[libc-commits] [libc] [libc] wchar string conversion functions mb to wc (PR #149423)

[Uzair Nawaz via libc-commits]

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@@ -0,0 +1,59 @@
+//===-- Implementation for mbsnrtowcs function ------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/__support/wchar/mbsnrtowcs.h"
+#include "hdr/errno_macros.h"
+#include "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/__support/common.h"
+#include "src/__support/error_or.h"
+#include "src/__support/macros/config.h"
+#include "src/__support/wchar/character_converter.h"
+#include "src/__support/wchar/mbstate.h"
+#include "src/__support/wchar/string_converter.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace internal {
+
+ErrorOr<size_t> mbsnrtowcs(wchar_t *__restrict dst, const char **__restrict src,
+                           size_t nmc, size_t len, mbstate *__restrict ps) {
+  if (*src == nullptr)
+    return 0;
+  // Checking if mbstate is valid
+  CharacterConverter char_conv(ps);
+  if (!char_conv.isValidState())
+    return Error(EINVAL);
+
+  StringConverter<char8_t> str_conv(reinterpret_cast<const char8_t *>(*src), ps,
+                                    len, nmc);
+  size_t dst_idx = 0;
+  ErrorOr<char32_t> converted = str_conv.popUTF32();
+  while (converted.has_value()) {
+    if (dst != nullptr)
+      dst[dst_idx] = converted.value();
+    // null terminator should not be counted in return value
+    if (converted.value() == L'\0') {
+      if (dst != nullptr)
+        *src = nullptr;
+      return dst_idx;
+    }
+    dst_idx++;
+    converted = str_conv.popUTF32();
+  }
+
+  if (converted.error() == -1) { // if we hit conversion limit
+    *src += str_conv.getSourceIndex();
----------------
uzairnawaz wrote:

Should we only increment src if dst != null? 

Didn't catch this in my own pr but: "**If dst is not a null pointer**, the pointer object pointed to by src shall be assigned either a null pointer (if conversion stopped due to reaching a terminating null character) or the address just past the last character converted (if any). "

https://github.com/llvm/llvm-project/pull/149423