wcstombs.cpp

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/***
*wcstombs.c - Convert wide char string to multibyte char string.
*
*       Copyright (c) Microsoft Corporation. All rights reserved.
*
*Purpose:
*       Convert a wide char string into the equivalent multibyte char string.
*
*******************************************************************************/
#include <corecrt_internal_mbstring.h>
#include <corecrt_internal_ptd_propagation.h>
#include <corecrt_internal_securecrt.h>
#include <ctype.h>
#include <errno.h>
#include <locale.h>
#include <stdint.h>
#include <stdlib.h>
 
/***
*size_t __cdecl wcsncnt - count wide characters in a string, up to n.
*
*Purpose:
*       Internal local support function. Counts characters in string including nullptr.
*       If nullptr not found in n chars, then return n.
*
*Entry:
*       const wchar_t *string   - start of string
*       size_t n                - character count
*
*Exit:
*       returns number of wide characters from start of string to
*       nullptr (inclusive), up to n.
*
*Exceptions:
*
*******************************************************************************/
 
_Post_satisfies_(return <= cnt && return <= _String_length_(string + 1))
static size_t __cdecl wcsncnt (
        _In_reads_or_z_(cnt) const wchar_t *string,
        _In_                 size_t cnt
        )
{
        size_t n = cnt+1;
        wchar_t *cp = (wchar_t *)string;
 
        while (--n && *cp)
            cp++;
 
        if (n && !*cp)
            return cp - string + 1;
        return cnt;
}
 
/***
*size_t wcstombs() - Convert wide char string to multibyte char string.
*
*Purpose:
*       Convert a wide char string into the equivalent multibyte char string,
*       according to the LC_CTYPE category of the current locale.
*       [ANSI].
*
*       The destination string is null terminated only if the null terminator
*       is copied from the source string.
*
*Entry:
*       char *s            = pointer to destination multibyte char string
*       const wchar_t *pwc = pointer to source wide character string
*       size_t           n = maximum number of bytes to store in s
*
*Exit:
*       If s != nullptr, returns    (size_t)-1 (if a wchar cannot be converted)
*       Otherwise:       Number of bytes modified (<=n), not including
*                    the terminating NUL, if any.
*
*Exceptions:
*       Returns (size_t)-1 if an error is encountered.
*       Input parameters are validated. Refer to the validation section of the function.
*
*******************************************************************************/
 
_Success_(return != static_cast<size_t>(-1))
static size_t __cdecl _wcstombs_l_helper(
    _Out_writes_(n) char *                 s,
    _In_z_          const wchar_t *        pwcs,
    _In_            size_t                 n,
    _Inout_         __crt_cached_ptd_host& ptd
    )
{
    size_t count = 0;
    int i, retval;
    char buffer[MB_LEN_MAX];
    BOOL defused = 0;
 
    if (s && n == 0)
        /* dest string exists, but 0 bytes converted */
        return 0;
 
    /* validation section */
    _UCRT_VALIDATE_RETURN(ptd, pwcs != nullptr, EINVAL, (size_t)-1);
 
 
    /* if destination string exists, fill it in */
    const _locale_t locale = ptd.get_locale();
 
    if (locale->locinfo->_public._locale_lc_codepage == CP_UTF8)
    {
        mbstate_t state{};
        return __crt_mbstring::__wcsrtombs_utf8(s, &pwcs, n, &state, ptd);
    }
 
    if (s)
    {
        if ( locale->locinfo->locale_name[LC_CTYPE] == nullptr )
        {
            /* C locale: easy and fast */
            /* Actually, there are such wchar_t characters which are > 255,
             * but they can be transformed to a valid single byte char
             * (i.e. a char in the C locale case). Like, for example,
             * alternative digits in unicode like Arabic-Indic U+0660..U+0669.
             * The problem is that WideCharToMultiByte() does not translate those
             * wchar_t unless we pass the correct codepage (1256, Arabic).
             * See bug VSW:192653.
             */
            while(count < n)
            {
                if (static_cast<uint16_t>(*pwcs) > 0xFF)  /* validate high byte */
                {
                    ptd.get_errno().set(EILSEQ);
                    return (size_t)-1;  /* error */
                }
                s[count] = (char) *pwcs;
                if (*pwcs++ == L'\0')
                {
                    return count;
                }
                count++;
            }
            return count;
        }
        else
        {
 
            if (1 == locale->locinfo->_public._locale_mb_cur_max)
            {
                /* If SBCS, one wchar_t maps to one char */
 
