From c00945ec1e5804003fb47798e86cd0c737a14d46 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Roman=20Smr=C5=BE?= <roman.smrz@seznam.cz>
Date: Sat, 6 Jun 2020 14:47:45 +0200
Subject: UUID: random generation and format checking functions

---
 include/erebos/uuid.h |  9 ++++++++-
 src/uuid.cpp          | 47 +++++++++++++++++++++++++++++++++++++++--------
 2 files changed, 47 insertions(+), 9 deletions(-)

diff --git a/include/erebos/uuid.h b/include/erebos/uuid.h
index 9b615f8..e67677a 100644
--- a/include/erebos/uuid.h
+++ b/include/erebos/uuid.h
@@ -1,15 +1,22 @@
 #pragma once
 
 #include <array>
+#include <optional>
 #include <string>
 
 namespace erebos {
 
 struct UUID
 {
-	explicit UUID(std::string);
+	UUID(): uuid({}) {}
+	explicit UUID(const std::string &);
 	explicit operator std::string() const;
 
+	static std::optional<UUID> fromString(const std::string &);
+	static bool fromString(const std::string &, UUID &);
+
+	static UUID generate();
+
 	bool operator==(const UUID &) const;
 	bool operator!=(const UUID &) const;
 
diff --git a/src/uuid.cpp b/src/uuid.cpp
index 9af32b7..a53bf27 100644
--- a/src/uuid.cpp
+++ b/src/uuid.cpp
@@ -2,8 +2,12 @@
 
 #include <stdexcept>
 
+#include <openssl/rand.h>
+
 using namespace erebos;
 
+using std::nullopt;
+using std::optional;
 using std::runtime_error;
 using std::string;
 
@@ -12,15 +16,9 @@ static const size_t UUID_STR_LEN = 36;
 static const char * FORMAT_STRING = "%02hhx%02hhx%02hhx%02hhx-%02hhx%02hhx-"
 	"%02hhx%02hhx-%02hhx%02hhx-%02hhx%02hhx%02hhx%02hhx%02hhx%02hhx";
 
-UUID::UUID(string str)
+UUID::UUID(const string & str)
 {
-	if (str.size() != UUID_STR_LEN)
-		throw runtime_error("invalid UUID");
-
-	if (sscanf(str.c_str(), FORMAT_STRING,
-				&uuid[0], &uuid[1], &uuid[2], &uuid[3], &uuid[4], &uuid[5], &uuid[6], &uuid[7],
-				&uuid[8], &uuid[9], &uuid[10], &uuid[11], &uuid[12], &uuid[13], &uuid[14], &uuid[15])
-			!= 16)
+	if (!fromString(str, *this))
 		throw runtime_error("invalid UUID");
 }
 
@@ -33,6 +31,39 @@ UUID::operator string() const
 	return str;
 }
 
+optional<UUID> UUID::fromString(const string & str)
+{
+	UUID u;
+	if (fromString(str, u))
+		return u;
+	return nullopt;
+}
+
+bool UUID::fromString(const string & str, UUID & u)
+{
+	if (str.size() != UUID_STR_LEN)
+		return false;
+
+	if (sscanf(str.c_str(), FORMAT_STRING,
+				&u.uuid[0], &u.uuid[1], &u.uuid[2], &u.uuid[3], &u.uuid[4], &u.uuid[5], &u.uuid[6], &u.uuid[7],
+				&u.uuid[8], &u.uuid[9], &u.uuid[10], &u.uuid[11], &u.uuid[12], &u.uuid[13], &u.uuid[14], &u.uuid[15])
+			!= 16)
+		return false;
+
+	return true;
+}
+
+UUID UUID::generate()
+{
+	UUID u;
+	if (RAND_bytes(u.uuid.data(), u.uuid.size()) != 1)
+		throw runtime_error("failed to generate random UUID");
+
+	u.uuid[6] = (u.uuid[6] & 0x0f) | 0x40;
+	u.uuid[8] = (u.uuid[8] & 0x3f) | 0x80;
+	return u;
+}
+
 bool UUID::operator==(const UUID & other) const
 {
 	return std::equal(std::begin(uuid), std::end(uuid), std::begin(other.uuid));
-- 
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