file.c

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#include "config.h"
#include <ctype.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <libgen.h>
#include <limits.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>
#include <utime.h>
#include "config/lib.h"
#include "core/lib.h"
#include "file.h"
#include "buffer.h"
#include "date.h"
#include "logging.h"
#include "memory.h"
#include "message.h"
#include "path.h"
#include "pool.h"
#include "string2.h"
#ifdef USE_FLOCK
#include <sys/file.h>
#endif
 
/* these characters must be escaped in regular expressions */
static const char rx_special_chars[] = "^.[$()|*+?{\\";
 
const char filename_safe_chars[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+@{}._-:%/";
 
#define MAX_LOCK_ATTEMPTS 5
 
/* This is defined in POSIX:2008 which isn't a build requirement */
#ifndef O_NOFOLLOW
#define O_NOFOLLOW 0
#endif
 
static bool compare_stat(struct stat *st_old, struct stat *st_new)
{
  return (st_old->st_dev == st_new->st_dev) && (st_old->st_ino == st_new->st_ino) &&
         (st_old->st_rdev == st_new->st_rdev);
}
 
static int mkwrapdir(const char *path, struct Buffer *newfile, struct Buffer *newdir)
{
  const char *basename = NULL;
  int rc = 0;
 
  struct Buffer parent = mutt_buffer_make(PATH_MAX);
  mutt_buffer_strcpy(&parent, NONULL(path));
 
  char *p = strrchr(parent.data, '/');
  if (p)
  {
    *p = '\0';
    basename = p + 1;
  }
  else
  {
    mutt_buffer_strcpy(&parent, ".");
    basename = path;
  }
 
  mutt_buffer_printf(newdir, "%s/%s", mutt_buffer_string(&parent), ".muttXXXXXX");
  if (!mkdtemp(newdir->data))
  {
    mutt_debug(LL_DEBUG1, "mkdtemp() failed\n");
    rc = -1;
    goto cleanup;
  }
 
  mutt_buffer_printf(newfile, "%s/%s", newdir->data, NONULL(basename));
 
cleanup:
  mutt_buffer_dealloc(&parent);
  return rc;
}
 
static int put_file_in_place(const char *path, const char *safe_file, const char *safe_dir)
{
  int rc;
 
  rc = mutt_file_safe_rename(safe_file, path);
  unlink(safe_file);
  rmdir(safe_dir);
  return rc;
}
 
int mutt_file_fclose(FILE **fp)
{
  if (!fp || !*fp)
    return 0;
 
  int rc = fclose(*fp);
  *fp = NULL;
  return rc;
}
 
int mutt_file_fsync_close(FILE **fp)
{
  if (!fp || !*fp)
    return 0;
 
  int rc = 0;
 
  if (fflush(*fp) || fsync(fileno(*fp)))
  {
    int save_errno = errno;
    rc = -1;
    mutt_file_fclose(fp);
    errno = save_errno;
  }
  else
    rc = mutt_file_fclose(fp);
 
  return rc;
}
 
void mutt_file_unlink(const char *s)
{
  if (!s)
    return;
 
  struct stat st = { 0 };
  /* Defend against symlink attacks */
 
  const bool is_regular_file = (lstat(s, &st) == 0) && S_ISREG(st.st_mode);
  if (!is_regular_file)
    return;
 
  const int fd = open(s, O_RDWR | O_NOFOLLOW);
  if (fd < 0)
    return;
 
  struct stat st2 = { 0 };
  if ((fstat(fd, &st2) != 0) || !S_ISREG(st2.st_mode) ||
      (st.st_dev != st2.st_dev) || (st.st_ino != st2.st_ino))
  {
    close(fd);
    return;
  }
 
  unlink(s);
  close(fd);
}
 
int mutt_file_copy_bytes(FILE *fp_in, FILE *fp_out, size_t size)
{
  if (!fp_in || !fp_out)
    return -1;
 
  while (size > 0)
  {
    char buf[2048] = { 0 };
    size_t chunk = (size > sizeof(buf)) ? sizeof(buf) : size;
    chunk = fread(buf, 1, chunk, fp_in);
    if (chunk < 1)
      break;
    if (fwrite(buf, 1, chunk, fp_out) != chunk)
      return -1;
 
