYMBOLS], temp[MAX_HUFCODE_BITS+1];
223 int minLen, maxLen, pp;
225 /* Read Huffman code lengths for each symbol. They're stored in
226 a way similar to mtf; record a starting value for the first symbol,
227 and an offset from the previous value for everys symbol after that.
228 (Subtracting 1 before the loop and then adding it back at the end is
229 an optimization that makes the test inside the loop simpler: symbol
230 length 0 becomes negative, so an unsigned inequality catches it.) */
232 t = get_bits(bd, 5) - 1;
233 for (i = 0; i < symCount; i++) {
235 if ((unsigned)t > (MAX_HUFCODE_BITS-1))
236 return RETVAL_DATA_ERROR;
238 /* If first bit is 0, stop. Else second bit indicates whether
239 to increment or decrement the value. Optimization: grab 2
240 bits and unget the second if the first was 0. */
248 /* Add one if second bit 1, else subtract 1. Avoids if/else */
250 t += (((k+1) & 2) - 1);
253 /* Correct for the initial -1, to get the final symbol length */
258 /* Find largest and smallest lengths in this group */
260 minLen = maxLen = length[0];
261 for (i = 1; i < symCount; i++) {
262 if (length[i] > maxLen) maxLen = length[i];
263 else if (length[i] < minLen) minLen = length[i];
266 /* Calculate permute[], base[], and limit[] tables from length[].
268 * permute[] is the lookup table for converting Huffman coded symbols
269 * into decoded symbols. base[] is the amount to subtract from the
270 * value of a Huffman symbol of a given length when using permute[].
272 * limit[] indicates the largest numerical value a symbol with a given
273 * number of bits can have. This is how the Huffman codes can vary in
274 * length: each code with a value>limit[length] needs another bit.
277 hufGroup = bd->groups + j;
278 hufGroup->minLen = minLen;
279 hufGroup->maxLen = maxLen;
281 /* Note that minLen can't be smaller than 1, so we adjust the base
282 and limit array pointers so we're not always wasting the first
283 entry. We do this again when using them (during symbol decoding).*/
285 base = hufGroup->base - 1;
286 limit = hufGroup->limit - 1;
288 /* Calculate permute[]. Concurently, initialize temp[] and limit[]. */
291 for (i = minLen; i <= maxLen; i++) {
292 temp[i] = limit[i] = 0;
293 for (t = 0; t < symCount; t++)
295 hufGroup->permute[pp++] = t;
298 /* Count symbols coded for at each bit length */
300 for (i = 0; i < symCount; i++) temp[length[i]]++;
302 /* Calculate limit[] (the largest symbol-coding value at each bit
303 * length, which is (previous limit<<1)+symbols at this level), and
304 * base[] (number of symbols to ignore at each bit length, which is
305 * limit minus the cumulative count of symbols coded for already). */
308 for (i = minLen; i < maxLen; i++) {
311 /* We read the largest possible symbol size and then unget bits
312 after determining how many we need, and those extra bits could
313 be set to anything. (They're noise from future symbols.) At
314 each level we're really only interested in the first few bits,
315 so here we set all the trailing to-be-ignored bits to 1 so they
316 don't affect the value>limit[length] comparison. */
318 limit[i] = (pp << (maxLen - i)) - 1;
323 limit[maxLen+1] = INT_MAX; /* Sentinal value for reading next sym. */
324 limit[maxLen] = pp + temp[maxLen] - 1;
328 /* We've finished reading and digesting the block header. Now read this
329 block's Huffman coded symbols from the file and undo the Huffman coding
330 and run length encoding, saving the result into dbuf[dbufCount++]=uc */
332 /* Initialize symbol occurrence counters and symbol Move To Front table */
334 for (i = 0; i < 256; i++) {
336 mtfSymbol[i] = (unsigned char)i;
339 /* Loop through compressed symbols. */
341 runPos = dbufCount = selector = 0;
344 /* fetch next Huffman coding group from list. */
346 symCount = GROUP_SIZE - 1;
347 if (selector >= nSelectors) return RETVAL_DATA_ERROR;
348 hufGroup = bd->groups + selectors[selector++];
349 base = hufGroup->base - 1;
350 limit = hufGroup->limit - 1;
353 /* Read next Huffman-coded symbol. */
