xref: /openbsd-src/gnu/llvm/libcxx/src/support/ibm/mbsnrtowcs.cpp (revision 4bdff4bed0e3d54e55670334c7d0077db4170f86)
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 }
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