path: root/urt/rle_open_f.c

/*
 * rle_open_f.c - Open a file with defaults.
 *
 * Author :     Jerry Winters
 *      EECS Dept.
 *      University of Michigan
 * Date:    11/14/89
 * Copyright (c) 1990, University of Michigan
 */

#define _XOPEN_SOURCE  /* Make sure fdopen() is in stdio.h */

#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>

#include "netpbm/pm_c_util.h"
#include "netpbm/nstring.h"
#include "rle_config.h"
#include "rle.h"



#define MAX_CHILDREN 100
    /* Maximum number of children we track; any more than this remain
       zombies.
    */


#ifndef NO_OPEN_PIPES
/* Need to have a SIGCHLD signal catcher. */
#include <signal.h>
#include <sys/wait.h>
#include <errno.h>



static FILE *
my_popen(const char * const cmd,
         const char * const mode,
         int  *       const pid) {

    FILE *retfile;
    int thepid = 0;
    int pipefd[2];
    int i;

    /* Check args. */
    if ( *mode != 'r' && *mode != 'w' )
    {
        errno = EINVAL;
        return NULL;
    }

    if (pm_pipe(pipefd) < 0 )
        return NULL;

    /* Flush known files. */
    fflush(stdout);
    fflush(stderr);
    if ( (thepid = fork()) < 0 )
    {
        close(pipefd[0]);
        close(pipefd[1]);
        return NULL;
    }
    else if (thepid == 0) {
        /* In child. */
        /* Rearrange file descriptors. */
        if ( *mode == 'r' )
        {
            /* Parent reads from pipe, so reset stdout. */
            close(1);
            dup2(pipefd[1],1);
        } else {
            /* Parent writing to pipe. */
            close(0);
            dup2(pipefd[0],0);
        }
        /* Close anything above fd 2. (64 is an arbitrary magic number). */
        for ( i = 3; i < 64; i++ )
            close(i);

        /* Finally, invoke the program. */
        if ( execl("/bin/sh", "sh", "-c", cmd, NULL) < 0 )
            exit(127);
        /* NOTREACHED */
    }

    /* Close file descriptors, and gen up a FILE ptr */
    if ( *mode == 'r' )
    {
        /* Parent reads from pipe. */
        close(pipefd[1]);
        retfile = fdopen( pipefd[0], mode );
    } else {
        /* Parent writing to pipe. */
        close(pipefd[0]);
        retfile = fdopen( pipefd[1], mode );
    }

    /* Return the PID. */
    *pid = thepid;

    return retfile;
}



static void
reapChildren(int *   const catchingChildrenP,
             pid_t * const pids) {

    /* Check for dead children. */

    if (*catchingChildrenP > 0) {
        unsigned int i;

        /* Check all children to see if any are dead, reap them if so. */
        for (i = 0; i < *catchingChildrenP; ++i) {
            /* The assumption here is that if it's dead, the kill
             * will fail, but, because we haven't waited for
             * it yet, it's a zombie.
             */
            if (kill(pids[i], 0) < 0) {
                int opid = pids[i], pid = 0;
                /* Wait for processes & delete them from the list,
                 * until we get the one we know is dead.
                 * When removing one earlier in the list than
                 * the one we found, decrement our loop index.
                 */
                while (pid != opid) {
                    unsigned int j;
                    pid = wait(NULL);
                    for (j = 0;
                         j < *catchingChildrenP && pids[j] != pid;
                         ++j)
                        ;
                    if (pid < 0)
                        break;
                    if (j < *catchingChildrenP) {
                        if (i >= j)
                            --i;
                        for (++j; j < *catchingChildrenP; ++j)
                            pids[j-1] = pids[j];
                        --*catchingChildrenP;
                    }
                }
            }
        }
    }
}
#endif  /* !NO_OPEN_PIPES */



static void
dealWithSubprocess(const char *  const file_name,
                   const char *  const mode,
                   int *         const catchingChildrenP,
                   pid_t *       const pids,
                   FILE **       const fpP,
                   bool *        const noSubprocessP,
                   const char ** const errorP) {

#ifdef NO_OPEN_PIPES
    *noSubprocessP = TRUE;
#else
    const char *cp;

    reapChildren(catchingChildrenP, pids);

