path: root/src/lfs.c

/*
** LuaFileSystem
** Copyright Kepler Project 2003 - 2020
** (http://keplerproject.github.io/luafilesystem)
**
** File system manipulation library.
** This library offers these functions:
**   lfs.attributes (filepath [, attributename | attributetable])
**   lfs.chdir (path)
**   lfs.currentdir ()
**   lfs.dir (path)
**   lfs.link (old, new[, symlink])
**   lfs.lock (fh, mode)
**   lfs.lock_dir (path)
**   lfs.mkdir (path)
**   lfs.rmdir (path)
**   lfs.setmode (filepath, mode)
**   lfs.symlinkattributes (filepath [, attributename])
**   lfs.touch (filepath [, atime [, mtime]])
**   lfs.unlock (fh)
*/

#ifndef LFS_DO_NOT_USE_LARGE_FILE
#ifndef _WIN32
#ifndef _AIX
#define _FILE_OFFSET_BITS 64    /* Linux, Solaris and HP-UX */
#else
#define _LARGE_FILES 1          /* AIX */
#endif
#endif
#endif

#ifdef _WIN32
#define _WIN32_WINNT 0x600
#endif

#ifndef LFS_DO_NOT_USE_LARGE_FILE
#define _LARGEFILE64_SOURCE
#endif

#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <time.h>
#include <sys/stat.h>

#ifdef _WIN32

#include <direct.h>
#include <windows.h>
#include <io.h>
#include <sys/locking.h>

#ifdef __BORLANDC__
#include <utime.h>
#else
#include <sys/utime.h>
#endif

#include <fcntl.h>

/* MAX_PATH seems to be 260. Seems kind of small. Is there a better one? */
#define LFS_MAXPATHLEN MAX_PATH

#else

#include <unistd.h>
#include <dirent.h>
#include <fcntl.h>
#include <sys/types.h>
#include <utime.h>
#include <sys/param.h>          /* for MAXPATHLEN */

#ifdef MAXPATHLEN
#define LFS_MAXPATHLEN MAXPATHLEN
#else
#include <limits.h>             /* for _POSIX_PATH_MAX */
#define LFS_MAXPATHLEN _POSIX_PATH_MAX
#endif

#endif

#include "lua.h"
#include "lauxlib.h"
#include "lualib.h"

#include "lfs.h"

#define LFS_VERSION "1.8.0"
#define LFS_LIBNAME "lfs"

#if LUA_VERSION_NUM >= 503      /* Lua 5.3+ */

#ifndef luaL_optlong
#define luaL_optlong luaL_optinteger
#endif

#endif

#if LUA_VERSION_NUM >= 502
#define new_lib(L, l) (luaL_newlib(L, l))
#else
#define new_lib(L, l) (lua_newtable(L), luaL_register(L, NULL, l))
#endif

/* Define 'strerror' for systems that do not implement it */
#ifdef NO_STRERROR
#define strerror(_)     "System unable to describe the error"
#endif

#define DIR_METATABLE "directory metatable"
typedef struct dir_data {
  int closed;
#ifdef _WIN32
  intptr_t hFile;
  char pattern[MAX_PATH + 1];
#else
  DIR *dir;
#endif
} dir_data;

#define LOCK_METATABLE "lock metatable"

#ifdef _WIN32

#ifdef __BORLANDC__
#define lfs_setmode(file, m)   (setmode(_fileno(file), m))
#define STAT_STRUCT struct stati64
#else
#define lfs_setmode(file, m)   (_setmode(_fileno(file), m))
#define STAT_STRUCT struct _stati64
#endif

#ifndef _S_IFLNK
#define _S_IFLNK 0x400
#endif

#ifndef S_ISDIR
#define S_ISDIR(mode)  (mode&_S_IFDIR)
#endif
#ifndef S_ISREG
#define S_ISREG(mode)  (mode&_S_IFREG)
#endif
#ifndef S_ISLNK
#define S_ISLNK(mode)  (mode&_S_IFLNK)
#endif
#ifndef S_ISSOCK
#define S_ISSOCK(mode)  (0)
#endif
#ifndef S_ISFIFO
#define S_ISFIFO(mode)  (0)
#endif
#ifndef S_ISCHR
#define S_ISCHR(mode)  (mode&_S_IFCHR)
#endif
#ifndef S_ISBLK
#define S_ISBLK(mode)  (0)
#endif

