dirent.h

/*
 * Dirent interface for Microsoft Visual Studio
 *
 * Copyright (C) 1998-2019 Toni Ronkko
 * This file is part of dirent.  Dirent may be freely distributed
 * under the MIT license.  For all details and documentation, see
 * https://github.com/tronkko/dirent
 */
#ifndef DIRENT_H
#define DIRENT_H

 /* Hide warnings about unreferenced local functions */
#if defined(__clang__)
#	pragma clang diagnostic ignored "-Wunused-function"
#elif defined(_MSC_VER)
#	pragma warning(disable:4505)
#elif defined(__GNUC__)
#	pragma GCC diagnostic ignored "-Wunused-function"
#endif

/*
 * Include windows.h without Windows Sockets 1.1 to prevent conflicts with
 * Windows Sockets 2.0.
 */
#ifndef WIN32_LEAN_AND_MEAN
#	define WIN32_LEAN_AND_MEAN
#endif
#include <windows.h>

#include <stdio.h>
#include <stdarg.h>
#include <wchar.h>
#include <string.h>
#include <stdlib.h>
#include <malloc.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>
#include <ctype.h>

 /* Indicates that d_type field is available in dirent structure */
#define _DIRENT_HAVE_D_TYPE

/* Indicates that d_namlen field is available in dirent structure */
#define _DIRENT_HAVE_D_NAMLEN

/* Entries missing from MSVC 6.0 */
#if !defined(FILE_ATTRIBUTE_DEVICE)
#	define FILE_ATTRIBUTE_DEVICE 0x40
#endif

/* File type and permission flags for stat(), general mask */
#if !defined(S_IFMT)
#	define S_IFMT _S_IFMT
#endif

/* Directory bit */
#if !defined(S_IFDIR)
#	define S_IFDIR _S_IFDIR
#endif

/* Character device bit */
#if !defined(S_IFCHR)
#	define S_IFCHR _S_IFCHR
#endif

/* Pipe bit */
#if !defined(S_IFFIFO)
#	define S_IFFIFO _S_IFFIFO
#endif

/* Regular file bit */
#if !defined(S_IFREG)
#	define S_IFREG _S_IFREG
#endif

/* Read permission */
#if !defined(S_IREAD)
#	define S_IREAD _S_IREAD
#endif

/* Write permission */
#if !defined(S_IWRITE)
#	define S_IWRITE _S_IWRITE
#endif

/* Execute permission */
#if !defined(S_IEXEC)
#	define S_IEXEC _S_IEXEC
#endif

/* Pipe */
#if !defined(S_IFIFO)
#	define S_IFIFO _S_IFIFO
#endif

/* Block device */
#if !defined(S_IFBLK)
#	define S_IFBLK 0
#endif

/*
 * Symbolic link.  Be ware that S_IFLNK value and S_ISLNK() macro are only
 * usable with dirent - they do not work with stat() function call!
 */
#if !defined(S_IFLNK)
#	define S_IFLNK (_S_IFDIR | _S_IFREG)
#endif

 /* Socket */
#if !defined(S_IFSOCK)
#	define S_IFSOCK 0
#endif

/* Read user permission */
#if !defined(S_IRUSR)
#	define S_IRUSR S_IREAD
#endif

/* Write user permission */
#if !defined(S_IWUSR)
#	define S_IWUSR S_IWRITE
#endif

/* Execute user permission */
#if !defined(S_IXUSR)
#	define S_IXUSR 0
#endif

/* User full permissions */
#if !defined(S_IRWXU)
#	define S_IRWXU (S_IRUSR | S_IWUSR | S_IXUSR)
#endif

/* Read group permission */
#if !defined(S_IRGRP)
#	define S_IRGRP 0
#endif

/* Write group permission */
#if !defined(S_IWGRP)
#	define S_IWGRP 0
#endif

/* Execute group permission */
#if !defined(S_IXGRP)
#	define S_IXGRP 0
#endif

/* Group full permissions */
#if !defined(S_IRWXG)
#	define S_IRWXG (S_IRGRP | S_IWGRP | S_IXGRP)
#endif

