1. James Taylor
  2. seek-bzip2

Commits

James Taylor  committed dfb5c1d

Major changes.

Now based on the newer (more complicated) micro-bunzip that is part of the
current version of busybox. The original code is in `micro-bunzip.orig.c`
for reference.

I modified it so that it allows external control over decompressing blocks,
rather than `read_bunzip` automatically filling the buffer, you have to do
that for it (it will return 0 bytes decoded, you then init the next block,
checking for the EOF block).

This allows for what we want to do (determining exactly where blocks are and
seeking to/decompressing a single block without waste -- the previous version
would have to suck another block from the file for each block desired).

bzip-table now uncompresses the entire block and reports the length in bytes.
Why? Because it has to, bzip2 blocks are NOT ALL THE SAME SIZE, despite
many reports on the web. Blocks are exactly bs * 100,000k AFTER run length
encoding, but before RLE they can be fairly arbitrary chunks of the input.

Everything seems to work (see make test). This is not ideal because of the
block sizes, we'll have to use a search rather than a lookup table to find
the block corresponding to a byte in the uncompressed file. But, it will
work -- and the limitations help the argument for a new file format.

  • Participants
  • Parent commits b2de099
  • Branches seek-bzip2

Comments (0)

Files changed (6)

File Makefile

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 CC = gcc
-CFLAGS = -O3
+CFLAGS = -O3 # -DTESTING
+
+PROGS=bzip-table seek-bunzip
+
+all: $(PROGS)
 
 bzip-table : bzip-table.o micro-bunzip.o
+seek-bunzip : seek-bunzip.o micro-bunzip.o
+
+test: bzip-table seek-bunzip
+	# Generate 10 megabytes of random data
+	dd if=/dev/random of=test_random.dat bs=1024k count=4
+	# Compress but keep original
+	bzip2 --force --keep test_random.dat
+	# Run bzip2recover to build a seperate bz2 file for each block
+	bzip2recover test_random.dat.bz2
+	# Build table
+	./bzip-table < test_random.dat.bz2 > test_random.dat.bz2t
+	# Grab each block using seek-bunzip and compare to recovered block
+	nl test_random.dat.bz2t | while read num pos size; \
+	do \
+		bzip2 -d -c < rec0000$${num}test_random.dat.bz2 > test_expected; \
+		./seek-bunzip $${pos} < test_random.dat.bz2 > test_actual; \
+		cmp test_expected test_actual; \
+		if [ $$? -ne 0 ]; then \
+			echo "FAILED: Blocks do not match"; \
+			exit 1; \
+		fi; \
+	done
+	@echo "SUCCESS!"
 
 clean:
-	rm -f *.o bzip-table
+	rm -f *.o $(PROGS) test* rec00*
 
 format:
 	astyle --options=astyle.opts *.c *.h

File bzip-table.c

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 #include "micro-bunzip.h"
 
+#define BUF_SIZE 8192
+
 /**
  * Read a bzip2 file from stdin and print
  * 1) The block size
 int main( int argc, char*argv[] )
 {
     bunzip_data *bd;
-    int i;
-    unsigned long position_before;
+    int status;
+    unsigned long position;
     char * c;
+    char buffer[BUF_SIZE];
+    int gotcount;
+    int totalcount;
 
     /* Attempt to open the bzip2 file, if successfull this consumes the
      * entire header and moves us to the start of the first block.
      */
-    if ( ! ( i = start_bunzip( &bd, 0, 0, 0 ) ) )
+    if ( ! ( status = start_bunzip( &bd, 0, 0, 0 ) ) )
     {
-        /* Print the block size */
-        fprintf( stdout, "Block size: %d\n", bd->dbufSize );
-
-        for ( ; ; )
-        {
-            /* Save the start of the block before reading it */
-            position_before = bd->inPosBits;
+        for( ; ; )
+        {               
+            /* Determine position */
+            position = lseek( bd->in_fd, 0, SEEK_CUR ) - bd->inbufCount + bd->inbufPos;
+            position = position * 8 - bd->inbufBitCount;
 
             /* Read one block */
-            int i = read_bunzip_data( bd );
+            status = get_next_block( bd );
+            
+            /* Reset the total size counter for each block */
+            totalcount = 0;
 