                /* WideCharToMultiByte will compare past nullptr - reset n */
                if (n > 0)
                {
                    n = wcsncnt(pwcs, n);
                }
                if ( ((count = __acrt_WideCharToMultiByte( locale->locinfo->_public._locale_lc_codepage,
                                                    0,
                                                    pwcs,
                                                    (int)n,
                                                    s,
                                                    (int)n,
                                                    nullptr,
                                                    &defused )) != 0) &&
                     (!defused) )
                {
                    if (s[count - 1] == '\0')
                    {
                        count--; /* don't count NUL */
                    }
 
                    return count;
                }
 
                ptd.get_errno().set(EILSEQ);
                return (size_t)-1;
            }
            else
            {
 
                /* If MBCS, wchar_t to char mapping unknown */
 
                /* Assume that usually the buffer is large enough */
                if ( ((count = __acrt_WideCharToMultiByte( locale->locinfo->_public._locale_lc_codepage,
                                                    0,
                                                    pwcs,
                                                    -1,
                                                    s,
                                                    (int)n,
                                                    nullptr,
                                                    &defused )) != 0) &&
                     (!defused) )
                {
                    return count - 1; /* don't count NUL */
                }
 
                if (defused || GetLastError() != ERROR_INSUFFICIENT_BUFFER)
                {
                    ptd.get_errno().set(EILSEQ);
                    return (size_t)-1;
                }
 
                /* buffer not large enough, must do char by char */
                while (count < n)
                {
                    int mb_cur_max = locale->locinfo->_public._locale_mb_cur_max;
                    if ( ((retval = __acrt_WideCharToMultiByte( locale->locinfo->_public._locale_lc_codepage,
                                                         0,
                                                         pwcs,
                                                         1,
                                                         buffer,
                                                         __min(MB_LEN_MAX, mb_cur_max),
                                                         nullptr,
                                                         &defused )) == 0)
                         || defused )
                    {
                        ptd.get_errno().set(EILSEQ);
                        return (size_t)-1;
                    }
 
                    /* enforce this for prefast */
                    if (retval < 0 ||
                        retval > _countof(buffer))
                    {
                        ptd.get_errno().set(EILSEQ);
                        return (size_t)-1;
                    }
 
                    if (count + retval > n)
                        return count;
 
                    for (i = 0; i < retval; i++, count++) /* store character */
                    {
                        if((s[count] = buffer[i])=='\0')
                        {
                            return count;
                        }
                    }
 
                    pwcs++;
                }
 
                return count;
            }
        }
    }
    else
    { /* s == nullptr, get size only, pwcs must be NUL-terminated */
        if ( locale->locinfo->locale_name[LC_CTYPE] == nullptr )
        {
            size_t len = 0;
            for (wchar_t *pw = (wchar_t *)pwcs; *pw != 0; pw++)  /* validate high byte */
            {
                if (*pw > 255)  /* validate high byte */
                {
                    ptd.get_errno().set(EILSEQ);
                    return (size_t)-1;  /* error */
                }
                ++len;
            }
 
            return len;
        }
        else
        {
            if ( ((count = __acrt_WideCharToMultiByte( locale->locinfo->_public._locale_lc_codepage,
                                                0,
                                                pwcs,
                                                -1,
                                                nullptr,
                                                0,
                                                nullptr,
                                                &defused )) == 0) ||
                 (defused) )
            {
                ptd.get_errno().set(EILSEQ);
                return (size_t)-1;
            }
 
            return count - 1;
        }
    }
}
 
extern "C" size_t __cdecl _wcstombs_l(
    char * s,
    const wchar_t * pwcs,
    size_t n,
    _locale_t plocinfo
    )
{
    __crt_cached_ptd_host ptd(plocinfo);
    return _wcstombs_l_helper(s, pwcs, n, ptd);
}
 
extern "C" size_t __cdecl wcstombs(
        char * s,
        const wchar_t * pwcs,
        size_t n
        )
{
    __crt_cached_ptd_host ptd;
    return _wcstombs_l_helper(s, pwcs, n, ptd);
}
 
