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544 lines
20 KiB
544 lines
20 KiB
3 years ago

/* vi: set sw=4 ts=4: */



/* Small bzip2 deflate implementation, by Rob Landley (rob@landley.net).






Based on bzip2 decompression code by Julian R Seward (jseward@acm.org),



which also acknowledges contributions by Mike Burrows, David Wheeler,



Peter Fenwick, Alistair Moffat, Radford Neal, Ian H. Witten,



Robert Sedgewick, and Jon L. Bentley.






This code is licensed under the LGPLv2:



LGPL (http://www.gnu.org/copyleft/lgpl.html



*/






/*



Size and speed optimizations by Manuel Novoa III (mjn3@codepoet.org).






More efficient reading of huffman codes, a streamlined read_bunzip()



function, and various other tweaks. In (limited) tests, approximately



20% faster than bzcat on x86 and about 10% faster on arm.






Note that about 2/3 of the time is spent in read_unzip() reversing



the BurrowsWheeler transformation. Much of that time is delay



resulting from cache misses.






I would ask that anyone benefiting from this work, especially those



using it in commercial products, consider making a donation to my local



nonprofit hospice organization (see www.hospiceacadiana.com) in the



name of the woman I loved, Toni W. Hagan, who passed away Feb. 12, 2003.






Manuel



*/






/* Modified by Macoy Madson:



 Give no errors with a C++ compiler (all fpermissive errors)



 Add header file



*/






#include "bunzip.h"






#include <stdio.h>



#include <stdlib.h>



#include <string.h>



#include <unistd.h>



#include <limits.h>






/* Return the next nnn bits of input. All reads from the compressed input



are done through this function. All reads are big endian */



static unsigned int get_bits(bunzip_data *bd, char bits_wanted)



{



unsigned int bits=0;






/* If we need to get more data from the byte buffer, do so. (Loop getting



one byte at a time to enforce endianness and avoid unaligned access.) */



while (bd>inbufBitCount<bits_wanted) {



/* If we need to read more data from file into byte buffer, do so */



if(bd>inbufPos==bd>inbufCount) {



if((bd>inbufCount = read(bd>in_fd, bd>inbuf, IOBUF_SIZE)) <= 0)



longjmp(bd>jmpbuf,RETVAL_UNEXPECTED_INPUT_EOF);



bd>inbufPos=0;



}



/* Avoid 32bit overflow (dump bit buffer to top of output) */



if(bd>inbufBitCount>=24) {



bits=bd>inbufBits&((1<<bd>inbufBitCount)1);



bits_wanted=bd>inbufBitCount;



bits<<=bits_wanted;



bd>inbufBitCount=0;



}



/* Grab next 8 bits of input from buffer. */



bd>inbufBits=(bd>inbufBits<<8)bd>inbuf[bd>inbufPos++];



bd>inbufBitCount+=8;



}



/* Calculate result */



bd>inbufBitCount=bits_wanted;



bits=(bd>inbufBits>>bd>inbufBitCount)&((1<<bits_wanted)1);






return bits;



}






/* Unpacks the next block and sets up for the inverse burrowswheeler step. */






static int get_next_block(bunzip_data *bd)



{



struct group_data *hufGroup;



int dbufCount,nextSym,dbufSize,groupCount,*base,*limit,selector,



i,j,k,t,runPos,symCount,symTotal,nSelectors,byteCount[256];



unsigned char uc, symToByte[256], mtfSymbol[256], *selectors;



unsigned int *dbuf,origPtr;






dbuf=bd>dbuf;



dbufSize=bd>dbufSize;



selectors=bd>selectors;



/* Reset longjmp I/O error handling */



i=setjmp(bd>jmpbuf);



if(i) return i;



/* Read in header signature and CRC, then validate signature.



(last block signature means CRC is for whole file, return now) */



i = get_bits(bd,24);



j = get_bits(bd,24);



bd>headerCRC=get_bits(bd,32);



if ((i == 0x177245) && (j == 0x385090)) return RETVAL_LAST_BLOCK;



if ((i != 0x314159)  (j != 0x265359)) return RETVAL_NOT_BZIP_DATA;



/* We can add support for blockRandomised if anybody complains. There was



some code for this in busybox 1.0.0pre3, but nobody ever noticed that



it didn't actually work. */



if(get_bits(bd,1)) return RETVAL_OBSOLETE_INPUT;



if((origPtr=get_bits(bd,24)) > dbufSize) return RETVAL_DATA_ERROR;



