From caa440daf6e7954cc9515fd090beb64b87493eca Mon Sep 17 00:00:00 2001
From: Joursoir <chat@joursoir.net>
Date: Mon, 2 Aug 2021 22:31:56 +0000
Subject: string: make memcpy(), memset(), memmove()

---
 kernel/string.c | 42 ++++++++++++++++++++++++++++++++++++++++++
 kernel/string.h |  3 +++
 2 files changed, 45 insertions(+)

(limited to 'kernel')

diff --git a/kernel/string.c b/kernel/string.c
index d038c27..006b907 100644
--- a/kernel/string.c
+++ b/kernel/string.c
@@ -7,3 +7,45 @@ size_t strlen(const char *str)
 		len++;
 	return len;
 }
+
+/*
+	Copy bytes in memory. If copying takes place between objects
+	that overlap, the behavior is undefined.
+*/
+void *memcpy(void *dest, const void *src, size_t n)
+{
+	size_t i;
+	const char *s = src;
+	char *d = dest;
+
+	for(i = 0; i < n; i++)
+		d[i] = s[i];
+	return dest;
+}
+
+void *memset(void *dest, int c, size_t n)
+{
+	char *d = dest;
+	while(n--)
+		*d++ = c;
+	return dest;
+}
+
+/*
+	Copy bytes in memory with overlapping areas.
+*/
+void *memmove(void *dest, const void *src, size_t n)
+{
+	const char *s = src;
+	char *d = dest;
+
+	if(dest == src)
+		return dest;
+
+	if(dest < src)
+		return memcpy(dest, src, n);
+
+	while(n--)
+		d[n] = s[n];
+	return dest;
+}
diff --git a/kernel/string.h b/kernel/string.h
index dc760a5..3c628b3 100644
--- a/kernel/string.h
+++ b/kernel/string.h
@@ -5,5 +5,8 @@
 #include <stdint.h>
 
 size_t strlen(const char *str);
+void *memcpy(void *dest, const void *src, size_t n);
+void *memset(void *dest, int c, size_t n);
+void *memmove(void *dest, const void *src, size_t n);
 
 #endif /* KERNEL_STRING */
-- 
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