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 <cwchar> // mbstate_t
10 #include <limits.h> // MB_LEN_MAX
11 #include <stdlib.h> // MB_CUR_MAX, size_t
12 #include <string.h> // memcpy
13
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 be
16 // `dst_size_bytes` bytes in size. Returns the number of bytes in the sequence
17 // 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_FUNC_VIS
wcsnrtombs(char * __restrict dst,const wchar_t ** __restrict src,size_t max_source_chars,size_t dst_size_bytes,mbstate_t * __restrict ps)21 size_t wcsnrtombs(char *__restrict dst, const wchar_t **__restrict src,
22 size_t max_source_chars, size_t dst_size_bytes,
23 mbstate_t *__restrict ps) {
24
25 const size_t invalid_wchar = static_cast<size_t>(-1);
26
27 size_t source_converted;
28 size_t dest_converted;
29 size_t result = 0;
30
31 // If `dst` is null then `dst_size_bytes` should be ignored according to the
32 // standard. Setting dst_size_bytes to a large value has this effect.
33 if (dst == nullptr)
34 dst_size_bytes = static_cast<size_t>(-1);
35
36 for (dest_converted = source_converted = 0;
37 source_converted < max_source_chars && (!dst || dest_converted < dst_size_bytes);
38 ++source_converted, dest_converted += result) {
39 wchar_t c = (*src)[source_converted];
40 size_t dest_remaining = dst_size_bytes - dest_converted;
41
42 if (dst == nullptr) {
43 result = wcrtomb(NULL, c, ps);
44 } else if (dest_remaining >= static_cast<size_t>(MB_CUR_MAX)) {
45 // dst has enough space to translate in-place.
46 result = wcrtomb(dst + dest_converted, c, ps);
47 } else {
48 /*
49 * dst may not have enough space, so use a temporary buffer.
50 *
51 * We need to save a copy of the conversion state
52 * here so we can restore it if the multibyte
53 * character is too long for the buffer.
54 */
55 char buff[MB_LEN_MAX];
56 mbstate_t mbstate_tmp;
57
58 if (ps != nullptr)
59 mbstate_tmp = *ps;
60 result = wcrtomb(buff, c, ps);
61
62 if (result > dest_remaining) {
63 // Multi-byte sequence for character won't fit.
64 if (ps != nullptr)
65 *ps = mbstate_tmp;
66 if (result != invalid_wchar)
67 break;
68 } else {
69 // The buffer was used, so we need copy the translation to dst.
70 memcpy(dst, buff, result);
71 }
72 }
73
74 // result (char_size) contains the size of the multi-byte-sequence converted.
75 // Otherwise, result (char_size) is (size_t) -1 and wcrtomb() sets the errno.
76 if (result == invalid_wchar) {
77 if (dst)
78 *src = *src + source_converted;
79 return invalid_wchar;
80 }
81
82 if (c == L'\0') {
83 if (dst)
84 *src = NULL;
85 return dest_converted;
86 }
87 }
88
89 if (dst)
90 *src = *src + source_converted;
91
92 return dest_converted;
93 }
94