/* mapping table: if some byte values are never used (encoding things



like ascii text), the compression code removes the gaps to have fewer



symbols to deal with, and writes a sparse bitfield indicating which



values were present. We make a translation table to convert the symbols



back to the corresponding bytes. */



t=get_bits(bd, 16);



symTotal=0;



for (i=0;i<16;i++) {



if(t&(1<<(15i))) {



k=get_bits(bd,16);



for(j=0;j<16;j++)



if(k&(1<<(15j))) symToByte[symTotal++]=(16*i)+j;



}



}



/* How many different huffman coding groups does this block use? */



groupCount=get_bits(bd,3);



if (groupCount<2  groupCount>MAX_GROUPS) return RETVAL_DATA_ERROR;



/* nSelectors: Every GROUP_SIZE many symbols we select a new huffman coding



group. Read in the group selector list, which is stored as MTF encoded



bit runs. (MTF=Move To Front, as each value is used it's moved to the



start of the list.) */



if(!(nSelectors=get_bits(bd, 15))) return RETVAL_DATA_ERROR;



for(i=0; i<groupCount; i++) mtfSymbol[i] = i;



for(i=0; i<nSelectors; i++) {



/* Get next value */



for(j=0;get_bits(bd,1);j++) if (j>=groupCount) return RETVAL_DATA_ERROR;



/* Decode MTF to get the next selector */



uc = mtfSymbol[j];



for(;j;j) mtfSymbol[j] = mtfSymbol[j1];



mtfSymbol[0]=selectors[i]=uc;



}



/* Read the huffman coding tables for each group, which code for symTotal



literal symbols, plus two run symbols (RUNA, RUNB) */



symCount=symTotal+2;



for (j=0; j<groupCount; j++) {



unsigned char length[MAX_SYMBOLS],temp[MAX_HUFCODE_BITS+1];



int minLen, maxLen, pp;



/* Read huffman code lengths for each symbol. They're stored in



a way similar to mtf; record a starting value for the first symbol,



and an offset from the previous value for everys symbol after that.



(Subtracting 1 before the loop and then adding it back at the end is



an optimization that makes the test inside the loop simpler: symbol



length 0 becomes negative, so an unsigned inequality catches it.) */



t=get_bits(bd, 5)1;



for (i = 0; i < symCount; i++) {



for(;;) {



if (((unsigned)t) > (MAX_HUFCODE_BITS1))



return RETVAL_DATA_ERROR;



/* If first bit is 0, stop. Else second bit indicates whether



to increment or decrement the value. Optimization: grab 2



bits and unget the second if the first was 0. */



k = get_bits(bd,2);



if (k < 2) {



bd>inbufBitCount++;



break;



}



/* Add one if second bit 1, else subtract 1. Avoids if/else */



t+=(((k+1)&2)1);



}



/* Correct for the initial 1, to get the final symbol length */



length[i]=t+1;



}



/* Find largest and smallest lengths in this group */



minLen=maxLen=length[0];



for(i = 1; i < symCount; i++) {



if(length[i] > maxLen) maxLen = length[i];



else if(length[i] < minLen) minLen = length[i];



}



/* Calculate permute[], base[], and limit[] tables from length[].



*



* permute[] is the lookup table for converting huffman coded symbols



* into decoded symbols. base[] is the amount to subtract from the



* value of a huffman symbol of a given length when using permute[].



*



* limit[] indicates the largest numerical value a symbol with a given



* number of bits can have. This is how the huffman codes can vary in



* length: each code with a value>limit[length] needs another bit.



*/



hufGroup=bd>groups+j;



hufGroup>minLen = minLen;



hufGroup>maxLen = maxLen;



/* Note that minLen can't be smaller than 1, so we adjust the base



and limit array pointers so we're not always wasting the first



entry. We do this again when using them (during symbol decoding).*/



base=hufGroup>base1;



limit=hufGroup>limit1;



/* Calculate permute[]. Concurently, initialize temp[] and limit[]. */



pp=0;



for(i=minLen;i<=maxLen;i++) {



temp[i]=limit[i]=0;



for(t=0;t<symCount;t++)



if(length[t]==i) hufGroup>permute[pp++] = t;



}



/* Count symbols coded for at each bit length */



for (i=0;i<symCount;i++) temp[length[i]]++;



/* Calculate limit[] (the largest symbolcoding value at each bit



* length, which is (previous limit<<1)+symbols at this level), and



* base[] (number of symbols to ignore at each bit length, which is



* limit minus the cumulative count of symbols coded for already). */



pp=t=0;



for (i=minLen; i<maxLen; i++) {



pp+=temp[i];



