fileutils.c

#include "Python.h"
#include "pycore_fileutils.h"
#include "osdefs.h"               // SEP
#include <locale.h>

#ifdef MS_WINDOWS
#  include <malloc.h>
#  include <windows.h>
extern int winerror_to_errno(int);
#endif

#ifdef HAVE_LANGINFO_H
#include <langinfo.h>
#endif

#ifdef HAVE_SYS_IOCTL_H
#include <sys/ioctl.h>
#endif

#ifdef HAVE_FCNTL_H
#include <fcntl.h>
#endif /* HAVE_FCNTL_H */

#ifdef O_CLOEXEC
/* Does open() support the O_CLOEXEC flag? Possible values:

   -1: unknown
    0: open() ignores O_CLOEXEC flag, ex: Linux kernel older than 2.6.23
    1: open() supports O_CLOEXEC flag, close-on-exec is set

   The flag is used by _Py_open(), _Py_open_noraise(), io.FileIO
   and os.open(). */
int _Py_open_cloexec_works = -1;
#endif


static int
get_surrogateescape(_Py_error_handler errors, int *surrogateescape)
{
    switch (errors)
    {
    case _Py_ERROR_STRICT:
        *surrogateescape = 0;
        return 0;
    case _Py_ERROR_SURROGATEESCAPE:
        *surrogateescape = 1;
        return 0;
    default:
        return -1;
    }
}


PyObject *
_Py_device_encoding(int fd)
{
#if defined(MS_WINDOWS)
    UINT cp;
#endif
    int valid;
    _Py_BEGIN_SUPPRESS_IPH
    valid = isatty(fd);
    _Py_END_SUPPRESS_IPH
    if (!valid)
        Py_RETURN_NONE;

#if defined(MS_WINDOWS)
    if (fd == 0)
        cp = GetConsoleCP();
    else if (fd == 1 || fd == 2)
        cp = GetConsoleOutputCP();
    else
        cp = 0;
    /* GetConsoleCP() and GetConsoleOutputCP() return 0 if the application
       has no console */
    if (cp != 0)
        return PyUnicode_FromFormat("cp%u", (unsigned int)cp);
#elif defined(CODESET)
    {
        char *codeset = nl_langinfo(CODESET);
        if (codeset != NULL && codeset[0] != 0)
            return PyUnicode_FromString(codeset);
    }
#endif
    Py_RETURN_NONE;
}

#if !defined(_Py_FORCE_UTF8_FS_ENCODING) && !defined(MS_WINDOWS)

#define USE_FORCE_ASCII

extern int _Py_normalize_encoding(const char *, char *, size_t);

/* Workaround FreeBSD and OpenIndiana locale encoding issue with the C locale
   and POSIX locale. nl_langinfo(CODESET) announces an alias of the
   ASCII encoding, whereas mbstowcs() and wcstombs() functions use the
   ISO-8859-1 encoding. The problem is that os.fsencode() and os.fsdecode() use
   locale.getpreferredencoding() codec. For example, if command line arguments
   are decoded by mbstowcs() and encoded back by os.fsencode(), we get a
   UnicodeEncodeError instead of retrieving the original byte string.

   The workaround is enabled if setlocale(LC_CTYPE, NULL) returns "C",
   nl_langinfo(CODESET) announces "ascii" (or an alias to ASCII), and at least
   one byte in range 0x80-0xff can be decoded from the locale encoding. The
   workaround is also enabled on error, for example if getting the locale
   failed.

   On HP-UX with the C locale or the POSIX locale, nl_langinfo(CODESET)
   announces "roman8" but mbstowcs() uses Latin1 in practice. Force also the
   ASCII encoding in this case.

   Values of force_ascii:

       1: the workaround is used: Py_EncodeLocale() uses
          encode_ascii_surrogateescape() and Py_DecodeLocale() uses
          decode_ascii()
       0: the workaround is not used: Py_EncodeLocale() uses wcstombs() and
          Py_DecodeLocale() uses mbstowcs()
      -1: unknown, need to call check_force_ascii() to get the value
*/
static int force_ascii = -1;

static int
check_force_ascii(void)
{
    char *loc = setlocale(LC_CTYPE, NULL);
    if (loc == NULL) {
        goto error;
    }
    if (strcmp(loc, "C") != 0 && strcmp(loc, "POSIX") != 0) {
        /* the LC_CTYPE locale is different than C and POSIX */
        return 0;
    }