/* Read others permission */
#if !defined(S_IROTH)
#	define S_IROTH 0
#endif

/* Write others permission */
#if !defined(S_IWOTH)
#	define S_IWOTH 0
#endif

/* Execute others permission */
#if !defined(S_IXOTH)
#	define S_IXOTH 0
#endif

/* Other full permissions */
#if !defined(S_IRWXO)
#	define S_IRWXO (S_IROTH | S_IWOTH | S_IXOTH)
#endif

/* Maximum length of file name */
#if !defined(PATH_MAX)
#	define PATH_MAX MAX_PATH
#endif
#if !defined(FILENAME_MAX)
#	define FILENAME_MAX MAX_PATH
#endif
#if !defined(NAME_MAX)
#	define NAME_MAX FILENAME_MAX
#endif

/* File type flags for d_type */
#define DT_UNKNOWN 0
#define DT_REG S_IFREG
#define DT_DIR S_IFDIR
#define DT_FIFO S_IFIFO
#define DT_SOCK S_IFSOCK
#define DT_CHR S_IFCHR
#define DT_BLK S_IFBLK
#define DT_LNK S_IFLNK

/* Macros for converting between st_mode and d_type */
#define IFTODT(mode) ((mode) & S_IFMT)
#define DTTOIF(type) (type)

/*
 * File type macros.  Note that block devices and sockets cannot be
 * distinguished on Windows, and the macros S_ISBLK and S_ISSOCK are only
 * defined for compatibility.  These macros should always return false on
 * Windows.
 */
#if !defined(S_ISFIFO)
#	define S_ISFIFO(mode) (((mode) & S_IFMT) == S_IFIFO)
#endif
#if !defined(S_ISDIR)
#	define S_ISDIR(mode) (((mode) & S_IFMT) == S_IFDIR)
#endif
#if !defined(S_ISREG)
#	define S_ISREG(mode) (((mode) & S_IFMT) == S_IFREG)
#endif
#if !defined(S_ISLNK)
#	define S_ISLNK(mode) (((mode) & S_IFMT) == S_IFLNK)
#endif
#if !defined(S_ISSOCK)
#	define S_ISSOCK(mode) (((mode) & S_IFMT) == S_IFSOCK)
#endif
#if !defined(S_ISCHR)
#	define S_ISCHR(mode) (((mode) & S_IFMT) == S_IFCHR)
#endif
#if !defined(S_ISBLK)
#	define S_ISBLK(mode) (((mode) & S_IFMT) == S_IFBLK)
#endif

 /* Return the exact length of the file name without zero terminator */
#define _D_EXACT_NAMLEN(p) ((p)->d_namlen)

/* Return the maximum size of a file name */
#define _D_ALLOC_NAMLEN(p) ((PATH_MAX)+1)


#ifdef __cplusplus
extern "C" {
#endif


	/* Wide-character version */
	struct _wdirent {
		/* Always zero */
		long d_ino;

		/* Position of next file in a directory stream */
		long d_off;

		/* Structure size */
		unsigned short d_reclen;

		/* Length of name without \0 */
		size_t d_namlen;

		/* File type */
		int d_type;

		/* File name */
		wchar_t d_name[PATH_MAX + 1];
	};
	typedef struct _wdirent _wdirent;

	struct _WDIR {
		/* Current directory entry */
		struct _wdirent ent;

		/* Private file data */
		WIN32_FIND_DATAW data;

		/* True if data is valid */
		int cached;

		/* True if next entry is invalid */
		int invalid;

		/* Win32 search handle */
		HANDLE handle;

		/* Initial directory name */
		wchar_t* patt;
	};
	typedef struct _WDIR _WDIR;

	/* Multi-byte character version */
	struct dirent {
		/* Always zero */
		long d_ino;

		/* Position of next file in a directory stream */
		long d_off;

		/* Structure size */
		unsigned short d_reclen;

		/* Length of name without \0 */
		size_t d_namlen;

		/* File type */
		int d_type;

		/* File name */
		char d_name[PATH_MAX + 1];
	};
	typedef struct dirent dirent;

	struct DIR {
		struct dirent ent;
		struct _WDIR* wdirp;
	};
	typedef struct DIR DIR;