             /* Non-zero return value indicates an error, break out */
-            if ( i ) break;
+            if ( status ) break;
+            
+            /* This is really the only other thing init_block does, hrmm */
+            bd->writeCRC = 0xffffffffUL;
+            
+            /* Decompress the block and throw away, but keep track of the 
+               total size of the decompressed data */
+            for ( ; ; )
+            {
+                gotcount = read_bunzip( bd, buffer, BUF_SIZE );
+                if ( gotcount < 0 )
+                {
+                    status = gotcount;
+                    goto bzip_table_finish;
+                }
+                else if ( gotcount == 0 )
+                {
+                    break;
+                }
+                else
+                {
+                    totalcount += gotcount;
+                }
+            }
+            /* Print the position of the first bit in the block header */
+            fprintf( stdout, "%u\t%d\n", position, totalcount );
+        }
+    }
+    
+bzip_table_finish:
 
-            /* Print the position of the first bit in the block header */
-            fprintf( stdout, "Block start at: %u\n", position_before );
-        }
+    /* If we reached the last block, do a CRC check */
+    if ( status == RETVAL_LAST_BLOCK && bd->headerCRC == bd->totalCRC) 
+    {
+        status = RETVAL_OK;
     }
 
     /* Free decompression buffer and bzip_data */
     free( bd );
 
     /* Print error if required */
-    if ( i )
+    if ( status )
     {
-        fprintf( stderr, "\n%s\n", bunzip_errors[-i] );
+        fprintf( stderr, "\n%s\n", bunzip_errors[-status] );
     }
 
-    return i;
+    return status;
 }

File micro-bunzip.c

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  • Ignore whitespace
 /* vi: set sw=4 ts=4: */
-/* micro-bunzip, a small, simple bzip2 decompression implementation.
- Copyright 2003 by Rob Landley (rob@landley.net).
+/*	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.
+	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.
 
- I hereby release this code under the GNU Library General Public License
- (LGPL) version 2, available at http://www.gnu.org/copyleft/lgpl.html
+	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 Burrows-Wheeler 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
+	non-profit hospice organization (see www.hospiceacadiana.com) in the
+    name of the woman I loved, Toni W. Hagan, who passed away Feb. 12, 2003.
+
+	Manuel
+ */
+
 #include <setjmp.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
+#include <limits.h>
 
 /* 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 */
-#define MAX_SYMBOLS   258  /* 256 literals + RUNA + RUNB */
-#define SYMBOL_RUNA   0
-#define SYMBOL_RUNB   1
+#define MAX_GROUPS			6
+#define GROUP_SIZE   		50		/* 64 would have been more efficient */
+#define MAX_HUFCODE_BITS 	20		/* Longest huffman code allowed */
+#define MAX_SYMBOLS 		258		/* 256 literals + RUNA + RUNB */
+#define SYMBOL_RUNA			0
+#define SYMBOL_RUNB			1
 
 /* Status return values */
-#define RETVAL_OK      0
-#define RETVAL_LAST_BLOCK    (-1)
-#define RETVAL_NOT_BZIP_DATA   (-2)
-#define RETVAL_UNEXPECTED_INPUT_EOF  (-3)
-#define RETVAL_UNEXPECTED_OUTPUT_EOF (-4)
-#define RETVAL_DATA_ERROR    (-5)
-#define RETVAL_OUT_OF_MEMORY   (-6)
-#define RETVAL_OBSOLETE_INPUT   (-7)
+#define RETVAL_OK						0
+#define RETVAL_LAST_BLOCK				(-1)
+#define RETVAL_NOT_BZIP_DATA			(-2)
+#define RETVAL_UNEXPECTED_INPUT_EOF		(-3)
+#define RETVAL_UNEXPECTED_OUTPUT_EOF	(-4)
+#define RETVAL_DATA_ERROR				(-5)
+#define RETVAL_OUT_OF_MEMORY			(-6)
+#define RETVAL_OBSOLETE_INPUT			(-7)
+
+#define RETVAL_END_OF_BLOCK             (-8)
 
 /* 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."};
+#define IOBUF_SIZE			4096
 
