Merge pull request #216 from DrXiao/libc/memset

Implement memset

Author: jserv

lib/c.c

@@ -140,6 +140,23 @@ char *memcpy(char *dest, char *src, int count)
     return dest;
 }
 
+void *memset(void *s, int c, int n)
+{
+    int i = 0;
+    char *ptr = s;
+    for (; i + 4 <= n; i += 4) {
+        ptr[i] = c;
+        ptr[i + 1] = c;
+        ptr[i + 2] = c;
+        ptr[i + 3] = c;
+    }
+
+    for (; i < n; i++)
+        ptr[i] = c;
+
+    return s;
+}
+
 /* set 10 digits (32bit) without div
  *
  * This function converts a given integer value to its string representation
@@ -683,22 +700,7 @@ void *calloc(int n, int size)
     if (!p)
         return NULL;
 
-    /* TODO: Replace the byte buffer clearing algorithm with memset once
-     * implemented.
-     */
-
-    /* Currently malloc uses mmap(2) to request allocation, which guarantees
-     * memory to be page-aligned
-     */
-    int *pi = p, num_words = total >> 2, offset = num_words << 2;
-
-    for (int i = 0; i < num_words; i++)
-        pi[i] = 0;
-
-    while (offset < total)
-        p[offset++] = 0;
-
-    return p;
+    return memset(p, 0, total);
 }
 
 void __rfree(void *ptr, int size)

tests/driver.sh

@@ -1823,4 +1823,36 @@ int main()
 }
 EOF
 
+# Test memset()
+ans=" 7d 7d 7d 7d 7d 7d 7d 7d 7d 7d 7d 00 00 00 00 00
+ 00 00 00 00 00 00 7d 7d 7d 7d 7d 00 00 00 00 00
+ 3a 3a 3a 3a 3a 3a 3a 3a 3a 3a 3a 3a 3a 3a 3a 3a"
+try_output 0 "$ans" << EOF
+void print_array(char *ptr, int sz)
+{
+    for (int i = 0; i < sz; i++)
+        printf(" %02x", ptr[i]);
+    printf("\n");
+}
+
+int main(void)
+{
+    int sz = sizeof(char) * 16;
+    char *ptr = malloc(sz);
+
+    if (ptr != memset(ptr, 0x7D, sizeof(char) * 11))
+        exit(1);
+    print_array(ptr, sz);
+    if (ptr != memset(ptr, 0, sizeof(char) * 6))
+        exit(1);
+    print_array(ptr, sz);
+    if (ptr != memset(ptr, 0x3A, sz))
+        exit(1);
+    print_array(ptr, sz);
+
+    free(ptr);
+    return 0;
+}
+EOF
+
 echo OK