    size -= chunk;
  }
 
  if (fflush(fp_out) != 0)
    return -1;
  return 0;
}
 
int mutt_file_copy_stream(FILE *fp_in, FILE *fp_out)
{
  if (!fp_in || !fp_out)
    return -1;
 
  size_t total = 0;
  size_t l;
  char buf[1024] = { 0 };
 
  while ((l = fread(buf, 1, sizeof(buf), fp_in)) > 0)
  {
    if (fwrite(buf, 1, l, fp_out) != l)
      return -1;
    total += l;
  }
 
  if (fflush(fp_out) != 0)
    return -1;
  return total;
}
 
int mutt_file_symlink(const char *oldpath, const char *newpath)
{
  struct stat st_old = { 0 };
  struct stat st_new = { 0 };
 
  if (!oldpath || !newpath)
    return -1;
 
  if ((unlink(newpath) == -1) && (errno != ENOENT))
    return -1;
 
  if (oldpath[0] == '/')
  {
    if (symlink(oldpath, newpath) == -1)
      return -1;
  }
  else
  {
    struct Buffer abs_oldpath = mutt_buffer_make(PATH_MAX);
 
    if (!mutt_path_getcwd(&abs_oldpath))
    {
      mutt_buffer_dealloc(&abs_oldpath);
      return -1;
    }
 
    mutt_buffer_addch(&abs_oldpath, '/');
    mutt_buffer_addstr(&abs_oldpath, oldpath);
    if (symlink(mutt_buffer_string(&abs_oldpath), newpath) == -1)
    {
      mutt_buffer_dealloc(&abs_oldpath);
      return -1;
    }
 
    mutt_buffer_dealloc(&abs_oldpath);
  }
 
  if ((stat(oldpath, &st_old) == -1) || (stat(newpath, &st_new) == -1) ||
      !compare_stat(&st_old, &st_new))
  {
    unlink(newpath);
    return -1;
  }
 
  return 0;
}
 
int mutt_file_safe_rename(const char *src, const char *target)
{
  struct stat st_src = { 0 };
  struct stat st_target = { 0 };
  int link_errno;
 
  if (!src || !target)
    return -1;
 
  if (link(src, target) != 0)
  {
    link_errno = errno;
 
    /* It is historically documented that link can return -1 if NFS
     * dies after creating the link.  In that case, we are supposed
     * to use stat to check if the link was created.
     *
     * Derek Martin notes that some implementations of link() follow a
     * source symlink.  It might be more correct to use stat() on src.
     * I am not doing so to minimize changes in behavior: the function
     * used lstat() further below for 20 years without issue, and I
     * believe was never intended to be used on a src symlink.  */
    if ((lstat(src, &st_src) == 0) && (lstat(target, &st_target) == 0) &&
        (compare_stat(&st_src, &st_target) == 0))
    {
      mutt_debug(LL_DEBUG1, "link (%s, %s) reported failure: %s (%d) but actually succeeded\n",
                 src, target, strerror(errno), errno);
      goto success;
    }
 
    errno = link_errno;
 
    /* Coda does not allow cross-directory links, but tells
     * us it's a cross-filesystem linking attempt.
     *
     * However, the Coda rename call is allegedly safe to use.
     *
     * With other file systems, rename should just fail when
     * the files reside on different file systems, so it's safe
     * to try it here. */
    mutt_debug(LL_DEBUG1, "link (%s, %s) failed: %s (%d)\n", src, target,
               strerror(errno), errno);
 