/* We read the largest possible symbol size and then unget bits



after determining how many we need, and those extra bits could



be set to anything. (They're noise from future symbols.) At



each level we're really only interested in the first few bits,



so here we set all the trailing tobeignored bits to 1 so they



don't affect the value>limit[length] comparison. */



limit[i]= (pp << (maxLen  i))  1;



pp<<=1;



base[i+1]=pp(t+=temp[i]);



}



limit[maxLen+1] = INT_MAX; /* Sentinal value for reading next sym. */



limit[maxLen]=pp+temp[maxLen]1;



base[minLen]=0;



}



/* We've finished reading and digesting the block header. Now read this



block's huffman coded symbols from the file and undo the huffman coding



and run length encoding, saving the result into dbuf[dbufCount++]=uc */






/* Initialize symbol occurrence counters and symbol Move To Front table */



for(i=0;i<256;i++) {



byteCount[i] = 0;



mtfSymbol[i]=(unsigned char)i;



}



/* Loop through compressed symbols. */



runPos=dbufCount=symCount=selector=0;



for(;;) {



/* Determine which huffman coding group to use. */



if(!(symCount)) {



symCount=GROUP_SIZE1;



if(selector>=nSelectors) return RETVAL_DATA_ERROR;



hufGroup=bd>groups+selectors[selector++];



base=hufGroup>base1;



limit=hufGroup>limit1;



}



/* Read next huffmancoded symbol. */



/* Note: It is far cheaper to read maxLen bits and back up than it is



to read minLen bits and then an additional bit at a time, testing



as we go. Because there is a trailing last block (with file CRC),



there is no danger of the overread causing an unexpected EOF for a



valid compressed file. As a further optimization, we do the read



inline (falling back to a call to get_bits if the buffer runs



dry). The following (up to got_huff_bits:) is equivalent to



j=get_bits(bd,hufGroup>maxLen);



*/



while (bd>inbufBitCount<hufGroup>maxLen) {



if(bd>inbufPos==bd>inbufCount) {



j = get_bits(bd,hufGroup>maxLen);



goto got_huff_bits;



}



bd>inbufBits=(bd>inbufBits<<8)bd>inbuf[bd>inbufPos++];



bd>inbufBitCount+=8;



};



bd>inbufBitCount=hufGroup>maxLen;



j = (bd>inbufBits>>bd>inbufBitCount)&((1<<hufGroup>maxLen)1);



got_huff_bits:



/* Figure how how many bits are in next symbol and unget extras */



i=hufGroup>minLen;



while(j>limit[i]) ++i;



bd>inbufBitCount += (hufGroup>maxLen  i);



/* Huffman decode value to get nextSym (with bounds checking) */



if ((i > hufGroup>maxLen)



 (((unsigned)(j=(j>>(hufGroup>maxLeni))base[i]))



>= MAX_SYMBOLS))



return RETVAL_DATA_ERROR;



nextSym = hufGroup>permute[j];



/* We have now decoded the symbol, which indicates either a new literal



byte, or a repeated run of the most recent literal byte. First,



check if nextSym indicates a repeated run, and if so loop collecting



how many times to repeat the last literal. */



if (((unsigned)nextSym) <= SYMBOL_RUNB) { /* RUNA or RUNB */



/* If this is the start of a new run, zero out counter */



if(!runPos) {



runPos = 1;



t = 0;



}



/* Neat trick that saves 1 symbol: instead of oring 0 or 1 at



each bit position, add 1 or 2 instead. For example,



1011 is 1<<0 + 1<<1 + 2<<2. 1010 is 2<<0 + 2<<1 + 1<<2.



You can make any bit pattern that way using 1 less symbol than



the basic or 0/1 method (except all bits 0, which would use no



symbols, but a run of length 0 doesn't mean anything in this



context). Thus space is saved. */



t += (runPos << nextSym); /* +runPos if RUNA; +2*runPos if RUNB */



runPos <<= 1;



continue;



}



/* When we hit the first nonrun symbol after a run, we now know



how many times to repeat the last literal, so append that many



copies to our buffer of decoded symbols (dbuf) now. (The last



literal used is the one at the head of the mtfSymbol array.) */



if(runPos) {



runPos=0;



if(dbufCount+t>=dbufSize) return RETVAL_DATA_ERROR;






uc = symToByte[mtfSymbol[0]];



byteCount[uc] += t;



while(t) dbuf[dbufCount++]=uc;



}



/* Is this the terminating symbol? */



if(nextSym>symTotal) break;



