87 lines
2.0 KiB
C
87 lines
2.0 KiB
C
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/*
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* compress routines:
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* is_compress() returns 0 if uncompressed, number of bits if compressed.
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* uncompress(old, n, newch) - uncompress old into new, return sizeof new
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* $Id: compress.c,v 1.1 1993/06/10 00:38:05 jtc Exp $
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <string.h>
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#include <sys/wait.h>
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#include "file.h"
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/* Check for compression, return nbits. Algorithm, in magic(4) format:
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* 0 string \037\235 compressed data
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* >2 byte&0x80 >0 block compressed
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* >2 byte&0x1f x %d bits
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*/
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int
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is_compress(p, b)
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const unsigned char *p;
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int *b;
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{
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if (*p != '\037' || *(/*signed*/ char*)(p+1) != '\235')
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return 0; /* not compress()ed */
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*b = *(p+2) & 0x80;
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return *(p+2) & 0x1f;
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}
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int
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uncompress(old, newch, n)
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const unsigned char *old;
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unsigned char **newch;
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int n;
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{
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int fdin[2], fdout[2];
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if (pipe(fdin) == -1 || pipe(fdout) == -1) {
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error("cannot create pipe (%s).\n", strerror(errno));
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/*NOTREACHED*/
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}
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switch (fork()) {
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case 0: /* child */
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(void) close(0);
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(void) dup(fdin[0]);
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(void) close(fdin[0]);
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(void) close(fdin[1]);
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(void) close(1);
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(void) dup(fdout[1]);
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(void) close(fdout[0]);
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(void) close(fdout[1]);
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execlp("uncompress", "uncompress", "-c", NULL);
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error("could not execute `uncompress' (%s).\n",
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strerror(errno));
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/*NOTREACHED*/
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case -1:
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error("could not fork (%s).\n", strerror(errno));
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/*NOTREACHED*/
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default: /* parent */
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(void) close(fdin[0]);
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(void) close(fdout[1]);
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if (write(fdin[1], old, n) != n) {
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error("write failed (%s).\n", strerror(errno));
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/*NOTREACHED*/
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}
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(void) close(fdin[1]);
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if ((*newch = (unsigned char *) malloc(n)) == NULL) {
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error("out of memory.\n");
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/*NOTREACHED*/
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}
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if ((n = read(fdout[0], *newch, n)) <= 0) {
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free(*newch);
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error("read failed (%s).\n", strerror(errno));
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/*NOTREACHED*/
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}
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(void) close(fdout[0]);
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(void) wait(NULL);
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return n;
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}
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}
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