From 86d2e0776812650bdeef4c8d9d70aaae6746ad95 Mon Sep 17 00:00:00 2001
From: Freya Murphy <freya@freyacat.org>
Date: Thu, 3 Apr 2025 16:47:01 -0400
Subject: volatile string fns

---
 include/string.h | 32 ++++++++++++++++++++++++++++++++
 lib/memcpyv.c    | 11 +++++++++++
 lib/memmovev.c   | 20 ++++++++++++++++++++
 lib/memsetv.c    | 10 ++++++++++
 4 files changed, 73 insertions(+)
 create mode 100644 lib/memcpyv.c
 create mode 100644 lib/memmovev.c
 create mode 100644 lib/memsetv.c

diff --git a/include/string.h b/include/string.h
index 4d32f57..e376918 100644
--- a/include/string.h
+++ b/include/string.h
@@ -51,6 +51,38 @@ extern void *memmove(void *restrict dest, const void *restrict src, size_t n);
  */
 extern void *memset(void *restrict dest, int c, size_t n);
 
+/**
+ * Copy the first n bytes from memory area src to memory area dest. The memory
+ * areas must not overlap.
+ * @param dest - the destination
+ * @param src - the source
+ * @param n - the byte count
+ * @returns a pointer to dest
+ */
+extern void *memcpyv(volatile void *restrict dest,
+					 const volatile void *restrict src, size_t n);
+
+/**
+ * Copy the first n bytes from memory area src to memory area dest. The memory
+ * areas may overlap; memmove behaves as though the bytes are first copied to a
+ * temporary array.
+ * @param dest - the destination
+ * @param src - the source
+ * @param n - the byte count
+ * @returns a pointer to dest
+ */
+extern void *memmovev(volatile void *restrict dest,
+					  const volatile void *restrict src, size_t n);
+
+/**
+ * Fill the first n bytes of the memory region dest with the constant byte c.
+ * @param dest - the destination
+ * @param c - the byte to write
+ * @param n - the byte count
+ * @returns a pointer to dest
+ */
+extern void *memsetv(volatile void *restrict dest, int c, size_t n);
+
 /**
  * Calculates the length of the string pointed to by str, excluding
  * the terminating null byte
diff --git a/lib/memcpyv.c b/lib/memcpyv.c
new file mode 100644
index 0000000..205d9c1
--- /dev/null
+++ b/lib/memcpyv.c
@@ -0,0 +1,11 @@
+#include <string.h>
+
+void *memcpyv(volatile void *restrict dest, const volatile void *restrict src,
+			  size_t n)
+{
+	char *d = dest;
+	const char *s = src;
+	for (; n; n--)
+		*d++ = *s++;
+	return dest;
+}
diff --git a/lib/memmovev.c b/lib/memmovev.c
new file mode 100644
index 0000000..d2fc683
--- /dev/null
+++ b/lib/memmovev.c
@@ -0,0 +1,20 @@
+#include <string.h>
+
+void *memmovev(volatile void *dest, const volatile void *src, size_t n)
+{
+	char *d = dest;
+	const char *s = src;
+
+	if (d == s)
+		return d;
+
+	if (d < s) {
+		for (; n; n--)
+			*d++ = *s++;
+	} else {
+		while (n)
+			n--, d[n] = s[n];
+	}
+
+	return dest;
+}
diff --git a/lib/memsetv.c b/lib/memsetv.c
new file mode 100644
index 0000000..9039cb7
--- /dev/null
+++ b/lib/memsetv.c
@@ -0,0 +1,10 @@
+#include <string.h>
+
+void *memsetv(volatile void *dest, int c, size_t n)
+{
+	unsigned char *d = dest;
+	for (; n; n--) {
+		*d++ = c;
+	};
+	return dest;
+}
-- 
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