[libc] mbsrtowcs implementation

libc/config/linux/x86_64/entrypoints.txt

@@ -1249,6 +1249,7 @@ if(LLVM_LIBC_FULL_BUILD)
 
     # wchar.h entrypoints
     libc.src.wchar.mbrtowc
+    libc.src.wchar.mbsrtowcs
     libc.src.wchar.mbtowc
     libc.src.wchar.wcrtomb
     libc.src.wchar.wctomb

libc/include/wchar.yaml

@@ -38,6 +38,15 @@ functions:
       - type: const char *__restrict
       - type: size_t
       - type: mbstate_t *__restrict
+  - name: mbsrtowcs
+    standards:
+      - stdc
+    return_type: size_t
+    arguments:
+      - type: wchar_t *__restrict
+      - type: const char **__restrict
+      - type: size_t
+      - type: mbstate_t *__restrict
   - name: mbtowc
     standards:
       - stdc

libc/src/__support/wchar/CMakeLists.txt

@@ -53,3 +53,19 @@ add_object_library(
   .character_converter
   .mbstate
 )
+
+add_object_library(
+  mbsrtowcs
+  HDRS
+    mbsrtowcs.h
+  SRCS
+    mbsrtowcs.cpp
+  DEPENDS
+  libc.hdr.types.wchar_t
+  libc.hdr.types.size_t
+  libc.src.__support.common
+  libc.src.__support.error_or
+  libc.src.__support.macros.config
+  .mbstate
+  .mbrtowc
+)

libc/src/__support/wchar/character_converter.cpp

@@ -27,7 +27,6 @@ constexpr uint32_t MASK_ENCODED_BITS =
     mask_trailing_ones<uint32_t, ENCODED_BITS_PER_UTF8>();
 // Maximum value for utf-32 for a utf-8 sequence of a given length
 constexpr char32_t MAX_VALUE_PER_UTF8_LEN[] = {0x7f, 0x7ff, 0xffff, 0x10ffff};
-constexpr int MAX_UTF8_LENGTH = 4;
 
 CharacterConverter::CharacterConverter(mbstate *mbstate) { state = mbstate; }
 

libc/src/__support/wchar/character_converter.h

@@ -18,6 +18,8 @@
 namespace LIBC_NAMESPACE_DECL {
 namespace internal {
 
+constexpr int MAX_UTF8_LENGTH = 4;
+
 class CharacterConverter {
 private:
   mbstate *state;

libc/src/__support/wchar/mbrtowc.cpp

@@ -36,7 +36,7 @@ ErrorOr<size_t> mbrtowc(wchar_t *__restrict pwc, const char *__restrict s,
       return Error(EILSEQ);
   }
   auto wc = char_conv.pop_utf32();
-  if (wc.has_value()) {
+  if (wc.has_value() && pwc != nullptr) {
     *pwc = wc.value();
     // null terminator -> return 0
     if (wc.value() == L'\0')

libc/src/__support/wchar/mbsrtowcs.cpp

@@ -0,0 +1,50 @@
+//===-- Implementation for mbsrtowcs 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/mbsrtowcs.h"
+#include "hdr/types/mbstate_t.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/mbrtowc.h"
+#include "src/__support/wchar/mbstate.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace internal {
+
+ErrorOr<size_t> mbsrtowcs(wchar_t *__restrict dst, const char **__restrict src,
+                          size_t len, mbstate *__restrict ps) {
+  size_t i = 0;
+  // Converting characters until we reach error or null terminator
+  for (; i < len; ++i) {
+    wchar_t temp;
+    auto check = internal::mbrtowc(dst == nullptr ? &temp : dst, *src,
+                                   MAX_UTF8_LENGTH, ps);
+    // Encoding error/invalid mbstate
+    if (!check.has_value())
+      return check;
+    // Successfully encoded, check for null terminator
+    if (temp == L'\0' || (dst != nullptr && *dst == L'\0')) {
+      *src = nullptr;
+      return i;
+    }
+    // Set src to point right after the last character converted
+    *src = *src + check.value();
+    // Incrementing destination
+    if (dst != nullptr)
+      ++dst;
+  }
+  return i;
+}
+
+} // namespace internal
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/__support/wchar/mbsrtowcs.h

