Tests: Add tests for memmove and memcmp + correct our memcmp implementation

libs/libc/src/string.cpp

@@ -27,13 +27,15 @@ extern "C"
 
     int memcmp(const void* a, const void* b, size_t n)
     {
-        const char* _a = (const char*)a;
-        const char* _b = (const char*)b;
-        for (; n && _a == _b; n--, _a++, _b++)
-            ;
         if (!n) return 0;
-        if (*_a > *_b) return 1;
+        const unsigned char* ap = (const unsigned char*)a;
-        return -1;
+        const unsigned char* bp = (const unsigned char*)b;
+        while (--n && *ap == *bp)
+        {
+            ap++;
+            bp++;
+        }
+        return *ap - *bp;
     }
 
     void* memmove(void* dest, const void* src, size_t n)

tests/libc/Test.c

@@ -4,6 +4,8 @@
 DEFINE_TEST(memset);
 DEFINE_TEST(memcpy);
 DEFINE_TEST(memchr);
+DEFINE_TEST(memcmp);
+DEFINE_TEST(memmove);
 DEFINE_TEST(strlen);
 DEFINE_TEST(strnlen);
 DEFINE_TEST(strcspn);
@@ -26,6 +28,8 @@ int main()
     RUN_TEST(memset);
     RUN_TEST(memcpy);
     RUN_TEST(memchr);
+    RUN_TEST(memcmp);
+    RUN_TEST(memmove);
     RUN_TEST(strlen);
     RUN_TEST(strnlen);
     RUN_TEST(strcspn);

tests/libc/string.c

@@ -67,6 +67,62 @@ DEFINE_TEST(memchr)
     TEST_SUCCESS();
 }
 
+DEFINE_TEST(memcmp)
+{
+    START_TEST(memcmp);
+
+    char buf[20] = "abcdefghijklmnopqrs";
+    char buf2[20] = "abcdefghijklmnopqrp";
+
+    int val = memcmp(buf, buf, 20);
+
+    EXPECT_EQ(val, 0);
+
+    val = memcmp(buf, buf2, 20);
+
+    EXPECT(val > 0);
+
+    val = memcmp(buf2, buf, 20);
+
+    EXPECT(val < 0);
+
+    TEST_SUCCESS();
+}
+
+DEFINE_TEST(memmove)
+{
+    START_TEST(memmove);
+
+    char buf[20] = "Nothing is going on";
+    const char* str = "Something is going!";
+
+    char* ptr = memmove(buf, str, 20);
+
+    EXPECT_EQ(ptr, buf);
+
+    for (int i = 0; i < 20; i++) { EXPECT_EQ(buf[i], str[i]); }
+
+    const char* new = "Well...";
+
+    ptr = memmove(buf, new, 7);
+
+    EXPECT_EQ(ptr, buf);
+
+    for (int i = 0; i < 7; i++) { EXPECT_EQ(buf[i], new[i]); }
+    for (int i = 7; i < 20; i++) { EXPECT_EQ(buf[i], str[i]); }
+
+    char newbuf[16] = "part_a is part_b";
+    char result[16] = "is part_b part_b";
+
+    ptr = memmove(newbuf, newbuf + 7, 9);
+
+    EXPECT_EQ(ptr, newbuf);
+
+    EXPECT(memcmp(newbuf, result, 16) == 0); // we have tested memcmp at this point
+
+    TEST_SUCCESS();
+}
+
 DEFINE_TEST(strlen)
 {
     START_TEST(strlen);