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#include <setjmp.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#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 consumed. This probably only makes sense for seeking to the
* start of a compressed block.
*/
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
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;
return pos;
}
/* Open, seek to block at pos, and uncompress */
int uncompressblock( int src_fd, unsigned long pos )
{
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;
/* Zero this so the current byte from before the seek is not written */
bd->writeCopies = 0;
/* 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] );
}
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