	/* Dirent functions */
	static DIR* opendir(const char* dirname);
	static _WDIR* _wopendir(const wchar_t* dirname);

	static struct dirent* readdir(DIR* dirp);
	static struct _wdirent* _wreaddir(_WDIR* dirp);

	static int readdir_r(
		DIR* dirp, struct dirent* entry, struct dirent** result);
	static int _wreaddir_r(
		_WDIR* dirp, struct _wdirent* entry, struct _wdirent** result);

	static int closedir(DIR* dirp);
	static int _wclosedir(_WDIR* dirp);

	static void rewinddir(DIR* dirp);
	static void _wrewinddir(_WDIR* dirp);

	static long telldir(DIR* dirp);
	static long _wtelldir(_WDIR* dirp);

	static void seekdir(DIR* dirp, long loc);
	static void _wseekdir(_WDIR* dirp, long loc);

	static int scandir(const char* dirname, struct dirent*** namelist,
		int (*filter)(const struct dirent*),
		int (*compare)(const struct dirent**, const struct dirent**));

	static int alphasort(const struct dirent** a, const struct dirent** b);

	static int versionsort(const struct dirent** a, const struct dirent** b);

	static int strverscmp(const char* a, const char* b);

	/* For compatibility with Symbian */
#define wdirent _wdirent
#define WDIR _WDIR
#define wopendir _wopendir
#define wreaddir _wreaddir
#define wclosedir _wclosedir
#define wrewinddir _wrewinddir
#define wtelldir _wtelldir
#define wseekdir _wseekdir

/* Compatibility with older Microsoft compilers and non-Microsoft compilers */
#if !defined(_MSC_VER) || _MSC_VER < 1400
#	define wcstombs_s dirent_wcstombs_s
#	define mbstowcs_s dirent_mbstowcs_s
#endif

/* Optimize dirent_set_errno() away on modern Microsoft compilers */
#if defined(_MSC_VER) && _MSC_VER >= 1400
#	define dirent_set_errno _set_errno
#endif


/* Internal utility functions */
	static WIN32_FIND_DATAW* dirent_first(_WDIR* dirp);
	static WIN32_FIND_DATAW* dirent_next(_WDIR* dirp);
	static long dirent_hash(WIN32_FIND_DATAW* datap);

#if !defined(_MSC_VER) || _MSC_VER < 1400
	static int dirent_mbstowcs_s(
		size_t* pReturnValue, wchar_t* wcstr, size_t sizeInWords,
		const char* mbstr, size_t count);
#endif

#if !defined(_MSC_VER) || _MSC_VER < 1400
	static int dirent_wcstombs_s(
		size_t* pReturnValue, char* mbstr, size_t sizeInBytes,
		const wchar_t* wcstr, size_t count);
#endif

#if !defined(_MSC_VER) || _MSC_VER < 1400
	static void dirent_set_errno(int error);
#endif


	/*
	 * Open directory stream DIRNAME for read and return a pointer to the
	 * internal working area that is used to retrieve individual directory
	 * entries.
	 */
	static _WDIR*
		_wopendir(const wchar_t* dirname)
	{
		wchar_t* p;

		/* Must have directory name */
		if (dirname == NULL || dirname[0] == '\0') {
			dirent_set_errno(ENOENT);
			return NULL;
		}

		/* Allocate new _WDIR structure */
		_WDIR* dirp = (_WDIR*)malloc(sizeof(struct _WDIR));
		if (!dirp)
			return NULL;

		/* Reset _WDIR structure */
		dirp->handle = INVALID_HANDLE_VALUE;
		dirp->patt = NULL;
		dirp->cached = 0;
		dirp->invalid = 0;

		/*
		 * Compute the length of full path plus zero terminator
		 *
		 * Note that on WinRT there's no way to convert relative paths
		 * into absolute paths, so just assume it is an absolute path.
		 */
#if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)
		 /* Desktop */
		DWORD n = GetFullPathNameW(dirname, 0, NULL, NULL);
#else
		 /* WinRT */
		size_t n = wcslen(dirname);
#endif

		/* Allocate room for absolute directory name and search pattern */
		dirp->patt = (wchar_t*)malloc(sizeof(wchar_t) * n + 16);
		if (dirp->patt == NULL)
			goto exit_closedir;

		/*
		 * Convert relative directory name to an absolute one.  This
		 * allows rewinddir() to function correctly even when current
		 * working directory is changed between opendir() and rewinddir().
		 *
		 * Note that on WinRT there's no way to convert relative paths
		 * into absolute paths, so just assume it is an absolute path.
		 */
#if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)
		 /* Desktop */
		n = GetFullPathNameW(dirname, n, dirp->patt, NULL);
		if (n <= 0)
			goto exit_closedir;
#else
		 /* WinRT */
		wcsncpy_s(dirp->patt, n + 1, dirname, n);
#endif

