diff options
| -rw-r--r-- | lib/bunzip.c | 616 |
1 files changed, 342 insertions, 274 deletions
diff --git a/lib/bunzip.c b/lib/bunzip.c index c6b61ec2..974fdf80 100644 --- a/lib/bunzip.c +++ b/lib/bunzip.c @@ -11,7 +11,7 @@ #include "toys.h" -/* Constants for huffman coding */ +// Constants for huffman coding #define MAX_GROUPS 6 #define GROUP_SIZE 50 /* 64 would have been more efficient */ #define MAX_HUFCODE_BITS 20 /* Longest huffman code allowed */ @@ -19,7 +19,10 @@ #define SYMBOL_RUNA 0 #define SYMBOL_RUNB 1 -/* Status return values */ +// Other housekeeping constants +#define IOBUF_SIZE 4096 + +// Status return values #define RETVAL_OK 0 #define RETVAL_LAST_BLOCK (-1) #define RETVAL_NOT_BZIP_DATA (-2) @@ -29,160 +32,185 @@ #define RETVAL_OUT_OF_MEMORY (-6) #define RETVAL_OBSOLETE_INPUT (-7) -/* Other housekeeping constants */ -#define IOBUF_SIZE 4096 - -char *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."}; +char *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." +}; -/* This is what we know about each huffman coding group */ +// This is what we know about each huffman coding group struct group_data { - int limit[MAX_HUFCODE_BITS],base[MAX_HUFCODE_BITS],permute[MAX_SYMBOLS]; + int limit[MAX_HUFCODE_BITS], base[MAX_HUFCODE_BITS], permute[MAX_SYMBOLS]; char minLen, maxLen; }; -/* Structure holding all the housekeeping data, including IO buffers and - memory that persists between calls to bunzip */ +// Structure holding all the housekeeping data, including IO buffers and +// memory that persists between calls to bunzip typedef struct { - /* For I/O error handling */ + + // For I/O error handling jmp_buf jmpbuf; - /* Input stream, input buffer, input bit buffer */ + + // Input stream, input buffer, input bit buffer int in_fd,inbufCount,inbufPos; unsigned char *inbuf; unsigned int inbufBitCount, inbufBits; - /* Output buffer */ + + // Output buffer char outbuf[IOBUF_SIZE]; int outbufPos; - /* The CRC values stored in the block header and calculated from the data */ - unsigned int crc32Table[256],headerCRC, dataCRC, totalCRC; - /* Intermediate buffer and its size (in bytes) */ + + // The CRC values stored in the block header and calculated from the data + unsigned int crc32Table[256], headerCRC, dataCRC, totalCRC; + + // Intermediate buffer and its size (in bytes) unsigned int *dbuf, dbufSize; - /* State for interrupting output loop */ - int writePos,writeRun,writeCount,writeCurrent; - /* These things are a bit too big to go on the stack */ - unsigned char selectors[32768]; /* nSelectors=15 bits */ - struct group_data groups[MAX_GROUPS]; /* huffman coding tables */ + // State for interrupting output loop + int writePos, writeRun, writeCount, writeCurrent; + + // These things are a bit too big to go on the stack + unsigned char selectors[32768]; // nSelectors=15 bits + struct group_data groups[MAX_GROUPS]; // huffman coding tables } bunzip_data; -/* Return the next nnn bits of input. All reads from the compressed input - are done through this function. All reads are big endian */ +// 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))) - longjmp(bd->jmpbuf,RETVAL_UNEXPECTED_INPUT_EOF); - bd->inbufPos=0; + 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))) + longjmp(bd->jmpbuf, RETVAL_UNEXPECTED_INPUT_EOF); + bd->inbufPos = 0; } - /* Avoid 32-bit 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; + + // Avoid 32-bit 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; + + // 