WCSChr Implementation (#141690)

implemented wcschr and tests

---------

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

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.wcschr
 
     # sys/uio.h entrypoints
     libc.src.sys.uio.writev

libc/include/wchar.yaml

@@ -27,3 +27,10 @@ functions:
     return_type: wint_t
     arguments:
       - type: int
+  - name: wcschr
+    standards:
+      - stdc
+    return_type: const wchar_t *
+    arguments: 
+      - type: const wchar_t *
+      - type: wchar_t

libc/src/wchar/CMakeLists.txt

@@ -33,3 +33,14 @@ add_entrypoint_object(
     libc.hdr.wchar_macros
     libc.src.__support.wctype_utils
 )
+
+add_entrypoint_object(
+  wcschr
+  SRCS
+    wcschr.cpp
+  HDRS
+    wcschr.h
+  DEPENDS
+    libc.hdr.wchar_macros
+    libc.src.__support.wctype_utils
+)

libc/src/wchar/wcschr.cpp

@@ -0,0 +1,25 @@
+//===-- Implementation of wcschr ------------------------------------------===//
+//
+// 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/wcschr.h"
+
+#include "hdr/types/wchar_t.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(const wchar_t *, wcschr, (const wchar_t *s, wchar_t c)) {
+  for (; *s && *s != c; ++s)
+    ;
+  if (*s == c)
+    return s;
+  return nullptr;
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/wchar/wcschr.h

@@ -0,0 +1,21 @@
+//===-- Implementation header for wcschr ----------------------------------===//
+//
+// 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_WCSCHR_H
+#define LLVM_LIBC_SRC_WCHAR_WCSCHR_H
+
+#include "hdr/types/wchar_t.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+const wchar_t *wcschr(const wchar_t *s, wchar_t c);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_WCHAR_WCSCHR_H

libc/test/src/wchar/CMakeLists.txt

@@ -32,3 +32,13 @@ add_libc_test(
   DEPENDS
     libc.src.wchar.wctob
 )
+
+add_libc_test(
+  wcschr_test
+  SUITE
+    libc_wchar_unittests
+  SRCS
+    wcschr_test.cpp
+  DEPENDS
+    libc.src.wchar.wcschr
+)

libc/test/src/wchar/wcschr_test.cpp

@@ -0,0 +1,61 @@
+//===-- Unittests for wcschr ----------------------------------------------===//
+//
+// 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/wchar_t.h"
+#include "src/wchar/wcschr.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcWCSChrTest, FindsFirstCharacter) {
+  // Should return pointer to original string since 'a' is the first character.
+  const wchar_t *src = L"abcde";
+  ASSERT_EQ(LIBC_NAMESPACE::wcschr(src, L'a'), src);
+}
+
+TEST(LlvmLibcWCSChrTest, FindsMiddleCharacter) {
+  // Should return pointer to 'c'.
+  const wchar_t *src = L"abcde";
+  ASSERT_EQ(LIBC_NAMESPACE::wcschr(src, L'c'), (src + 2));
+}
+
+TEST(LlvmLibcWCSChrTest, FindsLastCharacterThatIsNotNullTerminator) {
+  // Should return pointer to 'e'.
+  const wchar_t *src = L"abcde";
+  ASSERT_EQ(LIBC_NAMESPACE::wcschr(src, L'e'), (src + 4));
+}
+
+TEST(LlvmLibcWCSChrTest, FindsNullTerminator) {
+  // Should return pointer to null terminator.
+  const wchar_t *src = L"abcde";
+  ASSERT_EQ(LIBC_NAMESPACE::wcschr(src, L'\0'), (src + 5));
+}
+
+TEST(LlvmLibcWCSChrTest, CharacterNotWithinStringShouldReturnNullptr) {
+  // Since 'z' is not within the string, should return nullptr.
+  const wchar_t *src = L"abcde";
+  ASSERT_EQ(LIBC_NAMESPACE::wcschr(src, L'z'), nullptr);
+}
+
+TEST(LlvmLibcWCSChrTest, ShouldFindFirstOfDuplicates) {
+  // Should return pointer to the first '1'.
+  const wchar_t *src = L"abc1def1ghi";
+  ASSERT_EQ((int)(LIBC_NAMESPACE::wcschr(src, L'1') - src), 3);
+
+  // Should return original string since 'X' is the first character.
+  const wchar_t *dups = L"XXXXX";
+  ASSERT_EQ(LIBC_NAMESPACE::wcschr(dups, L'X'), dups);
+}
+
+TEST(LlvmLibcWCSChrTest, EmptyStringShouldOnlyMatchNullTerminator) {
+  // Null terminator should match
+  const wchar_t *src = L"";
+  ASSERT_EQ(src, LIBC_NAMESPACE::wcschr(src, L'\0'));
+  // All other characters should not match
+  ASSERT_EQ(LIBC_NAMESPACE::wcschr(src, L'Z'), nullptr);
+  ASSERT_EQ(LIBC_NAMESPACE::wcschr(src, L'3'), nullptr);
+  ASSERT_EQ(LIBC_NAMESPACE::wcschr(src, L'*'), nullptr);
+}