LibC: Implement wmemchr

Author: https://github.com/timschumi
Commit: https://github.com/SerenityOS/serenity/commit/0ca1df4dc64
Pull-request: https://github.com/SerenityOS/serenity/pull/10298
Reviewed-by: https://github.com/bgianfo ✅

Tests/LibC/TestWchar.cpp

@@ -65,6 +65,38 @@ TEST_CASE(wcsstr)
     EXPECT_EQ(ret, nullptr);
 }
 
+TEST_CASE(wmemchr)
+{
+    const wchar_t* input = L"abcde";
+    wchar_t* ret;
+
+    // Empty haystack returns nothing.
+    ret = wmemchr(L"", L'c', 0);
+    EXPECT_EQ(ret, nullptr);
+
+    // Not included character returns nothing.
+    ret = wmemchr(input, L'z', 5);
+    EXPECT_EQ(ret, nullptr);
+
+    // Match at string start.
+    ret = wmemchr(input, L'a', 5);
+    EXPECT_EQ(ret, input);
+
+    // Match at string end.
+    ret = wmemchr(input, L'e', 5);
+    EXPECT_EQ(ret, input + 4);
+
+    input = L"abcde\0fg";
+
+    // Handle finding null characters.
+    ret = wmemchr(input, L'\0', 8);
+    EXPECT_EQ(ret, input + 5);
+
+    // Don't stop at null characters.
+    ret = wmemchr(input, L'f', 8);
+    EXPECT_EQ(ret, input + 6);
+}
+
 TEST_CASE(wcscoll)
 {
     // Check if wcscoll is sorting correctly. At the moment we are doing raw char comparisons,

Userland/Libraries/LibC/wchar.cpp

@@ -375,4 +375,14 @@ wchar_t* wcsstr(const wchar_t* haystack, const wchar_t* needle)
 
     return nullptr;
 }
+
+wchar_t* wmemchr(const wchar_t* s, wchar_t c, size_t n)
+{
+    for (size_t i = 0; i < n; i++) {
+        if (s[i] == c)
+            return const_cast<wchar_t*>(&s[i]);
+    }
+
+    return nullptr;
+}
 }

Userland/Libraries/LibC/wchar.h

@@ -43,5 +43,6 @@ int wctob(wint_t);
 int mbsinit(const mbstate_t*);
 wchar_t* wcspbrk(const wchar_t*, const wchar_t*);
 wchar_t* wcsstr(const wchar_t*, const wchar_t*);
+wchar_t* wmemchr(const wchar_t*, wchar_t, size_t);
 
 __END_DECLS