NetBSD/usr.bin/file/compress.c

91 lines
2.0 KiB
C

/*
* compress routines:
* is_compress() returns 0 if uncompressed, number of bits if compressed.
* uncompress(old, n, newch) - uncompress old into new, return sizeof new
*/
#ifndef lint
static char rcsid[] = "$Id: compress.c,v 1.2 1993/08/02 18:35:01 mycroft Exp $";
#endif /* not lint */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/wait.h>
#include "file.h"
/* Check for compression, return nbits. Algorithm, in magic(4) format:
* 0 string \037\235 compressed data
* >2 byte&0x80 >0 block compressed
* >2 byte&0x1f x %d bits
*/
int
is_compress(p, b)
const unsigned char *p;
int *b;
{
if (*p != '\037' || *(/*signed*/ char*)(p+1) != '\235')
return 0; /* not compress()ed */
*b = *(p+2) & 0x80;
return *(p+2) & 0x1f;
}
int
uncompress(old, newch, n)
const unsigned char *old;
unsigned char **newch;
int n;
{
int fdin[2], fdout[2];
if (pipe(fdin) == -1 || pipe(fdout) == -1) {
error("cannot create pipe (%s).\n", strerror(errno));
/*NOTREACHED*/
}
switch (fork()) {
case 0: /* child */
(void) close(0);
(void) dup(fdin[0]);
(void) close(fdin[0]);
(void) close(fdin[1]);
(void) close(1);
(void) dup(fdout[1]);
(void) close(fdout[0]);
(void) close(fdout[1]);
execlp("uncompress", "uncompress", "-c", NULL);
error("could not execute `uncompress' (%s).\n",
strerror(errno));
/*NOTREACHED*/
case -1:
error("could not fork (%s).\n", strerror(errno));
/*NOTREACHED*/
default: /* parent */
(void) close(fdin[0]);
(void) close(fdout[1]);
if (write(fdin[1], old, n) != n) {
error("write failed (%s).\n", strerror(errno));
/*NOTREACHED*/
}
(void) close(fdin[1]);
if ((*newch = (unsigned char *) malloc(n)) == NULL) {
error("out of memory.\n");
/*NOTREACHED*/
}
if ((n = read(fdout[0], *newch, n)) <= 0) {
free(*newch);
error("read failed (%s).\n", strerror(errno));
/*NOTREACHED*/
}
(void) close(fdout[0]);
(void) wait(NULL);
return n;
}
}