 /* 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];
-    char minLen, maxLen;
+struct group_data {
+	/* We have an extra slot at the end of limit[] for a sentinal value. */
+	int limit[MAX_HUFCODE_BITS+1],base[MAX_HUFCODE_BITS],permute[MAX_SYMBOLS];
+	int minLen, maxLen;
 };
 
 /* Structure holding all the housekeeping data, including IO buffers and
    memory that persists between calls to bunzip */
-typedef struct
-{
-    /* For I/O error handling */
-    jmp_buf jmpbuf;
-    /* Input stream, input buffer, input bit buffer */
-    int in_fd, inbufCount, inbufPos;
-    unsigned char *inbuf;
-    unsigned int inbufBitCount, inbufBits;
-    /* 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) */
-    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 */
-    /* james@bx.psu.edu: Keep track of position in in_fd in bits */
-    unsigned long inPosBits;
-}
-bunzip_data;
+typedef struct {
+	/* State for interrupting output loop */
+	int writeCopies,writePos,writeRunCountdown,writeCount,writeCurrent;
+	/* I/O tracking data (file handles, buffers, positions, etc.) */
+	int in_fd,out_fd,inbufCount,inbufPos /*,outbufPos*/;
+	unsigned char *inbuf /*,*outbuf*/;
+	unsigned int inbufBitCount, inbufBits;
+	/* The CRC values stored in the block header and calculated from the data */
+	unsigned int crc32Table[256],headerCRC, totalCRC, writeCRC;
+	/* Intermediate buffer and its size (in bytes) */
+	unsigned int *dbuf, dbufSize;
+	/* 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 */
+	/* For I/O error handling */
+	jmp_buf jmpbuf;
+} 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 */
-static unsigned int get_bits( bunzip_data *bd, char bits_wanted )
+unsigned int get_bits(bunzip_data *bd, char bits_wanted)
 {
-    unsigned int bits = 0;
+	unsigned int bits=0;
 
-    /* james@bx.psu.edu: Increment position in bits */
-    bd->inPosBits += bits_wanted;
+	/* 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 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;
+	}
+	/* Calculate result */
+	bd->inbufBitCount-=bits_wanted;
+	bits|=(bd->inbufBits>>bd->inbufBitCount)&((1<<bits_wanted)-1);
 
-    /* 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;
-        }
-        /* 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;
+	return bits;
 }
 
-/* Decompress a block of text to into intermediate buffer */
+/* Unpacks the next block and sets up for the inverse burrows-wheeler step. */
 
-extern int read_bunzip_data( bunzip_data *bd )
+int get_next_block(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];
-    unsigned char uc, symToByte[256], mtfSymbol[256], *selectors;
-    unsigned int *dbuf;
+	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;
 
-    /* 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" ) )
-        return RETVAL_NOT_BZIP_DATA;
+	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 1.0.0-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);
+	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);
+	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[j-1];
+		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_BITS-1))
+					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->base-1;
+		limit=hufGroup->limit-1;
+		/* 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 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 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 to-be-ignored 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 */
 
-    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 );
-    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;
-        }
-    }
-    /* 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 */
-        uc = mtfSymbol[j];
-        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;
-    for ( j = 0; j < groupCount; j++ )
-    {
-        unsigned char length[MAX_SYMBOLS], temp[MAX_HUFCODE_BITS+1];
-        int minLen, maxLen, pp;
-        /* 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--;
-            }
-            length[i] = t;
-        }
-        /* 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.  It lets us know when to stop reading.
-         *
-         * 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->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->base - 1;
-        limit = hufGroup->limit - 1;
-        /* 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]]++;
-        /* 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;
-        for ( i = minLen; i < maxLen; 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;
-    }
-    /* 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_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. */
+		/* 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->maxLen-i))-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 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.
+			   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 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;
 
-    /* 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 */
-        i = hufGroup->minLen;
-        j = get_bits( bd, i );
-        for ( ;; )
-        {
-            if ( i > hufGroup->maxLen ) return RETVAL_DATA_ERROR;
-            if ( j <= limit[i] ) break;
-            i++;
+			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 non-literal 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[i-1];
+		} 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 huffman-coded 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 Burrows-Wheeler transform on dbuf.
+	   See http://dogma.net/markn/articles/bwt/bwt.htm
+	 */
+	/* 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;
+	}
+	/* 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;
 
