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//===----------------------- mbsnrtowcs.cpp -------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include <cstddef> // size_t
#include <cwchar> // mbstate_t
#include <limits.h> // MB_LEN_MAX
#include <string.h> // wmemcpy
// Returns the number of wide characters found in the multi byte sequence `src`
// (of `src_size_bytes`), that fit in the buffer `dst` (of `max_dest_chars`
// elements size). The count returned excludes the null terminator.
// When `dst` is NULL, no characters are copied to `dst`.
// Returns (size_t) -1 when an invalid sequence is encountered.
// Leaves *`src` pointing to the next character to convert or NULL
// if a null character was converted from *`src`.
_LIBCPP_FUNC_VIS
size_t mbsnrtowcs(wchar_t *__restrict dst, const char **__restrict src,
size_t src_size_bytes, size_t max_dest_chars,
mbstate_t *__restrict ps) {
const size_t terminated_sequence = static_cast<size_t>(0);
const size_t invalid_sequence = static_cast<size_t>(-1);
const size_t incomplete_sequence = static_cast<size_t>(-2);
size_t source_converted;
size_t dest_converted;
size_t result = 0;
// If `dst` is null then `max_dest_chars` should be ignored according to the
// standard. Setting `max_dest_chars` to a large value has this effect.
if (dst == nullptr)
max_dest_chars = static_cast<size_t>(-1);
for (dest_converted = source_converted = 0;
source_converted < src_size_bytes && (!dst || dest_converted < max_dest_chars);
++dest_converted, source_converted += result) {
// Converts one multi byte character.
// If result (char_size) is greater than 0, it's the size in bytes of that character.
// If result (char_size) is zero, it indicates that the null character has been found.
// Otherwise, it's an error and errno may be set.
size_t source_remaining = src_size_bytes - source_converted;
size_t dest_remaining = max_dest_chars - dest_converted;
if (dst == nullptr) {
result = mbrtowc(NULL, *src + source_converted, source_remaining, ps);
} else if (dest_remaining >= source_remaining) {
// dst has enough space to translate in-place.
result = mbrtowc(dst + dest_converted, *src + source_converted, source_remaining, ps);
} else {
/*
* dst may not have enough space, so use a temporary buffer.
*
* We need to save a copy of the conversion state
* here so we can restore it if the multibyte
* character is too long for the buffer.
*/
wchar_t buff[MB_LEN_MAX];
mbstate_t mbstate_tmp;
if (ps != nullptr)
mbstate_tmp = *ps;
result = mbrtowc(buff, *src + source_converted, source_remaining, ps);
if (result > dest_remaining) {
// Multi-byte sequence for character won't fit.
if (ps != nullptr)
*ps = mbstate_tmp;
break;
} else {
// The buffer was used, so we need copy the translation to dst.
wmemcpy(dst, buff, result);
}
}
// Don't do anything to change errno from here on.
if (result == invalid_sequence || result == terminated_sequence || result == incomplete_sequence) {
break;
}
}
if (dst) {
if (result == terminated_sequence)
*src = NULL;
else
*src += source_converted;
}
if (result == invalid_sequence)
return invalid_sequence;
return dest_converted;
}
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