/* At this point, nextSym indicates a new literal character. Subtract



one to get the position in the MTF array at which this literal is



currently to be found. (Note that the result can't be 1 or 0,



because 0 and 1 are RUNA and RUNB. But another instance of the



first symbol in the mtf array, position 0, would have been handled



as part of a run above. Therefore 1 unused mtf position minus



2 nonliteral nextSym values equals 1.) */



if(dbufCount>=dbufSize) return RETVAL_DATA_ERROR;



i = nextSym  1;



uc = mtfSymbol[i];



/* Adjust the MTF array. Since we typically expect to move only a



* small number of symbols, and are bound by 256 in any case, using



* memmove here would typically be bigger and slower due to function



* call overhead and other assorted setup costs. */



do {



mtfSymbol[i] = mtfSymbol[i1];



} while (i);



mtfSymbol[0] = uc;



uc=symToByte[uc];



/* We have our literal byte. Save it into dbuf. */



byteCount[uc]++;



dbuf[dbufCount++] = (unsigned int)uc;



}



/* At this point, we've read all the huffmancoded symbols (and repeated



runs) for this block from the input stream, and decoded them into the



intermediate buffer. There are dbufCount many decoded bytes in dbuf[].



Now undo the BurrowsWheeler transform on dbuf.



See http://dogma.net/markn/articles/bwt/bwt.htm



*/



/* Turn byteCount into cumulative occurrence counts of 0 to n1. */



j=0;



for(i=0;i<256;i++) {



k=j+byteCount[i];



byteCount[i] = j;



j=k;



}



/* Figure out what order dbuf would be in if we sorted it. */



for (i=0;i<dbufCount;i++) {



uc=(unsigned char)(dbuf[i] & 0xff);



dbuf[byteCount[uc]] = (i << 8);



byteCount[uc]++;



}



/* Decode first byte by hand to initialize "previous" byte. Note that it



doesn't get output, and if the first three characters are identical



it doesn't qualify as a run (hence writeRunCountdown=5). */



if(dbufCount) {



if(origPtr>=dbufCount) return RETVAL_DATA_ERROR;



bd>writePos=dbuf[origPtr];



bd>writeCurrent=(unsigned char)(bd>writePos&0xff);



bd>writePos>>=8;



bd>writeRunCountdown=5;



}



bd>writeCount=dbufCount;






return RETVAL_OK;



}






/* Undo burrowswheeler transform on intermediate buffer to produce output.



If start_bunzip was initialized with out_fd=1, then up to len bytes of



data are written to outbuf. Return value is number of bytes written or



error (all errors are negative numbers). If out_fd!=1, outbuf and len



are ignored, data is written to out_fd and return is RETVAL_OK or error.



*/






int read_bunzip(bunzip_data *bd, char *outbuf, int len)



{



const unsigned int *dbuf;



int pos,current,previous,gotcount;






/* If last read was short due to end of file, return last block now */



if(bd>writeCount<0) return bd>writeCount;






gotcount = 0;



dbuf=bd>dbuf;



pos=bd>writePos;



current=bd>writeCurrent;






/* We will always have pending decoded data to write into the output



buffer unless this is the very first call (in which case we haven't



huffmandecoded a block into the intermediate buffer yet). */






if (bd>writeCopies) {



/* Inside the loop, writeCopies means extra copies (beyond 1) */



bd>writeCopies;



/* Loop outputting bytes */



for(;;) {



/* If the output buffer is full, snapshot state and return */



if(gotcount >= len) {



bd>writePos=pos;



bd>writeCurrent=current;



bd>writeCopies++;



return len;



}



/* Write next byte into output buffer, updating CRC */



outbuf[gotcount++] = current;



bd>writeCRC=(((bd>writeCRC)<<8)



^bd>crc32Table[((bd>writeCRC)>>24)^current]);



/* Loop now if we're outputting multiple copies of this byte */



if (bd>writeCopies) {



bd>writeCopies;



continue;



}



decode_next_byte:



if (!bd>writeCount) break;



/* Follow sequence vector to undo BurrowsWheeler transform */



previous=current;



pos=dbuf[pos];



current=pos&0xff;



pos>>=8;



/* After 3 consecutive copies of the same byte, the 4th is a repeat



count. We count down from 4 instead



* of counting up because testing for nonzero is faster */



if(bd>writeRunCountdown) {



if(current!=previous) bd>writeRunCountdown=4;



} else {



/* We have a repeated run, this byte indicates the count */



bd>writeCopies=current;



current=previous;



bd>writeRunCountdown=5;



/* Sometimes there are just 3 bytes (run length 0) */



if(!bd>writeCopies) goto decode_next_byte;



/* Subtract the 1 copy we'd output anyway to get extras */



bd>writeCopies;