#define STAT_FUNC _stati64
#define LSTAT_FUNC lfs_win32_lstat

#else

#define _O_TEXT               0
#define _O_BINARY             0
#define lfs_setmode(file, m)   ((void)file, (void)m, 0)
#define STAT_STRUCT struct stat
#define STAT_FUNC stat
extern int lstat(const char * pathname, struct stat * statbuf);
#define LSTAT_FUNC lstat

#endif

#ifdef _WIN32
#define lfs_mkdir _mkdir
#else
#define lfs_mkdir(path) (mkdir((path), \
    S_IRUSR | S_IWUSR | S_IXUSR | S_IRGRP | S_IWGRP | S_IXGRP | S_IROTH | S_IXOTH))
#endif

#ifdef _WIN32

int lfs_win32_pusherror(lua_State * L)
{
  int en = GetLastError();
  lua_pushnil(L);
  if (en == ERROR_FILE_EXISTS || en == ERROR_SHARING_VIOLATION)
    lua_pushstring(L, "File exists");
  else
    lua_pushstring(L, strerror(en));
  return 2;
}

#define TICKS_PER_SECOND 10000000
#define EPOCH_DIFFERENCE 11644473600LL
time_t windowsToUnixTime(FILETIME ft)
{
  ULARGE_INTEGER uli;
  uli.LowPart = ft.dwLowDateTime;
  uli.HighPart = ft.dwHighDateTime;
  return (time_t) (uli.QuadPart / TICKS_PER_SECOND - EPOCH_DIFFERENCE);
}

int lfs_win32_lstat(const char *path, STAT_STRUCT * buffer)
{
  WIN32_FILE_ATTRIBUTE_DATA win32buffer;
  if (GetFileAttributesEx(path, GetFileExInfoStandard, &win32buffer)) {
    if (!(win32buffer.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT)) {
      return STAT_FUNC(path, buffer);
    }
    buffer->st_mode = _S_IFLNK;
    buffer->st_dev = 0;
    buffer->st_ino = 0;
    buffer->st_nlink = 0;
    buffer->st_uid = 0;
    buffer->st_gid = 0;
    buffer->st_rdev = 0;
    buffer->st_atime = windowsToUnixTime(win32buffer.ftLastAccessTime);
    buffer->st_mtime = windowsToUnixTime(win32buffer.ftLastWriteTime);
    buffer->st_ctime = windowsToUnixTime(win32buffer.ftCreationTime);
    buffer->st_size = 0;
    return 0;
  } else {
    return 1;
  }
}

#endif

/*
** Utility functions
*/
static int pusherror(lua_State * L, const char *info)
{
  lua_pushnil(L);
  if (info == NULL)
    lua_pushstring(L, strerror(errno));
  else
    lua_pushfstring(L, "%s: %s", info, strerror(errno));
  lua_pushinteger(L, errno);
  return 3;
}

static int pushresult(lua_State * L, int res, const char *info)
{
  if (res == -1) {
    return pusherror(L, info);
  } else {
    lua_pushboolean(L, 1);
    return 1;
  }
}


/*
** Check if the given element on the stack is a file and returns it.
*/
static FILE *check_file(lua_State * L, int idx, const char *funcname)
{
#if LUA_VERSION_NUM == 501
  FILE **fh = (FILE **) luaL_checkudata(L, idx, "FILE*");
  if (*fh == NULL) {
    luaL_error(L, "%s: closed file", funcname);
    return 0;
  } else
    return *fh;
#elif LUA_VERSION_NUM >= 502 && LUA_VERSION_NUM <= 504
  luaL_Stream *fh = (luaL_Stream *) luaL_checkudata(L, idx, "FILE*");
  if (fh->closef == 0 || fh->f == NULL) {
    luaL_error(L, "%s: closed file", funcname);
    return 0;
  } else
    return fh->f;
#else
#error unsupported Lua version
#endif
}