355 /* Note: It is far cheaper to read maxLen bits and back up than it is
356 to read minLen bits and then an additional bit at a time, testing
357 as we go. Because there is a trailing last block (with file CRC),
358 there is no danger of the overread causing an unexpected EOF for a
359 valid compressed file. As a further optimization, we do the read
360 inline (falling back to a call to get_bits if the buffer runs
361 dry). The following (up to got_huff_bits:) is equivalent to
362 j = get_bits(bd, hufGroup->maxLen);
365 while (bd->inbufBitCount < hufGroup->maxLen) {
366 if (bd->inbufPos == bd->inbufCount) {
367 j = get_bits(bd, hufGroup->maxLen);
370 bd->inbufBits = (bd->inbufBits << 8) | bd->inbuf[bd->inbufPos++];
371 bd->inbufBitCount += 8;
373 bd->inbufBitCount -= hufGroup->maxLen;
374 j = (bd->inbufBits >> bd->inbufBitCount) & ((1 << hufGroup->maxLen) - 1);
378 /* Figure how how many bits are in next symbol and unget extras */
380 i = hufGroup->minLen;
381 while (j > limit[i]) ++i;
382 bd->inbufBitCount += (hufGroup->maxLen - i);
384 /* Huffman decode value to get nextSym (with bounds checking) */
386 if (i > hufGroup->maxLen)
387 return RETVAL_DATA_ERROR;
388 j = (j >> (hufGroup->maxLen - i)) - base[i];
389 if ((unsigned)j >= MAX_SYMBOLS)
390 return RETVAL_DATA_ERROR;
391 nextSym = hufGroup->permute[j];
393 /* We have now decoded the symbol, which indicates either a new literal
394 byte, or a repeated run of the most recent literal byte. First,
395 check if nextSym indicates a repeated run, and if so loop collecting
396 how many times to repeat the last literal. */
398 if ((unsigned)nextSym <= SYMBOL_RUNB) { /* RUNA or RUNB */
400 /* If this is the start of a new run, zero out counter */
407 /* Neat trick that saves 1 symbol: instead of or-ing 0 or 1 at
408 each bit position, add 1 or 2 instead. For example,
409 1011 is 1<<0 + 1<<1 + 2<<2. 1010 is 2<<0 + 2<<1 + 1<<2.
410 You can make any bit pattern that way using 1 less symbol than
411 the basic or 0/1 method (except all bits 0, which would use no
412 symbols, but a run of length 0 doesn't mean anything in this
413 context). Thus space is saved. */
415 t += (runPos << nextSym); /* +runPos if RUNA; +2*runPos if RUNB */
416 if (runPos < dbufSize) runPos <<= 1;
417 goto end_of_huffman_loop;
420 /* When we hit the first non-run symbol after a run, we now know
421 how many times to repeat the last literal, so append that many
422 copies to our buffer of decoded symbols (dbuf) now. (The last
423 literal used is the one at the head of the mtfSymbol array.) */
427 if (dbufCount + t >= dbufSize) return RETVAL_DATA_ERROR;
429 uc = symToByte[mtfSymbol[0]];
431 while (t--) dbuf[dbufCount++] = uc;
434 /* Is this the terminating symbol? */
436 if (nextSym > symTotal) break;
438 /* At this point, nextSym indicates a new literal character. Subtract
439 one to get the position in the MTF array at which this literal is
440 currently to be found. (Note that the result can't be -1 or 0,
441 because 0 and 1 are RUNA and RUNB. But another instance of the
442 first symbol in the mtf array, position 0, would have been handled
443 as part of a run above. Therefore 1 unused mtf position minus
444 2 non-literal nextSym values equals -1.) */
446 if (dbufCount >= dbufSize) return RETVAL_DATA_ERROR;
450 /* Adjust the MTF array. Since we typically expect to move only a
451 * small number of symbols, and are bound by 256 in any case, using
452 * memmove here would typically be bigger and slower due to function
453 * call overhead and other assorted setup costs. */
456 mtfSymbol[i] = mtfSymbol[i-1];
461 /* We have our literal byte. Save it into dbuf. */
464 dbuf[dbufCount++] = (unsigned)uc;
466 /* Skip group initialization if we're not done with this group. Done
467 * this way to avoid compiler warning. */
470 if (symCount--) goto continue_this_group;
473 /* At this point, we've read all the Huffman-coded symbols (and repeated
474 runs) for this block from the input stream, and decoded them into the
475 intermediate buffer. There are dbufCount many decoded bytes in dbuf[].
