/*

 * State diagram and cleanup

 * -------------------------

 *

 * If the program exits while a temporary file is active, we want to

 * make sure that we remove it. This is done by remembering the active

 * temporary files in a linked list, `tempfile_list`. An `atexit(3)`

 * handler and a signal handler are registered, to clean up any active

 * temporary files.

 *

 * Because the signal handler can run at any time, `tempfile_list` and

 * the `tempfile` objects that comprise it must be kept in

 * self-consistent states at all times.

 *

 * The possible states of a `tempfile` object are as follows:

 *

 * - Inactive/unallocated. The only way to get a tempfile is via a creation

 *   function like create_tempfile(). Once allocated, the tempfile is on the

 *   global tempfile_list and considered active.

 *

 * - Active, file open (after `create_tempfile()` or

 *   `reopen_tempfile()`). In this state:

 *

 *   - the temporary file exists

 *   - `filename` holds the filename of the temporary file

 *   - `fd` holds a file descriptor open for writing to it

 *   - `fp` holds a pointer to an open `FILE` object if and only if

 *     `fdopen_tempfile()` has been called on the object

 *   - `owner` holds the PID of the process that created the file

 *

 * - Active, file closed (after `close_tempfile_gently()`). Same

 *   as the previous state, except that the temporary file is closed,

 *   `fd` is -1, and `fp` is `NULL`.

 *

 * - Inactive (after `delete_tempfile()`, `rename_tempfile()`, or a

 *   failed attempt to create a temporary file). The struct is removed from

 *   the global tempfile_list and deallocated.

 *

 * A temporary file is owned by the process that created it. The

 * `tempfile` has an `owner` field that records the owner's PID. This

 * field is used to prevent a forked process from deleting a temporary

 * file created by its parent.

 */

#include "git-compat-util.h"

#include "abspath.h"

#include "path.h"

#include "tempfile.h"

#include "sigchain.h"

static VOLATILE_LIST_HEAD(tempfile_list);

static int remove_template_directory(struct tempfile *tempfile,

              int in_signal_handler)

{

  if (tempfile->directory) {

    if (in_signal_handler)

      return rmdir(tempfile->directory);

    else

      return rmdir_or_warn(tempfile->directory);

  }

  return 0;

}

static void remove_tempfiles(int in_signal_handler)

{

  pid_t me = getpid();

  volatile struct volatile_list_head *pos;

  list_for_each(pos, &tempfile_list) {

    struct tempfile *p = list_entry(pos, struct tempfile, list);

    if (!is_tempfile_active(p) || p->owner != me)

      continue;

    if (p->fd >= 0)

      close(p->fd);

    if (in_signal_handler)

      unlink(p->filename.buf);

    else

      unlink_or_warn(p->filename.buf);

    remove_template_directory(p, in_signal_handler);

  }

}

static void remove_tempfiles_on_exit(void)

{

  remove_tempfiles(0);

}

static void remove_tempfiles_on_signal(int signo)

{

  remove_tempfiles(1);

  sigchain_pop(signo);

  raise(signo);

}

static struct tempfile *new_tempfile(void)

{

  struct tempfile *tempfile = xmalloc(sizeof(*tempfile));

  tempfile->fd = -1;

  tempfile->fp = NULL;

  tempfile->owner = 0;

  INIT_LIST_HEAD(&tempfile->list);

  strbuf_init(&tempfile->filename, 0);

  tempfile->directory = NULL;

  return tempfile;

}

static void activate_tempfile(struct tempfile *tempfile)

{

  static int initialized;

  if (!initialized) {

    sigchain_push_common(remove_tempfiles_on_signal);

    atexit(remove_tempfiles_on_exit);

    initialized = 1;

  }

  volatile_list_add(&tempfile->list, &tempfile_list);

  tempfile->owner = getpid();

}

static void deactivate_tempfile(struct tempfile *tempfile)

{

  volatile_list_del(&tempfile->list);

  strbuf_release(&tempfile->filename);

  free(tempfile->directory);

  free(tempfile);

}

/* Make sure errno contains a meaningful value on error */

struct tempfile *create_tempfile_mode(const char *path, int mode)

{

  struct tempfile *tempfile = new_tempfile();

  strbuf_add_absolute_path(&tempfile->filename, path);

  tempfile->fd = open(tempfile->filename.buf,

          O_RDWR | O_CREAT | O_EXCL | O_CLOEXEC, mode);

  if (O_CLOEXEC && tempfile->fd < 0 && errno == EINVAL)

    /* Try again w/o O_CLOEXEC: the kernel might not support it */

    tempfile->fd = open(tempfile->filename.buf,

            O_RDWR | O_CREAT | O_EXCL, mode);

  if (tempfile->fd < 0) {

    deactivate_tempfile(tempfile);

    return NULL;

  }

  activate_tempfile(tempfile);

  if (adjust_shared_perm(tempfile->filename.buf)) {

    int save_errno = errno;

    error("cannot fix permission bits on %s", tempfile->filename.buf);

    delete_tempfile(&tempfile);

    errno = save_errno;

    return NULL;

  }

  return tempfile;

}

struct tempfile *register_tempfile(const char *path)

{

  struct tempfile *tempfile = new_tempfile();

  strbuf_add_absolute_path(&tempfile->filename, path);

  activate_tempfile(tempfile);

  return tempfile;

}

struct tempfile *mks_tempfile_sm(const char *filename_template, int suffixlen, int mode)

{

  struct tempfile *tempfile = new_tempfile();

  strbuf_add_absolute_path(&tempfile->filename, filename_template);

  tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);

  if (tempfile->fd < 0) {

    deactivate_tempfile(tempfile);

    return NULL;