    /* FUSE may return ENOSYS. VFAT may return EPERM. FreeBSD's
     * msdosfs may return EOPNOTSUPP.  ENOTSUP can also appear. */
    if ((errno == EXDEV) || (errno == ENOSYS) || errno == EPERM
#ifdef ENOTSUP
        || errno == ENOTSUP
#endif
#ifdef EOPNOTSUPP
        || errno == EOPNOTSUPP
#endif
    )
    {
      mutt_debug(LL_DEBUG1, "trying rename\n");
      if (rename(src, target) == -1)
      {
        mutt_debug(LL_DEBUG1, "rename (%s, %s) failed: %s (%d)\n", src, target,
                   strerror(errno), errno);
        return -1;
      }
      mutt_debug(LL_DEBUG1, "rename succeeded\n");
 
      return 0;
    }
 
    return -1;
  }
 
  /* Remove the compare_stat() check, because it causes problems with maildir
   * on filesystems that don't properly support hard links, such as sshfs.  The
   * filesystem creates the link, but the resulting file is given a different
   * inode number by the sshfs layer.  This results in an infinite loop
   * creating links.  */
#if 0
  /* Stat both links and check if they are equal. */
  if (lstat(src, &st_src) == -1)
  {
    mutt_debug(LL_DEBUG1, "#1 can't stat %s: %s (%d)\n", src, strerror(errno), errno);
    return -1;
  }
 
  if (lstat(target, &st_target) == -1)
  {
    mutt_debug(LL_DEBUG1, "#2 can't stat %s: %s (%d)\n", src, strerror(errno), errno);
    return -1;
  }
 
  /* pretend that the link failed because the target file did already exist. */
 
  if (!compare_stat(&st_src, &st_target))
  {
    mutt_debug(LL_DEBUG1, "stat blocks for %s and %s diverge; pretending EEXIST\n", src, target);
    errno = EEXIST;
    return -1;
  }
#endif
 
success:
  /* Unlink the original link.
   * Should we really ignore the return value here? XXX */
  if (unlink(src) == -1)
  {
    mutt_debug(LL_DEBUG1, "unlink (%s) failed: %s (%d)\n", src, strerror(errno), errno);
  }
 
  return 0;
}
 
int mutt_file_rmtree(const char *path)
{
  if (!path)
    return -1;
 
  struct dirent *de = NULL;
  struct stat st = { 0 };
  int rc = 0;
 
  DIR *dirp = opendir(path);
  if (!dirp)
  {
    mutt_debug(LL_DEBUG1, "error opening directory %s\n", path);
    return -1;
  }
 
  /* We avoid using the buffer pool for this function, because it
   * invokes recursively to an unknown depth. */
  struct Buffer cur = mutt_buffer_make(PATH_MAX);
 
  while ((de = readdir(dirp)))
  {
    if ((strcmp(".", de->d_name) == 0) || (strcmp("..", de->d_name) == 0))
      continue;
 
    mutt_buffer_printf(&cur, "%s/%s", path, de->d_name);
    /* XXX make nonrecursive version */
 
    if (stat(mutt_buffer_string(&cur), &st) == -1)
    {
      rc = 1;
      continue;
    }
 
    if (S_ISDIR(st.st_mode))
      rc |= mutt_file_rmtree(mutt_buffer_string(&cur));
    else
      rc |= unlink(mutt_buffer_string(&cur));
  }
  closedir(dirp);
 
  rc |= rmdir(path);
 
  mutt_buffer_dealloc(&cur);
  return rc;
}
 
const char *mutt_file_rotate(const char *path, int count)
{
  if (!path)
    return NULL;
 
  struct Buffer *old_file = mutt_buffer_pool_get();
  struct Buffer *new_file = mutt_buffer_pool_get();
 
  /* rotate the old debug logs */
  for (count -= 2; count >= 0; count--)
  {
    mutt_buffer_printf(old_file, "%s%d", path, count);
    mutt_buffer_printf(new_file, "%s%d", path, count + 1);
    (void) rename(mutt_buffer_string(old_file), mutt_buffer_string(new_file));
  }
 
  path = mutt_buffer_strdup(old_file);
  mutt_buffer_pool_release(&old_file);
  mutt_buffer_pool_release(&new_file);
 
  return path;
}
 
int mutt_file_open(const char *path, uint32_t flags)
{
  if (!path)
    return -1;
 
  int fd;
  struct Buffer safe_file = mutt_buffer_make(0);
  struct Buffer safe_dir = mutt_buffer_make(0);
 
  if (flags & O_EXCL)
  {
    mutt_buffer_alloc(&safe_file, PATH_MAX);
    mutt_buffer_alloc(&safe_dir, PATH_MAX);
 
    if (mkwrapdir(path, &safe_file, &safe_dir) == -1)
    {
      fd = -1;
      goto cleanup;
    }
 
    fd = open(mutt_buffer_string(&safe_file), flags, 0600);
    if (fd < 0)
    {
      rmdir(mutt_buffer_string(&safe_dir));
      goto cleanup;
    }
 