/*
**
*/
static int _file_lock(lua_State * L, FILE * fh, const char *mode,
                      const long start, long len, const char *funcname)
{
  int code;
#ifdef _WIN32
  /* lkmode valid values are:
     LK_LOCK    Locks the specified bytes. If the bytes cannot be locked,
     the program immediately tries again after 1 second.
     If, after 10 attempts, the bytes cannot be locked,
     the constant returns an error.
     LK_NBLCK   Locks the specified bytes. If the bytes cannot be locked,
     the constant returns an error.
     LK_NBRLCK  Same as _LK_NBLCK.
     LK_RLCK    Same as _LK_LOCK.
     LK_UNLCK   Unlocks the specified bytes, which must have been
     previously locked.

     Regions should be locked only briefly and should be unlocked
     before closing a file or exiting the program.

     http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vclib/html/_crt__locking.asp
   */
  int lkmode;
  switch (*mode) {
  case 'r':
    lkmode = LK_NBLCK;
    break;
  case 'w':
    lkmode = LK_NBLCK;
    break;
  case 'u':
    lkmode = LK_UNLCK;
    break;
  default:
    return luaL_error(L, "%s: invalid mode", funcname);
  }
  if (!len) {
    fseek(fh, 0L, SEEK_END);
    len = ftell(fh);
  }
  fseek(fh, start, SEEK_SET);
#ifdef __BORLANDC__
  code = locking(fileno(fh), lkmode, len);
#else
  code = _locking(fileno(fh), lkmode, len);
#endif
#else
  struct flock f;
  switch (*mode) {
  case 'w':
    f.l_type = F_WRLCK;
    break;
  case 'r':
    f.l_type = F_RDLCK;
    break;
  case 'u':
    f.l_type = F_UNLCK;
    break;
  default:
    return luaL_error(L, "%s: invalid mode", funcname);
  }
  f.l_whence = SEEK_SET;
  f.l_start = (off_t) start;
  f.l_len = (off_t) len;
  code = fcntl(fileno(fh), F_SETLK, &f);
#endif
  return (code != -1);
}

#ifdef _WIN32
typedef struct lfs_Lock {
  HANDLE fd;
} lfs_Lock;
static int lfs_lock_dir(lua_State * L)
{
  size_t pathl;
  HANDLE fd;
  lfs_Lock *lock;
  char *ln;
  const char *lockfile = "/lockfile.lfs";
  const char *path = luaL_checklstring(L, 1, &pathl);
  ln = (char *) malloc(pathl + strlen(lockfile) + 1);
  if (!ln) {
    lua_pushnil(L);
    lua_pushstring(L, strerror(errno));
    return 2;
  }
  strcpy(ln, path);
  strcat(ln, lockfile);
  fd = CreateFile(ln, GENERIC_WRITE, 0, NULL, CREATE_ALWAYS,
                  FILE_ATTRIBUTE_NORMAL | FILE_FLAG_DELETE_ON_CLOSE, NULL);
  free(ln);
  if (fd == INVALID_HANDLE_VALUE) {
    return lfs_win32_pusherror(L);
  }
  lock = (lfs_Lock *) lua_newuserdata(L, sizeof(lfs_Lock));
  lock->fd = fd;
  luaL_getmetatable(L, LOCK_METATABLE);
  lua_setmetatable(L, -2);
  return 1;
}