#if defined(HAVE_LANGINFO_H) && defined(CODESET)
    const char *codeset = nl_langinfo(CODESET);
    if (!codeset || codeset[0] == '\0') {
        /* CODESET is not set or empty */
        goto error;
    }

    char encoding[20];   /* longest name: "iso_646.irv_1991\0" */
    if (!_Py_normalize_encoding(codeset, encoding, sizeof(encoding))) {
        goto error;
    }

#ifdef __hpux
    if (strcmp(encoding, "roman8") == 0) {
        unsigned char ch;
        wchar_t wch;
        size_t res;

        ch = (unsigned char)0xA7;
        res = mbstowcs(&wch, (char*)&ch, 1);
        if (res != (size_t)-1 && wch == L'\xA7') {
            /* On HP-UX withe C locale or the POSIX locale,
               nl_langinfo(CODESET) announces "roman8", whereas mbstowcs() uses
               Latin1 encoding in practice. Force ASCII in this case.

               Roman8 decodes 0xA7 to U+00CF. Latin1 decodes 0xA7 to U+00A7. */
            return 1;
        }
    }
#else
    const char* ascii_aliases[] = {
        "ascii",
        /* Aliases from Lib/encodings/aliases.py */
        "646",
        "ansi_x3.4_1968",
        "ansi_x3.4_1986",
        "ansi_x3_4_1968",
        "cp367",
        "csascii",
        "ibm367",
        "iso646_us",
        "iso_646.irv_1991",
        "iso_ir_6",
        "us",
        "us_ascii",
        NULL
    };

    int is_ascii = 0;
    for (const char **alias=ascii_aliases; *alias != NULL; alias++) {
        if (strcmp(encoding, *alias) == 0) {
            is_ascii = 1;
            break;
        }
    }
    if (!is_ascii) {
        /* nl_langinfo(CODESET) is not "ascii" or an alias of ASCII */
        return 0;
    }

    for (unsigned int i=0x80; i<=0xff; i++) {
        char ch[1];
        wchar_t wch[1];
        size_t res;

        unsigned uch = (unsigned char)i;
        ch[0] = (char)uch;
        res = mbstowcs(wch, ch, 1);
        if (res != (size_t)-1) {
            /* decoding a non-ASCII character from the locale encoding succeed:
               the locale encoding is not ASCII, force ASCII */
            return 1;
        }
    }
    /* None of the bytes in the range 0x80-0xff can be decoded from the locale
       encoding: the locale encoding is really ASCII */
#endif   /* !defined(__hpux) */
    return 0;
#else
    /* nl_langinfo(CODESET) is not available: always force ASCII */
    return 1;
#endif   /* defined(HAVE_LANGINFO_H) && defined(CODESET) */

error:
    /* if an error occurred, force the ASCII encoding */
    return 1;
}


int
_Py_GetForceASCII(void)
{
    if (force_ascii == -1) {
        force_ascii = check_force_ascii();
    }
    return force_ascii;
}


void
_Py_ResetForceASCII(void)
{
    force_ascii = -1;
}


static int
encode_ascii(const wchar_t *text, char **str,
             size_t *error_pos, const char **reason,
             int raw_malloc, _Py_error_handler errors)
{
    char *result = NULL, *out;
    size_t len, i;
    wchar_t ch;

    int surrogateescape;
    if (get_surrogateescape(errors, &surrogateescape) < 0) {
        return -3;
    }

    len = wcslen(text);

    /* +1 for NULL byte */
    if (raw_malloc) {
        result = PyMem_RawMalloc(len + 1);
    }
    else {
        result = PyMem_Malloc(len + 1);
    }
    if (result == NULL) {
        return -1;
    }

    out = result;
    for (i=0; i<len; i++) {
        ch = text[i];

        if (ch <= 0x7f) {
            /* ASCII character */
            *out++ = (char)ch;
        }
        else if (surrogateescape && 0xdc80 <= ch && ch <= 0xdcff) {
            /* UTF-8b surrogate */
            *out++ = (char)(ch - 0xdc00);
        }
        else {
            if (raw_malloc) {
                PyMem_RawFree(result);
            }
            else {
                PyMem_Free(result);
            }
            if (error_pos != NULL) {
                *error_pos = i;
            }
            if (reason) {
                *reason = "encoding error";
            }
            return -2;
        }
    }
    *out = '\0';
    *str = result;
    return 0;
}
#else
int
_Py_GetForceASCII(void)
{
    return 0;
}

void
_Py_ResetForceASCII(void)
{
    /* nothing to do */
}
#endif   /* !defined(_Py_FORCE_UTF8_FS_ENCODING) && !defined(MS_WINDOWS) */


