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/* nomarch 1.0 - extract old `.arc' archives.
* Copyright (C) 2001 Russell Marks. See main.c for license details.
*
* readhuff.c - read RLE+Huffman-compressed files (the CP/M `SQ' scheme).
*/
/* I was originally going to adapt some old GPL'd Huffman code,
* but it turns out the format pretty much forces an array-based
* implementation. Not that I mind that :-), it just makes it
* a bit unusual. So this is from scratch (though it wasn't too hard).
*/
#include <stdio.h>
#include <stdlib.h>
#include "readrle.h"
#include "readhuff.h"
struct huff_node_tag
{
/* data is stored as a negative `pointer' */
int kids[2];
};
#define READ_WORD(x) (x)=rawinput(),(x)|=(rawinput()<<8)
#define VALUE_CONV(x) ((x)^0xffff)
#define HUFF_EOF 256
static int bitbox,bitsleft;
static unsigned char *data_in_point,*data_in_max;
static unsigned char *data_out_point,*data_out_max;
static int rawinput(void)
{
if(data_in_point<data_in_max)
return(*data_in_point++);
return(-1);
}
static void rawoutput(int byte)
{
if(data_out_point<data_out_max)
*data_out_point++=byte;
}
static void bit_init(void)
{
bitbox=0; bitsleft=0;
}
static int bit_input(void)
{
if(bitsleft==0)
{
bitbox=rawinput();
if(bitbox==-1) return(-1);
bitsleft=8;
}
bitsleft--;
return((bitbox&(1<<(7-bitsleft)))?1:0);
}
unsigned char *convert_huff(unsigned char *data_in,
unsigned long in_len,
unsigned long orig_len)
{
unsigned char *data_out;
struct huff_node_tag *nodearr;
int nodes,f,b;
if((data_out=malloc(orig_len))==NULL)
fprintf(stderr,"nomarch: out of memory!\n"),exit(1);
data_in_point=data_in; data_in_max=data_in+in_len;
data_out_point=data_out; data_out_max=data_out+orig_len;
READ_WORD(nodes);
if(!nodes)
{
free(data_out);
return(NULL);
}
if((nodearr=malloc(sizeof(struct huff_node_tag)*nodes))==NULL)
fprintf(stderr,"nomarch: out of memory!\n"),exit(1);
/* apparently the tree can be empty (zero-length file?), so
* there's a preset entry which is required. In the context of
* .arc I'm sure this is cruft which we don't actually need,
* but just in case...
*/
nodearr[0].kids[0]=nodearr[0].kids[1]=VALUE_CONV(HUFF_EOF);
for(f=0;f<nodes;f++)
{
READ_WORD(nodearr[f].kids[0]);
READ_WORD(nodearr[f].kids[1]);
}
/* after the table, we get the codes to interpret; this is
* a bitstream, with EOF marked by the code HUFF_EOF.
*/
bit_init();
outputrle(-1,NULL);
do
{
f=0;
while((f&0x8000)==0)
{
if(f>=nodes)
{
/* must be corrupt */
free(nodearr);
free(data_out);
return(NULL);
}
/* it seems we can't rely on getting the EOF code (even though we
* do >95% of the time!), so check for `real' EOF too.
* (worth checking in case of corrupt file too, I guess.)
*/
if((b=bit_input())==-1)
{
f=VALUE_CONV(HUFF_EOF);
break;
}
f=nodearr[f].kids[b];
}
f=VALUE_CONV(f);
if(f!=HUFF_EOF)
outputrle(f,rawoutput);
}
while(f!=HUFF_EOF);
free(nodearr);
return(data_out);
}
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