static int lfs_unlock_dir(lua_State * L)
{
  lfs_Lock *lock = (lfs_Lock *) luaL_checkudata(L, 1, LOCK_METATABLE);
  if (lock->fd != INVALID_HANDLE_VALUE) {
    CloseHandle(lock->fd);
    lock->fd = INVALID_HANDLE_VALUE;
  }
  return 0;
}
#else
typedef struct lfs_Lock {
  char *ln;
} lfs_Lock;
static int lfs_lock_dir(lua_State * L)
{
  lfs_Lock *lock;
  size_t pathl;
  char *ln;
  const char *lockfile = "/lockfile.lfs";
  const char *path = luaL_checklstring(L, 1, &pathl);
  lock = (lfs_Lock *) lua_newuserdata(L, sizeof(lfs_Lock));
  ln = (char *) malloc(pathl + strlen(lockfile) + 1);
  if (!ln) {
    lua_pushnil(L);
    lua_pushstring(L, strerror(errno));
    return 2;
  }
  strcpy(ln, path);
  strcat(ln, lockfile);
  if (symlink("lock", ln) == -1) {
    free(ln);
    lua_pushnil(L);
    lua_pushstring(L, strerror(errno));
    return 2;
  }
  lock->ln = ln;
  luaL_getmetatable(L, LOCK_METATABLE);
  lua_setmetatable(L, -2);
  return 1;
}

static int lfs_unlock_dir(lua_State * L)
{
  lfs_Lock *lock = (lfs_Lock *) luaL_checkudata(L, 1, LOCK_METATABLE);
  if (lock->ln) {
    unlink(lock->ln);
    free(lock->ln);
    lock->ln = NULL;
  }
  return 0;
}
#endif

static int lfs_g_setmode(lua_State * L, FILE * f, int arg)
{
  static const int mode[] = { _O_BINARY, _O_TEXT };
  static const char *const modenames[] = { "binary", "text", NULL };
  int op = luaL_checkoption(L, arg, NULL, modenames);
  int res = lfs_setmode(f, mode[op]);
  if (res != -1) {
    int i;
    lua_pushboolean(L, 1);
    for (i = 0; modenames[i] != NULL; i++) {
      if (mode[i] == res) {
        lua_pushstring(L, modenames[i]);
        return 2;
      }
    }
    lua_pushnil(L);
    return 2;
  } else {
    return pusherror(L, NULL);
  }
}

static int lfs_f_setmode(lua_State * L)
{
  return lfs_g_setmode(L, check_file(L, 1, "setmode"), 2);
}

/*
** Locks a file.
** @param #1 File handle.
** @param #2 String with lock mode ('w'rite, 'r'ead).
** @param #3 Number with start position (optional).
** @param #4 Number with length (optional).
*/
static int file_lock(lua_State * L)
{
  FILE *fh = check_file(L, 1, "lock");
  const char *mode = luaL_checkstring(L, 2);
  const long start = (long) luaL_optinteger(L, 3, 0);
  long len = (long) luaL_optinteger(L, 4, 0);
  if (_file_lock(L, fh, mode, start, len, "lock")) {
    lua_pushboolean(L, 1);
    return 1;
  } else {
    lua_pushnil(L);
    lua_pushfstring(L, "%s", strerror(errno));
    return 2;
  }
}


/*
** Unlocks a file.
** @param #1 File handle.
** @param #2 Number with start position (optional).
** @param #3 Number with length (optional).
*/
static int file_unlock(lua_State * L)
{
  FILE *fh = check_file(L, 1, "unlock");
  const long start = (long) luaL_optinteger(L, 2, 0);
  long len = (long) luaL_optinteger(L, 3, 0);
  if (_file_lock(L, fh, "u", start, len, "unlock")) {
    lua_pushboolean(L, 1);
    return 1;
  } else {
    lua_pushnil(L);
    lua_pushfstring(L, "%s", strerror(errno));
    return 2;
  }
}


/*
** Creates a link.
** @param #1 Object to link to.
** @param #2 Name of link.
** @param #3 True if link is symbolic (optional).
*/
static int make_link(lua_State * L)
{
  const char *oldpath = luaL_checkstring(L, 1);
  const char *newpath = luaL_checkstring(L, 2);
#ifndef _WIN32
  return pushresult(L,
                    (lua_toboolean(L, 3) ? symlink : link) (oldpath,
                                                            newpath),
                    NULL);
#else
  int symbolic = lua_toboolean(L, 3);
  STAT_STRUCT oldpathinfo;
  int is_dir = 0;
  if (STAT_FUNC(oldpath, &oldpathinfo) == 0) {
    is_dir = S_ISDIR(oldpathinfo.st_mode) != 0;
  }
  if (!symbolic && is_dir) {
    lua_pushnil(L);
    lua_pushstring(L,
                   "hard links to directories are not supported on Windows");
    return 2;
  }

  int result = symbolic ? CreateSymbolicLink(newpath, oldpath, is_dir)
      : CreateHardLink(newpath, oldpath, NULL);

  if (result) {
    return pushresult(L, result, NULL);
  } else {
    lua_pushnil(L);
    lua_pushstring(L, symbolic ? "make_link CreateSymbolicLink() failed"
                   : "make_link CreateHardLink() failed");
    return 2;
  }
#endif
}