#if !defined(HAVE_MBRTOWC) || defined(USE_FORCE_ASCII)
static int
decode_ascii(const char *arg, wchar_t **wstr, size_t *wlen,
             const char **reason, _Py_error_handler errors)
{
    wchar_t *res;
    unsigned char *in;
    wchar_t *out;
    size_t argsize = strlen(arg) + 1;

    int surrogateescape;
    if (get_surrogateescape(errors, &surrogateescape) < 0) {
        return -3;
    }

    if (argsize > PY_SSIZE_T_MAX / sizeof(wchar_t)) {
        return -1;
    }
    res = PyMem_RawMalloc(argsize * sizeof(wchar_t));
    if (!res) {
        return -1;
    }

    out = res;
    for (in = (unsigned char*)arg; *in; in++) {
        unsigned char ch = *in;
        if (ch < 128) {
            *out++ = ch;
        }
        else {
            if (!surrogateescape) {
                PyMem_RawFree(res);
                if (wlen) {
                    *wlen = in - (unsigned char*)arg;
                }
                if (reason) {
                    *reason = "decoding error";
                }
                return -2;
            }
            *out++ = 0xdc00 + ch;
        }
    }
    *out = 0;

    if (wlen != NULL) {
        *wlen = out - res;
    }
    *wstr = res;
    return 0;
}
#endif   /* !HAVE_MBRTOWC */

static int
decode_current_locale(const char* arg, wchar_t **wstr, size_t *wlen,
                      const char **reason, _Py_error_handler errors)
{
    wchar_t *res;
    size_t argsize;
    size_t count;
#ifdef HAVE_MBRTOWC
    unsigned char *in;
    wchar_t *out;
    mbstate_t mbs;
#endif

    int surrogateescape;
    if (get_surrogateescape(errors, &surrogateescape) < 0) {
        return -3;
    }

#ifdef HAVE_BROKEN_MBSTOWCS
    /* Some platforms have a broken implementation of
     * mbstowcs which does not count the characters that
     * would result from conversion.  Use an upper bound.
     */
    argsize = strlen(arg);
#else
    argsize = mbstowcs(NULL, arg, 0);
#endif
    if (argsize != (size_t)-1) {
        if (argsize > PY_SSIZE_T_MAX / sizeof(wchar_t) - 1) {
            return -1;
        }
        res = (wchar_t *)PyMem_RawMalloc((argsize + 1) * sizeof(wchar_t));
        if (!res) {
            return -1;
        }

        count = mbstowcs(res, arg, argsize + 1);
        if (count != (size_t)-1) {
            wchar_t *tmp;
            /* Only use the result if it contains no
               surrogate characters. */
            for (tmp = res; *tmp != 0 &&
                         !Py_UNICODE_IS_SURROGATE(*tmp); tmp++)
                ;
            if (*tmp == 0) {
                if (wlen != NULL) {
                    *wlen = count;
                }
                *wstr = res;
                return 0;
            }
        }
        PyMem_RawFree(res);
    }

    /* Conversion failed. Fall back to escaping with surrogateescape. */
#ifdef HAVE_MBRTOWC
    /* Try conversion with mbrtwoc (C99), and escape non-decodable bytes. */

    /* Overallocate; as multi-byte characters are in the argument, the
       actual output could use less memory. */
    argsize = strlen(arg) + 1;
    if (argsize > PY_SSIZE_T_MAX / sizeof(wchar_t)) {
        return -1;
    }
    res = (wchar_t*)PyMem_RawMalloc(argsize * sizeof(wchar_t));
    if (!res) {
        return -1;
    }

    in = (unsigned char*)arg;
    out = res;
    memset(&mbs, 0, sizeof mbs);
    while (argsize) {
        size_t converted = mbrtowc(out, (char*)in, argsize, &mbs);
        if (converted == 0) {
            /* Reached end of string; null char stored. */
            break;
        }

        if (converted == (size_t)-2) {
            /* Incomplete character. This should never happen,
               since we provide everything that we have -
               unless there is a bug in the C library, or I
               misunderstood how mbrtowc works. */
            goto decode_error;
        }

        if (converted == (size_t)-1) {
            if (!surrogateescape) {
                goto decode_error;
            }

