1*4bdff4beSrobert //===----------------------------------------------------------------------===//
2*4bdff4beSrobert //
3*4bdff4beSrobert // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4*4bdff4beSrobert // See https://llvm.org/LICENSE.txt for license information.
5*4bdff4beSrobert // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6*4bdff4beSrobert //
7*4bdff4beSrobert //===----------------------------------------------------------------------===//
8*4bdff4beSrobert
9*4bdff4beSrobert #include <cstddef> // size_t
10*4bdff4beSrobert #include <cwchar> // mbstate_t
11*4bdff4beSrobert #include <limits.h> // MB_LEN_MAX
12*4bdff4beSrobert #include <string.h> // wmemcpy
13*4bdff4beSrobert
14*4bdff4beSrobert // Returns the number of wide characters found in the multi byte sequence `src`
15*4bdff4beSrobert // (of `src_size_bytes`), that fit in the buffer `dst` (of `max_dest_chars`
16*4bdff4beSrobert // elements size). The count returned excludes the null terminator.
17*4bdff4beSrobert // When `dst` is NULL, no characters are copied to `dst`.
18*4bdff4beSrobert // Returns (size_t) -1 when an invalid sequence is encountered.
19*4bdff4beSrobert // Leaves *`src` pointing to the next character to convert or NULL
20*4bdff4beSrobert // if a null character was converted from *`src`.
21*4bdff4beSrobert _LIBCPP_FUNC_VIS
mbsnrtowcs(wchar_t * __restrict dst,const char ** __restrict src,size_t src_size_bytes,size_t max_dest_chars,mbstate_t * __restrict ps)22*4bdff4beSrobert size_t mbsnrtowcs(wchar_t *__restrict dst, const char **__restrict src,
23*4bdff4beSrobert size_t src_size_bytes, size_t max_dest_chars,
24*4bdff4beSrobert mbstate_t *__restrict ps) {
25*4bdff4beSrobert const size_t terminated_sequence = static_cast<size_t>(0);
26*4bdff4beSrobert const size_t invalid_sequence = static_cast<size_t>(-1);
27*4bdff4beSrobert const size_t incomplete_sequence = static_cast<size_t>(-2);
28*4bdff4beSrobert
29*4bdff4beSrobert size_t source_converted;
30*4bdff4beSrobert size_t dest_converted;
31*4bdff4beSrobert size_t result = 0;
32*4bdff4beSrobert
33*4bdff4beSrobert // If `dst` is null then `max_dest_chars` should be ignored according to the
34*4bdff4beSrobert // standard. Setting `max_dest_chars` to a large value has this effect.
35*4bdff4beSrobert if (dst == nullptr)
36*4bdff4beSrobert max_dest_chars = static_cast<size_t>(-1);
37*4bdff4beSrobert
38*4bdff4beSrobert for (dest_converted = source_converted = 0;
39*4bdff4beSrobert source_converted < src_size_bytes && (!dst || dest_converted < max_dest_chars);
40*4bdff4beSrobert ++dest_converted, source_converted += result) {
41*4bdff4beSrobert // Converts one multi byte character.
42*4bdff4beSrobert // If result (char_size) is greater than 0, it's the size in bytes of that character.
43*4bdff4beSrobert // If result (char_size) is zero, it indicates that the null character has been found.
44*4bdff4beSrobert // Otherwise, it's an error and errno may be set.
45*4bdff4beSrobert size_t source_remaining = src_size_bytes - source_converted;
46*4bdff4beSrobert size_t dest_remaining = max_dest_chars - dest_converted;
47*4bdff4beSrobert
48*4bdff4beSrobert if (dst == nullptr) {
49*4bdff4beSrobert result = mbrtowc(NULL, *src + source_converted, source_remaining, ps);
50*4bdff4beSrobert } else if (dest_remaining >= source_remaining) {
51*4bdff4beSrobert // dst has enough space to translate in-place.
52*4bdff4beSrobert result = mbrtowc(dst + dest_converted, *src + source_converted, source_remaining, ps);
53*4bdff4beSrobert } else {
54*4bdff4beSrobert /*
55*4bdff4beSrobert * dst may not have enough space, so use a temporary buffer.
56*4bdff4beSrobert *
57*4bdff4beSrobert * We need to save a copy of the conversion state
58*4bdff4beSrobert * here so we can restore it if the multibyte
59*4bdff4beSrobert * character is too long for the buffer.
60*4bdff4beSrobert */
61*4bdff4beSrobert wchar_t buff[MB_LEN_MAX];
62*4bdff4beSrobert mbstate_t mbstate_tmp;
63*4bdff4beSrobert
64*4bdff4beSrobert if (ps != nullptr)
65*4bdff4beSrobert mbstate_tmp = *ps;
66*4bdff4beSrobert result = mbrtowc(buff, *src + source_converted, source_remaining, ps);
67*4bdff4beSrobert
68*4bdff4beSrobert if (result > dest_remaining) {
69*4bdff4beSrobert // Multi-byte sequence for character won't fit.
70*4bdff4beSrobert if (ps != nullptr)
71*4bdff4beSrobert *ps = mbstate_tmp;
72*4bdff4beSrobert break;
73*4bdff4beSrobert } else {
74*4bdff4beSrobert // The buffer was used, so we need copy the translation to dst.
75*4bdff4beSrobert wmemcpy(dst, buff, result);
76*4bdff4beSrobert }
77*4bdff4beSrobert }
78*4bdff4beSrobert
79*4bdff4beSrobert // Don't do anything to change errno from here on.
80*4bdff4beSrobert if (result == invalid_sequence || result == terminated_sequence || result == incomplete_sequence) {
81*4bdff4beSrobert break;
82*4bdff4beSrobert }
83*4bdff4beSrobert }
84*4bdff4beSrobert
85*4bdff4beSrobert if (dst) {
86*4bdff4beSrobert if (result == terminated_sequence)
87*4bdff4beSrobert *src = NULL;
88*4bdff4beSrobert else
89*4bdff4beSrobert *src += source_converted;
90*4bdff4beSrobert }
91*4bdff4beSrobert if (result == invalid_sequence)
92*4bdff4beSrobert return invalid_sequence;
93*4bdff4beSrobert
94*4bdff4beSrobert return dest_converted;
95*4bdff4beSrobert }
96