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); + + // Calculate result + bd->inbufBitCount -= bits_wanted; + bits |= (bd->inbufBits>>bd->inbufBitCount) & ((1<<bits_wanted)-1); return bits; } -/* Decompress a block of text to into intermediate buffer */ - +// Decompress a block of text to into intermediate buffer extern int read_bunzip_data(bunzip_data *bd) { struct group_data *hufGroup; - int dbufCount,nextSym,dbufSize,origPtr,groupCount,*base,*limit,selector, - i,j,k,t,runPos,symCount,symTotal,nSelectors,byteCount[256]; + int dbufCount, nextSym, dbufSize, origPtr, 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; - /* Read in header signature (borrowing mtfSymbol for temp space). */ - for(i=0;i<6;i++) mtfSymbol[i]=get_bits(bd,8); - mtfSymbol[6]=0; - /* Read CRC (which is stored big endian). */ - bd->headerCRC=get_bits(bd,32); - /* Is this the last block (with CRC for file)? */ - if(!strcmp(mtfSymbol,"\x17\x72\x45\x38\x50\x90")) + // Read in header signature (borrowing mtfSymbol for temp space). + for (i=0; i<6; i++) mtfSymbol[i] = get_bits(bd,8); + mtfSymbol[6] = 0; + + // Read CRC (which is stored big endian). + bd->headerCRC = get_bits(bd,32); + + // Is this the last block (with CRC for file)? + if (!strcmp(mtfSymbol, "\x17\x72\x45\x38\x50\x90")) return RETVAL_LAST_BLOCK; - /* If it's not a valid data block, barf. */ - if(strcmp(mtfSymbol,"\x31\x41\x59\x26\x53\x59")) + + // If it's not a valid data block, barf. + if (strcmp(mtfSymbol, "\x31\x41\x59\x26\x53\x59")) return RETVAL_NOT_BZIP_DATA; - dbuf=bd->dbuf; - dbufSize=bd->dbufSize; - selectors=bd->selectors; - /* We can add support for blockRandomised if anybody complains. There was - some code for this in busybox 1.0.0-pre3, 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); + dbuf = bd->dbuf; + dbufSize = bd->dbufSize; + selectors = bd->selectors; + + // We can add support for blockRandomised if anybody complains. + 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); memset(symToByte,0,256); - symTotal=0; - for (i=0;i<16;i++) { - if(t&(1<<(15-i))) { - k=get_bits(bd,16); - for(j=0;j<16;j++) - if(k&(1<<(15-j))) symToByte[symTotal++]=(16*i)+j; + symTotal = 0; + for (i=0; i<16; i++) { + if (t&(1<<(15-i))) { + k = get_bits(bd,16); + for (j=0;j<16;j++) + if (k&(1<<(15-j))) symToByte[symTotal++] = (16*i)+j; } } - /* How many different huffman coding groups does this block use? */ - groupCount=get_bits(bd,3); + + // 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. */ - 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 */ + + // 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. + 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]; - memmove(mtfSymbol+1,mtfSymbol,j); - mtfSymbol[0]=selectors[i]=uc; + memmove(mtfSymbol+1, mtfSymbol, j); + 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; + // 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]; + unsigned char length[MAX_SYMBOLS], temp[MAX_HUFCODE_BITS+1]; int minLen, maxLen, pp; - /* Read lengths */ - t=get_bits(bd, 5); + + // Read lengths + t = get_bits(bd, 5); for (i = 0; i < symCount; i++) { for(;;) { if (t < 1 || t > MAX_HUFCODE_BITS) return RETVAL_DATA_ERROR; - if(!get_bits(bd, 1)) break; - if(!get_bits(bd, 1)) t++; - else t--; + if(!get_bits(bd, 1)) break; + if(!get_bits(bd, 1)) t++; + else t--; } length[i] = t; } - /* Find largest and smallest lengths in this group */ - minLen=maxLen=length[0]; - for(i = 1; i < symCount; i++) { + + // 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 @@ -192,79 +220,91 @@ extern int read_bunzip_data(bunzip_data *bd) * limit[] indicates the largest numerical value a symbol with a given * number of bits can have. It lets us know when to stop reading. * - * To use these, keep reading bits until value<=limit[bitcount] or + * To use these, keep reading bits until value <= limit[bitcount] or * you've read over 20 bits (error). Then the decoded symbol * equals permute[hufcode_value-base[hufcode_bitcount]]. */ - hufGroup=bd->groups+j; + 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).*/ + + // 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->base-1; limit=hufGroup->limit-1; - /* Calculate permute[] */ + + // Calculate permute[] pp = 0; - for(i=minLen;i<=maxLen;i++) - for(t=0;t<symCount;t++) - if(length[t]==i) hufGroup->permute[pp++] = t; - /* Count cumulative symbols coded for at each bit length */ - for (i=minLen;i<=maxLen;i++) temp[i]=limit[i]=0; - for (i=0;i<symCount;i++) temp[length[i]]++; + for (i=minLen; i<=maxLen; i++) + for (t=0;t<symCount;t++) + if (length[t]==i) hufGroup->permute[pp++] = t; + + // Count cumulative symbols coded for at each bit length + for (i=minLen; i<=maxLen; i++) temp[i] = limit[i] = 0; + for (i=0; i<symCount; i++) temp[length[i]]++; + /* Calculate limit[] (the largest symbol-coding 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-cumulative count of symbols coded for already). */ - pp=t=0; + pp = t = 0; for (i=minLen; i<maxLen; i++) { - pp+=temp[i]; - limit[i]=pp-1; - pp<<=1; - base[i+1]=pp-(t+=temp[i]); + pp += temp[i]; + limit[i] = pp-1; + pp <<= 1; + base[i+1] = pp-(t+=temp[i]); } - limit[maxLen]=pp+temp[maxLen]-1; - base[minLen]=0; + 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 mtf table */ - memset(byteCount,0,256*sizeof(int)); - for(i=0;i<256;i++) 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_SIZE-1; - if(selector>=nSelectors) return RETVAL_DATA_ERROR; - hufGroup=bd->groups+selectors[selector++]; - base=hufGroup->base-1; - limit=hufGroup->limit-1; + + // 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 mtf table + memset(byteCount, 0, 256*sizeof(int)); + for(i=0; i<256; i++) 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_SIZE-1; + if (selector >= nSelectors) return RETVAL_DATA_ERROR; + hufGroup = bd->groups+selectors[selector++]; + base = hufGroup->base-1; + limit = hufGroup->limit-1; } - /* Read next huffman-coded symbol */ + + // Read next huffman-coded symbol i = hufGroup->minLen; - j=get_bits(bd, i); - for(;;) { + j = get_bits(bd, i); + for (;;) { if (i > hufGroup->maxLen) return RETVAL_DATA_ERROR; if (j <= limit[i]) break; i++; j = (j << 1) | get_bits(bd,1); } - /* Huffman decode nextSym (with bounds checking) */ + + // Huffman decode nextSym (with bounds checking) j-=base[i]; if (j < 0 || j >= MAX_SYMBOLS) return RETVAL_DATA_ERROR; nextSym = hufGroup->permute[j]; - /* If this is a repeated run, loop collecting data */ + + // If this is a repeated run, loop collecting data if (nextSym == SYMBOL_RUNA || nextSym == SYMBOL_RUNB) { - /* If this is the start of a new run, zero out counter */ + + // 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 or-ing 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. @@ -277,226 +317,254 @@ extern int read_bunzip_data(bunzip_data *bd) runPos <<= 1; continue; } + /* When we hit the first non-run 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; + if (runPos) { + runPos = 0; + if (dbufCount+t >= dbufSize) return RETVAL_DATA_ERROR; uc = symToByte[mtfSymbol[0]]; byteCount[uc] += t; - while(t--) dbuf[dbufCount++]=uc; + while (t--) dbuf[dbufCount++] = uc; } - /* Is this the terminating symbol? */ - if(nextSym>symTotal) break; + + // Is this the terminating symbol? + if (nextSym>symTotal) break; + /* At this point, the symbol we just decoded 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. Another instance of the first symbol in the mtf array, position 0, would have been handled as part of a run.) */ - if(dbufCount>=dbufSize) return RETVAL_DATA_ERROR; + if (dbufCount>=dbufSize) return RETVAL_DATA_ERROR; i = nextSym - 1; uc = mtfSymbol[i]; - memmove(mtfSymbol+1,mtfSymbol,i); + memmove(mtfSymbol+1, mtfSymbol, i); mtfSymbol[0] = uc; - uc=symToByte[uc]; - /* We have our literal byte. Save it into dbuf. */ + uc = symToByte[uc]; + + // We have our literal byte. Save it into dbuf. byteCount[uc]++; dbuf[dbufCount++] = (unsigned int)uc; } + /* At this point, we've finished reading huffman-coded symbols and compressed runs from the input stream. There are dbufCount many of them in dbuf[]. Now undo the Burrows-Wheeler transform on dbuf. - See http://dogma.net/markn/articles/bwt/bwt.htm + See http://marknelson.us/1996/09/01/bwt/ */ - /* Now we know what dbufCount is, do a better sanity check on origPtr. */ + // Now we know what dbufCount is, do a better sanity check on origPtr. if (origPtr<0 || origPtr>=dbufCount) return RETVAL_DATA_ERROR; - /* Turn byteCount into cumulative occurrence counts of 0 to n-1. */ - j=0; - for(i=0;i<256;i++) { - k=j+byteCount[i]; + + // Turn byteCount into cumulative occurrence counts of 0 to n-1. + j = 0; + for (i=0;i<256;i++) { + k = j+byteCount[i]; byteCount[i] = j; - j=k; + j = k; } - /* Figure out what order dbuf would be in if we sorted it. */ - for (i=0;i<dbufCount;i++) { + + // 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]++; } - /* blockRandomised support would go here. */ - /* Using i as position, j as previous character, t as current character, - and uc as run count */ + // blockRandomised support would go here. + + // Using i as position, j as previous character, t as current character, + // and uc as run count. bd->dataCRC = 0xffffffffL; + /* 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 uc=255, which will either wrap to 1 or get reset). */ - if(dbufCount) { - bd->writePos=dbuf[origPtr]; - bd->writeCurrent=(unsigned char)(bd->writePos&0xff); - bd->writePos>>=8; - bd->writeRun=-1; + if (dbufCount) { + bd->writePos = dbuf[origPtr]; + bd->writeCurrent = (unsigned char)(bd->writePos&0xff); + bd->writePos >>= 8; + bd->writeRun = -1; } - bd->writeCount=dbufCount; + bd->writeCount = dbufCount; return RETVAL_OK; } -/* Flush output buffer to disk */ +// Flush output buffer to disk extern void flush_bunzip_outbuf(bunzip_data *bd, int out_fd) { - if(bd->outbufPos) { - if(write(out_fd, bd->outbuf, bd->outbufPos) != bd->outbufPos) + if (bd->outbufPos) { + if (write(out_fd, bd->outbuf, bd->outbufPos) != bd->outbufPos) longjmp(bd->jmpbuf,RETVAL_UNEXPECTED_OUTPUT_EOF); - bd->outbufPos=0; + bd->outbufPos = 0; } } - -/* Undo burrows-wheeler transform on intermediate buffer to produce output. - If !len, write up to len bytes of data to buf. Otherwise write to out_fd. - Returns len ? bytes written : RETVAL_OK. Notice all errors negative #'s. */ +// Undo burrows-wheeler transform on intermediate buffer to produce output. +// If !len, write up to len bytes of data to buf. Otherwise write to out_fd. +// Returns len ? bytes written : RETVAL_OK. Notice all