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_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 the
33 // 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 state
53 * here so we can restore it if the multibyte
54 * 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

source code of libcxx/src/support/ibm/wcsnrtombs.cpp