[libc] wcslcpy implementation (#146571)

Implemented wcslcpy and tests.

---------

Co-authored-by: Sriya Pratipati <sriyap@google.com>

Author: sribee8

libc/config/linux/x86_64/entrypoints.txt

@@ -385,6 +385,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.wchar.wcsstr
     libc.src.wchar.wcsncat
     libc.src.wchar.wcscpy
+    libc.src.wchar.wcslcpy
     libc.src.wchar.wmemchr
     libc.src.wchar.wcpcpy
     libc.src.wchar.wcpncpy

libc/include/wchar.yaml

@@ -203,6 +203,14 @@ functions:
     arguments:
       - type: wchar_t *__restrict
       - type: const wchar_t *__restrict
+  - name: wcslcpy
+    standards:
+      - stdc
+    return_type: size_t
+    arguments:
+      - type: wchar_t *__restrict
+      - type: const wchar_t *__restrict
+      - type: size_t
   - name: wcstok
     standards:
       - stdc

libc/src/wchar/CMakeLists.txt

@@ -340,3 +340,14 @@ add_entrypoint_object(
     libc.hdr.wchar_macros
     libc.src.string.string_utils
 )
+
+add_entrypoint_object(
+  wcslcpy
+  SRCS
+    wcslcpy.cpp
+  HDRS
+    wcslcpy.h
+  DEPENDS
+    libc.hdr.types.size_t
+    libc.hdr.wchar_macros
+)

libc/src/wchar/wcslcpy.cpp

@@ -0,0 +1,32 @@
+//===-- Implementation of wcslcpy -----------------------------------------===//
+//
+// 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/wcslcpy.h"
+
+#include "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+#include "src/string/string_utils.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(size_t, wcslcpy,
+                   (wchar_t *__restrict dst, const wchar_t *__restrict src,
+                    size_t dstsize)) {
+  size_t len = internal::string_length(src);
+  if (dstsize == 0)
+    return len;
+  size_t i = 0;
+  for (; i < dstsize - 1 && src[i] != L'\0'; ++i)
+    dst[i] = src[i];
+  dst[i] = L'\0';
+  return len;
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/wchar/wcslcpy.h

@@ -0,0 +1,23 @@
+//===-- Implementation header for wcslcpy ---------------------------------===//
+//
+// 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_WCSLCPY_H
+#define LLVM_LIBC_SRC_WCHAR_WCSLCPY_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 wcslcpy(wchar_t *__restrict dst, const wchar_t *__restrict src,
+               size_t dstsize);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_WCHAR_WCSLCPY_H

libc/test/src/wchar/CMakeLists.txt

@@ -303,6 +303,17 @@ add_libc_test(
     libc.src.wchar.wcpcpy
 )
 
+add_libc_test(
+  wcslcpy_test
+  SUITE
+    libc_wchar_unittests
+  SRCS
+    wcslcpy_test.cpp
+  DEPENDS
+    libc.hdr.types.size_t
+    libc.src.wchar.wcslcpy
+)
+
 add_libc_test(
   wcpncpy_test
   SUITE

libc/test/src/wchar/wcslcpy_test.cpp

@@ -0,0 +1,65 @@
+//===-- Unittests for wcslcpy ---------------------------------------------===//
+//
+// 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/wcslcpy.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcWCSLCpyTest, BiggerSource) {
+  const wchar_t *src = L"abcde";
+  wchar_t dst[3];
+  size_t res = LIBC_NAMESPACE::wcslcpy(dst, src, 3);
+  ASSERT_TRUE(dst[0] == L'a');
+  ASSERT_TRUE(dst[1] == L'b');
+  // Should append null terminator
+  ASSERT_TRUE(dst[2] == L'\0');
+  // Should still return length of src
+  ASSERT_EQ(res, size_t(5));
+}
+
+TEST(LlvmLibcWCSLCpyTest, CopyZero) {
+  const wchar_t *src = L"abcde";
+  wchar_t dst = L'f';
+  // Copying zero should not change destination
+  size_t res = LIBC_NAMESPACE::wcslcpy(&dst, src, 0);
+  ASSERT_TRUE(dst == L'f');
+  // Should still return length of src
+  ASSERT_EQ(res, size_t(5));
+}
+
+TEST(LlvmLibcWCSLCpyTest, SmallerSource) {
+  const wchar_t *src = L"abc";
+  wchar_t dst[7]{L"123456"};
+  size_t res = LIBC_NAMESPACE::wcslcpy(dst, src, 7);
+  ASSERT_TRUE(dst[0] == L'a');
+  ASSERT_TRUE(dst[1] == L'b');
+  ASSERT_TRUE(dst[2] == L'c');
+  // Should append null terminator after copying source
+  ASSERT_TRUE(dst[3] == L'\0');
+  // Should not change following characters
+  ASSERT_TRUE(dst[4] == L'5');
+  ASSERT_TRUE(dst[5] == L'6');
+  ASSERT_TRUE(dst[6] == L'\0');
+  // Should still return length of src
+  ASSERT_EQ(res, size_t(3));
+}
+
+TEST(LlvmLibcWCSLCpyTest, DoesNotCopyAfterNull) {
+  const wchar_t src[5] = {L'a', L'b', L'\0', L'c', L'd'};
+  wchar_t dst[5]{L"1234"};
+  size_t res = LIBC_NAMESPACE::wcslcpy(dst, src, 5);
+  ASSERT_TRUE(dst[0] == L'a');
+  ASSERT_TRUE(dst[1] == L'b');
+  ASSERT_TRUE(dst[2] == L'\0');
+  // Should not change following characters
+  ASSERT_TRUE(dst[3] == L'4');
+  ASSERT_TRUE(dst[4] == L'\0');
+  // Should still return length of src
+  ASSERT_EQ(res, size_t(2));
+}

utils/bazel/llvm-project-overlay/libc/BUILD.bazel

@@ -5829,6 +5829,19 @@ libc_function(
     ],
 )
 
+libc_function(
+    name = "wcslcpy",
+    srcs = ["src/wchar/wcslcpy.cpp"],
+    hdrs = ["src/wchar/wcslcpy.h"],
+    deps = [
+        ":__support_common",
+        ":__support_macros_config",
+        ":string_utils",
+        ":types_size_t",
+        ":types_wchar_t",
+    ],
+)
+
 libc_function(
     name = "wcslen",
     srcs = ["src/wchar/wcslen.cpp"],

utils/bazel/llvm-project-overlay/libc/test/src/wchar/BUILD.bazel

@@ -83,6 +83,16 @@ libc_test(
     ],
 )
 
+libc_test(
+    name = "wcslcpy_test",
+    srcs = ["wcslcpy_test.cpp"],
+    deps = [
+        "//libc:types_size_t",
+        "//libc:types_wchar_t",
+        "//libc:wcslcpy",
+    ],
+)
+
 libc_test(
     name = "wcslen_test",
     srcs = ["wcslen_test.cpp"],