[libc] Implemented wcsnlen

[sribee8]

Implemented wcsnlen and tests for the function.

[llvmbot]

@llvm/pr-subscribers-libc

Author: None (sribee8)

Changes

Implemented wcsnlen and tests for the function.

---

Full diff: https://github.com/llvm/llvm-project/pull/145610.diff

7 Files Affected:

• (modified) libc/config/linux/x86_64/entrypoints.txt (+1)
• (modified) libc/include/wchar.yaml (+7)
• (modified) libc/src/wchar/CMakeLists.txt (+12)
• (added) libc/src/wchar/wcsnlen.cpp (+24)
• (added) libc/src/wchar/wcsnlen.h (+22)
• (modified) libc/test/src/wchar/CMakeLists.txt (+12)
• (added) libc/test/src/wchar/wcsnlen_test.cpp (+46)

diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index c8a6d6e648af9..01bd6ce195bca 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -366,6 +366,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     # wchar.h entrypoints
     libc.src.wchar.btowc
     libc.src.wchar.wcslen
+    libc.src.wchar.wcsnlen
     libc.src.wchar.wctob
     libc.src.wchar.wmemmove
     libc.src.wchar.wmemset
diff --git a/libc/include/wchar.yaml b/libc/include/wchar.yaml
index 98cb3bdaf0ac9..a9f785a45b9a2 100644
--- a/libc/include/wchar.yaml
+++ b/libc/include/wchar.yaml
@@ -17,6 +17,13 @@ functions:
     return_type: size_t
     arguments:
       - type: const wchar_t *
+  - name: wcsnlen
+    standards:
+      - stdc
+    return_type: size_t
+    arguments:
+      - type: const wchar_t *
+      - type: size_t
   - name: wctob
     standards:
       - stdc
diff --git a/libc/src/wchar/CMakeLists.txt b/libc/src/wchar/CMakeLists.txt
index f390785e5817b..3be70b0422377 100644
--- a/libc/src/wchar/CMakeLists.txt
+++ b/libc/src/wchar/CMakeLists.txt
@@ -10,6 +10,18 @@ add_entrypoint_object(
     libc.src.string.string_utils
 )
 
+add_entrypoint_object(
+  wcsnlen
+  SRCS
+    wcsnlen.cpp
+  HDRS
+    wcsnlen.h
+  DEPENDS
+    libc.hdr.types.size_t
+    libc.hdr.types.wchar_t
+    libc.src.string.string_utils
+)
+
 add_entrypoint_object(
   wctob
   SRCS
diff --git a/libc/src/wchar/wcsnlen.cpp b/libc/src/wchar/wcsnlen.cpp
new file mode 100644
index 0000000000000..d54301b210b6d
--- /dev/null
+++ b/libc/src/wchar/wcsnlen.cpp
@@ -0,0 +1,24 @@
+//===-- Implementation of wcsnlen -----------------------------------------===//
+//
+// 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/wcsnlen.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" // string_length_trivial
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(size_t, wcsnlen, (const wchar_t *src, size_t maxlen)) {
+  size_t temp = internal::string_length(src);
+  return temp > maxlen ? maxlen : temp;
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/wchar/wcsnlen.h b/libc/src/wchar/wcsnlen.h
new file mode 100644
index 0000000000000..5a4c92d368a54
--- /dev/null
+++ b/libc/src/wchar/wcsnlen.h
@@ -0,0 +1,22 @@
+//===-- Implementation header for wcsnlen ---------------------------------===//
+//
+// 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_WCSNLEN_H
+#define LLVM_LIBC_SRC_WCHAR_WCSNLEN_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 wcsnlen(const wchar_t *src, size_t maxlen);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_WCHAR_WCSNLEN_H
diff --git a/libc/test/src/wchar/CMakeLists.txt b/libc/test/src/wchar/CMakeLists.txt
index 48688b3bdd1f3..8dd5d8fc6399f 100644
--- a/libc/test/src/wchar/CMakeLists.txt
+++ b/libc/test/src/wchar/CMakeLists.txt
@@ -12,6 +12,18 @@ add_libc_test(
     libc.src.wchar.wcslen
 )
 
+add_libc_test(
+  wcsnlen_test
+  SUITE
+    libc_wchar_unittests
+  SRCS
+    wcsnlen_test.cpp
+  DEPENDS
+    libc.hdr.types.size_t
+    libc.hdr.types.wchar_t
+    libc.src.wchar.wcsnlen
+)
+
 add_libc_test(
   btowc_test
   SUITE
diff --git a/libc/test/src/wchar/wcsnlen_test.cpp b/libc/test/src/wchar/wcsnlen_test.cpp
new file mode 100644
index 0000000000000..771df44d81641
--- /dev/null
+++ b/libc/test/src/wchar/wcsnlen_test.cpp
@@ -0,0 +1,46 @@
+//===-- Unittests for wcsnlen ---------------------------------------------===//
+//
+// 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/wcsnlen.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcWCSNLenTest, EmptyString) {
+  ASSERT_EQ(static_cast<size_t>(0), LIBC_NAMESPACE::wcsnlen(L"", 0));
+  // If N is greater than string length, this should still return 0.
+  ASSERT_EQ(static_cast<size_t>(0), LIBC_NAMESPACE::wcsnlen(L"", 1));
+}
+
+TEST(LlvmLibcWCSNLenTest, OneCharacterString) {
+  const wchar_t *src = L"A";
+  ASSERT_EQ(static_cast<size_t>(1), LIBC_NAMESPACE::wcsnlen(src, 1));
+  // If N is 0, this should return 0.
+  ASSERT_EQ(static_cast<size_t>(0), LIBC_NAMESPACE::wcsnlen(src, 0));
+  // If N is greater than string length, this should still return 1.
+  ASSERT_EQ(static_cast<size_t>(1), LIBC_NAMESPACE::wcsnlen(src, 3));
+}
+
+TEST(LlvmLibcWCSNLenTest, ManyCharacterString) {
+  const wchar_t *src = L"123456789";
+  ASSERT_EQ(static_cast<size_t>(9), LIBC_NAMESPACE::wcsnlen(src, 9));
+  // If N is 0, this should return 0.
+  ASSERT_EQ(static_cast<size_t>(0), LIBC_NAMESPACE::wcsnlen(src, 0));
+  // If N is smaller than the string length, it should return N.
+  ASSERT_EQ(static_cast<size_t>(3), LIBC_NAMESPACE::wcsnlen(src, 3));
+  // If N is greater than string length, this should still return 9.
+  ASSERT_EQ(static_cast<size_t>(9), LIBC_NAMESPACE::wcsnlen(src, 42));
+}
+
+TEST(LlvmLibcWCSNLenTest, IgnoreCharactersAfterNullTerminator) {
+  const wchar_t src[5] = {L'a', L'b', L'c', L'\0', L'd'};
+  ASSERT_EQ(static_cast<size_t>(3), LIBC_NAMESPACE::wcsnlen(src, 3));
+  // This should only read up to the null terminator.
+  ASSERT_EQ(static_cast<size_t>(3), LIBC_NAMESPACE::wcsnlen(src, 4));
+  ASSERT_EQ(static_cast<size_t>(3), LIBC_NAMESPACE::wcsnlen(src, 5));
+}

[michaelrj-google]

LGTM with a minor fix