From a0f6cc161c779db655dc91160f0fd1b296ad4269 Mon Sep 17 00:00:00 2001
From: Billy Laws <blaws05@gmail.com>
Date: Sat, 13 Feb 2021 12:53:17 +0000
Subject: [PATCH] Add a UUID struct for holding and generating RFC4122 UUIDs

Time uses UUIDs for clock identification.
---
 app/CMakeLists.txt                       |  1 +
 app/src/main/cpp/skyline/common/uuid.cpp | 76 ++++++++++++++++++++++++
 app/src/main/cpp/skyline/common/uuid.h   | 27 +++++++++
 3 files changed, 104 insertions(+)
 create mode 100644 app/src/main/cpp/skyline/common/uuid.cpp
 create mode 100644 app/src/main/cpp/skyline/common/uuid.h

diff --git a/app/CMakeLists.txt b/app/CMakeLists.txt
index d5d41dbe..7f82c8b9 100644
--- a/app/CMakeLists.txt
+++ b/app/CMakeLists.txt
@@ -39,6 +39,7 @@ add_library(skyline SHARED
         ${source_DIR}/skyline/common.cpp
         ${source_DIR}/skyline/common/settings.cpp
         ${source_DIR}/skyline/common/signal.cpp
+        ${source_DIR}/skyline/common/uuid.cpp
         ${source_DIR}/skyline/nce/guest.S
         ${source_DIR}/skyline/nce.cpp
         ${source_DIR}/skyline/jvm.cpp
diff --git a/app/src/main/cpp/skyline/common/uuid.cpp b/app/src/main/cpp/skyline/common/uuid.cpp
new file mode 100644
index 00000000..9b3bfa61
--- /dev/null
+++ b/app/src/main/cpp/skyline/common/uuid.cpp
@@ -0,0 +1,76 @@
+#include <random>
+#include "uuid.h"
+
+namespace skyline {
+    namespace {
+        union UuidLayout {
+            struct {
+                u64 high;
+                u64 low;
+            };
+
+            struct {
+                u32 timeLow;
+                u16 timeMid;
+                union {
+                    u16 timeHighAndVersion;
+
+                    struct {
+                        u16 timeHigh : 12;
+                        u8 version : 4;
+                    };
+                };
+
+                union {
+                    u8 clockSeqHighAndReserved;
+
+                    struct {
+                        u8 clockSeqHigh : 6;
+                        u8 reserved : 2;
+                    };
+                };
+                u8 clockSeqLow;
+
+                union __attribute__((packed)) {
+                    u64 node : 48;
+
+                    struct {
+                        std::array<u8, 6> nodeRaw;
+                    };
+                };
+            };
+
+            UUID Swap() {
+                UuidLayout swappedLayout{*this};
+                swappedLayout.timeLow = util::SwapEndianness(timeLow);
+                swappedLayout.timeMid = util::SwapEndianness(timeMid);
+                swappedLayout.timeHighAndVersion = util::SwapEndianness(timeHighAndVersion);
+                swappedLayout.nodeRaw = util::SwapEndianness(nodeRaw);
+
+                UUID out;
+                std::memcpy(&out, &swappedLayout, sizeof(UUID));
+                return out;
+            }
+        };
+        static_assert(sizeof(UuidLayout) == 0x10);
+    }
+
+    UUID UUID::GenerateUuidV4() {
+        constexpr u8 reserved{0x1}; // RFC4122 variant
+        constexpr u8 version{0x4}; // v4 UUIDs are generated entirely from random numbers
+
+        std::random_device rd;
+        std::mt19937_64 gen(rd());
+
+        std::uniform_int_distribution <u64> dist;
+
+        UuidLayout uuid;
+        uuid.low = dist(gen);
+        uuid.high = dist(gen);
+
+        uuid.reserved = reserved;
+        uuid.version = version;
+
+        return uuid.Swap();
+    }
+}
\ No newline at end of file
diff --git a/app/src/main/cpp/skyline/common/uuid.h b/app/src/main/cpp/skyline/common/uuid.h
new file mode 100644
index 00000000..591f8d63
--- /dev/null
+++ b/app/src/main/cpp/skyline/common/uuid.h
@@ -0,0 +1,27 @@
+#pragma once
+
+#include <compare>
+#include <common.h>
+
+namespace skyline {
+    /**
+     * @brief Contains an RFC4122 BE format UUID
+     */
+    struct UUID {
+        u128 raw{};
+
+        /**
+         * @brief Generates a random version 4 UUID
+         */
+        static UUID GenerateUuidV4();
+
+        /**
+         * @brief Checks if a UUID is an invalid nil UUID
+         */
+        bool Valid() {
+            return raw != 0;
+        }
+
+        auto operator<=>(const UUID &) const = default;
+    };
+}
\ No newline at end of file