path: root/other/pamexec.c

/******************************************************************************
                               pamexec
*******************************************************************************
  Split a Netpbm format input file into multiple Netpbm format output streams
  with one image per output stream and pipe this into the specified command.

  By Bryan Henderson, Olympia WA; June 2000
  and Michael Pot, New Zealand, August 2011

  Contributed to the public domain by its authors.

******************************************************************************/

#define _DEFAULT_SOURCE 1  /* New name for SVID & BSD source defines */
#define _BSD_SOURCE 1      /* Make sure strdup() is in string.h */
#define _XOPEN_SOURCE 500  /* Make sure strdup() is in string.h */

#include <stdbool.h>
#include <string.h>
#include <stdio.h>
#include <signal.h>
#include <setjmp.h>
#include <errno.h>

#include "pm_c_util.h"
#include "shhopt.h"
#include "nstring.h"
#include "mallocvar.h"
#include "pam.h"


/* About SIGPIPE:

   Unix has a strange function where by default, if you write into a pipe when
   the reading side of the pipe has been closed, it generates a signal (of
   class SIGPIPE), but if you tell the OS to ignore signals of class SIGPIPE,
   then instead of generating that signal, the system call to write to the
   pipe just fails.

   Pamexec writes to a pipe when it feeds an image to the user's program's
   Standard Input.  Should the user's program close its end of the pipe (such
   as by exiting) before reading the whole image, that would, if we did
   nothing to deal with it, cause Pamexec to receive a SIGPIPE signal, which
   would make the OS terminate Pamexec.

   We don't want that, so we tell the OS to ignore SIGPIPE signals, so that
   instead our attempt to write to the pipe just fails and we fail with a
   meaningful error message.
*/

struct CmdlineInfo {
    /* All the information the user supplied in the command line,
       in a form easy for the program to use.
    */
    const char * command;
    const char * inputFileName;
    unsigned int debug;
    unsigned int check;
};




static void
parseCommandLine(int argc, const char ** argv,
                 struct CmdlineInfo * const cmdlineP) {
/*----------------------------------------------------------------------------
   Note that the pointers we place into *cmdlineP are sometimes to storage
   in the argv array.
-----------------------------------------------------------------------------*/
    optEntry * option_def;
    optStruct3 opt;

    unsigned int option_def_index;

    MALLOCARRAY_NOFAIL(option_def, 100);

    option_def_index = 0;   /* incremented by OPTENT3 */
    OPTENT3(0,   "debug",   OPT_FLAG,   NULL,         &cmdlineP->debug, 0);
    OPTENT3(0,   "check",   OPT_FLAG,   NULL,         &cmdlineP->check, 0);

    opt.opt_table = option_def;
    opt.short_allowed = false; /* We have no short (old-fashioned) options */
    opt.allowNegNum = false;   /* We have no parms that are negative numbers */

    pm_optParseOptions4(&argc, argv, opt, sizeof(opt), 0);
        /* Uses and sets argc, argv, and some of *cmdlineP and others. */

    if (argc-1 < 1)
        pm_error("You must specify at least one argument: the shell command "
                 "to execute");
    else {
        cmdlineP->command = argv[1];

        if (argc-1 < 2)
            cmdlineP->inputFileName = "-";
        else {
            cmdlineP->inputFileName = argv[2];

            if (argc-1 > 2)
                pm_error("Too many arguments.  There are at most two: "
                         "command and input file name");
        }
    }
}



static void
pipeOneImage(FILE * const infileP,
             FILE * const outfileP) {

    struct pam inpam;
    struct pam outpam;
    enum pm_check_code checkRetval;

    unsigned int row;
    tuple * tuplerow;

    pnm_readpaminit(infileP, &inpam, PAM_STRUCT_SIZE(tuple_type));

    pnm_checkpam(&inpam, PM_CHECK_BASIC, &checkRetval);

    outpam = inpam;
    outpam.file = outfileP;

    pnm_writepaminit(&outpam);

    tuplerow = pnm_allocpamrow(&inpam);

    {
        jmp_buf jmpbuf;
        int rc;
        rc = setjmp(jmpbuf);
        if (rc == 0) {
            pm_setjmpbuf(&jmpbuf);

            for (row = 0; row < inpam.height; ++row) {
                pnm_readpamrow(&inpam, tuplerow);
                pnm_writepamrow(&outpam, tuplerow);
            }
        } else {
            pm_setjmpbuf(NULL);
            pm_error("Failed to read image and pipe it to program's "
                     "Standard Input.  If previous messages indicate "
                     "a broken pipe error, that means the program closed "
                     "its Standard Error (possibly by exiting) before "
                     "it had read the entire image>");
        }
    }

    pnm_freepamrow(tuplerow);
}



static void
doOneImage(FILE *        const ifP,
           const char *  const command,
           bool          const check,
           const char ** const errorP) {
/*----------------------------------------------------------------------------
   Run command 'command' on the next image in stream *ifP.

   Return as *errorP a text explanation of how we failed, or NULL if we
   didn't.
-----------------------------------------------------------------------------*/
    FILE * ofP;

    ofP = popen(command, "w");

    if (ofP == NULL)
        pm_asprintf(errorP,
                    "Failed to start shell to run command '%s'.  "
                    "errno = %d (%s)",
                    command, errno, strerror(errno));
    else {
        int rc;

        pipeOneImage(ifP, ofP);

        rc = pclose(ofP);

        if (check && rc != 0)
            pm_asprintf(errorP, "Command '%s' terminated abnormally "
                        "or with nonzero exit status", command);
        else
            *errorP = NULL;
    }
}



int
main(int argc, const char *argv[]) {

    struct CmdlineInfo cmdline;

    FILE *       ifP;         /* Input file pointer */
    int          eof;         /* No more images in input */
    unsigned int imageSeq;
        /* Sequence number of current image in input file.  First = 0.
           (Useful for tracking down problems).
        */

    pm_proginit(&argc, argv);

    parseCommandLine(argc, argv, &cmdline);

    /* Make write to closed pipe fail rather than generate a signal.
       See comments at top of program.
    */
    signal(SIGPIPE, SIG_IGN);

    ifP = pm_openr(cmdline.inputFileName);

    for (eof = false, imageSeq = 0; !eof; ++imageSeq) {
        const char * error;

        doOneImage(ifP, cmdline.command, cmdline.check, &error);

        if (error) {
            pm_error("Failed on image %u: %s", imageSeq, error);
            pm_strfree(error);
        }

        pnm_nextimage(ifP, &eof);
    }
    pm_close(ifP);

    return 0;
}