Add UUID generation.

lib/std/math/math_random.c3

@@ -173,7 +173,8 @@ interface Random
 	fn void next_bytes(char[] buffer);
 }
 
-macro init_default_random() @local
+
+macro init_default_random() @private
 {
 	if (!default_random_initialized)
 	{

lib/std/math/uuid.c3

@@ -0,0 +1,41 @@
+module std::math::uuid;
+import std::math::random @public;
+import std::io;
+
+distinct Uuid (Printable) = char[16];
+
+/**
+ * Generate a version 4 UUID from the default random.
+ **/
+fn Uuid generate()
+{
+	random::init_default_random();
+	return generate_from_random(&random::default_random);
+}
+
+/**
+ * Generate a version 4 UUID from the given random.
+ **/
+fn Uuid generate_from_random(Random random)
+{
+	Uuid uuid;
+	random.next_bytes(&(char[16])uuid);
+	uuid[6] = (uuid[6] & 0b0000_1111) | 0b0100_0000;
+	uuid[8] = (uuid[8] & 0b0011_1111) | 0b1000_0000;
+	return uuid;
+}
+
+fn usz! Uuid.to_format(&self, Formatter* formatter) @dynamic
+{
+	return formatter.printf("%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x",
+		(*self)[0], (*self)[1], (*self)[2], (*self)[3],
+		(*self)[4], (*self)[5],
+		(*self)[6], (*self)[7],
+		(*self)[8], (*self)[9],
+		(*self)[10], (*self)[11], (*self)[12], (*self)[13], (*self)[14], (*self)[15]);
+}
+
+fn String Uuid.to_string(&self, Allocator allocator) @dynamic
+{
+	return string::new_format("%s", *self, allocator: allocator);
+}