videosource/bidirpipe.cpp

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/*  popen.c -  a version of the Unix popen() library function
 *      FILE *popen( char *command, char *mode )
 *              command is a regular shell command
 *              mode is "r" or "w" 
 *              returns a stream attached to the command, or NULL
 *              execls "sh" "-c" command
 *    todo: what about signal handling for child process?
 */
#include "bidirpipe.h"
#include        <signal.h>
#include        <sys/wait.h>
#include        <errno.h>
#include        <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>


#define SHELL   "/bin/sh"

bidir_pipe::bidir_pipe() {
        read=write=0;
        pid=0;
}

bool bidir_pipe::open(const char *cmdstring, const char *type)
{
        printf("Executing: %s\n", cmdstring);
        int pfd[2];
        int pfd2[2];

        if (pipe(pfd) < 0)
                return(false);  /* errno set by pipe() */

        if (*type!='r' && *type != 'w') {
                if (pipe(pfd2) < 0)
                        return(false);  /* errno set by pipe() */
        }

        if ( (pid = fork()) < 0)
                return(false);  /* errno set by fork() */

        else if (pid == 0) { /* child */
                if (*type == 'r') {
			::close(pfd[0]);
                        if (pfd[1] != STDOUT_FILENO) {
                                dup2(pfd[1], STDOUT_FILENO);
				::close(pfd[1]);
                        }
                } else if (*type == 'r') {
			::close(pfd[1]);
                        if (pfd[0] != STDIN_FILENO) {
                                dup2(pfd[0], STDIN_FILENO);
				::close(pfd[0]);
                        }
                } else {
                        if (pfd[1] != STDOUT_FILENO) {
                                dup2(pfd[1], STDOUT_FILENO);
				::close(pfd[1]);
                        }
                        if (pfd2[0] != STDIN_FILENO) {
                                dup2(pfd2[0], STDIN_FILENO);
				::close(pfd2[0]);
                        }
                }

                setpgid(0,0);
                execl(SHELL, "sh", "-c", cmdstring, (char *) 0);
                _exit(127);
        }

        /* parent */
        if (*type == 'r') {
		::close(pfd[1]);
                write=0;
                if ( (read = fdopen(pfd[0], type)) == NULL)
                        return(false);
        } else if (*type == 'w') {
		::close(pfd[0]);
                read=0;
                if ( (write = fdopen(pfd[1], type)) == NULL)
                        return(false);
        } else {
		::close(pfd[1]);
		::close(pfd2[0]);
                if ( (read = fdopen(pfd[0], "r")) == NULL)
                        return(false);
                if ( (write = fdopen(pfd2[1], "w")) == NULL) {
                        fclose(read);
                        read=0;
                        return(false);
                }
        }
        return(true);
}

int bidir_pipe::close(bool k)
{
        if (pid==0) return -1;

        if (read) fclose(read);
        read=0;
        if (write) fclose(write);
        write=0;

        if (k) {
                if (killpg(pid, SIGTERM)<0) {
                        char str[64];
                        sprintf(str,"killpg %d",pid);
                        perror(str);
                }
        } 
        int stat;
        while (waitpid(pid, &stat, 0) < 0)
                if (errno != EINTR)
                        return(-1);     /* error other than EINTR from waitpid() */
        pid=0;

        return(stat);   /* return child's termination status */
}

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