-            j = ( j << 1 ) | get_bits( bd, 1 );
-        }
-        /* 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 ( nextSym == SYMBOL_RUNA || nextSym == SYMBOL_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 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.
-               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. */
-            if ( nextSym == SYMBOL_RUNA ) t += runPos;
-            else t += 2 * runPos;
-            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;
+	return RETVAL_OK;
+}
 
-            uc = symToByte[mtfSymbol[0]];
-            byteCount[uc] += t;
-            while ( t-- ) dbuf[dbufCount++] = uc;
-        }
-        /* 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;
-        i = nextSym - 1;
-        uc = mtfSymbol[i];
-        memmove( mtfSymbol + 1, mtfSymbol, 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 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
-     */
+/* Undo burrows-wheeler 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.
+*/
 
-    /* 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];
-        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]++;
-    }
-    /* blockRandomised support would go here. */
+extern int read_bunzip(bunzip_data *bd, char *outbuf, int len)
+{
+	const unsigned int *dbuf;
+	int pos,current,previous,gotcount;
 
-    /* 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;
-    }
-    bd->writeCount = dbufCount;
+	/* If last read was short due to end of file, return last block now */
+	/* if(bd->writeCount<0) return bd->writeCount; */
+	
+	/* james@bx.psu.edu: writeCount goes to -1 when the buffer is fully
+	   decoded, which results in this returning RETVAL_LAST_BLOCK, also
+	   equal to -1... Confusing, I'm returning 0 here to indicate no 
+	   bytes written into the buffer */
+    if(bd->writeCount<0) return 0;
 
+	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
+	   huffman-decoded 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(;;) {
+			/* Write next byte into output buffer, updating CRC */
+			/* If the output buffer is full, snapshot state and return */
+			if(gotcount >= len) {
+				bd->writePos=pos;
+				bd->writeCurrent=current;
+				bd->writeCopies++;
+				return len;
+			}
+			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 Burrows-Wheeler 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 non-zero 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;
+		}
+		/* james@bx.psu.edu -- rather than falling through we return here */
+        return gotcount;
+	}
+	
+    goto decode_next_byte;
+}
+
+int init_block( bunzip_data *bd )
+{
+    int status;
+    /* Refill the intermediate buffer by huffman-decoding next block of input */
+	/* (previous is just a convenient unused temp variable here) */
+	status=get_next_block(bd);
+	if(status) {
+		bd->writeCount=status;
+        return status;
+	}
+	bd->writeCRC=0xffffffffUL;
     return RETVAL_OK;
 }
 
-/* Flush output buffer to disk */
-extern void flush_bunzip_outbuf( bunzip_data *bd, int out_fd )
+/* 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. */
+extern int start_bunzip(bunzip_data **bdp, int in_fd, char *inbuf, int len)
 {
-    if ( bd->outbufPos )
-    {
-        if ( write( out_fd, bd->outbuf, bd->outbufPos ) != bd->outbufPos )
-            longjmp( bd->jmpbuf, RETVAL_UNEXPECTED_OUTPUT_EOF );
-        bd->outbufPos = 0;
-    }
-}
+	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=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=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;
 
-/* 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;
+	/* Ensure that file starts with "BZh['1'-'9']." */
+	i = get_bits(bd,32);
+	if (((unsigned int)(i-BZh0-1)) >= 9) return RETVAL_NOT_BZIP_DATA;
 
-    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;
-            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;
-            }
-            else
-            {
-                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 );
-                bd->outbuf[bd->outbufPos++] = outbyte;
-                bd->dataCRC = ( bd->dataCRC << 8 )
-                              ^ bd->crc32Table[( bd->dataCRC >> 24 ) ^ outbyte];
-            }
-            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;
-            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;
-                return gotcount;
-            }
-        }
-    }
-}
+	/* Fourth byte (ascii '1'-'9'), indicates block size in units of 100k of
+	   uncompressed data.  Allocate intermediate buffer for block. */
+	bd->dbufSize=100000*(i-BZh0);
 