/*
** Creates a directory.
** @param #1 Directory path.
*/
static int make_dir(lua_State * L)
{
  const char *path = luaL_checkstring(L, 1);
  return pushresult(L, lfs_mkdir(path), NULL);
}


/*
** Removes a directory.
** @param #1 Directory path.
*/
static int remove_dir(lua_State * L)
{
  const char *path = luaL_checkstring(L, 1);
  return pushresult(L, rmdir(path), NULL);
}


/*
** Directory iterator
*/
static int dir_iter(lua_State * L)
{
#ifdef _WIN32
  struct _finddata_t c_file;
#else
  struct dirent *entry;
#endif
  dir_data *d = (dir_data *) luaL_checkudata(L, 1, DIR_METATABLE);
  luaL_argcheck(L, d->closed == 0, 1, "closed directory");
#ifdef _WIN32
  if (d->hFile == 0L) {         /* first entry */
    if ((d->hFile = _findfirst(d->pattern, &c_file)) == -1L) {
      lua_pushnil(L);
      lua_pushstring(L, strerror(errno));
      d->closed = 1;
      return 2;
    } else {
      lua_pushstring(L, c_file.name);
      return 1;
    }
  } else {                      /* next entry */
    if (_findnext(d->hFile, &c_file) == -1L) {
      /* no more entries => close directory */
      _findclose(d->hFile);
      d->closed = 1;
      return 0;
    } else {
      lua_pushstring(L, c_file.name);
      return 1;
    }
  }
#else
  if ((entry = readdir(d->dir)) != NULL) {
    lua_pushstring(L, entry->d_name);
    return 1;
  } else {
    /* no more entries => close directory */
    closedir(d->dir);
    d->closed = 1;
    return 0;
  }
#endif
}


/*
** Closes directory iterators
*/
static int dir_close(lua_State * L)
{
  dir_data *d = (dir_data *) lua_touserdata(L, 1);
#ifdef _WIN32
  if (!d->closed && d->hFile) {
    _findclose(d->hFile);
  }
#else
  if (!d->closed && d->dir) {
    closedir(d->dir);
  }
#endif
  d->closed = 1;
  return 0;
}


/*
** Factory of directory iterators
*/
static int dir_iter_factory(lua_State * L)
{
  const char *path = luaL_checkstring(L, 1);
  dir_data *d;
  lua_pushcfunction(L, dir_iter);
  d = (dir_data *) lua_newuserdata(L, sizeof(dir_data));
  luaL_getmetatable(L, DIR_METATABLE);
  lua_setmetatable(L, -2);
  d->closed = 0;
#ifdef _WIN32
  d->hFile = 0L;
  if (strlen(path) > MAX_PATH - 2)
    luaL_error(L, "path too long: %s", path);
  else
    sprintf(d->pattern, "%s/*", path);
#else
  d->dir = opendir(path);
  if (d->dir == NULL)
    luaL_error(L, "cannot open %s: %s", path, strerror(errno));
#endif
#if LUA_VERSION_NUM >= 504
  lua_pushnil(L);
  lua_pushvalue(L, -2);
  return 4;
#else
  return 2;
#endif
}


/*
** Creates directory metatable.
*/
static int dir_create_meta(lua_State * L)
{
  luaL_newmetatable(L, DIR_METATABLE);

  /* Method table */
  lua_newtable(L);
  lua_pushcfunction(L, dir_iter);
  lua_setfield(L, -2, "next");
  lua_pushcfunction(L, dir_close);
  lua_setfield(L, -2, "close");