476 Now undo the Burrows-Wheeler transform on dbuf.
477 See http://dogma.net/markn/articles/bwt/bwt.htm
480 /* Turn byteCount into cumulative occurrence counts of 0 to n-1. */
483 for (i = 0; i < 256; i++) {
484 k = j + byteCount[i];
489 /* Figure out what order dbuf would be in if we sorted it. */
491 for (i = 0; i < dbufCount; i++) {
492 uc = (unsigned char)(dbuf[i] & 0xff);
493 dbuf[byteCount[uc]] |= (i << 8);
497 /* Decode first byte by hand to initialize "previous" byte. Note that it
498 doesn't get output, and if the first three characters are identical
499 it doesn't qualify as a run (hence writeRunCountdown=5). */
502 if (origPtr >= dbufCount) return RETVAL_DATA_ERROR;
503 bd->writePos = dbuf[origPtr];
504 bd->writeCurrent = (unsigned char)(bd->writePos & 0xff);
506 bd->writeRunCountdown = 5;
508 bd->writeCount = dbufCount;
513 /* Undo burrows-wheeler transform on intermediate buffer to produce output.
514 If start_bunzip was initialized with out_fd=-1, then up to len bytes of
515 data are written to outbuf. Return value is number of bytes written or
516 error (all errors are negative numbers). If out_fd!=-1, outbuf and len
517 are ignored, data is written to out_fd and return is RETVAL_OK or error.
520 int read_bunzip(bunzip_data *bd, char *outbuf, int len)
522 const unsigned *dbuf;
523 int pos, current, previous, gotcount;
525 /* If last read was short due to end of file, return last block now */
526 if (bd->writeCount < 0) return bd->writeCount;
531 current = bd->writeCurrent;
533 /* We will always have pending decoded data to write into the output
534 buffer unless this is the very first call (in which case we haven't
535 Huffman-decoded a block into the intermediate buffer yet). */
537 if (bd->writeCopies) {
539 /* Inside the loop, writeCopies means extra copies (beyond 1) */
543 /* Loop outputting bytes */
547 /* If the output buffer is full, snapshot state and return */
549 if (gotcount >= len) {
551 bd->writeCurrent = current;
556 /* Write next byte into output buffer, updating CRC */
558 outbuf[gotcount++] = current;
559 bd->writeCRC = (bd->writeCRC << 8)
560 ^ bd->crc32Table[(bd->writeCRC >> 24) ^ current];
562 /* Loop now if we're outputting multiple copies of this byte */
564 if (bd->writeCopies) {
569 if (!bd->writeCount--) break;
570 /* Follow sequence vector to undo Burrows-Wheeler transform */
573 current = pos & 0xff;
576 /* After 3 consecutive copies of the same byte, the 4th is a repeat
577 count. We count down from 4 instead
578 * of counting up because testing for non-zero is faster */
580 if (--bd->writeRunCountdown) {
581 if (current != previous)
582 bd->writeRunCountdown = 4;
585 /* We have a repeated run, this byte indicates the count */
587 bd->writeCopies = current;
589 bd->writeRunCountdown = 5;
591 /* Sometimes there are just 3 bytes (run length 0) */
593 if (!bd->writeCopies) goto decode_next_byte;
595 /* Subtract the 1 copy we'd output anyway to get extras */
601 /* Decompression of this block completed successfully */
603 bd->writeCRC = ~bd->writeCRC;
604 bd->totalCRC = ((bd->totalCRC << 1) | (bd->totalCRC >> 31)) ^ bd->writeCRC;
606 /* If this block had a CRC error, force file level CRC error. */
608 if (bd->writeCRC != bd->headerCRC) {
609 bd->totalCRC = bd->headerCRC+1;