/***
*errno_t wcstombs_s() - Convert wide char string to multibyte char string.
*
*Purpose:
*       Convert a wide char string into the equivalent multibyte char string,
*       according to the LC_CTYPE category of the current locale.
*
*       The destination string is always null terminated.
*
*Entry:
*       size_t *pConvertedChars = Number of bytes modified including the terminating nullptr
*                                 This pointer can be nullptr.
*       char *dst = pointer to destination multibyte char string
*       size_t sizeInBytes = size of the destination buffer
*       const wchar_t *src = pointer to source wide character string
*       size_t n = maximum number of bytes to store in s (not including the terminating nullptr)
*
*Exit:
*       The error code.
*
*Exceptions:
*       Input parameters are validated. Refer to the validation section of the function.
*
*******************************************************************************/
 
static errno_t __cdecl _wcstombs_internal (
    size_t *               pConvertedChars,
    char *                 dst,
    size_t                 sizeInBytes,
    const wchar_t *        src,
    size_t                 n,
    __crt_cached_ptd_host& ptd
    )
{
    size_t retsize;
    errno_t retvalue = 0;
 
    /* validation section */
    _UCRT_VALIDATE_RETURN_ERRCODE(ptd, (dst != nullptr && sizeInBytes > 0) || (dst == nullptr && sizeInBytes == 0), EINVAL);
    if (dst != nullptr)
    {
        _RESET_STRING(dst, sizeInBytes);
    }
 
    if (pConvertedChars != nullptr)
    {
        *pConvertedChars = 0;
    }
 
    size_t bufferSize = n > sizeInBytes ? sizeInBytes : n;
    _UCRT_VALIDATE_RETURN_ERRCODE(ptd, bufferSize <= INT_MAX, EINVAL);
 
    retsize = _wcstombs_l_helper(dst, src, bufferSize, ptd);
 
    if (retsize == (size_t)-1)
    {
        if (dst != nullptr)
        {
            _RESET_STRING(dst, sizeInBytes);
        }
        return ptd.get_errno().value_or(0);
    }
 
    /* count the null terminator */
    retsize++;
 
    if (dst != nullptr)
    {
        /* return error if the string does not fit, unless n == _TRUNCATE */
        if (retsize > sizeInBytes)
        {
            if (n != _TRUNCATE)
            {
                _RESET_STRING(dst, sizeInBytes);
                _UCRT_VALIDATE_RETURN_ERRCODE(ptd, sizeInBytes > retsize, ERANGE);
            }
            retsize = sizeInBytes;
            retvalue = STRUNCATE;
        }
 
        /* ensure the string is null terminated */
        dst[retsize - 1] = '\0';
    }
 
    if (pConvertedChars != nullptr)
    {
        *pConvertedChars = retsize;
    }
 
    return retvalue;
}
 
extern "C" errno_t __cdecl _wcstombs_s_l (
    size_t *pConvertedChars,
    char * dst,
    size_t sizeInBytes,
    const wchar_t * src,
    size_t n,
    _locale_t plocinfo
    )
{
    __crt_cached_ptd_host ptd(plocinfo);
    return _wcstombs_internal(pConvertedChars, dst, sizeInBytes, src, n, ptd);
}
 
extern "C" errno_t __cdecl wcstombs_s (
    size_t *pConvertedChars,
    char * dst,
    size_t sizeInBytes,
    const wchar_t * src,
    size_t n
    )
{
    __crt_cached_ptd_host ptd;
    return _wcstombs_internal(pConvertedChars, dst, sizeInBytes, src, n, ptd);
}