[libc] wcslcat implementation

libc/config/linux/x86_64/entrypoints.txt

@@ -384,6 +384,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.wchar.wcscat
     libc.src.wchar.wcsstr
     libc.src.wchar.wcsncat
+    libc.src.wchar.wcslcat
     libc.src.wchar.wcscpy
     libc.src.wchar.wmemchr
     libc.src.wchar.wcpcpy

libc/include/wchar.yaml

@@ -166,6 +166,14 @@ functions:
     arguments: 
       - type: wchar_t *__restrict
       - type: const wchar_t *__restrict
+  - name: wcslcat
+    standards:
+      - stdc
+    return_type: size_t
+    arguments:
+      - type: wchar_t *__restrict
+      - type: const wchar_t *__restrict
+      - type: size_t
   - name: wcsstr
     standards:
       - stdc

libc/src/wchar/CMakeLists.txt

@@ -307,6 +307,18 @@ add_entrypoint_object(
     libc.src.string.string_utils
 )
 
+add_entrypoint_object(
+  wcslcat
+  SRCS
+    wcslcat.cpp
+  HDRS
+    wcslcat.h
+  DEPENDS
+    libc.hdr.types.size_t
+    libc.hdr.wchar_macros
+    libc.src.string.string_utils
+)
+
 add_entrypoint_object(
   wmemchr
   SRCS

libc/src/wchar/wcslcat.cpp

@@ -0,0 +1,39 @@
+//===-- Implementation of wcslcat -----------------------------------------===//
+//
+// 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/wcslcat.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, wcslcat,
+                   (wchar_t *__restrict dst, const wchar_t *__restrict src,
+                    size_t dstsize)) {
+  size_t dstlen = internal::string_length(dst);
+  size_t srclen = internal::string_length(src);
+  size_t limit = dstsize - dstlen - 1;
+
+  if (static_cast<int>(limit) < 0)
+    return (dstsize < dstlen ? dstsize : dstlen) + srclen;
+  size_t i = 0;
+  for (; i < limit && src[i] != L'\0'; ++i) {
+    dst[dstlen + i] = src[i];
+  }
+
+  // appending null terminator if there is room
+  if (dstlen + i < dstlen + dstsize)
+    dst[dstlen + i] = L'\0';
+  return (dstsize < dstlen ? dstsize : dstlen) + srclen;
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/wchar/wcslcat.h

@@ -0,0 +1,23 @@
+//===-- Implementation header for wcslcat ---------------------------------===//
+//
+// 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_WCSLCAT_H
+#define LLVM_LIBC_SRC_WCHAR_WCSLCAT_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 wcslcat(wchar_t *__restrict dst, const wchar_t *__restrict src,
+               size_t dstsize);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_WCHAR_WCSLCAT_H

libc/test/src/wchar/CMakeLists.txt

@@ -283,6 +283,17 @@ add_libc_test(
     libc.src.wchar.wcsncat
 )
 
+add_libc_test(
+  wcslcat_test
+  SUITE
+    libc_wchar_unittests
+  SRCS
+    wcslcat_test.cpp
+  DEPENDS
+    libc.src.wchar.wcslcat
+    libc.hdr.types.size_t
+)
+
 add_libc_test(
   wcscpy_test
   SUITE

libc/test/src/wchar/wcslcat_test.cpp

@@ -0,0 +1,72 @@
+//===-- Unittests for wcslcat ---------------------------------------------===//
+//
+// 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/wcslcat.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcWCSLCatTest, TooBig) {
+  const wchar_t *src = L"cd";
+  wchar_t dst[4]{L"ab"};
+  size_t res = LIBC_NAMESPACE::wcslcat(dst, src, 3);
+  ASSERT_TRUE(dst[0] == L'a');
+  ASSERT_TRUE(dst[1] == L'b');
+  ASSERT_TRUE(dst[2] == L'\0');
+  // Should still return src length + dst length
+  ASSERT_EQ(res, size_t(4));
+  // Not enough space to copy d
+  res = LIBC_NAMESPACE::wcslcat(dst, src, 4);
+  ASSERT_TRUE(dst[0] == L'a');
+  ASSERT_TRUE(dst[1] == L'b');
+  ASSERT_TRUE(dst[2] == L'c');
+  ASSERT_TRUE(dst[3] == L'\0');
+  ASSERT_EQ(res, size_t(4));
+}
+
+TEST(LlvmLibcWCSLCatTest, Smaller) {
+  const wchar_t *src = L"cd";
+  wchar_t dst[7]{L"ab"};
+  size_t res = LIBC_NAMESPACE::wcslcat(dst, src, 7);
+  ASSERT_TRUE(dst[0] == L'a');
+  ASSERT_TRUE(dst[1] == L'b');
+  ASSERT_TRUE(dst[2] == L'c');
+  ASSERT_TRUE(dst[3] == L'd');
+  ASSERT_TRUE(dst[4] == L'\0');
+  ASSERT_EQ(res, size_t(4));
+}
+
+TEST(LlvmLibcWCSLCatTest, SmallerNoOverwriteAfter0) {
+  const wchar_t *src = L"cd";
+  wchar_t dst[8]{L"ab\0\0efg"};
+  size_t res = LIBC_NAMESPACE::wcslcat(dst, src, 8);
+  ASSERT_TRUE(dst[0] == L'a');
+  ASSERT_TRUE(dst[1] == L'b');
+  ASSERT_TRUE(dst[2] == L'c');
+  ASSERT_TRUE(dst[3] == L'd');
+  ASSERT_TRUE(dst[4] == L'\0');
+  ASSERT_TRUE(dst[5] == L'f');
+  ASSERT_TRUE(dst[6] == L'g');
+  ASSERT_TRUE(dst[7] == L'\0');
+  ASSERT_EQ(res, size_t(4));
+}
+
+TEST(LlvmLibcWCSLCatTest, No0) {
+  const wchar_t *src = L"cd";
+  wchar_t dst[7]{L"ab"};
+  size_t res = LIBC_NAMESPACE::wcslcat(dst, src, 1);
+  ASSERT_TRUE(dst[0] == L'a');
+  ASSERT_TRUE(dst[1] == L'b');
+  ASSERT_TRUE(dst[2] == L'\0');
+  ASSERT_EQ(res, size_t(3));
+  res = LIBC_NAMESPACE::wcslcat(dst, src, 2);
+  ASSERT_TRUE(dst[0] == L'a');
+  ASSERT_TRUE(dst[1] == L'b');
+  ASSERT_TRUE(dst[2] == L'\0');
+  ASSERT_EQ(res, size_t(4));
+}

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

@@ -5827,6 +5827,19 @@ libc_function(
     ],
 )
 
+libc_function(
+    name = "wcslcat",
+    srcs = ["src/wchar/wcslcat.cpp"],
+    hdrs = ["src/wchar/wcslcat.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 +83,17 @@ libc_test(
     ],
 )
 
+
+libc_test(
+    name = "wcslcat_test",
+    srcs = ["wcslcat_test.cpp"],
+    deps = [
+        "//libc:types_size_t",
+        "//libc:types_wchar_t",
+        "//libc:wcslcat",
+    ],
+)
+
 libc_test(
     name = "wcslen_test",
     srcs = ["wcslen_test.cpp"],