    /* NFS and I believe cygwin do not handle movement of open files well */
    close(fd);
    if (put_file_in_place(path, mutt_buffer_string(&safe_file),
                          mutt_buffer_string(&safe_dir)) == -1)
    {
      fd = -1;
      goto cleanup;
    }
  }
 
  fd = open(path, flags & ~O_EXCL, 0600);
  if (fd < 0)
    goto cleanup;
 
  /* make sure the file is not symlink */
  struct stat st_old = { 0 };
  struct stat st_new = { 0 };
  if (((lstat(path, &st_old) < 0) || (fstat(fd, &st_new) < 0)) ||
      !compare_stat(&st_old, &st_new))
  {
    close(fd);
    fd = -1;
    goto cleanup;
  }
 
cleanup:
  mutt_buffer_dealloc(&safe_file);
  mutt_buffer_dealloc(&safe_dir);
 
  return fd;
}
 
FILE *mutt_file_fopen(const char *path, const char *mode)
{
  if (!path || !mode)
    return NULL;
 
  if (mode[0] == 'w')
  {
    uint32_t flags = O_CREAT | O_EXCL | O_NOFOLLOW;
 
    if (mode[1] == '+')
      flags |= O_RDWR;
    else
      flags |= O_WRONLY;
 
    int fd = mutt_file_open(path, flags);
    if (fd < 0)
      return NULL;
 
    return fdopen(fd, mode);
  }
  else
    return fopen(path, mode);
}
 
void mutt_file_sanitize_filename(char *path, bool slash)
{
  if (!path)
    return;
 
  for (; *path; path++)
  {
    if ((slash && (*path == '/')) || !strchr(filename_safe_chars, *path))
      *path = '_';
  }
}
 
int mutt_file_sanitize_regex(struct Buffer *dest, const char *src)
{
  if (!dest || !src)
    return -1;
 
  mutt_buffer_reset(dest);
  while (*src != '\0')
  {
    if (strchr(rx_special_chars, *src))
      mutt_buffer_addch(dest, '\\');
    mutt_buffer_addch(dest, *src++);
  }
 
  return 0;
}
 
bool mutt_file_seek(FILE *fp, LOFF_T offset, int whence)
{
  if (!fp)
  {
    return false;
  }
 
  if (fseeko(fp, offset, whence) != 0)
  {
    mutt_perror(_("Failed to seek file: %s"), strerror(errno));
    return false;
  }
 
  return true;
}
 
char *mutt_file_read_line(char *line, size_t *size, FILE *fp, int *line_num, ReadLineFlags flags)
{
  if (!size || !fp)
    return NULL;
 
  size_t offset = 0;
  char *ch = NULL;
 
  if (!line)
  {
    *size = 256;
    line = mutt_mem_malloc(*size);
  }
 
  while (true)
  {
    if (!fgets(line + offset, *size - offset, fp))
    {
      FREE(&line);
      return NULL;
    }
    ch = strchr(line + offset, '\n');
    if (ch)
    {
      if (line_num)
        (*line_num)++;
      if (flags & MUTT_RL_EOL)
        return line;
      *ch = '\0';
      if ((ch > line) && (*(ch - 1) == '\r'))
        *--ch = '\0';
      if (!(flags & MUTT_RL_CONT) || (ch == line) || (*(ch - 1) != '\\'))
        return line;
      offset = ch - line - 1;
    }
    else
    {
      int c;
      c = getc(fp); /* This is kind of a hack. We want to know if the
                        char at the current point in the input stream is EOF.
                        feof() will only tell us if we've already hit EOF, not
                        if the next character is EOF. So, we need to read in
                        the next character and manually check if it is EOF. */
      if (c == EOF)
      {
        /* The last line of fp isn't \n terminated */
        if (line_num)
          (*line_num)++;
        return line;
      }
      else
      {
        ungetc(c, fp); /* undo our damage */
        /* There wasn't room for the line -- increase "line" */
        offset = *size - 1; /* overwrite the terminating 0 */
        *size += 256;
        mutt_mem_realloc(&line, *size);
      }
    }
  }
}
 
