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-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #include <cstddef> // size_t 10 #include <cwchar> // mbstate_t 11 #include <limits.h> // MB_LEN_MAX 12 #include <string.h> // wmemcpy 13 14 // Returns the number of wide characters found in the multi byte sequence `src` 15 // (of `src_size_bytes`), that fit in the buffer `dst` (of `max_dest_chars` 16 // elements size). The count returned excludes the null terminator. 17 // When `dst` is NULL, no characters are copied to `dst`. 18 // Returns (size_t) -1 when an invalid sequence is encountered. 19 // Leaves *`src` pointing to the next character to convert or NULL 20 // if a null character was converted from *`src`. 21 _LIBCPP_EXPORTED_FROM_ABI 22 size_t mbsnrtowcs(wchar_t *__restrict dst, const char **__restrict src, 23 size_t src_size_bytes, size_t max_dest_chars, 24 mbstate_t *__restrict ps) { 25 const size_t terminated_sequence = static_cast<size_t>(0); 26 const size_t invalid_sequence = static_cast<size_t>(-1); 27 const size_t incomplete_sequence = static_cast<size_t>(-2); 28 29 size_t source_converted; 30 size_t dest_converted; 31 size_t result = 0; 32 33 // If `dst` is null then `max_dest_chars` should be ignored according to the 34 // standard. Setting `max_dest_chars` to a large value has this effect. 35 if (dst == nullptr) 36 max_dest_chars = static_cast<size_t>(-1); 37 38 for (dest_converted = source_converted = 0; 39 source_converted < src_size_bytes && (!dst || dest_converted < max_dest_chars); 40 ++dest_converted, source_converted += result) { 41 // Converts one multi byte character. 42 // If result (char_size) is greater than 0, it's the size in bytes of that character. 43 // If result (char_size) is zero, it indicates that the null character has been found. 44 // Otherwise, it's an error and errno may be set. 45 size_t source_remaining = src_size_bytes - source_converted; 46 size_t dest_remaining = max_dest_chars - dest_converted; 47 48 if (dst == nullptr) { 49 result = mbrtowc(NULL, *src + source_converted, source_remaining, ps); 50 } else if (dest_remaining >= source_remaining) { 51 // dst has enough space to translate in-place. 52 result = mbrtowc(dst + dest_converted, *src + source_converted, source_remaining, ps); 53 } else { 54 /* 55 * dst may not have enough space, so use a temporary buffer. 56 * 57 * We need to save a copy of the conversion state 58 * here so we can restore it if the multibyte 59 * character is too long for the buffer. 60 */ 61 wchar_t buff[MB_LEN_MAX]; 62 mbstate_t mbstate_tmp; 63 64 if (ps != nullptr) 65 mbstate_tmp = *ps; 66 result = mbrtowc(buff, *src + source_converted, source_remaining, ps); 67 68 if (result > dest_remaining) { 69 // Multi-byte sequence for character won't fit. 70 if (ps != nullptr) 71 *ps = mbstate_tmp; 72 break; 73 } else { 74 // The buffer was used, so we need copy the translation to dst. 75 wmemcpy(dst, buff, result); 76 } 77 } 78 79 // Don't do anything to change errno from here on. 80 if (result == invalid_sequence || result == terminated_sequence || result == incomplete_sequence) { 81 break; 82 } 83 } 84 85 if (dst) { 86 if (result == terminated_sequence) 87 *src = NULL; 88 else 89 *src += source_converted; 90 } 91 if (result == invalid_sequence) 92 return invalid_sequence; 93 94 return dest_converted; 95 } 96