From 8025e6b92a09fcf584c13fea3f04f2a0be9cbe64 Mon Sep 17 00:00:00 2001
From: Wojtek Kosior <kwojtus@protonmail.com>
Date: Tue, 31 Dec 2019 11:05:33 +0100
Subject: add memcpy

---
 strings.c | 16 ++++++++++++++--
 strings.h |  3 +++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/strings.c b/strings.c
index 4164467..94cb6ac 100644
--- a/strings.c
+++ b/strings.c
@@ -1,5 +1,3 @@
-#include <stddef.h>
-
 #include "strings.h"
 
 void uint32_to_dec(uint32_t number, char buf[10])
@@ -79,3 +77,17 @@ size_t strlen(char string[])
 
   return len;
 }
+
+void memcpy(void *dst, void *src, size_t nbytes)
+{
+  size_t iter;
+
+  // copying by word is faster than by byte
+  // copy by word as much as possible
+  for (iter = 0; iter < nbytes / 4; iter++)
+    ((volatile uint32_t*) dst)[iter] = ((uint32_t*) src)[iter];
+
+  // copy the remaining 1, 2 or 3 bytes by byte
+  for (iter *= 4; iter < nbytes; iter++)
+    ((volatile uint8_t*) dst)[iter] = ((uint8_t*) src)[iter];
+}
diff --git a/strings.h b/strings.h
index 7e772d3..1eb291c 100644
--- a/strings.h
+++ b/strings.h
@@ -1,6 +1,7 @@
 #ifndef STRINGS_H
 #define STRINGS_H
 
+#include <stddef.h>
 #include <stdint.h>
 
 void uint32_to_dec(uint32_t number, char buf[10]);
@@ -23,4 +24,6 @@ void uint32_to_hexstringt(uint32_t number, char buf[9]);
 
 size_t strlen(char string[]);
 
+void memcpy(void *dst, void *src, size_t nbytes);
+  
 #endif // STRINGS_H
-- 
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