bool mutt_file_iter_line(struct MuttFileIter *iter, FILE *fp, ReadLineFlags flags)
{
  if (!iter)
    return false;
 
  char *p = mutt_file_read_line(iter->line, &iter->size, fp, &iter->line_num, flags);
  if (!p)
    return false;
  iter->line = p;
  return true;
}
 
bool mutt_file_map_lines(mutt_file_map_t func, void *user_data, FILE *fp, ReadLineFlags flags)
{
  if (!func || !fp)
    return false;
 
  struct MuttFileIter iter = { 0 };
  while (mutt_file_iter_line(&iter, fp, flags))
  {
    if (!(*func)(iter.line, iter.line_num, user_data))
    {
      FREE(&iter.line);
      return false;
    }
  }
  return true;
}
 
size_t mutt_file_quote_filename(const char *filename, char *buf, size_t buflen)
{
  if (!buf)
    return 0;
 
  if (!filename)
  {
    *buf = '\0';
    return 0;
  }
 
  size_t j = 0;
 
  /* leave some space for the trailing characters. */
  buflen -= 6;
 
  buf[j++] = '\'';
 
  for (size_t i = 0; (j < buflen) && filename[i]; i++)
  {
    if ((filename[i] == '\'') || (filename[i] == '`'))
    {
      buf[j++] = '\'';
      buf[j++] = '\\';
      buf[j++] = filename[i];
      buf[j++] = '\'';
    }
    else
      buf[j++] = filename[i];
  }
 
  buf[j++] = '\'';
  buf[j] = '\0';
 
  return j;
}
 
void mutt_buffer_quote_filename(struct Buffer *buf, const char *filename, bool add_outer)
{
  if (!buf || !filename)
    return;
 
  mutt_buffer_reset(buf);
  if (add_outer)
    mutt_buffer_addch(buf, '\'');
 
  for (; *filename != '\0'; filename++)
  {
    if ((*filename == '\'') || (*filename == '`'))
    {
      mutt_buffer_addch(buf, '\'');
      mutt_buffer_addch(buf, '\\');
      mutt_buffer_addch(buf, *filename);
      mutt_buffer_addch(buf, '\'');
    }
    else
      mutt_buffer_addch(buf, *filename);
  }
 
  if (add_outer)
    mutt_buffer_addch(buf, '\'');
}
 
int mutt_file_mkdir(const char *path, mode_t mode)
{
  if (!path || (*path == '\0'))
  {
    errno = EINVAL;
    return -1;
  }
 
  errno = 0;
  char tmp_path[PATH_MAX] = { 0 };
  const size_t len = strlen(path);
 
  if (len >= sizeof(tmp_path))
  {
    errno = ENAMETOOLONG;
    return -1;
  }
 
  struct stat st = { 0 };
  if ((stat(path, &st) == 0) && S_ISDIR(st.st_mode))
    return 0;
 
  /* Create a mutable copy */
  mutt_str_copy(tmp_path, path, sizeof(tmp_path));
 
  for (char *p = tmp_path + 1; *p; p++)
  {
    if (*p != '/')
      continue;
 
    /* Temporarily truncate the path */
    *p = '\0';
 
    if ((mkdir(tmp_path, S_IRWXU | S_IRWXG | S_IRWXO) != 0) && (errno != EEXIST))
      return -1;
 
    *p = '/';
  }
 
  if ((mkdir(tmp_path, mode) != 0) && (errno != EEXIST))
    return -1;
 
  return 0;
}
 
FILE *mutt_file_mkstemp_full(const char *file, int line, const char *func)
{
  char name[PATH_MAX] = { 0 };
 
  const char *const c_tmpdir = cs_subset_path(NeoMutt->sub, "tmpdir");
  int n = snprintf(name, sizeof(name), "%s/neomutt-XXXXXX", NONULL(c_tmpdir));
  if (n < 0)
    return NULL;
 
  int fd = mkstemp(name);
  if (fd == -1)
    return NULL;
 