errors negative #'s. extern int write_bunzip_data(bunzip_data *bd, int out_fd, char *outbuf, int len) { - unsigned int *dbuf=bd->dbuf; - int count,pos,current, run,copies,outbyte,previous,gotcount=0; - - for(;;) { - /* If last read was short due to end of file, return last block now */ - if(bd->writeCount<0) return bd->writeCount; - /* If we need to refill dbuf, do it. */ - if(!bd->writeCount) { - int i=read_bunzip_data(bd); - if(i) { - if(i==RETVAL_LAST_BLOCK) { - bd->writeCount=i; + unsigned int *dbuf = bd->dbuf; + int count, pos, current, run, copies, outbyte, previous, gotcount = 0; + + for (;;) { + + // If last read was short due to end of file, return last block now + if (bd->writeCount < 0) return bd->writeCount; + + // If we need to refill dbuf, do it. + if (!bd->writeCount) { + int i = read_bunzip_data(bd); + if (i) { + if (i == RETVAL_LAST_BLOCK) { + bd->writeCount = i; return gotcount; } else return i; } } - /* Loop generating output */ - count=bd->writeCount; - pos=bd->writePos; - current=bd->writeCurrent; - run=bd->writeRun; - while(count) { - /* If somebody (like busybox tar) wants a certain number of bytes of - data from memory instead of written to a file, humor them */ - if(len && bd->outbufPos>=len) goto dataus_interruptus; + + // Loop generating output + count = bd->writeCount; + pos = bd->writePos; + current = bd->writeCurrent; + run = bd->writeRun; + while (count) { + + // If somebody (like tar) wants a certain number of bytes of + // data from memory instead of written to a file, humor them. + if (len && bd->outbufPos>=len) goto dataus_interruptus; count--; - /* Follow sequence vector to undo Burrows-Wheeler transform */ - previous=current; - pos=dbuf[pos]; - current=pos&0xff; - pos>>=8; - /* Whenever we see 3 consecutive copies of the same byte, - the 4th is a repeat count */ - if(run++==3) { - copies=current; - outbyte=previous; - current=-1; + + // Follow sequence vector to undo Burrows-Wheeler transform. + previous = current; + pos = dbuf[pos]; + current = pos&0xff; + pos >>= 8; + + // Whenever we see 3 consecutive copies of the same byte, + // the 4th is a repeat count + if (run++ == 3) { + copies = current; + outbyte = previous; + current = -1; } else { - copies=1; - outbyte=current; + copies = 1; + outbyte = current; } - /* Output bytes to buffer, flushing to file if necessary */ - while(copies--) { - if(bd->outbufPos == IOBUF_SIZE) flush_bunzip_outbuf(bd,out_fd); + + // Output bytes to buffer, flushing to file if necessary + while (copies--) { + if (bd->outbufPos == IOBUF_SIZE) flush_bunzip_outbuf(bd,out_fd); bd->outbuf[bd->outbufPos++] = outbyte; bd->dataCRC = (bd->dataCRC << 8) ^ bd->crc32Table[(bd->dataCRC >> 24) ^ outbyte]; } - if(current!=previous) run=0; + if (current!=previous) run=0; } - /* Decompression of this block completed successfully */ - bd->dataCRC=~(bd->dataCRC); - bd->totalCRC=((bd->totalCRC << 1) | (bd->totalCRC >> 31)) ^ bd->dataCRC; - /* If this block had a CRC error, force file level CRC error. */ - if(bd->dataCRC!