[libc] Implemented wcstrombs internal and public function

libc/config/linux/x86_64/entrypoints.txt

@@ -1252,6 +1252,7 @@ if(LLVM_LIBC_FULL_BUILD)
     libc.src.wchar.mbtowc
     libc.src.wchar.wcrtomb
     libc.src.wchar.wctomb
+    libc.src.wchar.wcsrtombs
   )
 endif()
 

libc/include/wchar.yaml

@@ -175,6 +175,15 @@ functions:
       - type: char *__restrict
       - type: wchar_t
       - type: mbstate_t *__restrict
+  - name: wcsrtombs
+    standards:
+      - stdc
+    return_type: size_t
+    arguments:
+      - type: char *__restrict
+      - type: wchar_t **__restrict
+      - type: size_t
+      - type: mbstate_t *__restrict
   - name: wctomb
     standards:
       - stdc

libc/src/__support/wchar/CMakeLists.txt

@@ -37,6 +37,24 @@ add_object_library(
     .mbstate
 )
 
+add_object_library(
+  wcsrtombs
+  HDRS
+    wcsrtombs.h
+  SRCS 
+    wcsrtombs.cpp
+  DEPENDS
+    libc.hdr.types.char32_t
+    libc.hdr.types.size_t
+    libc.hdr.types.wchar_t
+    libc.src.__support.error_or
+    libc.src.__support.common
+    libc.src.__support.libc_assert
+    .character_converter
+    .mbstate
+    .wcrtomb
+)
+
 add_object_library(
   mbrtowc
   HDRS

libc/src/__support/wchar/wcrtomb.cpp

@@ -21,31 +21,39 @@
 namespace LIBC_NAMESPACE_DECL {
 namespace internal {
 
-ErrorOr<size_t> wcrtomb(char *__restrict s, wchar_t wc,
-                        mbstate *__restrict ps) {
+ErrorOr<size_t> wcrtomb(char *__restrict s, wchar_t wc, mbstate *__restrict ps,
+                        size_t max_written) {
   static_assert(sizeof(wchar_t) == 4);
 
   CharacterConverter cr(ps);
 
   if (!cr.isValidState())
     return Error(EINVAL);
 
+  char buf[sizeof(wchar_t) / sizeof(char)];
   if (s == nullptr)
-    return Error(EILSEQ);
+    s = buf;
 
-  int status = cr.push(static_cast<char32_t>(wc));
-  if (status != 0)
-    return Error(EILSEQ);
+  // if cr isnt empty, it should be represented in mbstate already
+  if (cr.isEmpty()) {
+    int status = cr.push(static_cast<char32_t>(wc));
+    if (status != 0)
+      return Error(EILSEQ);
+  }
 
   size_t count = 0;
-  while (!cr.isEmpty()) {
+  while (!cr.isEmpty() && count < max_written) {
     auto utf8 = cr.pop_utf8(); // can never fail as long as the push succeeded
     LIBC_ASSERT(utf8.has_value());
 
     *s = utf8.value();
     s++;
     count++;
   }
+
+  if (!cr.isEmpty()) // didn't complete the conversion
+    return -1;
+
   return count;
 }
 

libc/src/__support/wchar/wcrtomb.h

@@ -18,7 +18,8 @@
 namespace LIBC_NAMESPACE_DECL {
 namespace internal {
 
-ErrorOr<size_t> wcrtomb(char *__restrict s, wchar_t wc, mbstate *__restrict ps);
+ErrorOr<size_t> wcrtomb(char *__restrict s, wchar_t wc, mbstate *__restrict ps,
+                        size_t max_written);
 
 } // namespace internal
 } // namespace LIBC_NAMESPACE_DECL

libc/src/__support/wchar/wcsrtombs.cpp

@@ -0,0 +1,55 @@
+//===-- Implementation of wcsrtombs ---------------------------------------===//
+//
+// 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/wcsrtombs.h"
+#include "hdr/types/char32_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/libc_assert.h"
+#include "src/__support/wchar/character_converter.h"
+#include "src/__support/wchar/mbstate.h"
+#include "src/__support/wchar/wcrtomb.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace internal {
+
+ErrorOr<size_t> wcsrtombs(char *__restrict dst, const wchar_t **__restrict src,
+                          size_t len, mbstate *__restrict ps) {
+  // ignore len parameter when theres no destination string
+  if (dst == nullptr)
+    len = SIZE_MAX;
+
+  size_t bytes_written = 0;
+  while (bytes_written < len) {
+    auto result =
+        internal::wcrtomb(dst == nullptr ? nullptr : dst + bytes_written, **src,
+                          ps, len - bytes_written);
+    if (!result.has_value())
+      return result; // forward the error
+
+    // couldn't complete conversion
+    if (result.value() == static_cast<size_t>(-1))
+      return len;
+
+    // terminate the loop after converting the null wide character
+    if (**src == L'\0') {
+      *src = nullptr;
+      return bytes_written;
+    }
+
+    bytes_written += result.value();
+    (*src)++;
+  }
+
+  return bytes_written;
+}
+
+} // namespace internal
+} // namespace LIBC_NAMESPACE_DECL

