95 lines · cpp
1//===----------------------------------------------------------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9#include <cwchar> // mbstate_t10#include <limits.h> // MB_LEN_MAX11#include <stdlib.h> // MB_CUR_MAX, size_t12#include <string.h> // memcpy13 14// Converts `max_source_chars` from the wide character buffer pointer to by *`src`,15// into the multi byte character sequence buffer stored at `dst`, which must be16// `dst_size_bytes` bytes in size. Returns the number of bytes in the sequence17// converted from *src, excluding the null terminator.18// Returns (size_t) -1 if an error occurs and sets errno.19// If `dst` is NULL, `dst_size_bytes` is ignored and no bytes are copied to `dst`.20_LIBCPP_EXPORTED_FROM_ABI size_t wcsnrtombs(21 char* __restrict dst,22 const wchar_t** __restrict src,23 size_t max_source_chars,24 size_t dst_size_bytes,25 mbstate_t* __restrict ps) {26 const size_t invalid_wchar = static_cast<size_t>(-1);27 28 size_t source_converted;29 size_t dest_converted;30 size_t result = 0;31 32 // If `dst` is null then `dst_size_bytes` should be ignored according to the33 // standard. Setting dst_size_bytes to a large value has this effect.34 if (dst == nullptr)35 dst_size_bytes = static_cast<size_t>(-1);36 37 for (dest_converted = source_converted = 0;38 source_converted < max_source_chars && (!dst || dest_converted < dst_size_bytes);39 ++source_converted, dest_converted += result) {40 wchar_t c = (*src)[source_converted];41 size_t dest_remaining = dst_size_bytes - dest_converted;42 43 if (dst == nullptr) {44 result = wcrtomb(nullptr, c, ps);45 } else if (dest_remaining >= static_cast<size_t>(MB_CUR_MAX)) {46 // dst has enough space to translate in-place.47 result = wcrtomb(dst + dest_converted, c, ps);48 } else {49 /*50 * dst may not have enough space, so use a temporary buffer.51 *52 * We need to save a copy of the conversion state53 * here so we can restore it if the multibyte54 * character is too long for the buffer.55 */56 char buff[MB_LEN_MAX];57 mbstate_t mbstate_tmp;58 59 if (ps != nullptr)60 mbstate_tmp = *ps;61 result = wcrtomb(buff, c, ps);62 63 if (result > dest_remaining) {64 // Multi-byte sequence for character won't fit.65 if (ps != nullptr)66 *ps = mbstate_tmp;67 if (result != invalid_wchar)68 break;69 } else {70 // The buffer was used, so we need copy the translation to dst.71 memcpy(dst, buff, result);72 }73 }74 75 // result (char_size) contains the size of the multi-byte-sequence converted.76 // Otherwise, result (char_size) is (size_t) -1 and wcrtomb() sets the errno.77 if (result == invalid_wchar) {78 if (dst)79 *src = *src + source_converted;80 return invalid_wchar;81 }82 83 if (c == L'\0') {84 if (dst)85 *src = nullptr;86 return dest_converted;87 }88 }89 90 if (dst)91 *src = *src + source_converted;92 93 return dest_converted;94}95