  FILE *fp = fdopen(fd, "w+");
 
  if ((unlink(name) != 0) && (errno != ENOENT))
  {
    mutt_file_fclose(&fp);
    return NULL;
  }
 
  MuttLogger(0, file, line, func, 1, "created temp file '%s'\n", name);
  return fp;
}
 
time_t mutt_file_decrease_mtime(const char *fp, struct stat *st)
{
  if (!fp)
    return -1;
 
  struct utimbuf utim;
  struct stat st2 = { 0 };
  time_t mtime;
 
  if (!st)
  {
    if (stat(fp, &st2) == -1)
      return -1;
    st = &st2;
  }
 
  mtime = st->st_mtime;
  if (mtime == mutt_date_epoch())
  {
    mtime -= 1;
    utim.actime = mtime;
    utim.modtime = mtime;
    int rc;
    do
    {
      rc = utime(fp, &utim);
    } while ((rc == -1) && (errno == EINTR));
 
    if (rc == -1)
      return -1;
  }
 
  return mtime;
}
 
void mutt_file_set_mtime(const char *from, const char *to)
{
  if (!from || !to)
    return;
 
  struct utimbuf utim;
  struct stat st = { 0 };
 
  if (stat(from, &st) != -1)
  {
    utim.actime = st.st_mtime;
    utim.modtime = st.st_mtime;
    utime(to, &utim);
  }
}
 
void mutt_file_touch_atime(int fd)
{
#ifdef HAVE_FUTIMENS
  struct timespec times[2] = { { 0, UTIME_NOW }, { 0, UTIME_OMIT } };
  futimens(fd, times);
#endif
}
 
int mutt_file_chmod(const char *path, mode_t mode)
{
  if (!path)
    return -1;
 
  return chmod(path, mode);
}
 
int mutt_file_chmod_add(const char *path, mode_t mode)
{
  return mutt_file_chmod_add_stat(path, mode, NULL);
}
 
int mutt_file_chmod_add_stat(const char *path, mode_t mode, struct stat *st)
{
  if (!path)
    return -1;
 
  struct stat st2 = { 0 };
 
  if (!st)
  {
    if (stat(path, &st2) == -1)
      return -1;
    st = &st2;
  }
  return chmod(path, st->st_mode | mode);
}
 
int mutt_file_chmod_rm(const char *path, mode_t mode)
{
  return mutt_file_chmod_rm_stat(path, mode, NULL);
}
 
int mutt_file_chmod_rm_stat(const char *path, mode_t mode, struct stat *st)
{
  if (!path)
    return -1;
 
  struct stat st2 = { 0 };
 
  if (!st)
  {
    if (stat(path, &st2) == -1)
      return -1;
    st = &st2;
  }
  return chmod(path, st->st_mode & ~mode);
}
 
#if defined(USE_FCNTL)
int mutt_file_lock(int fd, bool excl, bool timeout)
{
  struct stat st = { 0 }, prev_sb = { 0 };
  int count = 0;
  int attempt = 0;
 
  struct flock lck;
  memset(&lck, 0, sizeof(struct flock));
  lck.l_type = excl ? F_WRLCK : F_RDLCK;
  lck.l_whence = SEEK_SET;
 
  while (fcntl(fd, F_SETLK, &lck) == -1)
  {
    mutt_debug(LL_DEBUG1, "fcntl errno %d\n", errno);
    if ((errno != EAGAIN) && (errno != EACCES))
    {
      mutt_perror("fcntl");
      return -1;
    }
 
    if (fstat(fd, &st) != 0)
      st.st_size = 0;
 
    if (count == 0)
      prev_sb = st;
 
