/* Capture output from a subprocess.

   Copyright (C) 2017-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public

   License as published by the Free Software Foundation; either

   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library; if not, see

   <http://www.gnu.org/licenses/>.  */

#include <support/capture_subprocess.h>

#include <errno.h>

#include <stdlib.h>

#include <support/check.h>

#include <support/xunistd.h>

#include <support/xsocket.h>

static void

transfer (const char *what, struct pollfd *pfd, struct xmemstream *stream)

{

  if (pfd->revents != 0)

    {

      char buf[1024];

      ssize_t ret = TEMP_FAILURE_RETRY (read (pfd->fd, buf, sizeof (buf)));

      if (ret < 0)

        {

          support_record_failure ();

          printf ("error: reading from subprocess %s: %m", what);

          pfd->events = 0;

          pfd->revents = 0;

        }

      else if (ret == 0)

        {

          /* EOF reached.  Stop listening.  */

          pfd->events = 0;

          pfd->revents = 0;

        }

      else

        /* Store the data just read.   */

        TEST_VERIFY (fwrite (buf, ret, 1, stream->out) == 1);

    }

}

struct support_capture_subprocess

support_capture_subprocess (void (*callback) (void *), void *closure)

{

  struct support_capture_subprocess result;

  xopen_memstream (&result.out);

  xopen_memstream (&result.err);

  int stdout_pipe[2];

  xpipe (stdout_pipe);

  int stderr_pipe[2];

  xpipe (stderr_pipe);

  TEST_VERIFY (fflush (stdout) == 0);

  TEST_VERIFY (fflush (stderr) == 0);

  pid_t pid = xfork ();

  if (pid == 0)

    {

      xclose (stdout_pipe[0]);

      xclose (stderr_pipe[0]);

      xdup2 (stdout_pipe[1], STDOUT_FILENO);

      xdup2 (stderr_pipe[1], STDERR_FILENO);

      callback (closure);

      _exit (0);

    }

  xclose (stdout_pipe[1]);

  xclose (stderr_pipe[1]);

  struct pollfd fds[2] =

    {

      { .fd = stdout_pipe[0], .events = POLLIN },

      { .fd = stderr_pipe[0], .events = POLLIN },

    };

  do

    {

      xpoll (fds, 2, -1);

      transfer ("stdout", &fds[0], &result.out);

      transfer ("stderr", &fds[1], &result.err);

    }

  while (fds[0].events != 0 || fds[1].events != 0);

  xclose (stdout_pipe[0]);

  xclose (stderr_pipe[0]);

  xfclose_memstream (&result.out);

  xfclose_memstream (&result.err);

  xwaitpid (pid, &result.status, 0);

  return result;

}

void

support_capture_subprocess_free (struct support_capture_subprocess *p)

{

  free (p->out.buffer);

  free (p->err.buffer);

}