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 *
  35 gz_open(FILE *compressed_file, int *pid)
  36 {
  37         int unzip_pipe[2];
  38         off_t floc;
  39         int cfile = -1;
  40
  41         gz_use_vfork = (getenv("OPKG_USE_VFORK") != NULL);
  42
  43         if (gz_use_vfork) {
  44                 /* Create a new file descriptor for the input stream
  45                  * (it *must* be associated with a file), and lseek()
  46                  * to the same position in that fd as the stream.
  47                  */
  48                 cfile = dup(fileno(compressed_file));
  49                 floc = ftello(compressed_file);
  50                 lseek(cfile, floc, SEEK_SET);
  51                 setenv("GZIP", "--quiet", 0);
  52         }
  53
  54         if (pipe(unzip_pipe)!=0) {
  55                 perror_msg("pipe");
  56                 return(NULL);
  57         }
  58
  59         /* If we don't flush, we end up with two copies of anything pending,
  60            one from the parent, one from the child */
  61         fflush(stdout);
  62         fflush(stderr);
  63
  64         if (gz_use_vfork) {
  65                 *pid = vfork();
  66         } else {
  67                 *pid = fork();
  68         }
  69
  70         if (*pid<0) {
  71                 perror_msg("fork");
  72                 return(NULL);
  73         }
  74
  75         if (*pid==0) {
  76                 /* child process */
  77                 close(unzip_pipe[0]);
  78                 if (gz_use_vfork) {
  79                         dup2(unzip_pipe[1], 1);
  80                         dup2(cfile, 0);
  81                         execlp("gunzip","gunzip",NULL);
  82                         /* If we get here, we had a failure */
  83                         _exit(EXIT_FAILURE);
  84                 } else {
  85                         unzip(compressed_file, fdopen(unzip_pipe[1], "w"));
  86                         fflush(NULL);
  87                         fclose(compressed_file);
  88                         close(unzip_pipe[1]);
  89                         _exit(EXIT_SUCCESS);
  90                 }
  91         }
  92         /* Parent process is executing here */
  93         if (gz_use_vfork) {
  94                 close(cfile);
  95         }
  96         close(unzip_pipe[1]);
  97         return(fdopen(unzip_pipe[0], "r"));
  98 }
  99
 100 int
 101 gz_close(int gunzip_pid)
 102 {
 103         int status;
 104         int ret;
 105
 106         if (gz_use_vfork) {
 107                 /* The gunzip process remains running in the background if we
 108                  * used the vfork()/exec() technique - so we have to kill it
 109                  * forcibly.  There might be a better way to do this, but that
 110                  * affect a lot of other parts of opkg, and this works fine.
 111                  */
 112                 if (kill(gunzip_pid, SIGTERM) == -1) {
 113                         perror_msg("gz_close(): unable to kill gunzip pid.");
 114                         return -1;
 115                 }
 116         }
 117
 118
 119         if (waitpid(gunzip_pid, &status, 0) == -1) {
 120                 perror_msg("waitpid");
 121                 return -1;
 122         }
 123
 124         if (gz_use_vfork) {
 125                 /* Bail out here if we used the vfork()/exec() technique. */
 126                 return 0;
 127         }
 128
 129         if (WIFSIGNALED(status)) {
 130                 error_msg("Unzip process killed by signal %d.\n",
 131                         WTERMSIG(status));
 132                 return -1;
 133         }
 134
 135         if (!WIFEXITED(status)) {
 136                 /* shouldn't happen */
 137                 error_msg("Your system is broken: got status %d from waitpid.\n",
 138                                 status);
 139                 return -1;
 140         }
 141
 142         if ((ret = WEXITSTATUS(status))) {
 143                 error_msg("Unzip process failed with return code %d.\n",
 144                                 ret);
 145                 return -1;
 146         }
 147
 148         return 0;
 149 }