/* ==========================================================================
 * setproctitle.c - Linux/Darwin setproctitle.
 * --------------------------------------------------------------------------
 * Copyright (C) 2010  William Ahern
 * Copyright (C) 2013  Salvatore Sanfilippo
 * Copyright (C) 2013  Stam He
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to permit
 * persons to whom the Software is furnished to do so, subject to the
 * following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
 * NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
 * USE OR OTHER DEALINGS IN THE SOFTWARE.
 * ==========================================================================
 */
#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif

#include <stdarg.h> /* va_list va_start va_end */
#include <stddef.h> /* NULL size_t */
#include <stdio.h>  /* vsnprintf(3) snprintf(3) */
#include <stdlib.h> /* malloc(3) setenv(3) clearenv(3) setproctitle(3) getprogname(3) */

#include <string.h> /* strlen(3) strchr(3) strdup(3) memset(3) memcpy(3) */

#include <errno.h> /* errno program_invocation_name program_invocation_short_name */

#if !defined(HAVE_SETPROCTITLE)
#if (defined __NetBSD__ || defined __FreeBSD__ || defined __OpenBSD__)
#define HAVE_SETPROCTITLE 1
#else
#define HAVE_SETPROCTITLE 0
#endif
#endif

#if !HAVE_SETPROCTITLE
#if (defined __linux || defined __APPLE__)

extern char **environ;

static struct {
  /* original value */
  const char *arg0;

  /* title space available */
  char *base, *end;

  /* pointer to original nul character within base */
  char *nul;

  _Bool reset;
  int error;
} SPT;

#ifndef SPT_MIN
#define SPT_MIN(a, b) (((a) < (b)) ? (a) : (b))
#endif

static inline size_t spt_min(size_t a, size_t b) {
  return SPT_MIN(a, b);
} /* spt_min() */

/*
 * For discussion on the portability of the various methods, see
 * http://lists.freebsd.org/pipermail/freebsd-stable/2008-June/043136.html
 */
static int spt_clearenv(void) {
#if __GLIBC__
  clearenv();

  return 0;
#else
  extern char **environ;
  static char **tmp;

  if (!(tmp = malloc(sizeof *tmp)))
    return errno;

  tmp[0] = NULL;
  environ = tmp;

  return 0;
#endif
} /* spt_clearenv() */

static int spt_copyenv(char *oldenv[]) {
  extern char **environ;
  char *eq;
  int i, error;

  if (environ != oldenv)
    return 0;

  if ((error = spt_clearenv()))
    goto error;

  for (i = 0; oldenv[i]; i++) {
    if (!(eq = strchr(oldenv[i], '=')))
      continue;

    *eq = '\0';
    error = (0 != setenv(oldenv[i], eq + 1, 1)) ? errno : 0;
    *eq = '=';

    if (error)
      goto error;
  }

  return 0;
error:
  environ = oldenv;

  return error;
} /* spt_copyenv() */

static int spt_copyargs(int argc, char *argv[]) {
  char *tmp;
  int i;

  for (i = 1; i < argc || (i >= argc && argv[i]); i++) {
    if (!argv[i])
      continue;

    if (!(tmp = strdup(argv[i])))
      return errno;

    argv[i] = tmp;
  }

  return 0;
} /* spt_copyargs() */

void spt_init(int argc, char *argv[]) {
  char **envp = environ;
  char *base, *end, *nul, *tmp;
  int i, error;

  if (!(base = argv[0]))
    return;

  nul = &base[strlen(base)];
  end = nul + 1;

  for (i = 0; i < argc || (i >= argc && argv[i]); i++) {
    if (!argv[i] || argv[i] < end)
      continue;

    end = argv[i] + strlen(argv[i]) + 1;
  }

  for (i = 0; envp[i]; i++) {
    if (envp[i] < end)
      continue;

    end = envp[i] + strlen(envp[i]) + 1;
  }

  if (!(SPT.arg0 = strdup(argv[0])))
    goto syerr;

#if __GLIBC__
  if (!(tmp = strdup(program_invocation_name)))
    goto syerr;

  program_invocation_name = tmp;

  if (!(tmp = strdup(program_invocation_short_name)))
    goto syerr;

  program_invocation_short_name = tmp;
#elif __APPLE__
  if (!(tmp = strdup(getprogname())))
    goto syerr;

  setprogname(tmp);
#endif

  if ((error = spt_copyenv(envp)))
    goto error;

  if ((error = spt_copyargs(argc, argv)))
    goto error;

  SPT.nul = nul;
  SPT.base = base;
  SPT.end = end;

  return;
syerr:
  error = errno;
error:
  SPT.error = error;
} /* spt_init() */

#ifndef SPT_MAXTITLE
#define SPT_MAXTITLE 255
#endif

void setproctitle(const char *fmt, ...) {
  char buf[SPT_MAXTITLE + 1]; /* use buffer in case argv[0] is passed */
  va_list ap;
  char *nul;
  int len, error;

  if (!SPT.base)
    return;

  if (fmt) {
    va_start(ap, fmt);
    len = vsnprintf(buf, sizeof buf, fmt, ap);
    va_end(ap);
  } else {
    len = snprintf(buf, sizeof buf, "%s", SPT.arg0);
  }

  if (len <= 0) {
    error = errno;
    goto error;
  }

  if (!SPT.reset) {
    memset(SPT.base, 0, SPT.end - SPT.base);
    SPT.reset = 1;
  } else {
    memset(SPT.base, 0, spt_min(sizeof buf, SPT.end - SPT.base));
  }

  len = spt_min(len, spt_min(sizeof buf, SPT.end - SPT.base) - 1);
  memcpy(SPT.base, buf, len);
  nul = &SPT.base[len];

  if (nul == SPT.nul && &nul[1] < SPT.end) {
    *SPT.nul = ' ';
    *++nul = '\0';
  }

  return;
error:
  SPT.error = error;
} /* setproctitle() */

#endif /* __linux || __APPLE__ */
#endif /* !HAVE_SETPROCTITLE */