            /* Conversion error. Escape as UTF-8b, and start over
               in the initial shift state. */
            *out++ = 0xdc00 + *in++;
            argsize--;
            memset(&mbs, 0, sizeof mbs);
            continue;
        }

        if (Py_UNICODE_IS_SURROGATE(*out)) {
            if (!surrogateescape) {
                goto decode_error;
            }

            /* Surrogate character.  Escape the original
               byte sequence with surrogateescape. */
            argsize -= converted;
            while (converted--) {
                *out++ = 0xdc00 + *in++;
            }
            continue;
        }
        /* successfully converted some bytes */
        in += converted;
        argsize -= converted;
        out++;
    }
    if (wlen != NULL) {
        *wlen = out - res;
    }
    *wstr = res;
    return 0;

decode_error:
    PyMem_RawFree(res);
    if (wlen) {
        *wlen = in - (unsigned char*)arg;
    }
    if (reason) {
        *reason = "decoding error";
    }
    return -2;
#else   /* HAVE_MBRTOWC */
    /* Cannot use C locale for escaping; manually escape as if charset
       is ASCII (i.e. escape all bytes > 128. This will still roundtrip
       correctly in the locale's charset, which must be an ASCII superset. */
    return decode_ascii(arg, wstr, wlen, reason, errors);
#endif   /* HAVE_MBRTOWC */
}


/* Decode a byte string from the locale encoding.

   Use the strict error handler if 'surrogateescape' is zero.  Use the
   surrogateescape error handler if 'surrogateescape' is non-zero: undecodable
   bytes are decoded as characters in range U+DC80..U+DCFF. If a byte sequence
   can be decoded as a surrogate character, escape the bytes using the
   surrogateescape error handler instead of decoding them.

   On success, return 0 and write the newly allocated wide character string into
   *wstr (use PyMem_RawFree() to free the memory). If wlen is not NULL, write
   the number of wide characters excluding the null character into *wlen.

   On memory allocation failure, return -1.

   On decoding error, return -2. If wlen is not NULL, write the start of
   invalid byte sequence in the input string into *wlen. If reason is not NULL,
   write the decoding error message into *reason.

   Return -3 if the error handler 'errors' is not supported.

   Use the Py_EncodeLocaleEx() function to encode the character string back to
   a byte string. */
int
_Py_DecodeLocaleEx(const char* arg, wchar_t **wstr, size_t *wlen,
                   const char **reason,
                   int current_locale, _Py_error_handler errors)
{
    if (current_locale) {
#ifdef _Py_FORCE_UTF8_LOCALE
        return _Py_DecodeUTF8Ex(arg, strlen(arg), wstr, wlen, reason,
                                errors);
#else
        return decode_current_locale(arg, wstr, wlen, reason, errors);
#endif
    }

#ifdef _Py_FORCE_UTF8_FS_ENCODING
    return _Py_DecodeUTF8Ex(arg, strlen(arg), wstr, wlen, reason,
                            errors);
#else
    int use_utf8 = (Py_UTF8Mode == 1);
#ifdef MS_WINDOWS
    use_utf8 |= !Py_LegacyWindowsFSEncodingFlag;
#endif
    if (use_utf8) {
        return _Py_DecodeUTF8Ex(arg, strlen(arg), wstr, wlen, reason,
                                errors);
    }

#ifdef USE_FORCE_ASCII
    if (force_ascii == -1) {
        force_ascii = check_force_ascii();
    }

    if (force_ascii) {
        /* force ASCII encoding to workaround mbstowcs() issue */
        return decode_ascii(arg, wstr, wlen, reason, errors);
    }
#endif

    return decode_current_locale(arg, wstr, wlen, reason, errors);
#endif   /* !_Py_FORCE_UTF8_FS_ENCODING */
}


/* Decode a byte string from the locale encoding with the
   surrogateescape error handler: undecodable bytes are decoded as characters
   in range U+DC80..U+DCFF. If a byte sequence can be decoded as a surrogate
   character, escape the bytes using the surrogateescape error handler instead
   of decoding them.

   Return a pointer to a newly allocated wide character string, use
   PyMem_RawFree() to free the memory. If size is not NULL, write the number of
   wide characters excluding the null character into *size

   Return NULL on decoding error or memory allocation error. If *size* is not
   NULL, *size is set to (size_t)-1 on memory error or set to (size_t)-2 on
   decoding error.