  /* Metamethods */
  lua_setfield(L, -2, "__index");
  lua_pushcfunction(L, dir_close);
  lua_setfield(L, -2, "__gc");

#if LUA_VERSION_NUM >= 504
  lua_pushcfunction(L, dir_close);
  lua_setfield(L, -2, "__close");
#endif
  return 1;
}


/*
** Creates lock metatable.
*/
static int lock_create_meta(lua_State * L)
{
  luaL_newmetatable(L, LOCK_METATABLE);

  /* Method table */
  lua_newtable(L);
  lua_pushcfunction(L, lfs_unlock_dir);
  lua_setfield(L, -2, "free");

  /* Metamethods */
  lua_setfield(L, -2, "__index");
  lua_pushcfunction(L, lfs_unlock_dir);
  lua_setfield(L, -2, "__gc");
  return 1;
}


/*
** Convert the inode protection mode to a string.
*/
#ifdef _WIN32
static const char *mode2string(unsigned short mode)
{
#else
static const char *mode2string(mode_t mode)
{
#endif
  if (S_ISREG(mode))
    return "file";
  else if (S_ISDIR(mode))
    return "directory";
  else if (S_ISLNK(mode))
    return "link";
  else if (S_ISSOCK(mode))
    return "socket";
  else if (S_ISFIFO(mode))
    return "named pipe";
  else if (S_ISCHR(mode))
    return "char device";
  else if (S_ISBLK(mode))
    return "block device";
  else
    return "other";
}


/*
** Set access time and modification values for a file.
** @param #1 File path.
** @param #2 Access time in seconds, current time is used if missing.
** @param #3 Modification time in seconds, access time is used if missing.
*/
static int file_utime(lua_State * L)
{
  const char *file = luaL_checkstring(L, 1);
  struct utimbuf utb, *buf;

  if (lua_gettop(L) == 1)       /* set to current date/time */
    buf = NULL;
  else {
    utb.actime = (time_t) luaL_optnumber(L, 2, 0);
    utb.modtime = (time_t) luaL_optinteger(L, 3, utb.actime);
    buf = &utb;
  }

  return pushresult(L, utime(file, buf), NULL);
}


/* inode protection mode */
static void push_st_mode(lua_State * L, STAT_STRUCT * info)
{
  lua_pushstring(L, mode2string(info->st_mode));
}

/* device inode resides on */
static void push_st_dev(lua_State * L, STAT_STRUCT * info)
{
  lua_pushinteger(L, (lua_Integer) info->st_dev);
}

/* inode's number */
static void push_st_ino(lua_State * L, STAT_STRUCT * info)
{
  lua_pushinteger(L, (lua_Integer) info->st_ino);
}

/* number of hard links to the file */
static void push_st_nlink(lua_State * L, STAT_STRUCT * info)
{
  lua_pushinteger(L, (lua_Integer) info->st_nlink);
}

/* user-id of owner */
static void push_st_uid(lua_State * L, STAT_STRUCT * info)
{
  lua_pushinteger(L, (lua_Integer) info->st_uid);
}

/* group-id of owner */
static void push_st_gid(lua_State * L, STAT_STRUCT * info)
{
  lua_pushinteger(L, (lua_Integer) info->st_gid);
}

/* device type, for special file inode */
static void push_st_rdev(lua_State * L, STAT_STRUCT * info)
{
  lua_pushinteger(L, (lua_Integer) info->st_rdev);
}

/* time of last access */
static void push_st_atime(lua_State * L, STAT_STRUCT * info)
{
  lua_pushinteger(L, (lua_Integer) info->st_atime);
}

/* time of last data modification */
static void push_st_mtime(lua_State * L, STAT_STRUCT * info)
{
  lua_pushinteger(L, (lua_Integer) info->st_mtime);
}

/* time of last file status change */
static void push_st_ctime(lua_State * L, STAT_STRUCT * info)
{
  lua_pushinteger(L, (lua_Integer) info->st_ctime);
}

/* file size, in bytes */
static void push_st_size(lua_State * L, STAT_STRUCT * info)
{
  lua_pushinteger(L, (lua_Integer) info->st_size);
}