		/* Append search pattern \* to the directory name */
		p = dirp->patt + n;
		switch (p[-1]) {
		case '\\':
		case '/':
		case ':':
			/* Directory ends in path separator, e.g. c:\temp\ */
			/*NOP*/;
			break;

		default:
			/* Directory name doesn't end in path separator */
			*p++ = '\\';
		}
		*p++ = '*';
		*p = '\0';

		/* Open directory stream and retrieve the first entry */
		if (!dirent_first(dirp))
			goto exit_closedir;

		/* Success */
		return dirp;

		/* Failure */
	exit_closedir:
		_wclosedir(dirp);
		return NULL;
	}

	/*
	 * Read next directory entry.
	 *
	 * Returns pointer to static directory entry which may be overwritten by
	 * subsequent calls to _wreaddir().
	 */
	static struct _wdirent*
		_wreaddir(_WDIR* dirp)
	{
		/*
		 * Read directory entry to buffer.  We can safely ignore the return
		 * value as entry will be set to NULL in case of error.
		 */
		struct _wdirent* entry;
		(void)_wreaddir_r(dirp, &dirp->ent, &entry);

		/* Return pointer to statically allocated directory entry */
		return entry;
	}

	/*
	 * Read next directory entry.
	 *
	 * Returns zero on success.  If end of directory stream is reached, then sets
	 * result to NULL and returns zero.
	 */
	static int
		_wreaddir_r(
			_WDIR* dirp, struct _wdirent* entry, struct _wdirent** result)
	{
		/* Validate directory handle */
		if (!dirp || dirp->handle == INVALID_HANDLE_VALUE || !dirp->patt) {
			dirent_set_errno(EBADF);
			*result = NULL;
			return -1;
		}

		/* Read next directory entry */
		WIN32_FIND_DATAW* datap = dirent_next(dirp);
		if (!datap) {
			/* Return NULL to indicate end of directory */
			*result = NULL;
			return /*OK*/0;
		}

		/*
		 * Copy file name as wide-character string.  If the file name is too
		 * long to fit in to the destination buffer, then truncate file name
		 * to PATH_MAX characters and zero-terminate the buffer.
		 */
		size_t i = 0;
		while (i < PATH_MAX && datap->cFileName[i] != 0) {
			entry->d_name[i] = datap->cFileName[i];
			i++;
		}
		entry->d_name[i] = 0;

		/* Length of file name excluding zero terminator */
		entry->d_namlen = i;

		/* Determine file type */
		DWORD attr = datap->dwFileAttributes;
		if ((attr & FILE_ATTRIBUTE_DEVICE) != 0)
			entry->d_type = DT_CHR;
		else if ((attr & FILE_ATTRIBUTE_REPARSE_POINT) != 0)
			entry->d_type = DT_LNK;
		else if ((attr & FILE_ATTRIBUTE_DIRECTORY) != 0)
			entry->d_type = DT_DIR;
		else
			entry->d_type = DT_REG;

		/* Read the next directory entry to cache */
		datap = dirent_next(dirp);
		if (datap) {
			/* Compute 31-bit hash of the next directory entry */
			entry->d_off = dirent_hash(datap);

			/* Push the next directory entry back to cache */
			dirp->cached = 1;
		}
		else {
			/* End of directory stream */
			entry->d_off = (long)((~0UL) >> 1);
		}

		/* Reset other fields */
		entry->d_ino = 0;
		entry->d_reclen = sizeof(struct _wdirent);

		/* Set result address */
		*result = entry;
		return /*OK*/0;
	}

	/*
	 * Close directory stream opened by opendir() function.  This invalidates the
	 * DIR structure as well as any directory entry read previously by
	 * _wreaddir().
	 */
	static int
		_wclosedir(_WDIR* dirp)
	{
		if (!dirp) {
			dirent_set_errno(EBADF);
			return /*failure*/-1;
		}

		/*
		 * Release search handle if we have one.  Being able to handle
		 * partially initialized _WDIR structure allows us to use this
		 * function to handle errors occuring within _wopendir.
		 */
		if (dirp->handle != INVALID_HANDLE_VALUE) {
			FindClose(dirp->handle);
		}