@@ -0,0 +1,29 @@
+//===-- Implementation header for mbsrtowcs 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_WCHAR_MBSRTOWCS
+#define LLVM_LIBC_SRC___SUPPORT_WCHAR_MBSRTOWCS
+
+#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/mbstate.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace internal {
+
+ErrorOr<size_t> mbsrtowcs(wchar_t *__restrict dst, const char **__restrict src,
+                          size_t len, mbstate *__restrict ps);
+
+} // namespace internal
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC___SUPPORT_WCHAR_MBSRTOWCS

libc/src/wchar/CMakeLists.txt

@@ -78,6 +78,24 @@ add_entrypoint_object(
     libc.src.__support.wchar.mbstate
 )
 
+add_entrypoint_object(
+  mbsrtowcs
+  SRCS
+    mbsrtowcs.cpp
+  HDRS
+    mbsrtowcs.h
+  DEPENDS
+    libc.hdr.types.size_t
+    libc.hdr.types.mbstate_t
+    libc.hdr.types.wchar_t
+    libc.src.__support.common
+    libc.src.__support.macros.config
+    libc.src.__support.wchar.mbsrtowcs
+    libc.src.__support.libc_errno
+    libc.src.__support.wchar.mbstate
+    libc.src.__support.macros.null_check
+)
+
 add_entrypoint_object(
   mbtowc
   SRCS

libc/src/wchar/mbsrtowcs.cpp

@@ -0,0 +1,41 @@
+//===-- Implementation of mbsrtowcs ---------------------------------------===//
+//
+// 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/wchar/mbsrtowcs.h"
+
+#include "hdr/types/mbstate_t.h"
+#include "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/__support/common.h"
+#include "src/__support/libc_errno.h"
+#include "src/__support/macros/config.h"
+#include "src/__support/macros/null_check.h"
+#include "src/__support/wchar/mbsrtowcs.h"
+#include "src/__support/wchar/mbstate.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(size_t, mbsrtowcs,
+                   (wchar_t *__restrict dst, const char **__restrict src,
+                    size_t len, mbstate_t *__restrict ps)) {
+  LIBC_CRASH_ON_NULLPTR(src);
+  static internal::mbstate internal_mbstate;
+  len = dst == nullptr ? SIZE_MAX : len;
+  auto ret = internal::mbsrtowcs(
+      dst, src, len,
+      ps == nullptr ? &internal_mbstate
+                    : reinterpret_cast<internal::mbstate *>(ps));
+  if (!ret.has_value()) {
+    // Encoding failure
+    libc_errno = ret.error();
+    return -1;
+  }
+  return ret.value();
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/wchar/mbsrtowcs.h

@@ -0,0 +1,24 @@
+//===-- Implementation header for mbsrtowcs -------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_WCHAR_MBSRTOWCS_H
+#define LLVM_LIBC_SRC_WCHAR_MBSRTOWCS_H
+
+#include "hdr/types/mbstate_t.h"
+#include "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+size_t mbsrtowcs(wchar_t *__restrict dst, const char **__restrict src,
+                 size_t len, mbstate_t *__restrict ps);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_WCHAR_MBSRTOWCS_H

libc/test/src/wchar/CMakeLists.txt

@@ -39,6 +39,20 @@ add_libc_test(
     libc.test.UnitTest.ErrnoCheckingTest
 )
 
+add_libc_test(
+  mbsrtowcs_test
+  SUITE
+    libc_wchar_unittests
+  SRCS
+    mbsrtowcs_test.cpp
+  DEPENDS
+    libc.src.__support.libc_errno
+    libc.src.string.memset
+    libc.src.wchar.mbsrtowcs
+    libc.hdr.types.mbstate_t
+    libc.hdr.types.wchar_t
+)
+
 add_libc_test(
   mbtowc_test
   SUITE