610 return RETVAL_LAST_BLOCK;
614 /* Refill the intermediate buffer by Huffman-decoding next block of input */
615 /* (previous is just a convenient unused temp variable here) */
617 previous = get_next_block(bd);
619 bd->writeCount = previous;
620 return (previous != RETVAL_LAST_BLOCK) ? previous : gotcount;
624 current = bd->writeCurrent;
625 goto decode_next_byte;
629 /* Allocate the structure, read file header. If in_fd==-1, inbuf must contain
630 a complete bunzip file (len bytes long). If in_fd!=-1, inbuf and len are
631 ignored, and data is read from file handle into temporary buffer. */
633 /* Because bunzip2 is used for help text unpacking, and because bb_show_usage()
634 should work for NOFORK applets too, we must be extremely careful to not leak
637 int start_bunzip(bunzip_data **bdp, int in_fd, const unsigned char *inbuf,
643 BZh0 = ('B' << 24) + ('Z' << 16) + ('h' << 8) + '0'
646 /* Figure out how much data to allocate */
648 i = sizeof(bunzip_data);
649 if (in_fd != -1) i += IOBUF_SIZE;
651 /* Allocate bunzip_data. Most fields initialize to zero. */
653 bd = *bdp = xzalloc(i);
655 /* Setup input buffer */
659 /* in this case, bd->inbuf is read-only */
660 bd->inbuf = (void*)inbuf; /* cast away const-ness */
661 bd->inbufCount = len;
663 bd->inbuf = (unsigned char *)(bd + 1);
665 /* Init the CRC32 table (big endian) */
667 crc32_filltable(bd->crc32Table, 1);
669 /* Setup for I/O error handling via longjmp */
671 i = setjmp(bd->jmpbuf);
674 /* Ensure that file starts with "BZh['1'-'9']." */
676 i = get_bits(bd, 32);
677 if ((unsigned)(i - BZh0 - 1) >= 9) return RETVAL_NOT_BZIP_DATA;
679 /* Fourth byte (ascii '1'-'9'), indicates block size in units of 100k of
680 uncompressed data. Allocate intermediate buffer for block. */
682 bd->dbufSize = 100000 * (i - BZh0);
684 /* Cannot use xmalloc - may leak bd in NOFORK case! */
685 bd->dbuf = malloc_or_warn(bd->dbufSize * sizeof(int));
693 void dealloc_bunzip(bunzip_data *bd)
700 /* Decompress src_fd to dst_fd. Stops at end of bzip data, not end of file. */
702 USE_DESKTOP(long long) int
703 unpack_bz2_stream(int src_fd, int dst_fd)
705 USE_DESKTOP(long long total_written = 0;)
710 outbuf = xmalloc(IOBUF_SIZE);
711 i = start_bunzip(&bd, src_fd, NULL, 0);
714 i = read_bunzip(bd, outbuf, IOBUF_SIZE);
716 if (i != safe_write(dst_fd, outbuf, i)) {
717 i = RETVAL_UNEXPECTED_OUTPUT_EOF;
720 USE_DESKTOP(total_written += i;)
724 /* Check CRC and release memory */
726 if (i == RETVAL_LAST_BLOCK) {
727 if (bd->headerCRC != bd->totalCRC) {
728 bb_error_msg("data integrity error when decompressing");
732 } else if (i == RETVAL_UNEXPECTED_OUTPUT_EOF) {
733 bb_error_msg("compressed file ends unexpectedly");
735 bb_error_msg("decompression failed");
740 return i ? i : USE_DESKTOP(total_written) + 0;
745 static char *const bunzip_errors[] = {
746 NULL, "Bad file checksum", "Not bzip data",
747 "Unexpected input EOF", "Unexpected output EOF", "Data error",
748 "Out of memory", "Obsolete (pre 0.9.5) bzip format not supported"
751 /* Dumb little test thing, decompress stdin to stdout */
752 int main(int argc, char **argv)
754 int i = unpack_bz2_stream(0, 1);
758 fprintf(stderr,"%s\n", bunzip_errors[-i]);
759 else if (read(0, &c, 1))
760 fprintf(stderr,"Trailing garbage ignored\n");