		/*
		 * Release search pattern.  Note that we don't need to care if
		 * dirp->patt is NULL or not: function free is guaranteed to act
		 * appropriately.
		 */
		free(dirp->patt);

		/* Release directory structure */
		free(dirp);
		return /*success*/0;
	}

	/*
	 * Rewind directory stream such that _wreaddir() returns the very first
	 * file name again.
	 */
	static void _wrewinddir(_WDIR* dirp)
	{
		/* Check directory pointer */
		if (!dirp || dirp->handle == INVALID_HANDLE_VALUE || !dirp->patt)
			return;

		/* Release existing search handle */
		FindClose(dirp->handle);

		/* Open new search handle */
		dirent_first(dirp);
	}

	/* Get first directory entry */
	static WIN32_FIND_DATAW*
		dirent_first(_WDIR* dirp)
	{
		/* Open directory and retrieve the first entry */
		dirp->handle = FindFirstFileExW(
			dirp->patt, FindExInfoStandard, &dirp->data,
			FindExSearchNameMatch, NULL, 0);
		if (dirp->handle == INVALID_HANDLE_VALUE)
			goto error;

		/* A directory entry is now waiting in memory */
		dirp->cached = 1;
		return &dirp->data;

	error:
		/* Failed to open directory: no directory entry in memory */
		dirp->cached = 0;
		dirp->invalid = 1;

		/* Set error code */
		DWORD errorcode = GetLastError();
		switch (errorcode) {
		case ERROR_ACCESS_DENIED:
			/* No read access to directory */
			dirent_set_errno(EACCES);
			break;

		case ERROR_DIRECTORY:
			/* Directory name is invalid */
			dirent_set_errno(ENOTDIR);
			break;

		case ERROR_PATH_NOT_FOUND:
		default:
			/* Cannot find the file */
			dirent_set_errno(ENOENT);
		}
		return NULL;
	}

	/* Get next directory entry */
	static WIN32_FIND_DATAW*
		dirent_next(_WDIR* dirp)
	{
		/* Return NULL if seek position was invalid */
		if (dirp->invalid)
			return NULL;

		/* Is the next directory entry already in cache? */
		if (dirp->cached) {
			/* Yes, a valid directory entry found in memory */
			dirp->cached = 0;
			return &dirp->data;
		}

		/* Read the next directory entry from stream */
		if (FindNextFileW(dirp->handle, &dirp->data) == FALSE) {
			/* End of directory stream */
			return NULL;
		}

		/* Success */
		return &dirp->data;
	}

	/*
	 * Compute 31-bit hash of file name.
	 *
	 * See djb2 at http://www.cse.yorku.ca/~oz/hash.html
	 */
	static long
		dirent_hash(WIN32_FIND_DATAW* datap)
	{
		unsigned long hash = 5381;
		unsigned long c;
		const wchar_t* p = datap->cFileName;
		const wchar_t* e = p + MAX_PATH;
		while (p != e && (c = *p++) != 0) {
			hash = (hash << 5) + hash + c;
		}

		return (long)(hash & ((~0UL) >> 1));
	}

	/* Open directory stream using plain old C-string */
	static DIR* opendir(const char* dirname)
	{
		/* Must have directory name */
		if (dirname == NULL || dirname[0] == '\0') {
			dirent_set_errno(ENOENT);
			return NULL;
		}

		/* Allocate memory for DIR structure */
		struct DIR* dirp = (DIR*)malloc(sizeof(struct DIR));
		if (!dirp)
			return NULL;

		/* Convert directory name to wide-character string */
		wchar_t wname[PATH_MAX + 1];
		size_t n;
		int error = mbstowcs_s(&n, wname, PATH_MAX + 1, dirname, PATH_MAX + 1);
		if (error)
			goto exit_failure;

		/* Open directory stream using wide-character name */
		dirp->wdirp = _wopendir(wname);
		if (!dirp->wdirp)
			goto exit_failure;

		/* Success */
		return dirp;

		/* Failure */
	exit_failure:
		free(dirp);
		return NULL;
	}

	/* Read next directory entry */
	static struct dirent*
		readdir(DIR* dirp)
	{
		/*
		 * Read directory entry to buffer.  We can safely ignore the return
		 * value as entry will be set to NULL in case of error.
		 */
		struct dirent* entry;
		(void)readdir_r(dirp, &dirp->ent, &entry);