   Decoding errors should never happen, unless there is a bug in the C
   library.

   Use the Py_EncodeLocale() function to encode the character string back to a
   byte string. */
wchar_t*
Py_DecodeLocale(const char* arg, size_t *wlen)
{
    wchar_t *wstr;
    int res = _Py_DecodeLocaleEx(arg, &wstr, wlen,
                                 NULL, 0,
                                 _Py_ERROR_SURROGATEESCAPE);
    if (res != 0) {
        assert(res != -3);
        if (wlen != NULL) {
            *wlen = (size_t)res;
        }
        return NULL;
    }
    return wstr;
}


static int
encode_current_locale(const wchar_t *text, char **str,
                      size_t *error_pos, const char **reason,
                      int raw_malloc, _Py_error_handler errors)
{
    const size_t len = wcslen(text);
    char *result = NULL, *bytes = NULL;
    size_t i, size, converted;
    wchar_t c, buf[2];

    int surrogateescape;
    if (get_surrogateescape(errors, &surrogateescape) < 0) {
        return -3;
    }

    /* The function works in two steps:
       1. compute the length of the output buffer in bytes (size)
       2. outputs the bytes */
    size = 0;
    buf[1] = 0;
    while (1) {
        for (i=0; i < len; i++) {
            c = text[i];
            if (c >= 0xdc80 && c <= 0xdcff) {
                if (!surrogateescape) {
                    goto encode_error;
                }
                /* UTF-8b surrogate */
                if (bytes != NULL) {
                    *bytes++ = c - 0xdc00;
                    size--;
                }
                else {
                    size++;
                }
                continue;
            }
            else {
                buf[0] = c;
                if (bytes != NULL) {
                    converted = wcstombs(bytes, buf, size);
                }
                else {
                    converted = wcstombs(NULL, buf, 0);
                }
                if (converted == (size_t)-1) {
                    goto encode_error;
                }
                if (bytes != NULL) {
                    bytes += converted;
                    size -= converted;
                }
                else {
                    size += converted;
                }
            }
        }
        if (result != NULL) {
            *bytes = '\0';
            break;
        }

        size += 1; /* nul byte at the end */
        if (raw_malloc) {
            result = PyMem_RawMalloc(size);
        }
        else {
            result = PyMem_Malloc(size);
        }
        if (result == NULL) {
            return -1;
        }
        bytes = result;
    }
    *str = result;
    return 0;

encode_error:
    if (raw_malloc) {
        PyMem_RawFree(result);
    }
    else {
        PyMem_Free(result);
    }
    if (error_pos != NULL) {
        *error_pos = i;
    }
    if (reason) {
        *reason = "encoding error";
    }
    return -2;
}


/* Encode a string to the locale encoding.

   Parameters:

   * raw_malloc: if non-zero, allocate memory using PyMem_RawMalloc() instead
     of PyMem_Malloc().
   * current_locale: if non-zero, use the current LC_CTYPE, otherwise use
     Python filesystem encoding.
   * errors: error handler like "strict" or "surrogateescape".

   Return value:

    0: success, *str is set to a newly allocated decoded string.
   -1: memory allocation failure
   -2: encoding error, set *error_pos and *reason (if set).
   -3: the error handler 'errors' is not supported.
 */
static int
encode_locale_ex(const wchar_t *text, char **str, size_t *error_pos,
                 const char **reason,
                 int raw_malloc, int current_locale, _Py_error_handler errors)
{
    if (current_locale) {
#ifdef _Py_FORCE_UTF8_LOCALE
        return _Py_EncodeUTF8Ex(text, str, error_pos, reason,
                                raw_malloc, errors);
#else
        return encode_current_locale(text, str, error_pos, reason,
                                     raw_malloc, errors);
#endif
    }

#ifdef _Py_FORCE_UTF8_FS_ENCODING
    return _Py_EncodeUTF8Ex(text, str, error_pos, reason,
                            raw_malloc, errors);
#else
    int use_utf8 = (Py_UTF8Mode == 1);
#ifdef MS_WINDOWS
    use_utf8 |= !Py_LegacyWindowsFSEncodingFlag;
#endif
    if (use_utf8) {
        return _Py_EncodeUTF8Ex(text, str, error_pos, reason,
                                raw_malloc, errors);
    }