=bd->headerCRC) { - bd->totalCRC=bd->headerCRC+1; + + // Decompression of this block completed successfully + bd->dataCRC = ~(bd->dataCRC); + bd->totalCRC = ((bd->totalCRC << 1) | (bd->totalCRC >> 31)) + ^ bd->dataCRC; + + // If this block had a CRC error, force file level CRC error. + if (bd->dataCRC != bd->headerCRC) { + bd->totalCRC = bd->headerCRC+1; + return RETVAL_LAST_BLOCK; } dataus_interruptus: - bd->writeCount=count; - if(len) { - gotcount+=bd->outbufPos; - memcpy(outbuf,bd->outbuf,len); - /* If we got enough data, checkpoint loop state and return */ - if((len-=bd->outbufPos)<1) { - bd->outbufPos-=len; - if(bd->outbufPos) - memmove(bd->outbuf,bd->outbuf+len,bd->outbufPos); - bd->writePos=pos; - bd->writeCurrent=current; - bd->writeRun=run; + bd->writeCount = count; + if (len) { + gotcount += bd->outbufPos; + memcpy(outbuf, bd->outbuf, len); + + // If we got enough data, checkpoint loop state and return + if ((len-=bd->outbufPos)<1) { + bd->outbufPos -= len; + if (bd->outbufPos) + memmove(bd->outbuf, bd->outbuf+len, bd->outbufPos); + bd->writePos = pos; + bd->writeCurrent = current; + bd->writeRun = run; + return gotcount; } } } } -/* Allocate the structure, read file header. If !len, src_fd contains - filehandle to read from. Else inbuf contains data. */ +// Allocate the structure, read file header. If !len, src_fd contains +// filehandle to read from. Else inbuf contains data. extern int start_bunzip(bunzip_data **bdp, int src_fd, char *inbuf, int len) { bunzip_data *bd; - unsigned int i,j,c; + unsigned int i, j, c; - /* Figure out how much data to allocate */ - i=sizeof(bunzip_data); - if(!len) i+=IOBUF_SIZE; - /* Allocate bunzip_data. Most fields initialize to zero. */ - if(!(bd=*bdp=malloc(i))) return RETVAL_OUT_OF_MEMORY; + // Figure out how much data to allocate. + i = sizeof(bunzip_data); + if (!len) i += IOBUF_SIZE; + + // Allocate bunzip_data. Most fields initialize to zero. + if (!(bd = *bdp = malloc(i))) return RETVAL_OUT_OF_MEMORY; memset(bd,0,sizeof(bunzip_data)); - if(len) { - bd->inbuf=inbuf; - bd->inbufCount=len; - bd->in_fd=-1; + if (len) { + bd->inbuf = inbuf; + bd->inbufCount = len; + bd->in_fd = -1; } else { - bd->inbuf=(char *)(bd+1); - bd->in_fd=src_fd; + bd->inbuf = (char *)(bd+1); + bd->in_fd = src_fd; } - /* Init the CRC32 table (big endian) */ - for(i=0;i<256;i++) { - c=i<<24; - for(j=8;j;j--) + + // 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; + 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" */ - for(i=0;i<3;i++) if(get_bits(bd,8)!="BZh"[i]) return RETVAL_NOT_BZIP_DATA; - /* Next byte ascii '1'-'9', indicates block size in units of 100k of - uncompressed data. Allocate intermediate buffer for block. */ - i=get_bits(bd,8); + + // Setup for I/O error handling via longjmp. + i = setjmp(bd->jmpbuf); + if (i) return i; + + // Ensure that file starts with "BZh". + for (i=0;i<3;i++) + if (get_bits(bd,8)!="BZh"[i]) return RETVAL_NOT_BZIP_DATA; + + // Next byte ascii '1'-'9', indicates block size in units of 100k of + // uncompressed data. Allocate intermediate buffer for block. + i = get_bits(bd, 8); if (i<'1' || i>'9') return RETVAL_NOT_BZIP_DATA; - bd->dbufSize=100000*(i-'0'); - if(!(bd->dbuf=malloc(bd->dbufSize * sizeof(int)))) + bd->dbufSize = 100000*(i-'0'); + if (!(bd->dbuf = 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.) */ +// Example usage: decompress src_fd to dst_fd. (Stops at end of bzip data, +// not end of file.) extern char *uncompressStream(int src_fd, int dst_fd) { bunzip_data *bd; int i; - if(!(i=start_bunzip(&bd,src_fd,0,0))) { - i=write_bunzip_data(bd,dst_fd,0,0); - if(i==RETVAL_LAST_BLOCK && bd->headerCRC==bd->totalCRC) i=RETVAL_OK; + if (!(i = start_bunzip(&bd,src_fd,0,0))) { + i = write_bunzip_data(bd,dst_fd,0,0); + if (i==RETVAL_LAST_BLOCK && bd->headerCRC==bd->totalCRC) i = RETVAL_OK; } flush_bunzip_outbuf(bd,dst_fd); - if(bd->dbuf) free(bd->dbuf); + free(bd->dbuf); free(bd); return bunzip_errors[-i]; } |