From bf4e733688b3bac9d48d463d584a95d1e6d73efb Mon Sep 17 00:00:00 2001
From: Max Wash <max@doorstuck.net>
Date: Fri, 17 Apr 2020 11:22:23 +0100
Subject: [PATCH] Implemented memcpy()

---
 photon/libc/include/string.h |  6 +++++
 photon/libc/string/memcpy.c  | 43 ++++++++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+)
 create mode 100644 photon/libc/string/memcpy.c

diff --git a/photon/libc/include/string.h b/photon/libc/include/string.h
index 631f22e..a0b904f 100644
--- a/photon/libc/include/string.h
+++ b/photon/libc/include/string.h
@@ -7,7 +7,13 @@
 extern "C" {
 #endif
 
+extern void *memcpy(void *dest, const void *src, size_t sz);
+extern void *memcmp(const void *a, const void *b, size_t sz);
+extern void *memmove(void *dest, const void *src, size_t sz);
+
 extern size_t strlen(const char *str);
+extern int strcmp(const char *a, const char *b);
+extern int strncmp(const char *a, const char *b, size_t sz);
 
 #if defined(__cplusplus)
 } /* extern "C" */
diff --git a/photon/libc/string/memcpy.c b/photon/libc/string/memcpy.c
new file mode 100644
index 0000000..7a1dc1d
--- /dev/null
+++ b/photon/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;
+}