libc/src/__support/wchar/wcsrtombs.h

@@ -0,0 +1,27 @@
+//===-- Implementation header for wcsrtombs -------------------------------===//
+//
+// 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_WCSRTOMBS_H
+#define LLVM_LIBC_SRC__SUPPORT_WCHAR_WCSRTOMBS_H
+
+#include "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.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> wcsrtombs(char *__restrict dst, const wchar_t **__restrict src,
+                          size_t len, mbstate *__restrict ps);
+
+} // namespace internal
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC__SUPPORT_WCHAR_WCSRTOMBS_H

libc/src/wchar/CMakeLists.txt

@@ -48,6 +48,20 @@ add_entrypoint_object(
     libc.src.__support.wchar.mbstate
 )
 
+add_entrypoint_object(
+  wcsrtombs
+  SRCS
+    wcsrtombs.cpp
+  HDRS
+    wcsrtombs.h
+  DEPENDS
+    libc.hdr.types.wchar_t
+    libc.hdr.types.mbstate_t
+    libc.src.__support.libc_errno
+    libc.src.__support.wchar.wcsrtombs
+    libc.src.__support.wchar.mbstate
+)
+
 add_entrypoint_object(
   wctomb
   SRCS

libc/src/wchar/wcrtomb.cpp

@@ -23,16 +23,14 @@ LLVM_LIBC_FUNCTION(size_t, wcrtomb,
   static internal::mbstate internal_mbstate;
 
   // when s is nullptr, this is equivalent to wcrtomb(buf, L'\0', ps)
-  char buf[sizeof(wchar_t) / sizeof(char)];
-  if (s == nullptr) {
-    s = buf;
+  if (s == nullptr)
     wc = L'\0';
-  }
 
   auto result = internal::wcrtomb(
       s, wc,
       ps == nullptr ? &internal_mbstate
-                    : reinterpret_cast<internal::mbstate *>(ps));
+                    : reinterpret_cast<internal::mbstate *>(ps),
+      sizeof(wchar_t));
 
   if (!result.has_value()) {
     libc_errno = result.error();

libc/src/wchar/wcsrtombs.cpp

@@ -0,0 +1,42 @@
+//===-- Implementation of wcsrtombs ---------------------------------------===//
+//
+// 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/wcsrtombs.h"
+
+#include "hdr/types/mbstate_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/mbstate.h"
+#include "src/__support/wchar/wcsrtombs.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(size_t, wcsrtombs,
+                   (char *__restrict dst, const wchar_t **__restrict src,
+                    size_t len, mbstate_t *__restrict ps)) {
+  static internal::mbstate internal_mbstate;
+
+  LIBC_CRASH_ON_NULLPTR(src);
+
+  auto result = internal::wcsrtombs(
+      dst, src, len,
+      ps == nullptr ? &internal_mbstate
+                    : reinterpret_cast<internal::mbstate *>(ps));
+
+  if (!result.has_value()) {
+    libc_errno = result.error();
+    return -1;
+  }
+
+  return result.value();
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/wchar/wcsrtombs.h

@@ -0,0 +1,24 @@
+//===-- Implementation header for wcsrtombs ---------------------*- 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_WCHAR_WCSRTOMBS_H
+#define LLVM_LIBC_SRC_WCHAR_WCSRTOMBS_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 wcsrtombs(char *__restrict dst, const wchar_t **__restrict src,
+                 size_t len, mbstate_t *__restrict ps);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_WCHAR_WCSRTOMBS_H

libc/src/wchar/wctomb.cpp

@@ -22,7 +22,7 @@ LLVM_LIBC_FUNCTION(int, wctomb, (char *s, wchar_t wc)) {
   if (s == nullptr)
     return 0;
 
-  auto result = internal::wcrtomb(s, wc, &internal_mbstate);
+  auto result = internal::wcrtomb(s, wc, &internal_mbstate, sizeof(wchar_t));
 
   if (!result.has_value()) { // invalid wide character
     libc_errno = EILSEQ;

libc/test/src/wchar/CMakeLists.txt

@@ -78,6 +78,21 @@ add_libc_test(
     libc.test.UnitTest.ErrnoCheckingTest
 )
 
+add_libc_test(
+  wcsrtombs_test
+  SUITE
+    libc_wchar_unittests
+  SRCS
+    wcsrtombs_test.cpp
+  DEPENDS
+    libc.src.wchar.wcsrtombs
+    libc.src.string.memset
+    libc.hdr.types.wchar_t
+    libc.hdr.types.mbstate_t
+    libc.src.__support.wchar.mbstate
+    libc.src.__support.libc_errno
+)
+
 add_libc_test(
   wctomb_test
   SUITE