[libc] Implemented wmemset and added tests

libc/config/linux/x86_64/entrypoints.txt

@@ -364,6 +364,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.wchar.btowc
     libc.src.wchar.wcslen
     libc.src.wchar.wctob
+    libc.src.wchar.wmemset
     libc.src.wchar.wcschr
 
     # sys/uio.h entrypoints

libc/include/wchar.yaml

@@ -27,6 +27,14 @@ functions:
     return_type: wint_t
     arguments:
       - type: int
+  - name: wmemset
+    standards:
+      - stdc
+    return_type: wchar_t*
+    arguments:
+      - type: wchar_t*
+      - type: wchar_t
+      - type: size_t
   - name: wcschr
     standards:
       - stdc

libc/src/wchar/CMakeLists.txt

@@ -34,6 +34,18 @@ add_entrypoint_object(
     libc.src.__support.wctype_utils
 )
 
+add_entrypoint_object(
+  wmemset
+  SRCS
+    wmemset.cpp
+  HDRS
+    wmemset.h
+  DEPENDS
+    libc.hdr.types.size_t
+    libc.hdr.types.wchar_t
+    libc.src.__support.wctype_utils
+)
+
 add_entrypoint_object(
   wcschr
   SRCS

libc/src/wchar/wmemset.cpp

@@ -0,0 +1,24 @@
+//===-- Implementation of wmemset -----------------------------------------===//
+//
+// 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/wmemset.h"
+
+#include "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(wchar_t *, wmemset, (wchar_t * s, wchar_t c, size_t n)) {
+  for (size_t i = 0; i < n; i++) 
+    s[i] = c;
+
+  return s;
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/wchar/wmemset.h

@@ -0,0 +1,23 @@
+//===-- Implementation header for wmemset
+//----------------------------------===//
+//
+// 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_WMEMSET_H
+#define LLVM_LIBC_SRC_WCHAR_WMEMSET_H
+
+#include "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_WCHAR_WMEMSET_H

libc/test/src/wchar/CMakeLists.txt

@@ -33,6 +33,18 @@ add_libc_test(
     libc.src.wchar.wctob
 )
 
+add_libc_test(
+  wmemset_test 
+  SUITE
+    libc_wchar_unittests
+  SRCS
+    wmemset_test.cpp
+  DEPENDS
+    libc.hdr.types.size_t
+    libc.hdr.types.wchar_t
+    libc.src.wchar.wmemset
+)
+
 add_libc_test(
   wcschr_test
   SUITE

libc/test/src/wchar/wmemset_test.cpp

@@ -0,0 +1,88 @@
+//===-- Unittests for wmemset ---------------------------------------------===//
+//
+// 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 "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/wchar/wmemset.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcWMemsetTest, SmallStringBoundCheck) {
+  wchar_t str[5];
+  for (int i = 0; i < 5; i++)
+    str[i] = 'A';
+
+  wchar_t *output = LIBC_NAMESPACE::wmemset(str + 1, 'B', 3);
+
+  EXPECT_EQ(output, str + 1);
+
+  // EXPECT_TRUE being used since there isn't currently support for printing
+  // wide chars in the future, it would be preferred to switch these to
+  // EXPECT_EQ
+  EXPECT_TRUE(str[0] == (wchar_t)'A');
+  EXPECT_TRUE(str[1] == (wchar_t)'B');
+  EXPECT_TRUE(str[2] == (wchar_t)'B');
+  EXPECT_TRUE(str[3] == (wchar_t)'B');
+  EXPECT_TRUE(str[4] == (wchar_t)'A');
+}
+
+TEST(LlvmLibcWMemsetTest, LargeStringBoundCheck) {
+  constexpr int str_size = 1000;
+  wchar_t str[str_size];
+  for (int i = 0; i < str_size; i++)
+    str[i] = 'A';
+
+  wchar_t *output = LIBC_NAMESPACE::wmemset(str + 1, 'B', str_size - 2);
+
+  EXPECT_EQ(output, str + 1);
+
+  EXPECT_TRUE(str[0] == (wchar_t)'A');
+  for (int i = 1; i < str_size - 1; i++)
+    EXPECT_TRUE(str[i] == (wchar_t)'B');
+
+  EXPECT_TRUE(str[str_size - 1] == (wchar_t)'A');
+}
+
+TEST(LlvmLibcWMemsetTest, WCharSizeSmallString) {
+  // ensure we can handle full range of widechars
+  wchar_t str[5];
+  const wchar_t target = WCHAR_MAX;
+
+  for (int i = 0; i < 5; i++)
+    str[i] = 'A';
+
+  wchar_t *output = LIBC_NAMESPACE::wmemset(str + 1, target, 3);
+
+  EXPECT_EQ(output, str + 1);
+
+  EXPECT_TRUE(str[0] == (wchar_t)'A');
+  EXPECT_TRUE(str[1] == target);
+  EXPECT_TRUE(str[2] == target);
+  EXPECT_TRUE(str[3] == target);
+  EXPECT_TRUE(str[4] == (wchar_t)'A');
+}
+
+TEST(LlvmLibcWMemsetTest, WCharSizeLargeString) {
+  // ensure we can handle full range of widechars
+  constexpr int str_size = 1000;
+  wchar_t str[str_size];
+
+  const wchar_t target = WCHAR_MAX;
+
+  for (int i = 0; i < str_size; i++)
+    str[i] = 'A';
+
+  wchar_t *output = LIBC_NAMESPACE::wmemset(str + 1, target, str_size - 2);
+
+  EXPECT_EQ(output, str + 1);
+
+  EXPECT_TRUE(str[0] == (wchar_t)'A');
+  for (int i = 1; i < str_size - 1; i++)
+    EXPECT_TRUE(str[i] == target);
+
+  EXPECT_TRUE(str[str_size - 1] == (wchar_t)'A');
+}