		/* Return pointer to statically allocated directory entry */
		return entry;
	}

	/*
	 * Read next directory entry into called-allocated buffer.
	 *
	 * Returns zero on success.  If the end of directory stream is reached, then
	 * sets result to NULL and returns zero.
	 */
	static int
		readdir_r(
			DIR* dirp, struct dirent* entry, struct dirent** result)
	{
		/* Read next directory entry */
		WIN32_FIND_DATAW* datap = dirent_next(dirp->wdirp);
		if (!datap) {
			/* No more directory entries */
			*result = NULL;
			return /*OK*/0;
		}

		/* Attempt to convert file name to multi-byte string */
		size_t n;
		int error = wcstombs_s(
			&n, entry->d_name, PATH_MAX + 1,
			datap->cFileName, PATH_MAX + 1);

		/*
		 * If the file name cannot be represented by a multi-byte string, then
		 * attempt to use old 8+3 file name.  This allows the program to
		 * access files although file names may seem unfamiliar to the user.
		 *
		 * Be ware that the code below cannot come up with a short file name
		 * unless the file system provides one.  At least VirtualBox shared
		 * folders fail to do this.
		 */
		if (error && datap->cAlternateFileName[0] != '\0') {
			error = wcstombs_s(
				&n, entry->d_name, PATH_MAX + 1,
				datap->cAlternateFileName, PATH_MAX + 1);
		}

		if (!error) {
			/* Length of file name excluding zero terminator */
			entry->d_namlen = n - 1;

			/* Determine file type */
			DWORD attr = datap->dwFileAttributes;
			if ((attr & FILE_ATTRIBUTE_DEVICE) != 0)
				entry->d_type = DT_CHR;
			else if ((attr & FILE_ATTRIBUTE_REPARSE_POINT) != 0)
				entry->d_type = DT_LNK;
			else if ((attr & FILE_ATTRIBUTE_DIRECTORY) != 0)
				entry->d_type = DT_DIR;
			else
				entry->d_type = DT_REG;

			/* Get offset of next file */
			datap = dirent_next(dirp->wdirp);
			if (datap) {
				/* Compute 31-bit hash of the next directory entry */
				entry->d_off = dirent_hash(datap);

				/* Push the next directory entry back to cache */
				dirp->wdirp->cached = 1;
			}
			else {
				/* End of directory stream */
				entry->d_off = (long)((~0UL) >> 1);
			}

			/* Reset fields */
			entry->d_ino = 0;
			entry->d_reclen = sizeof(struct dirent);
		}
		else {
			/*
			 * Cannot convert file name to multi-byte string so construct
			 * an erroneous directory entry and return that.  Note that
			 * we cannot return NULL as that would stop the processing
			 * of directory entries completely.
			 */
			entry->d_name[0] = '?';
			entry->d_name[1] = '\0';
			entry->d_namlen = 1;
			entry->d_type = DT_UNKNOWN;
			entry->d_ino = 0;
			entry->d_off = -1;
			entry->d_reclen = 0;
		}

		/* Return pointer to directory entry */
		*result = entry;
		return /*OK*/0;
	}

	/* Close directory stream */
	static int
		closedir(DIR* dirp)
	{
		int ok;

		if (!dirp)
			goto exit_failure;

		/* Close wide-character directory stream */
		ok = _wclosedir(dirp->wdirp);
		dirp->wdirp = NULL;

		/* Release multi-byte character version */
		free(dirp);
		return ok;

	exit_failure:
		/* Invalid directory stream */
		dirent_set_errno(EBADF);
		return /*failure*/-1;
	}

	/* Rewind directory stream to beginning */
	static void
		rewinddir(DIR* dirp)
	{
		if (!dirp)
			return;

		/* Rewind wide-character string directory stream */
		_wrewinddir(dirp->wdirp);
	}

	/* Get position of directory stream */
	static long
		_wtelldir(_WDIR* dirp)
	{
		if (!dirp || dirp->handle == INVALID_HANDLE_VALUE) {
			dirent_set_errno(EBADF);
			return /*failure*/-1;
		}

		/* Read next file entry */
		WIN32_FIND_DATAW* datap = dirent_next(dirp);
		if (!datap) {
			/* End of directory stream */
			return (long)((~0UL) >> 1);
		}