-/* 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;
-
-    /* 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;
-    }
-    else
-    {
-        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-- )
-            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" */
-    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 ) ) ) )
-        return RETVAL_OUT_OF_MEMORY;
-    return RETVAL_OK;
+	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.) */
-extern char *uncompressStream( int src_fd, int dst_fd )
+extern int uncompressStream(int src_fd, int dst_fd)
 {
-    bunzip_data *bd;
-    int i;
+	char *outbuf;
+	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;
-    }
-    flush_bunzip_outbuf( bd, dst_fd );
-    if ( bd->dbuf ) free( bd->dbuf );
-    free( bd );
-    return bunzip_errors[-i];
+	if(!(outbuf=malloc(IOBUF_SIZE))) return RETVAL_OUT_OF_MEMORY;
+	if(!(i=start_bunzip(&bd,src_fd,0,0))) {
+		for(;;) {
+            if (((i=init_block(bd)) < 0)) break;
+            // fprintf( stderr, "init: %d\n", i );
+            for(;;)
+            {
+			    if((i=read_bunzip(bd,outbuf,IOBUF_SIZE)) <= 0) break;
+                // fprintf( stderr, "read: %d\n", i );
+			    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;
 }
 
-/* james@bx.psu.edu: comment out main for 'library' use */
+#ifdef MICRO_BUNZIP_MAIN
+
+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 main(int argc, char *argv[])
 {
- char *c=uncompressStream(0,1);
- fprintf(stderr,"\n%s\n", c ? c : "Completed OK");
-}*/
+	int i=uncompressStream(0,1);
+	char c;
+
+	if(i) fprintf(stderr,"%d: %s\n", i, bunzip_errors[-i]);
+    else if(read(0,&c,1)) fprintf(stderr,"Trailing garbage ignored\n");
+	return -i;
+}
+
+#endif

File micro-bunzip.h

View file
  • Ignore whitespace
 #ifndef __MICRO_BUNZIP_H__
 #define __MICRO_BUNZIP_H__
 
+/* ---- Duplicated from micro-bzip.c -------------------------------------- */
+
 #include <setjmp.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
-
-/* ---- Duplicated from micro-bzip.c -------------------------------------- */
+#include <limits.h>
 
 /* 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 */
-#define MAX_SYMBOLS   258  /* 256 literals + RUNA + RUNB */
-#define SYMBOL_RUNA   0
-#define SYMBOL_RUNB   1
+#define MAX_GROUPS			6
+#define GROUP_SIZE   		50		/* 64 would have been more efficient */
+#define MAX_HUFCODE_BITS 	20		/* Longest huffman code allowed */
+#define MAX_SYMBOLS 		258		/* 256 literals + RUNA + RUNB */
+#define SYMBOL_RUNA			0
+#define SYMBOL_RUNB			1
 
 /* Status return values */
-#define RETVAL_OK      0
-#define RETVAL_LAST_BLOCK    (-1)
-#define RETVAL_NOT_BZIP_DATA   (-2)
-#define RETVAL_UNEXPECTED_INPUT_EOF  (-3)
-#define RETVAL_UNEXPECTED_OUTPUT_EOF (-4)
-#define RETVAL_DATA_ERROR    (-5)
-#define RETVAL_OUT_OF_MEMORY   (-6)
-#define RETVAL_OBSOLETE_INPUT   (-7)
+#define RETVAL_OK						0
+#define RETVAL_LAST_BLOCK				(-1)
+#define RETVAL_NOT_BZIP_DATA			(-2)
+#define RETVAL_UNEXPECTED_INPUT_EOF		(-3)
+#define RETVAL_UNEXPECTED_OUTPUT_EOF	(-4)
+#define RETVAL_DATA_ERROR				(-5)
+#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."};
-
-extern char *bunzip_errors[];
+#define IOBUF_SIZE			4096
 
 /* 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];
-    char minLen, maxLen;
+struct group_data {
+	/* We have an extra slot at the end of limit[] for a sentinal value. */
+	int limit[MAX_HUFCODE_BITS+1],base[MAX_HUFCODE_BITS],permute[MAX_SYMBOLS];
+	int minLen, maxLen;
 };
 
