/* expand.c */
/* Copyright 1994 by Philip Gage */
#include <stdio.h>
/* Decompress data from input to output */
void expand (FILE *input, FILE *output)
{
unsigned char left[256], right[256], stack[30];
short int c, count, i, size;
/* Unpack each block until end of file */
while ((count = getc(input)) != EOF) {
/* Set left to itself as literal flag */
for (i = 0; i < 256; i++)
left[i] = i;
/* Read pair table */
for (c = 0;;) {
/* Skip range of literal bytes */
if (count > 127) {
c += count - 127;
count = 0;
}
if (c == 256) break;
/* Read pairs, skip right if literal */
for (i = 0; i <= count; i++, c++) {
left[c] = getc(input);
if (c != left[c])
right[c] = getc(input);
}
if (c == 256) break;
count = getc(input);
}
/* Calculate packed data block size */
size = 256 * getc(input) + getc(input);
/* Unpack data block */
for (i = 0;;) {
/* Pop byte from stack or read byte */
if (i)
c = stack[--i];
else {
if (!size--) break;
c = getc(input);
}
/* Output byte or push pair on stack */
if (c == left[c])
putc(c,output);
else {
stack[i++] = right[c];
stack[i++] = left[c];
}
}
}
}
void main (int argc, char *argv[])
{
FILE *infile, *outfile;
if (argc != 3)
printf("Usage: expand infile outfile\n");
else if ((infile=fopen(argv[1],"rb"))==NULL)
printf("Error opening input %s\n",argv[1]);
else if ((outfile=fopen(argv[2],"wb"))==NULL)
printf("Error opening output %s\n",argv[2]);
else {
expand(infile,outfile);
fclose(outfile);
fclose(infile);
}
}
/* End of File */