		/* Store file entry to cache for readdir() */
		dirp->cached = 1;

		/* Return the 31-bit hash code to be used as stream position */
		return dirent_hash(datap);
	}

	/* Get position of directory stream */
	static long
		telldir(DIR* dirp)
	{
		if (!dirp) {
			dirent_set_errno(EBADF);
			return -1;
		}

		return _wtelldir(dirp->wdirp);
	}

	/* Seek directory stream to offset */
	static void
		_wseekdir(_WDIR* dirp, long loc)
	{
		if (!dirp)
			return;

		/* Directory must be open */
		if (dirp->handle == INVALID_HANDLE_VALUE)
			goto exit_failure;

		/* Ensure that seek position is valid */
		if (loc < 0)
			goto exit_failure;

		/* Restart directory stream from the beginning */
		FindClose(dirp->handle);
		if (!dirent_first(dirp))
			goto exit_failure;

		/* Reset invalid flag so that we can read from the stream again */
		dirp->invalid = 0;

		/*
		 * Read directory entries from the beginning until the hash matches a
		 * file name.  Be ware that hash code is only 31 bits longs and
		 * duplicates are possible: the hash code cannot return the position
		 * with 100.00% accuracy! Moreover, the method is slow for large
		 * directories.
		 */
		long hash;
		do {
			/* Read next directory entry */
			WIN32_FIND_DATAW* datap = dirent_next(dirp);
			if (!datap) {
				/*
				 * End of directory stream was reached before finding
				 * the requested location.  Perhaps the file in
				 * question was deleted or moved out of the directory.
				 */
				goto exit_failure;
			}

			/* Does the file name match the hash? */
			hash = dirent_hash(datap);
		} while (hash != loc);

		/*
		 * File name matches the hash!  Push the directory entry back to cache
		 * from where next readdir() will return it.
		 */
		dirp->cached = 1;
		dirp->invalid = 0;
		return;

	exit_failure:
		/* Ensure that readdir will return NULL */
		dirp->invalid = 1;
	}

	/* Seek directory stream to offset */
	static void
		seekdir(DIR* dirp, long loc)
	{
		if (!dirp)
			return;

		_wseekdir(dirp->wdirp, loc);
	}

	/* Scan directory for entries */
	static int
		scandir(
			const char* dirname, struct dirent*** namelist,
			int (*filter)(const struct dirent*),
			int (*compare)(const struct dirent**, const struct dirent**))
	{
		int result;

		/* Open directory stream */
		DIR* dir = opendir(dirname);
		if (!dir) {
			/* Cannot open directory */
			return /*Error*/ -1;
		}

		/* Read directory entries to memory */
		struct dirent* tmp = NULL;
		struct dirent** files = NULL;
		size_t size = 0;
		size_t allocated = 0;
		while (1) {
			/* Allocate room for a temporary directory entry */
			if (!tmp) {
				tmp = (struct dirent*)malloc(sizeof(struct dirent));
				if (!tmp)
					goto exit_failure;
			}

			/* Read directory entry to temporary area */
			struct dirent* entry;
			if (readdir_r(dir, tmp, &entry) != /*OK*/0)
				goto exit_failure;

			/* Stop if we already read the last directory entry */
			if (entry == NULL)
				goto exit_success;

			/* Determine whether to include the entry in results */
			if (filter && !filter(tmp))
				continue;

			/* Enlarge pointer table to make room for another pointer */
			if (size >= allocated) {
				/* Compute number of entries in the new table */
				size_t num_entries = size * 2 + 16;

				/* Allocate new pointer table or enlarge existing */
				void* p = realloc(files, sizeof(void*) * num_entries);
				if (!p)
					goto exit_failure;

				/* Got the memory */
				files = (dirent**)p;
				allocated = num_entries;
			}

			/* Store the temporary entry to ptr table */
			files[size++] = tmp;
			tmp = NULL;
		}

	exit_failure:
		/* Release allocated entries */
		for (size_t i = 0; i < size; i++) {
			free(files[i]);
		}

		/* Release the pointer table */
		free(files);
		files = NULL;

		/* Exit with error code */
		result = /*error*/ -1;
		goto exit_status;

	exit_success:
		/* Sort directory entries */
		if (size > 1 && compare) {
			qsort(files, size, sizeof(void*),
				(int (*) (const void*, const void*)) compare);
		}

