strings: Implement poor mans memmove

Implemented a simple memmove and added another "unittest" for that.

Signed-off-by: Martin Mazein <[email protected]>

include/string.h

@@ -106,6 +106,38 @@ static inline void *memcpy(void *d, void *s, size_t n) {
     return d;
 }
 
+static inline void *memmove(void *d, const void *s, size_t n) {
+
+    /* dst and src are the same */
+    if (d == s) {
+        return d;
+    }
+
+    /* if we don't have a range overlap, just use memcpy */
+    if ((d > s && d > s + n) || (d < s && d + n < s)) {
+        return memcpy(d, (void *) s, n);
+    }
+
+    /*
+     * s ------
+     * d    ------
+     * needs reverse moving
+     */
+    if (s < d) {
+        while (n--)
+            *((char *) d + n) = *((char *) s + n);
+    }
+    else
+        /*
+         * s     ------
+         * d   -----
+         * normal copy
+         */
+        return memcpy(d, (void *) s, n);
+
+    return d;
+}
+
 static inline int memcmp(const void *m1, const void *m2, size_t n) {
     const uint8_t *_m1 = m1;
     const uint8_t *_m2 = m2;

tests/test.c

@@ -43,6 +43,10 @@ bool_cmd("boolean", opt_bool);
 
 static bool opt_booltwo = 0;
 bool_cmd("booleantwo", opt_booltwo);
+
+static char memmove_string[4];
+static char range_string[] = "123456";
+static char *src, *dst;
 #endif
 
 static int __user_text func(void *arg) { return 0; }
@@ -80,6 +84,26 @@ void test_main(void) {
     else {
         printk("Boolean parameter parsing works!\n");
     }
+
+    printk("\nMemmove testing:\n");
+    (void) memmove(memmove_string, opt_string, sizeof(opt_string));
+    if (!strcmp(memmove_string, opt_string)) {
+        printk("Moving around memory works!\n");
+    }
+    else {
+        printk("Memmove'ing did not work: %s (%p) != %s (%p)\n", memmove_string,
+               memmove_string, opt_string, opt_string);
+    }
+
+    src = (char *) range_string;
+    dst = (char *) range_string + 2;
+    (void) memmove(dst, src, 4);
+    if (!strcmp(range_string, "121234")) {
+        printk("Moving around memory with overlaping ranges works!\n");
+    }
+    else {
+        printk("Overlaping memmove'ing did not work: %s != %s\n", range_string, "121234");
+    }
 #endif
 
     wait_for_all_tasks();