#ifndef _WIN32
/* blocks allocated for file */
static void push_st_blocks(lua_State * L, STAT_STRUCT * info)
{
  lua_pushinteger(L, (lua_Integer) info->st_blocks);
}

/* optimal file system I/O blocksize */
static void push_st_blksize(lua_State * L, STAT_STRUCT * info)
{
  lua_pushinteger(L, (lua_Integer) info->st_blksize);
}
#endif

 /*
  ** Convert the inode protection mode to a permission list.
  */

#ifdef _WIN32
static const char *perm2string(unsigned short mode)
{
  static char perms[10] = "---------";
  int i;
  for (i = 0; i < 9; i++)
    perms[i] = '-';
  if (mode & _S_IREAD) {
    perms[0] = 'r';
    perms[3] = 'r';
    perms[6] = 'r';
  }
  if (mode & _S_IWRITE) {
    perms[1] = 'w';
    perms[4] = 'w';
    perms[7] = 'w';
  }
  if (mode & _S_IEXEC) {
    perms[2] = 'x';
    perms[5] = 'x';
    perms[8] = 'x';
  }
  return perms;
}
#else
static const char *perm2string(mode_t mode)
{
  static char perms[10] = "---------";
  int i;
  for (i = 0; i < 9; i++)
    perms[i] = '-';
  if (mode & S_IRUSR)
    perms[0] = 'r';
  if (mode & S_IWUSR)
    perms[1] = 'w';
  if (mode & S_IXUSR)
    perms[2] = 'x';
  if (mode & S_IRGRP)
    perms[3] = 'r';
  if (mode & S_IWGRP)
    perms[4] = 'w';
  if (mode & S_IXGRP)
    perms[5] = 'x';
  if (mode & S_IROTH)
    perms[6] = 'r';
  if (mode & S_IWOTH)
    perms[7] = 'w';
  if (mode & S_IXOTH)
    perms[8] = 'x';
  return perms;
}
#endif

/* permssions string */
static void push_st_perm(lua_State * L, STAT_STRUCT * info)
{
  lua_pushstring(L, perm2string(info->st_mode));
}

typedef void (*_push_function)(lua_State * L, STAT_STRUCT * info);

struct _stat_members {
  const char *name;
  _push_function push;
};

struct _stat_members members[] = {
  { "mode", push_st_mode },
  { "dev", push_st_dev },
  { "ino", push_st_ino },
  { "nlink", push_st_nlink },
  { "uid", push_st_uid },
  { "gid", push_st_gid },
  { "rdev", push_st_rdev },
  { "access", push_st_atime },
  { "modification", push_st_mtime },
  { "change", push_st_ctime },
  { "size", push_st_size },
  { "permissions", push_st_perm },
#ifndef _WIN32
  { "blocks", push_st_blocks },
  { "blksize", push_st_blksize },
#endif
  { NULL, NULL }
};

/*
** Get file or symbolic link information
*/
static int _file_info_(lua_State * L,
                       int (*st)(const char *, STAT_STRUCT *))
{
  STAT_STRUCT info;
  const char *file = luaL_checkstring(L, 1);
  int i;

  if (st(file, &info)) {
    lua_pushnil(L);
    lua_pushfstring(L, "cannot obtain information from file '%s': %s",
                    file, strerror(errno));
    lua_pushinteger(L, errno);
    return 3;
  }
  if (lua_isstring(L, 2)) {
    const char *member = lua_tostring(L, 2);
    for (i = 0; members[i].name; i++) {
      if (strcmp(members[i].name, member) == 0) {
        /* push member value and return */
        members[i].push(L, &info);
        return 1;
      }
    }
    /* member not found */
    return luaL_error(L, "invalid attribute name '%s'", member);
  }
  /* creates a table if none is given, removes extra arguments */
  lua_settop(L, 2);
  if (!lua_istable(L, 2)) {
    lua_newtable(L);
  }
  /* stores all members in table on top of the stack */
  for (i = 0; members[i].name; i++) {
    lua_pushstring(L, members[i].name);
    members[i].push(L, &info);
    lua_rawset(L, -3);
  }
  return 1;
}