  }

  activate_tempfile(tempfile);

  return tempfile;

}

struct tempfile *mks_tempfile_tsm(const char *filename_template, int suffixlen, int mode)

{

  struct tempfile *tempfile = new_tempfile();

  const char *tmpdir;

  tmpdir = getenv("TMPDIR");

  if (!tmpdir)

    tmpdir = "/tmp";

  strbuf_addf(&tempfile->filename, "%s/%s", tmpdir, filename_template);

  tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);

  if (tempfile->fd < 0) {

    deactivate_tempfile(tempfile);

    return NULL;

  }

  activate_tempfile(tempfile);

  return tempfile;

}

struct tempfile *mks_tempfile_dt(const char *directory_template,

         const char *filename)

{

  struct tempfile *tempfile;

  const char *tmpdir;

  struct strbuf sb = STRBUF_INIT;

  int fd;

  size_t directorylen;

  if (!ends_with(directory_template, "XXXXXX")) {

    errno = EINVAL;

    return NULL;

  }

  tmpdir = getenv("TMPDIR");

  if (!tmpdir)

    tmpdir = "/tmp";

  strbuf_addf(&sb, "%s/%s", tmpdir, directory_template);

  directorylen = sb.len;

  if (!mkdtemp(sb.buf)) {

    int orig_errno = errno;

    strbuf_release(&sb);

    errno = orig_errno;

    return NULL;

  }

  strbuf_addf(&sb, "/%s", filename);

  fd = open(sb.buf, O_CREAT | O_EXCL | O_RDWR, 0600);

  if (fd < 0) {

    int orig_errno = errno;

    strbuf_setlen(&sb, directorylen);

    rmdir(sb.buf);

    strbuf_release(&sb);

    errno = orig_errno;

    return NULL;

  }

  tempfile = new_tempfile();

  strbuf_swap(&tempfile->filename, &sb);

  tempfile->directory = xmemdupz(tempfile->filename.buf, directorylen);

  tempfile->fd = fd;

  activate_tempfile(tempfile);

  return tempfile;

}

struct tempfile *xmks_tempfile_m(const char *filename_template, int mode)

{

  struct tempfile *tempfile;

  struct strbuf full_template = STRBUF_INIT;

  strbuf_add_absolute_path(&full_template, filename_template);

  tempfile = mks_tempfile_m(full_template.buf, mode);

  if (!tempfile)

    die_errno("Unable to create temporary file '%s'",

        full_template.buf);

  strbuf_release(&full_template);

  return tempfile;

}

FILE *fdopen_tempfile(struct tempfile *tempfile, const char *mode)

{

  if (!is_tempfile_active(tempfile))

    BUG("fdopen_tempfile() called for inactive object");

  if (tempfile->fp)

    BUG("fdopen_tempfile() called for open object");

  tempfile->fp = fdopen(tempfile->fd, mode);

  return tempfile->fp;

}

const char *get_tempfile_path(struct tempfile *tempfile)

{

  if (!is_tempfile_active(tempfile))

    BUG("get_tempfile_path() called for inactive object");

  return tempfile->filename.buf;

}

int get_tempfile_fd(struct tempfile *tempfile)

{

  if (!is_tempfile_active(tempfile))

    BUG("get_tempfile_fd() called for inactive object");

  return tempfile->fd;

}

FILE *get_tempfile_fp(struct tempfile *tempfile)

{

  if (!is_tempfile_active(tempfile))

    BUG("get_tempfile_fp() called for inactive object");

  return tempfile->fp;

}

int close_tempfile_gently(struct tempfile *tempfile)

{

  int fd;

  FILE *fp;

  int err;

  if (!is_tempfile_active(tempfile) || tempfile->fd < 0)

    return 0;

  fd = tempfile->fd;

  fp = tempfile->fp;

  tempfile->fd = -1;

  if (fp) {

    tempfile->fp = NULL;

    if (ferror(fp)) {

      err = -1;

      if (!fclose(fp))

        errno = EIO;

    } else {

      err = fclose(fp);

    }

  } else {

    err = close(fd);

  }

  return err ? -1 : 0;

}

int reopen_tempfile(struct tempfile *tempfile)

{

  if (!is_tempfile_active(tempfile))

    BUG("reopen_tempfile called for an inactive object");

  if (0 <= tempfile->fd)

    BUG("reopen_tempfile called for an open object");

  tempfile->fd = open(tempfile->filename.buf, O_WRONLY|O_TRUNC);

  return tempfile->fd;

}

int rename_tempfile(struct tempfile **tempfile_p, const char *path)

{

  struct tempfile *tempfile = *tempfile_p;

  if (!is_tempfile_active(tempfile))

    BUG("rename_tempfile called for inactive object");

  if (close_tempfile_gently(tempfile)) {

    delete_tempfile(tempfile_p);

    return -1;

  }

  if (rename(tempfile->filename.buf, path)) {

    int save_errno = errno;

    delete_tempfile(tempfile_p);

    errno = save_errno;

    return -1;

  }

  deactivate_tempfile(tempfile);

  *tempfile_p = NULL;

  return 0;

}

int delete_tempfile(struct tempfile **tempfile_p)

{

  struct tempfile *tempfile = *tempfile_p;

  int err = 0;

  if (!is_tempfile_active(tempfile))

    return 0;

  err |= close_tempfile_gently(tempfile);

  err |= unlink_or_warn(tempfile->filename.buf);

  err |= remove_template_directory(tempfile, 0);

  deactivate_tempfile(tempfile);

  *tempfile_p = NULL;

  return err ? -1 : 0;

}