		/* Pass pointer table to caller */
		if (namelist)
			*namelist = files;

		/* Return the number of directory entries read */
		result = (int)size;

	exit_status:
		/* Release temporary directory entry, if we had one */
		free(tmp);

		/* Close directory stream */
		closedir(dir);
		return result;
	}

	/* Alphabetical sorting */
	static int
		alphasort(const struct dirent** a, const struct dirent** b)
	{
		return strcoll((*a)->d_name, (*b)->d_name);
	}

	/* Sort versions */
	static int
		versionsort(const struct dirent** a, const struct dirent** b)
	{
		return strverscmp((*a)->d_name, (*b)->d_name);
	}

	/* Compare strings */
	static int
		strverscmp(const char* a, const char* b)
	{
		size_t i = 0;
		size_t j;

		/* Find first difference */
		while (a[i] == b[i]) {
			if (a[i] == '\0') {
				/* No difference */
				return 0;
			}
			++i;
		}

		/* Count backwards and find the leftmost digit */
		j = i;
		while (j > 0 && isdigit(a[j - 1])) {
			--j;
		}

		/* Determine mode of comparison */
		if (a[j] == '0' || b[j] == '0') {
			/* Find the next non-zero digit */
			while (a[j] == '0' && a[j] == b[j]) {
				j++;
			}

			/* String with more digits is smaller, e.g 002 < 01 */
			if (isdigit(a[j])) {
				if (!isdigit(b[j])) {
					return -1;
				}
			}
			else if (isdigit(b[j])) {
				return 1;
			}
		}
		else if (isdigit(a[j]) && isdigit(b[j])) {
			/* Numeric comparison */
			size_t k1 = j;
			size_t k2 = j;

			/* Compute number of digits in each string */
			while (isdigit(a[k1])) {
				k1++;
			}
			while (isdigit(b[k2])) {
				k2++;
			}

			/* Number with more digits is bigger, e.g 999 < 1000 */
			if (k1 < k2)
				return -1;
			else if (k1 > k2)
				return 1;
		}

		/* Alphabetical comparison */
		return (int)((unsigned char)a[i]) - ((unsigned char)b[i]);
	}

	/* Convert multi-byte string to wide character string */
#if !defined(_MSC_VER) || _MSC_VER < 1400
	static int
		dirent_mbstowcs_s(
			size_t* pReturnValue, wchar_t* wcstr,
			size_t sizeInWords, const char* mbstr, size_t count)
	{
		/* Older Visual Studio or non-Microsoft compiler */
		size_t n = mbstowcs(wcstr, mbstr, sizeInWords);
		if (wcstr && n >= count)
			return /*error*/ 1;

		/* Zero-terminate output buffer */
		if (wcstr && sizeInWords) {
			if (n >= sizeInWords)
				n = sizeInWords - 1;
			wcstr[n] = 0;
		}

		/* Length of multi-byte string with zero terminator */
		if (pReturnValue) {
			*pReturnValue = n + 1;
		}

		/* Success */
		return 0;
	}
#endif

	/* Convert wide-character string to multi-byte string */
#if !defined(_MSC_VER) || _MSC_VER < 1400
	static int
		dirent_wcstombs_s(
			size_t* pReturnValue, char* mbstr,
			size_t sizeInBytes, const wchar_t* wcstr, size_t count)
	{
		/* Older Visual Studio or non-Microsoft compiler */
		size_t n = wcstombs(mbstr, wcstr, sizeInBytes);
		if (mbstr && n >= count)
			return /*error*/1;

		/* Zero-terminate output buffer */
		if (mbstr && sizeInBytes) {
			if (n >= sizeInBytes) {
				n = sizeInBytes - 1;
			}
			mbstr[n] = '\0';
		}

		/* Length of resulting multi-bytes string WITH zero-terminator */
		if (pReturnValue) {
			*pReturnValue = n + 1;
		}

		/* Success */
		return 0;
	}
#endif

	/* Set errno variable */
#if !defined(_MSC_VER) || _MSC_VER < 1400
	static void
		dirent_set_errno(int error)
	{
		/* Non-Microsoft compiler or older Microsoft compiler */
		errno = error;
	}
#endif

#ifdef __cplusplus
}
#endif
#endif /*DIRENT_H*/