/*
** Get file information using stat.
*/
static int file_info(lua_State * L)
{
  return _file_info_(L, STAT_FUNC);
}


/*
** Push the symlink target to the top of the stack.
** Assumes the file name is at position 1 of the stack.
** Returns 1 if successful (with the target on top of the stack),
** 0 on failure (with stack unchanged, and errno set).
*/
static int push_link_target(lua_State * L)
{
  const char *file = luaL_checkstring(L, 1);
#ifdef _WIN32
  HANDLE h = CreateFile(file, GENERIC_READ,
                        FILE_SHARE_READ | FILE_SHARE_WRITE, NULL,
                        OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
  if (h == INVALID_HANDLE_VALUE) {
    return lfs_win32_pusherror(L);
  }
#endif
  char *target = NULL;
  int tsize, size = 256;        /* size = initial buffer capacity */
  int ok = 0;
  while (!ok) {
    char *target2 = realloc(target, size);
    if (!target2) {             /* failed to allocate */
      break;
    }
    target = target2;
#ifdef _WIN32
    tsize = GetFinalPathNameByHandle(h, target, size, FILE_NAME_OPENED);
#else
    tsize = readlink(file, target, size);
#endif
    if (tsize < 0) {            /* a readlink() error occurred */
      break;
    }
    if (tsize < size) {
#ifdef _WIN32
      if (tsize > 4 && strncmp(target, "\\\\?\\", 4) == 0) {
        memmove_s(target, tsize - 3, target + 4, tsize - 3);
        tsize -= 4;
      }
#endif
      ok = 1;
      break;
    }
    /* possibly truncated readlink() result, double size and retry */
    size *= 2;
  }
  if (ok) {
    target[tsize] = '\0';
    lua_pushlstring(L, target, tsize);
  }
#ifdef _WIN32
  CloseHandle(h);
#endif
  free(target);
  return ok;
}

/*
** Get symbolic link information using lstat.
*/
static int link_info(lua_State * L)
{
  int ret;
  if (lua_isstring(L, 2) && (strcmp(lua_tostring(L, 2), "target") == 0)) {
    int ok = push_link_target(L);
    return ok ? 1 : pusherror(L, "could not obtain link target");
  }
  ret = _file_info_(L, LSTAT_FUNC);
  if (ret == 1 && lua_type(L, -1) == LUA_TTABLE) {
    int ok = push_link_target(L);
    if (ok) {
      lua_setfield(L, -2, "target");
    }
  }
  return ret;
}


/*
** Assumes the table is on top of the stack.
*/
static void set_info(lua_State * L)
{
  lua_pushliteral(L, "Copyright (C) 2003-2017 Kepler Project");
  lua_setfield(L, -2, "_COPYRIGHT");
  lua_pushliteral(L,
                  "LuaFileSystem is a Lua library developed to complement "
                  "the set of functions related to file systems offered by "
                  "the standard Lua distribution");
  lua_setfield(L, -2, "_DESCRIPTION");
  lua_pushliteral(L, "LuaFileSystem " LFS_VERSION);
  lua_setfield(L, -2, "_VERSION");
}


static const struct luaL_Reg fslib[] = {
  { "attributes", file_info },
  /* no 'chdir' without sandboxing it */
  /* no 'currentdir' without sandboxing it */
  { "dir", dir_iter_factory },
  { "link", make_link },
  { "lock", file_lock },
  { "mkdir", make_dir },
  { "rmdir", remove_dir },
  { "symlinkattributes", link_info },
  { "setmode", lfs_f_setmode },
  { "touch", file_utime },
  { "unlock", file_unlock },
  { "lock_dir", lfs_lock_dir },
  { NULL, NULL },
};

LFS_EXPORT int luaopen_lfs(lua_State * L)
{
  dir_create_meta(L);
  lock_create_meta(L);
  new_lib(L, fslib);
  lua_pushvalue(L, -1);
  lua_setglobal(L, LFS_LIBNAME);
  set_info(L);
  return 1;
}