 /* Structure holding all the housekeeping data, including IO buffers and
    memory that persists between calls to bunzip */
-typedef struct
-{
-    /* For I/O error handling */
-    jmp_buf jmpbuf;
-    /* Input stream, input buffer, input bit buffer */
-    int in_fd, inbufCount, inbufPos;
-    unsigned char *inbuf;
-    unsigned int inbufBitCount, inbufBits;
-    /* 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) */
-    unsigned int *dbuf, dbufSize;
-    /* State for interrupting output loop */
-    int writePos, writeRun, writeCount, writeCurrent;
+typedef struct {
+	/* State for interrupting output loop */
+	int writeCopies,writePos,writeRunCountdown,writeCount,writeCurrent;
+	/* I/O tracking data (file handles, buffers, positions, etc.) */
+	int in_fd,out_fd,inbufCount,inbufPos /*,outbufPos*/;
+	unsigned char *inbuf /*,*outbuf*/;
+	unsigned int inbufBitCount, inbufBits;
+	/* The CRC values stored in the block header and calculated from the data */
+	unsigned int crc32Table[256],headerCRC, totalCRC, writeCRC;
+	/* Intermediate buffer and its size (in bytes) */
+	unsigned int *dbuf, dbufSize;
+	/* 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 */
+	/* For I/O error handling */
+	jmp_buf jmpbuf;
+} bunzip_data;
 
-    /* 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 */
-    /* james@bx.psu.edu: Keep track of position in in_fd in bits */
-    unsigned long inPosBits;
-}
-bunzip_data;
+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."};
 
 /* ---- Forward declarations for micro-bzip.c ---------------------------- */
 
-extern int read_bunzip_data( bunzip_data *bd );
+extern int get_next_block( bunzip_data *bd );
 
 #endif

File micro-bunzip.orig.c

View file
  • Ignore whitespace
+/* 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 Burrows-Wheeler 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
+	non-profit hospice organization (see www.hospiceacadiana.com) in the
+    name of the woman I loved, Toni W. Hagan, who passed away Feb. 12, 2003.
+
+	Manuel
+ */
+
+#include <setjmp.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <limits.h>
+
+/* 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 */
+#define MAX_SYMBOLS 		258		/* 256 literals + RUNA + RUNB */
+#define SYMBOL_RUNA			0
+#define SYMBOL_RUNB			1
+
+/* Status return values */
+#define RETVAL_OK						0
+#define RETVAL_LAST_BLOCK				(-1)
+#define RETVAL_NOT_BZIP_DATA			(-2)
+#define RETVAL_UNEXPECTED_INPUT_EOF		(-3)
+#define RETVAL_UNEXPECTED_OUTPUT_EOF	(-4)
+#define RETVAL_DATA_ERROR				(-5)
+#define RETVAL_OUT_OF_MEMORY			(-6)
+#define RETVAL_OBSOLETE_INPUT			(-7)
+
+/* Other housekeeping constants */
+#define IOBUF_SIZE			4096
+
+/* This is what we know about each huffman coding group */
+struct group_data {
+	/* We have an extra slot at the end of limit[] for a sentinal value. */
+	int limit[MAX_HUFCODE_BITS+1],base[MAX_HUFCODE_BITS],permute[MAX_SYMBOLS];
+	int minLen, maxLen;
+};
+
+/* Structure holding all the housekeeping data, including IO buffers and
+   memory that persists between calls to bunzip */
+typedef struct {
+	/* State for interrupting output loop */
+	int writeCopies,writePos,writeRunCountdown,writeCount,writeCurrent;
+	/* I/O tracking data (file handles, buffers, positions, etc.) */
+	int in_fd,out_fd,inbufCount,inbufPos /*,outbufPos*/;
+	unsigned char *inbuf /*,*outbuf*/;
+	unsigned int inbufBitCount, inbufBits;
+	/* The CRC values stored in the block header and calculated from the data */
+	unsigned int crc32Table[256],headerCRC, totalCRC, writeCRC;
+	/* Intermediate buffer and its size (in bytes) */
+	unsigned int *dbuf, dbufSize;
+	/* 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 */
+	/* For I/O error handling */
+	jmp_buf jmpbuf;
+} 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 */
+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 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;
+	}
+	/* 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 burrows-wheeler 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 1.0.0-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);
+	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);
+	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[j-1];
+		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_BITS-1))
+					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->base-1;
+		limit=hufGroup->limit-1;
+		/* 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 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 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 to-be-ignored 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_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. */
+		/* 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->maxLen-i))-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 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.
+			   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 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;
+
+			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 non-literal 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[i-1];
+		} 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 huffman-coded 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 Burrows-Wheeler transform on dbuf.
+	   See http://dogma.net/markn/articles/bwt/bwt.htm
+	 */
+	/* 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;
+	}
+	/* 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 burrows-wheeler 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.
+*/
+
+extern 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
+	   huffman-decoded 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 Burrows-Wheeler 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 non-zero 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 huffman-decoding 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. */
+extern 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=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=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)(i-BZh0-1)) >= 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*(i-BZh0);
+
+	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.) */
+extern int uncompressStream(int src_fd, int dst_fd)
+{
+	char *outbuf;
+	bunzip_data *bd;
+	int i;
+
+	if(!(outbuf=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

