libbb/gz_open.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * Utility routines.
   4  *
   5  * Copyright (C) many different people.  If you wrote this, please
   6  * acknowledge your work.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful, but
  14  * WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16  * General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
  21  * USA
  22  */
  23
  24 #include <sys/types.h>
  25 #include <sys/wait.h>
  26 #include <signal.h>
  27 #include <stdlib.h>
  28 #include <string.h>
  29 #include <unistd.h>
  30 #include "libbb.h"
  31
  32 static int gz_use_vfork;
  33
  34 FILE *gz_open(FILE * compressed_file, int *pid)
  35 {
  36         int unzip_pipe[2];
  37         off_t floc;
  38         int cfile = -1;
  39
  40         gz_use_vfork = (getenv("OPKG_USE_VFORK") != NULL);
  41
  42         if (gz_use_vfork) {
  43                 /* Create a new file descriptor for the input stream
  44                  * (it *must* be associated with a file), and lseek()
  45                  * to the same position in that fd as the stream.
  46                  */
  47                 cfile = dup(fileno(compressed_file));
  48                 floc = ftello(compressed_file);
  49                 lseek(cfile, floc, SEEK_SET);
  50                 setenv("GZIP", "--quiet", 0);
  51         }
  52
  53         if (pipe(unzip_pipe) != 0) {
  54                 perror_msg("pipe");
  55                 return (NULL);
  56         }
  57
  58         /* If we don't flush, we end up with two copies of anything pending,
  59            one from the parent, one from the child */
  60         fflush(stdout);
  61         fflush(stderr);
  62
  63         if (gz_use_vfork) {
  64                 *pid = vfork();
  65         } else {
  66                 *pid = fork();
  67         }
  68
  69         if (*pid < 0) {
  70                 perror_msg("fork");
  71                 return (NULL);
  72         }
  73
  74         if (*pid == 0) {
  75                 /* child process */
  76                 close(unzip_pipe[0]);
  77                 if (gz_use_vfork) {
  78                         dup2(unzip_pipe[1], 1);
  79                         dup2(cfile, 0);
  80                         execlp("gunzip", "gunzip", NULL);
  81                         /* If we get here, we had a failure */
  82                         _exit(EXIT_FAILURE);
  83                 } else {
  84                         unzip(compressed_file, fdopen(unzip_pipe[1], "w"));
  85                         fflush(NULL);
  86                         fclose(compressed_file);
  87                         close(unzip_pipe[1]);
  88                         _exit(EXIT_SUCCESS);
  89                 }
  90         }
  91         /* Parent process is executing here */
  92         if (gz_use_vfork) {
  93                 close(cfile);
  94         }
  95         close(unzip_pipe[1]);
  96         return (fdopen(unzip_pipe[0], "r"));
  97 }
  98
  99 int gz_close(int gunzip_pid)
 100 {
 101         int status;
 102         int ret;
 103
 104         if (gz_use_vfork) {
 105                 /* The gunzip process remains running in the background if we
 106                  * used the vfork()/exec() technique - so we have to kill it
 107                  * forcibly.  There might be a better way to do this, but that
 108                  * affect a lot of other parts of opkg, and this works fine.
 109                  */
 110                 if (kill(gunzip_pid, SIGTERM) == -1) {
 111                         perror_msg("gz_close(): unable to kill gunzip pid.");
 112                         return -1;
 113                 }
 114         }
 115
 116         if (waitpid(gunzip_pid, &status, 0) == -1) {
 117                 perror_msg("waitpid");
 118                 return -1;
 119         }
 120
 121         if (gz_use_vfork) {
 122                 /* Bail out here if we used the vfork()/exec() technique. */
 123                 return 0;
 124         }
 125
 126         if (WIFSIGNALED(status)) {
 127                 error_msg("Unzip process killed by signal %d.\n",
 128                           WTERMSIG(status));
 129                 return -1;
 130         }
 131
 132         if (!WIFEXITED(status)) {
 133                 /* shouldn't happen */
 134                 error_msg
 135                     ("Your system is broken: got status %d from waitpid.\n",
 136                      status);
 137                 return -1;
 138         }
 139
 140         if ((ret = WEXITSTATUS(status))) {
 141                 error_msg("Unzip process failed with return code %d.\n", ret);
 142                 return -1;
 143         }
 144
 145         return 0;
 146 }