    /* only unlock file if it is unchanged */
    if ((prev_sb.st_size == st.st_size) && (++count >= (timeout ? MAX_LOCK_ATTEMPTS : 0)))
    {
      if (timeout)
        mutt_error(_("Timeout exceeded while attempting fcntl lock"));
      return -1;
    }
 
    prev_sb = st;
 
    mutt_message(_("Waiting for fcntl lock... %d"), ++attempt);
    sleep(1);
  }
 
  return 0;
}
 
int mutt_file_unlock(int fd)
{
  struct flock unlockit;
 
  memset(&unlockit, 0, sizeof(struct flock));
  unlockit.l_type = F_UNLCK;
  unlockit.l_whence = SEEK_SET;
  (void) fcntl(fd, F_SETLK, &unlockit);
 
  return 0;
}
#elif defined(USE_FLOCK)
int mutt_file_lock(int fd, bool excl, bool timeout)
{
  struct stat st = { 0 }, prev_sb = { 0 };
  int rc = 0;
  int count = 0;
  int attempt = 0;
 
  while (flock(fd, (excl ? LOCK_EX : LOCK_SH) | LOCK_NB) == -1)
  {
    if (errno != EWOULDBLOCK)
    {
      mutt_perror("flock");
      rc = -1;
      break;
    }
 
    if (fstat(fd, &st) != 0)
      st.st_size = 0;
 
    if (count == 0)
      prev_sb = st;
 
    /* only unlock file if it is unchanged */
    if ((prev_sb.st_size == st.st_size) && (++count >= (timeout ? MAX_LOCK_ATTEMPTS : 0)))
    {
      if (timeout)
        mutt_error(_("Timeout exceeded while attempting flock lock"));
      rc = -1;
      break;
    }
 
    prev_sb = st;
 
    mutt_message(_("Waiting for flock attempt... %d"), ++attempt);
    sleep(1);
  }
 
  /* release any other locks obtained in this routine */
  if (rc != 0)
  {
    flock(fd, LOCK_UN);
  }
 
  return rc;
}
 
int mutt_file_unlock(int fd)
{
  flock(fd, LOCK_UN);
  return 0;
}
#else
#error "You must select a locking mechanism via USE_FCNTL or USE_FLOCK"
#endif
 
void mutt_file_unlink_empty(const char *path)
{
  if (!path)
    return;
 
  struct stat st = { 0 };
 
  int fd = open(path, O_RDWR);
  if (fd == -1)
    return;
 
  if (mutt_file_lock(fd, true, true) == -1)
  {
    close(fd);
    return;
  }
 
  if ((fstat(fd, &st) == 0) && (st.st_size == 0))
    unlink(path);
 
  mutt_file_unlock(fd);
  close(fd);
}
 
int mutt_file_rename(const char *oldfile, const char *newfile)
{
  if (!oldfile || !newfile)
    return -1;
  if (access(oldfile, F_OK) != 0)
    return 1;
  if (access(newfile, F_OK) == 0)
    return 2;
 
  FILE *fp_old = fopen(oldfile, "r");
  if (!fp_old)
    return 3;
  FILE *fp_new = mutt_file_fopen(newfile, "w");
  if (!fp_new)
  {
    mutt_file_fclose(&fp_old);
    return 3;
  }
  mutt_file_copy_stream(fp_old, fp_new);
  mutt_file_fclose(&fp_new);
  mutt_file_fclose(&fp_old);
  mutt_file_unlink(oldfile);
  return 0;
}
 
char *mutt_file_read_keyword(const char *file, char *buf, size_t buflen)
{
  FILE *fp = mutt_file_fopen(file, "r");
  if (!fp)
    return NULL;
 
  buf = fgets(buf, buflen, fp);
  mutt_file_fclose(&fp);
 
  if (!buf)
    return NULL;
 
  SKIPWS(buf);
  char *start = buf;
 
  while ((*buf != '\0') && !isspace(*buf))
    buf++;
 
