feat: initial version

srcs/ft_memset64.c

@@ -0,0 +1,38 @@
+#include <stddef.h>
+#include <stdint.h>
+
+void *ft_memset64(void *s, int c, size_t n)
+{
+	unsigned char   *ptr = (unsigned char *)s;
+	uint64_t        pattern;
+	uint64_t        *long_ptr;
+
+	unsigned char byte = (unsigned char)c;
+
+	while (n > 0 && ((uintptr_t)ptr % 8 != 0))
+	{
+		*ptr++ = byte;
+		n--;
+	}
+
+	if (n >= 8)
+	{
+		pattern = byte;
+		pattern |= pattern << 8;
+		pattern |= pattern << 16;
+		pattern |= pattern << 32;
+
+		long_ptr = (uint64_t *)ptr;
+		while (n >= 8)
+		{
+			*long_ptr++ = pattern;
+			n -= 8;
+		}
+		ptr = (unsigned char *)long_ptr;
+	}
+
+	while (n--)
+		*ptr++ = byte;
+
+	return s;
+}