meta: move photon/libc to root

libc/string/memcpy.c

@@ -0,0 +1,43 @@
+#include <stddef.h>
+
+#define ALIGNED(p) (!((long)p & (sizeof(long) - 1)))
+#define QUADBLOCKSIZE (sizeof(long) << 2)
+#define BLOCKSIZE (sizeof(long))
+
+void *memcpy(void *dest, const void *src, size_t sz)
+{
+    /* Only try word-writing if the pointers are aligned and
+     * the buffer is big enough */
+    if (sz >= BLOCKSIZE && ALIGNED(dest) && ALIGNED(src)) {
+        long *dest_word = dest;
+        const long *src_word = src;
+
+        /* First try copying 4x blocks per iteration */
+        while (sz >= QUADBLOCKSIZE) {
+            *dest_word++ = *src_word++;
+            *dest_word++ = *src_word++;
+            *dest_word++ = *src_word++;
+            *dest_word++ = *src_word++;
+            sz -= QUADBLOCKSIZE;
+        }
+
+        /* Then try copying 1x words per iteration */
+        while (sz >= BLOCKSIZE) {
+            *dest_word++ = *src_word++;
+            sz -= BLOCKSIZE;
+        }
+
+        /* Then go back to the byte-level copying */
+        dest = dest_word;
+        src = src_word;
+    }
+
+    char *dest0 = dest;
+    const char *src0 = src;
+
+    while (sz-- > 0) {
+        *dest0++ = *src0++;
+    }
+
+    return dest;
+}