  *buf = '\0';
 
  return start;
}
 
int mutt_file_check_empty(const char *path)
{
  if (!path)
    return -1;
 
  struct stat st = { 0 };
  if (stat(path, &st) == -1)
    return -1;
 
  return st.st_size == 0;
}
 
void mutt_buffer_file_expand_fmt_quote(struct Buffer *dest, const char *fmt, const char *src)
{
  struct Buffer tmp = mutt_buffer_make(PATH_MAX);
 
  mutt_buffer_quote_filename(&tmp, src, true);
  mutt_file_expand_fmt(dest, fmt, mutt_buffer_string(&tmp));
  mutt_buffer_dealloc(&tmp);
}
 
void mutt_file_expand_fmt(struct Buffer *dest, const char *fmt, const char *src)
{
  if (!dest || !fmt || !src)
    return;
 
  const char *p = NULL;
  bool found = false;
 
  mutt_buffer_reset(dest);
 
  for (p = fmt; *p; p++)
  {
    if (*p == '%')
    {
      switch (p[1])
      {
        case '%':
          mutt_buffer_addch(dest, *p++);
          break;
        case 's':
          found = true;
          mutt_buffer_addstr(dest, src);
          p++;
          break;
        default:
          mutt_buffer_addch(dest, *p);
          break;
      }
    }
    else
    {
      mutt_buffer_addch(dest, *p);
    }
  }
 
  if (!found)
  {
    mutt_buffer_addch(dest, ' ');
    mutt_buffer_addstr(dest, src);
  }
}
 
long mutt_file_get_size(const char *path)
{
  if (!path)
    return 0;
 
  struct stat st = { 0 };
  if (stat(path, &st) != 0)
    return 0;
 
  return st.st_size;
}
 
long mutt_file_get_size_fp(FILE *fp)
{
  if (!fp)
    return 0;
 
  struct stat st = { 0 };
  if (fstat(fileno(fp), &st) != 0)
    return 0;
 
  return st.st_size;
}
 
int mutt_file_timespec_compare(struct timespec *a, struct timespec *b)
{
  if (!a || !b)
    return 0;
  if (a->tv_sec < b->tv_sec)
    return -1;
  if (a->tv_sec > b->tv_sec)
    return 1;
 
  if (a->tv_nsec < b->tv_nsec)
    return -1;
  if (a->tv_nsec > b->tv_nsec)
    return 1;
  return 0;
}
 
void mutt_file_get_stat_timespec(struct timespec *dest, struct stat *st, enum MuttStatType type)
{
  if (!dest || !st)
    return;
 
  dest->tv_sec = 0;
  dest->tv_nsec = 0;
 
  switch (type)
  {
    case MUTT_STAT_ATIME:
      dest->tv_sec = st->st_atime;
#ifdef HAVE_STRUCT_STAT_ST_ATIM_TV_NSEC
      dest->tv_nsec = st->st_atim.tv_nsec;
#endif
      break;
    case MUTT_STAT_MTIME:
      dest->tv_sec = st->st_mtime;
#ifdef HAVE_STRUCT_STAT_ST_MTIM_TV_NSEC
      dest->tv_nsec = st->st_mtim.tv_nsec;
#endif
      break;
    case MUTT_STAT_CTIME:
      dest->tv_sec = st->st_ctime;
#ifdef HAVE_STRUCT_STAT_ST_CTIM_TV_NSEC
      dest->tv_nsec = st->st_ctim.tv_nsec;
#endif
      break;
  }
}
 
int mutt_file_stat_timespec_compare(struct stat *st, enum MuttStatType type,
                                    struct timespec *b)
{
  if (!st || !b)
    return 0;
 
  struct timespec a = { 0 };
 
  mutt_file_get_stat_timespec(&a, st, type);
  return mutt_file_timespec_compare(&a, b);
}
 
int mutt_file_stat_compare(struct stat *st1, enum MuttStatType st1_type,
                           struct stat *st2, enum MuttStatType st2_type)
{
  if (!st1 || !st2)
    return 0;
 
  struct timespec a = { 0 };
  struct timespec b = { 0 };
 
  mutt_file_get_stat_timespec(&a, st1, st1_type);
  mutt_file_get_stat_timespec(&b, st2, st2_type);
  return mutt_file_timespec_compare(&a, &b);
}
 
void mutt_file_resolve_symlink(struct Buffer *buf)
{
  struct stat st = { 0 };
  int rc = lstat(mutt_buffer_string(buf), &st);
  if ((rc != -1) && S_ISLNK(st.st_mode))
  {
    char path[PATH_MAX] = { 0 };
    if (realpath(mutt_buffer_string(buf), path))
    {
      mutt_buffer_strcpy(buf, path);
    }
  }
}