#ifdef USE_FORCE_ASCII
    if (force_ascii == -1) {
        force_ascii = check_force_ascii();
    }

    if (force_ascii) {
        return encode_ascii(text, str, error_pos, reason,
                            raw_malloc, errors);
    }
#endif

    return encode_current_locale(text, str, error_pos, reason,
                                 raw_malloc, errors);
#endif   /* _Py_FORCE_UTF8_FS_ENCODING */
}

static char*
encode_locale(const wchar_t *text, size_t *error_pos,
              int raw_malloc, int current_locale)
{
    char *str;
    int res = encode_locale_ex(text, &str, error_pos, NULL,
                               raw_malloc, current_locale,
                               _Py_ERROR_SURROGATEESCAPE);
    if (res != -2 && error_pos) {
        *error_pos = (size_t)-1;
    }
    if (res != 0) {
        return NULL;
    }
    return str;
}

/* Encode a wide character string to the locale encoding with the
   surrogateescape error handler: surrogate characters in the range
   U+DC80..U+DCFF are converted to bytes 0x80..0xFF.

   Return a pointer to a newly allocated byte string, use PyMem_Free() to free
   the memory. Return NULL on encoding or memory allocation error.

   If error_pos is not NULL, *error_pos is set to (size_t)-1 on success, or set
   to the index of the invalid character on encoding error.

   Use the Py_DecodeLocale() function to decode the bytes string back to a wide
   character string. */
char*
Py_EncodeLocale(const wchar_t *text, size_t *error_pos)
{
    return encode_locale(text, error_pos, 0, 0);
}


/* Similar to Py_EncodeLocale(), but result must be freed by PyMem_RawFree()
   instead of PyMem_Free(). */
char*
_Py_EncodeLocaleRaw(const wchar_t *text, size_t *error_pos)
{
    return encode_locale(text, error_pos, 1, 0);
}


int
_Py_EncodeLocaleEx(const wchar_t *text, char **str,
                   size_t *error_pos, const char **reason,
                   int current_locale, _Py_error_handler errors)
{
    return encode_locale_ex(text, str, error_pos, reason, 1,
                            current_locale, errors);
}


#ifdef MS_WINDOWS
static __int64 secs_between_epochs = 11644473600; /* Seconds between 1.1.1601 and 1.1.1970 */

static void
FILE_TIME_to_time_t_nsec(FILETIME *in_ptr, time_t *time_out, int* nsec_out)
{
    /* XXX endianness. Shouldn't matter, as all Windows implementations are little-endian */
    /* Cannot simply cast and dereference in_ptr,
       since it might not be aligned properly */
    __int64 in;
    memcpy(&in, in_ptr, sizeof(in));
    *nsec_out = (int)(in % 10000000) * 100; /* FILETIME is in units of 100 nsec. */
    *time_out = Py_SAFE_DOWNCAST((in / 10000000) - secs_between_epochs, __int64, time_t);
}

void
_Py_time_t_to_FILE_TIME(time_t time_in, int nsec_in, FILETIME *out_ptr)
{
    /* XXX endianness */
    __int64 out;
    out = time_in + secs_between_epochs;
    out = out * 10000000 + nsec_in / 100;
    memcpy(out_ptr, &out, sizeof(out));
}

/* Below, we *know* that ugo+r is 0444 */
#if _S_IREAD != 0400
#error Unsupported C library
#endif
static int
attributes_to_mode(DWORD attr)
{
    int m = 0;
    if (attr & FILE_ATTRIBUTE_DIRECTORY)
        m |= _S_IFDIR | 0111; /* IFEXEC for user,group,other */
    else
        m |= _S_IFREG;
    if (attr & FILE_ATTRIBUTE_READONLY)
        m |= 0444;
    else
        m |= 0666;
    return m;
}

