From 93cd8ccdd9a19fae5bae268740fd2cbc8825875c Mon Sep 17 00:00:00 2001
From: Nick Hastings <nshastings@gmail.com>
Date: Wed, 24 Oct 2018 23:46:35 -0400
Subject: [PATCH 1/2] Improve GameID support for mods and shortcuts.

---
 SteamKit2/SteamKit2/Types/GameID.cs | 31 ++++++++++++++++++++++++++
 SteamKit2/Tests/GameIDFacts.cs      | 34 +++++++++++++++++++++++++++++
 2 files changed, 65 insertions(+)
 create mode 100644 SteamKit2/Tests/GameIDFacts.cs

diff --git a/SteamKit2/SteamKit2/Types/GameID.cs b/SteamKit2/SteamKit2/Types/GameID.cs
index 1419c9559..1a26d94bb 100644
--- a/SteamKit2/SteamKit2/Types/GameID.cs
+++ b/SteamKit2/SteamKit2/Types/GameID.cs
@@ -64,6 +64,36 @@ public GameID( Int32 nAppID )
             : this( ( UInt64 )nAppID )
         {
         }
+        /// <summary>
+        /// Initializes a new instance of the <see cref="GameID"/> class.
+        /// </summary>
+        /// <param name="nAppID">The base app id of the mod.</param>
+        /// <param name="modPath">The game folder name of the mod.</param>
+        public GameID( UInt32 nAppID, string modPath )
+            : this(0)
+        {
+            AppID = nAppID;
+            AppType = GameType.GameMod;
+            ModID = BitConverter.ToUInt32(CryptoHelper.CRCHash(System.Text.Encoding.ASCII.GetBytes(modPath)), 0);
+        }
+        /// <summary>
+        /// Initializes a new instance of the <see cref="GameID"/> class.
+        /// </summary>
+        /// <param name="exePath">The path to the executable, usually quoted.</param>
+        /// <param name="appName">The name of the application shortcut.</param>
+        public GameID( string exePath, string appName )
+            : this(0)
+        {
+            string combined = string.Empty;
+            if (exePath != null)
+                combined += exePath;
+            if (appName != null)
+                combined += appName;
+
+            AppID = 0;
+            AppType = GameType.Shortcut;
+            ModID = BitConverter.ToUInt32(CryptoHelper.CRCHash(System.Text.Encoding.ASCII.GetBytes(combined)), 0);
+        }
 
 
         /// <summary>
@@ -179,6 +209,7 @@ public UInt32 ModID
             set
             {
                 gameid[ 32, 0xFFFFFFFF ] = ( UInt64 )value;
+                gameid[ 63, 0xFF ] = 1;
             }
         }
 
diff --git a/SteamKit2/Tests/GameIDFacts.cs b/SteamKit2/Tests/GameIDFacts.cs
new file mode 100644
index 000000000..06816480e
--- /dev/null
+++ b/SteamKit2/Tests/GameIDFacts.cs
@@ -0,0 +1,34 @@
+using System;
+using SteamKit2;
+using Xunit;
+
+namespace Tests
+{
+    public class GameIDFacts
+    {
+        [Fact]
+        public void ModCRCCorrect()
+        {
+            GameID gameId = new GameID(420, "Research and Development");
+
+            Assert.True(gameId.IsMod);
+            Assert.Equal(gameId.AppID, 420u);
+            Assert.Equal(gameId, new GameID(10210309621176861092));
+
+            GameID gameId2 = new GameID(215, "hidden");
+
+            Assert.True(gameId2.IsMod);
+            Assert.Equal(gameId2.AppID, 215u);
+            Assert.Equal(gameId2, new GameID(9826266959967158487));
+        }
+
+        [Fact]
+        public void ShortcutCRCCorrect()
+        {
+            GameID gameId = new GameID("\"C:\\Program Files (x86)\\Git\\mingw64\\bin\\wintoast.exe\"", "Git for Windows");
+
+            Assert.True(gameId.IsShortcut);
+            Assert.Equal(gameId, new GameID(12754778225939316736));
+        }
+    }
+}

From 4c4a538d37773fdaaa4b02b2a4c67887790cb61d Mon Sep 17 00:00:00 2001
From: Nick Hastings <nshastings@gmail.com>
Date: Thu, 25 Oct 2018 17:05:24 -0400
Subject: [PATCH 2/2] Switch to more direct CRC call and fix encoding.

---
 SteamKit2/SteamKit2/Types/GameID.cs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/SteamKit2/SteamKit2/Types/GameID.cs b/SteamKit2/SteamKit2/Types/GameID.cs
index 1a26d94bb..4ac122ede 100644
--- a/SteamKit2/SteamKit2/Types/GameID.cs
+++ b/SteamKit2/SteamKit2/Types/GameID.cs
@@ -74,7 +74,7 @@ public GameID( UInt32 nAppID, string modPath )
         {
             AppID = nAppID;
             AppType = GameType.GameMod;
-            ModID = BitConverter.ToUInt32(CryptoHelper.CRCHash(System.Text.Encoding.ASCII.GetBytes(modPath)), 0);
+            ModID = Crc32.Compute(System.Text.Encoding.UTF8.GetBytes(modPath));
         }
         /// <summary>
         /// Initializes a new instance of the <see cref="GameID"/> class.
@@ -92,7 +92,7 @@ public GameID( string exePath, string appName )
 
             AppID = 0;
             AppType = GameType.Shortcut;
-            ModID = BitConverter.ToUInt32(CryptoHelper.CRCHash(System.Text.Encoding.ASCII.GetBytes(combined)), 0);
+            ModID = Crc32.Compute(System.Text.Encoding.UTF8.GetBytes(combined));
         }