File seek-bunzip.c

View file
  • Ignore whitespace
 
 #include "micro-bunzip.h"
 
+#define BUF_SIZE 8192
+
 /**
  * Seek the bunzip_data `bz` to a specific position in bits `pos` by lseeking
  * the underlying file descriptor and priming the buffer with appropriate
- * bits already consuming. This probably only makes sense for seeking to the
+ * bits already consumed. This probably only makes sense for seeking to the
  * start of a compressed block.
  */
-static unsigned int seek_bits( bunzip_data *bd, unsigned long pos )
+unsigned int seek_bits( bunzip_data *bd, unsigned long pos )
 {
     off_t n_byte = pos / 8;
     char n_bit = pos % 8;
 
     // Seek the underlying file descriptor
-    lseek( bd->in_fd, n_byte, SEEK_SET );
+    if ( lseek( bd->in_fd, n_byte, SEEK_SET ) != n_byte )
+    {
+        return -1;
+    }
 
     // Init the buffer at the right bit position
     bd->inbufBitCount = bd->inbufPos = bd->inbufCount = 0;
     get_bits( bd, n_bit );
 
-    // Update the bit position counter to match
-    bd->inPosBits = pos;
+    // // Update the bit position counter to match
+    // bd->inPosBits = pos;
+    
+    return pos;
 }
 
-/**
- * Attempt to uncompress exactly one block of data from the bunzip_data `bz`
- * to the output buffer `outbuf`. The bunzip_data should be primed at the
- * start of a block (see `seek_bits`), and outbuf should be large enough
- * to accomodate `bd->dbufSize` bytes (the block size of the bzip file).
- */
-int uncompress_block_to_buffer( bunzip_data *bd, char* outbuf )
+/* Open, seek to block at pos, and uncompress */
+ 
+int uncompressblock( int src_fd, unsigned long pos )
 {
-    write_bunzip_data( bd, -1, outbuf, bd->dbufSize );
+    bunzip_data *bd;
+    int status;
+    int gotcount;
+    char outbuf[BUF_SIZE];
+
+    if ( !( status = start_bunzip( &bd, src_fd, 0, 0 ) ) )
+    {        
+        seek_bits( bd, pos );
+
+        /* Fill the decode buffer for the block */
+        if ( (status = get_next_block( bd ) ) )
+            goto seek_bunzip_finish;
+        
+        /* Init the CRC for writing */
+        bd->writeCRC = 0xffffffffUL;
+        
+        /* Decompress the block and write to stdout */
+        for ( ; ; )
+        {
+            gotcount = read_bunzip( bd, outbuf, BUF_SIZE );
+            if ( gotcount < 0 )
+            {
+                status = gotcount;
+                break;
+            }
+            else if ( gotcount == 0 )
+            {
+                break;
+            }
+            else
+            {
+                write( 1, outbuf, gotcount ); 
+            }
+        }
+    }
+    
+seek_bunzip_finish:
+
+    if ( bd->dbuf ) free( bd->dbuf );
+    free( bd );
+
+    return status;
 }
+
+int main(int argc, char *argv[])
+{
+ unsigned long pos = atol( argv[1] );
+ int status = uncompressblock(0,pos);
+ if ( status )
+     fprintf(stderr,"\n%s\n", bunzip_errors[-status] );
+}