LibC: Implement wmemmove

Author: https://github.com/timschumi
Commit: https://github.com/SerenityOS/serenity/commit/05b283f552b
Pull-request: https://github.com/SerenityOS/serenity/pull/10298
Reviewed-by: https://github.com/bgianfo ✅

Tests/LibC/TestWchar.cpp

@@ -137,6 +137,32 @@ TEST_CASE(wmemset)
     free(buf);
 }
 
+TEST_CASE(wmemmove)
+{
+    wchar_t* ret;
+    const wchar_t* string = L"abc\0def";
+    auto buf = static_cast<wchar_t*>(calloc(32, sizeof(wchar_t)));
+
+    if (!buf) {
+        FAIL("Could not allocate memory for target buffer");
+        return;
+    }
+
+    // Test moving to smaller addresses.
+    wmemcpy(buf + 3, string, 8);
+    ret = wmemmove(buf + 1, buf + 3, 8);
+    EXPECT_EQ(ret, buf + 1);
+    EXPECT_EQ(memcmp(string, buf + 1, 8 * sizeof(wchar_t)), 0);
+
+    // Test moving to larger addresses.
+    wmemcpy(buf + 16, string, 8);
+    ret = wmemmove(buf + 18, buf + 16, 8);
+    EXPECT_EQ(ret, buf + 18);
+    EXPECT_EQ(memcmp(string, buf + 18, 8 * sizeof(wchar_t)), 0);
+
+    free(buf);
+}
+
 TEST_CASE(wcscoll)
 {
     // Check if wcscoll is sorting correctly. At the moment we are doing raw char comparisons,

Userland/Libraries/LibC/wchar.cpp

@@ -402,4 +402,19 @@ wchar_t* wmemset(wchar_t* wcs, wchar_t wc, size_t n)
 
     return wcs;
 }
+
+wchar_t* wmemmove(wchar_t* dest, const wchar_t* src, size_t n)
+{
+    if (dest > src) {
+        for (size_t i = 1; i <= n; i++) {
+            dest[n - i] = src[n - i];
+        }
+    } else if (dest < src) {
+        for (size_t i = 0; i < n; i++) {
+            dest[i] = src[i];
+        }
+    }
+
+    return dest;
+}
 }

Userland/Libraries/LibC/wchar.h

@@ -46,5 +46,6 @@ wchar_t* wcsstr(const wchar_t*, const wchar_t*);
 wchar_t* wmemchr(const wchar_t*, wchar_t, size_t);
 wchar_t* wmemcpy(wchar_t*, const wchar_t*, size_t);
 wchar_t* wmemset(wchar_t*, wchar_t, size_t);
+wchar_t* wmemmove(wchar_t*, const wchar_t*, size_t);
 
 __END_DECLS