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

/* Link */
#if !defined(S_IFLNK)
#   define S_IFLNK 0
#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

/* 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

/* 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

/* 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, sockets and links cannot be
 * distinguished on Windows and the macros S_ISBLK, S_ISSOCK and S_ISLNK 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;

    /* File position within 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;

    /* 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;

    /* File position within 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 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

/* 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);

#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;

    /*
     * 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)
{
    /* 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 n = 0;
    while (n < PATH_MAX && datap->cFileName[n] != 0) {
        entry->d_name[n] = datap->cFileName[n];
        n++;
    }
    entry->d_name[n] = 0;

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

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

    /* Reset dummy fields */
    entry->d_ino = 0;
    entry->d_off = 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 (dirp->handle != INVALID_HANDLE_VALUE)
        FindClose(dirp->handle);

    /* Release search pattern */
    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)
{
    if (!dirp)
        return;

    /* Release existing search handle */
    if (dirp->handle != INVALID_HANDLE_VALUE)
        FindClose(dirp->handle);

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

/* Get first directory entry */
static WIN32_FIND_DATAW *dirent_first(_WDIR *dirp)
{
    if (!dirp)
        return NULL;

    /* 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;

    /* 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)
{
    /* 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;
    }

    /* No directory entry in cache */
    if (dirp->handle == INVALID_HANDLE_VALUE)
        return NULL;

    /* Read the next directory entry from stream */
    if (FindNextFileW(dirp->handle, &dirp->data) == FALSE)
        goto exit_close;

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

    /* Failure */
exit_close:
    FindClose(dirp->handle);
    dirp->handle = INVALID_HANDLE_VALUE;
    return NULL;
}

/* 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;

        /* File attributes */
        DWORD attr = datap->dwFileAttributes;
        if ((attr & FILE_ATTRIBUTE_DEVICE) != 0)
            entry->d_type = DT_CHR;
        else if ((attr & FILE_ATTRIBUTE_DIRECTORY) != 0)
            entry->d_type = DT_DIR;
        else
            entry->d_type = DT_REG;

        /* Reset dummy fields */
        entry->d_ino = 0;
        entry->d_off = 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);
}

/* 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 file 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 */
    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*/