    /*  Real file, not stdin or stdout.  If name ends in ".Z",
     *  pipe from/to un/compress (depending on r/w mode).
     *
     *  If it starts with "|", popen that command.
     */

    cp = file_name + strlen(file_name) - 2;
    /* Pipe case. */
    if (file_name[0] == '|') {
        pid_t thepid;     /* PID from my_popen */

        *noSubprocessP = FALSE;

        *fpP = my_popen(file_name + 1, mode, &thepid);
        if (*fpP == NULL)
            *errorP = "%s: can't invoke <<%s>> for %s: ";
        else {
            /* One more child to catch, eventually. */
            if (*catchingChildrenP < MAX_CHILDREN)
                pids[(*catchingChildrenP)++] = thepid;
        }
    } else if (cp > file_name && *cp == '.' && *(cp + 1) == 'Z' ) {
        /* Compress case. */
        pid_t thepid;     /* PID from my_popen. */
        const char * command;

        *noSubprocessP = FALSE;

        if (*mode == 'w')
            pm_asprintf(&command, "compress > %s", file_name);
        else if (*mode == 'a')
            pm_asprintf(&command, "compress >> %s", file_name);
        else
            pm_asprintf(&command, "compress -d < %s", file_name);

        *fpP = my_popen(command, mode, &thepid);

        if (*fpP == NULL)
            *errorP = "%s: can't invoke 'compress' program, "
                "trying to open %s for %s";
        else {
            /* One more child to catch, eventually. */
            if (*catchingChildrenP < MAX_CHILDREN)
                pids[(*catchingChildrenP)++] = thepid;
        }
        pm_strfree(command);
    } else {
        *noSubprocessP = TRUE;
        *errorP = NULL;
    }
#endif
}



/*
 *  Purpose : Open a file for input or output as controlled by the mode
 *  parameter.  If no file name is specified (ie. file_name is null) then
 *  a pointer to stdin or stdout will be returned.  The calling routine may
 *  call this routine with a file name of "-".  For this case rle_open_f
 *  will return a pointer to stdin or stdout depending on the mode.
 *    If the user specifies a non-null file name and an I/O error occurs
 *  when trying to open the file, rle_open_f will terminate execution with
 *  an appropriate error message.
 *
 *  parameters
 *   input:
 *     prog_name:   name of the calling program.
 *     file_name :  name of the file to open
 *     mode :       either "r" for read or input file or "w" for write or
 *                  output file
 *
 *   output:
 *     a file pointer
 *
 */
FILE *
rle_open_f_noexit(const char * const prog_name,
                  const char * const file_name,
                  const char * const mode ) {

    FILE * retval;
    FILE * fp;
    const char * err_str;
    int catching_children;
    pid_t pids[MAX_CHILDREN];

    catching_children = 0;

    if (*mode == 'w' || *mode == 'a')
        fp = stdout;     /* Set the default value */
    else
        fp = stdin;

    if (file_name != NULL && !streq(file_name, "-")) {
        bool noSubprocess;
        dealWithSubprocess(file_name, mode, &catching_children, pids,
                           &fp, &noSubprocess, &err_str);

        if (!err_str) {
            if (noSubprocess) {
                /* Ordinary, boring file case. */
                /* In the original code, the code to add the "b" was
                   conditionally included only if the macro
                   STDIO_NEEDS_BINARY was defined.  But for Netpbm,
                   there is no need make a distinction; we always add
                   the "b".  -BJH 2000.07.20.
                */
                char mode_string[32];   /* Should be enough. */

                /* Concatenate a 'b' onto the mode. */
                mode_string[0] = mode[0];
                mode_string[1] = 'b';
                strcpy( mode_string + 2, mode + 1 );

                fp = fopen(file_name, mode_string);
                if (fp == NULL )
                    err_str = "%s: can't open %s for %s: ";
            }
        }
    } else
        err_str = NULL;

    if (err_str) {
        fprintf(stderr, err_str,
                prog_name, file_name,
                (*mode == 'w') ? "output" :
                (*mode == 'a') ? "append" :
                "input" );
        fprintf(stderr, "errno = %d (%s)\n", errno, strerror(errno));
        retval = NULL;
    } else
        retval = fp;

    return retval;
}



FILE *
rle_open_f(const char * prog_name, const char * file_name, const char * mode)
{
    FILE *fp;

    if ( (fp = rle_open_f_noexit( prog_name, file_name, mode )) == NULL )
        exit( -1 );

    return fp;
}