+ /*
+ * Here's what we're doing to do.
+ *
+ * - Fork ourselves and start writing data to the write side of the
+ * input pipe (fdinput[1]).
+ *
+ * - Fork and exec our filter program. We set the standard input of
+ * our filter program to be the read side of our input pipe (fdinput[0]).
+ * Standard output is set to the write side of our output pipe
+ * (fdoutput[1]).
+ *
+ * - We read from the read side of the output pipe (fdoutput[0]).
+ *
+ * We're forking because that's the simplest way to prevent any deadlocks.
+ * (without doing something like switching to non-blocking I/O and using
+ * select or poll, and I'm not interested in doing that).
+ */
+
+ switch (writerpid = fork()) {
+ case 0:
+ /*
+ * Our child process - just write to the filter input (fdinput[1]).
+ * Close all other descriptors that we don't need.
+ */
+
+ close(fdinput[0]);
+ close(fdoutput[0]);
+ close(fdoutput[1]);
+
+ /*
+ * Call m_getfld() until we're no longer in the BODY state
+ */
+
+ while (state == BODY) {
+ int bufsz2 = bufsz;
+ write(fdinput[1], buf, strlen(buf));
+ state = m_getfld (&gstate, name, buf, &bufsz2, fp);
+ }
+
+ /*
+ * We should be done; time to exit.
+ */
+
+ close(fdinput[1]);
+ /*
+ * Make sure we call _exit(), otherwise we may flush out the stdio
+ * buffers that we have duplicated from the parent.
+ */
+ _exit(0);
+ case -1:
+ adios(NULL, "Unable to fork for filter writer process");
+ break;
+ }
+
+ /*
+ * Fork and exec() our filter program, after redirecting standard in
+ * and standard out appropriately.
+ */
+
+ switch (filterpid = fork()) {
+ char **args, *program;
+ struct arglist *a;
+ int i, dat[5], s, argp;
+
+ case 0:
+ /*
+ * Configure an argument array for us
+ */
+
+ args = argsplit(formatproc, &program, &argp);
+ args[argp + filter_nargs] = NULL;
+ dat[0] = 0;
+ dat[1] = 0;
+ dat[2] = 0;
+ dat[3] = BUFSIZ;
+ dat[4] = 0;
+
+ /*
+ * Pull out each argument and scan them.
+ */
+
+ for (a = arglist_head, i = argp; a != NULL; a = a->a_next, i++) {
+ args[i] = mh_xmalloc(BUFSIZ);
+ fmt_scan(a->a_fmt, args[i], BUFSIZ - 1, BUFSIZ, dat, NULL);
+ /*
+ * fmt_scan likes to put a trailing newline at the end of the
+ * format string. If we have one, get rid of it.
+ */
+ s = strlen(args[i]);
+ if (args[i][s - 1] == '\n')
+ args[i][s - 1] = '\0';
+
+ if (mhldebug)
+ fprintf(stderr, "filterarg: fmt=\"%s\", output=\"%s\"\n",
+ a->a_nfs, args[i]);
+ }
+
+ if (dup2(fdinput[0], STDIN_FILENO) < 0) {
+ adios("formatproc", "Unable to dup2() standard input");
+ }
+ if (dup2(fdoutput[1], STDOUT_FILENO) < 0) {
+ adios("formatproc", "Unable to dup2() standard output");
+ }
+
+ /*
+ * Close everything (especially the old input and output
+ * descriptors, since they've been dup'd to stdin and stdout),
+ * and exec the formatproc.
+ */
+
+ close(fdinput[0]);
+ close(fdinput[1]);
+ close(fdoutput[0]);
+ close(fdoutput[1]);
+
+ execvp(formatproc, args);
+
+ adios(formatproc, "Unable to execute filter");
+
+ break;
+
+ case -1:
+ adios(NULL, "Unable to fork format program");
+ }
+
+ /*
+ * Close everything except our reader (fdoutput[0]);
+ */
+
+ close(fdinput[0]);
+ close(fdinput[1]);
+ close(fdoutput[1]);
+
+ /*
+ * As we read in this data, send it to putcomp
+ */
+
+ holder.c_text = buf;
+
+ while ((cc = read(fdoutput[0], buf, bufsz - 1)) > 0) {
+ buf[cc] = '\0';
+ putcomp(c1, &holder, BODYCOMP);
+ }
+
+ if (cc < 0) {
+ adios(NULL, "reading from formatproc");
+ }
+
+ /*
+ * See if we got any errors along the way. I'm a little leery of calling
+ * waitpid() without WNOHANG, but it seems to be the most correct solution.
+ */
+
+ if (waitpid(filterpid, &waitstat, 0) < 0) {
+ if (errno != ECHILD) {
+ adios("filterproc", "Unable to determine status");
+ }
+ } else {
+ if (! (WIFEXITED(waitstat) && WEXITSTATUS(waitstat) == 0)) {
+ pidstatus(waitstat, stderr, "filterproc");
+ }
+ }
+
+ if (waitpid(writerpid, &waitstat, 0) < 0) {
+ if (errno != ECHILD) {
+ adios("writer process", "Unable to determine status");
+ done(1);
+ }
+ } else {
+ if (! (WIFEXITED(waitstat) && WEXITSTATUS(waitstat) == 0)) {
+ pidstatus(waitstat, stderr, "writer process");
+ done(1);
+ }
projects / nmh / blobdiff