void
_Py_attribute_data_to_stat(BY_HANDLE_FILE_INFORMATION *info, ULONG reparse_tag,
                           struct _Py_stat_struct *result)
{
    memset(result, 0, sizeof(*result));
    result->st_mode = attributes_to_mode(info->dwFileAttributes);
    result->st_size = (((__int64)info->nFileSizeHigh)<<32) + info->nFileSizeLow;
    result->st_dev = info->dwVolumeSerialNumber;
    result->st_rdev = result->st_dev;
    FILE_TIME_to_time_t_nsec(&info->ftCreationTime, &result->st_ctime, &result->st_ctime_nsec);
    FILE_TIME_to_time_t_nsec(&info->ftLastWriteTime, &result->st_mtime, &result->st_mtime_nsec);
    FILE_TIME_to_time_t_nsec(&info->ftLastAccessTime, &result->st_atime, &result->st_atime_nsec);
    result->st_nlink = info->nNumberOfLinks;
    result->st_ino = (((uint64_t)info->nFileIndexHigh) << 32) + info->nFileIndexLow;
    /* bpo-37834: Only actual symlinks set the S_IFLNK flag. But lstat() will
       open other name surrogate reparse points without traversing them. To
       detect/handle these, check st_file_attributes and st_reparse_tag. */
    result->st_reparse_tag = reparse_tag;
    if (info->dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT &&
        reparse_tag == IO_REPARSE_TAG_SYMLINK) {
        /* first clear the S_IFMT bits */
        result->st_mode ^= (result->st_mode & S_IFMT);
        /* now set the bits that make this a symlink */
        result->st_mode |= S_IFLNK;
    }
    result->st_file_attributes = info->dwFileAttributes;
}
#endif

/* Return information about a file.

   On POSIX, use fstat().

   On Windows, use GetFileType() and GetFileInformationByHandle() which support
   files larger than 2 GiB.  fstat() may fail with EOVERFLOW on files larger
   than 2 GiB because the file size type is a signed 32-bit integer: see issue
   #23152.

   On Windows, set the last Windows error and return nonzero on error. On
   POSIX, set errno and return nonzero on error. Fill status and return 0 on
   success. */
int
_Py_fstat_noraise(int fd, struct _Py_stat_struct *status)
{
#ifdef MS_WINDOWS
    BY_HANDLE_FILE_INFORMATION info;
    HANDLE h;
    int type;

    _Py_BEGIN_SUPPRESS_IPH
    h = (HANDLE)_get_osfhandle(fd);
    _Py_END_SUPPRESS_IPH

    if (h == INVALID_HANDLE_VALUE) {
        /* errno is already set by _get_osfhandle, but we also set
           the Win32 error for callers who expect that */
        SetLastError(ERROR_INVALID_HANDLE);
        return -1;
    }
    memset(status, 0, sizeof(*status));

    type = GetFileType(h);
    if (type == FILE_TYPE_UNKNOWN) {
        DWORD error = GetLastError();
        if (error != 0) {
            errno = winerror_to_errno(error);
            return -1;
        }
        /* else: valid but unknown file */
    }

    if (type != FILE_TYPE_DISK) {
        if (type == FILE_TYPE_CHAR)
            status->st_mode = _S_IFCHR;
        else if (type == FILE_TYPE_PIPE)
            status->st_mode = _S_IFIFO;
        return 0;
    }

    if (!GetFileInformationByHandle(h, &info)) {
        /* The Win32 error is already set, but we also set errno for
           callers who expect it */
        errno = winerror_to_errno(GetLastError());
        return -1;
    }

    _Py_attribute_data_to_stat(&info, 0, status);
    /* specific to fstat() */
    status->st_ino = (((uint64_t)info.nFileIndexHigh) << 32) + info.nFileIndexLow;
    return 0;
#else
    return fstat(fd, status);
#endif
}

/* Return information about a file.

   On POSIX, use fstat().

   On Windows, use GetFileType() and GetFileInformationByHandle() which support
   files larger than 2 GiB.  fstat() may fail with EOVERFLOW on files larger
   than 2 GiB because the file size type is a signed 32-bit integer: see issue
   #23152.

   Raise an exception and return -1 on error. On Windows, set the last Windows
   error on error. On POSIX, set errno on error. Fill status and return 0 on
   success.

   Release the GIL to call GetFileType() and GetFileInformationByHandle(), or
   to call fstat(). The caller must hold the GIL. */
int
_Py_fstat(int fd, struct _Py_stat_struct *status)
{
    int res;

    assert(PyGILState_Check());

    Py_BEGIN_ALLOW_THREADS
    res = _Py_fstat_noraise(fd, status);
    Py_END_ALLOW_THREADS

    if (res != 0) {
#ifdef MS_WINDOWS
        PyErr_SetFromWindowsErr(0);
#else
        PyErr_SetFromErrno(PyExc_OSError);
#endif
        return -1;
    }
    return 0;
}

/* Call _wstat() on Windows, or encode the path to the filesystem encoding and
   call stat() otherwise. Only fill st_mode attribute on Windows.