}



}



/* Decompression of this block completed successfully */



bd>writeCRC=~bd>writeCRC;



bd>totalCRC=((bd>totalCRC<<1)  (bd>totalCRC>>31)) ^ bd>writeCRC;



/* If this block had a CRC error, force file level CRC error. */



if(bd>writeCRC!=bd>headerCRC) {



bd>totalCRC=bd>headerCRC+1;



return RETVAL_LAST_BLOCK;



}



}






/* Refill the intermediate buffer by huffmandecoding next block of input */



/* (previous is just a convenient unused temp variable here) */



previous=get_next_block(bd);



if(previous) {



bd>writeCount=previous;



return (previous!=RETVAL_LAST_BLOCK) ? previous : gotcount;



}



bd>writeCRC=0xffffffffUL;



pos=bd>writePos;



current=bd>writeCurrent;



goto decode_next_byte;



}






/* Allocate the structure, read file header. If in_fd==1, inbuf must contain



a complete bunzip file (len bytes long). If in_fd!=1, inbuf and len are



ignored, and data is read from file handle into temporary buffer. */



int start_bunzip(bunzip_data **bdp, int in_fd, char *inbuf, int len)



{



bunzip_data *bd;



unsigned int i,j,c;



const unsigned int BZh0=(((unsigned int)'B')<<24)+(((unsigned int)'Z')<<16)



+(((unsigned int)'h')<<8)+(unsigned int)'0';






/* Figure out how much data to allocate */



i=sizeof(bunzip_data);



if(in_fd!=1) i+=IOBUF_SIZE;



/* Allocate bunzip_data. Most fields initialize to zero. */



if(!(bd=*bdp=(bunzip_data*)malloc(i))) return RETVAL_OUT_OF_MEMORY;



memset(bd,0,sizeof(bunzip_data));



/* Setup input buffer */



if(1==(bd>in_fd=in_fd)) {



bd>inbuf=(unsigned char*)inbuf;



bd>inbufCount=len;



} else bd>inbuf=(unsigned char *)(bd+1);



/* Init the CRC32 table (big endian) */



for(i=0;i<256;i++) {



c=i<<24;



for(j=8;j;j)



c=c&0x80000000 ? (c<<1)^0x04c11db7 : (c<<1);



bd>crc32Table[i]=c;



}



/* Setup for I/O error handling via longjmp */



i=setjmp(bd>jmpbuf);



if(i) return i;






/* Ensure that file starts with "BZh['1''9']." */



i = get_bits(bd,32);



if (((unsigned int)(iBZh01)) >= 9) return RETVAL_NOT_BZIP_DATA;






/* Fourth byte (ascii '1''9'), indicates block size in units of 100k of



uncompressed data. Allocate intermediate buffer for block. */



bd>dbufSize=100000*(iBZh0);






if(!(bd>dbuf=(unsigned int*)malloc(bd>dbufSize * sizeof(int))))



return RETVAL_OUT_OF_MEMORY;



return RETVAL_OK;



}






/* Example usage: decompress src_fd to dst_fd. (Stops at end of bzip data,



not end of file.) */



extern int uncompressStream(int src_fd, int dst_fd)



{



char *outbuf;



bunzip_data *bd;



int i;






if(!(outbuf=(char*)malloc(IOBUF_SIZE))) return RETVAL_OUT_OF_MEMORY;



if(!(i=start_bunzip(&bd,src_fd,0,0))) {



for(;;) {



if((i=read_bunzip(bd,outbuf,IOBUF_SIZE)) <= 0) break;



if(i!=write(dst_fd,outbuf,i)) {



i=RETVAL_UNEXPECTED_OUTPUT_EOF;



break;



}



}



}



/* Check CRC and release memory */



if(i==RETVAL_LAST_BLOCK && bd>headerCRC==bd>totalCRC) i=RETVAL_OK;



if(bd>dbuf) free(bd>dbuf);



free(bd);



free(outbuf);



return i;



}






#ifdef TESTING






static char * const bunzip_errors[]={NULL,"Bad file checksum","Not bzip data",



"Unexpected input EOF","Unexpected output EOF","Data error",



"Out of memory","Obsolete (pre 0.9.5) bzip format not supported."};






/* Dumb little test thing, decompress stdin to stdout */



int main(int argc, char *argv[])



{



int i=uncompressStream(0,1);



char c;






if(i) fprintf(stderr,"%s\n", bunzip_errors[i]);



else if(read(0,&c,1)) fprintf(stderr,"Trailing garbage ignored\n");



return i;



}



#endif
