From 296145ba2d3a46f9745cc4560a2bf788e2481e2d Mon Sep 17 00:00:00 2001
From: YoshiRulz <OSSYoshiRulz@gmail.com>
Date: Sun, 20 Feb 2022 23:34:16 +1000
Subject: [PATCH] Clean up dummy/zero checksums

see #3159
---
 src/BizHawk.Client.Common/XmlGame.cs                   |  2 +-
 src/BizHawk.Common/checksums/MD5Checksum.cs            |  2 ++
 src/BizHawk.Common/checksums/SHA1Checksum.cs           |  6 ++++++
 src/BizHawk.Emulation.Common/Database/Database.cs      |  2 +-
 .../Database/FirmwareDatabase.cs                       | 10 ++++++----
 5 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/src/BizHawk.Client.Common/XmlGame.cs b/src/BizHawk.Client.Common/XmlGame.cs
index 28cbd18c55..ac109183a7 100644
--- a/src/BizHawk.Client.Common/XmlGame.cs
+++ b/src/BizHawk.Client.Common/XmlGame.cs
@@ -112,7 +112,7 @@ namespace BizHawk.Client.Common
 				}
 				else
 				{
-					ret.GI.Hash = "0000000000000000000000000000000000000000";
+					ret.GI.Hash = SHA1Checksum.Zero;
 				}
 
 				return ret;
diff --git a/src/BizHawk.Common/checksums/MD5Checksum.cs b/src/BizHawk.Common/checksums/MD5Checksum.cs
index 5ccfcf817e..9a867733ce 100644
--- a/src/BizHawk.Common/checksums/MD5Checksum.cs
+++ b/src/BizHawk.Common/checksums/MD5Checksum.cs
@@ -17,6 +17,8 @@ namespace BizHawk.Common
 
 		internal const string PREFIX = "MD5";
 
+		public /*static readonly*/const string EmptyFile = "D41D8CD98F00B204E9800998ECF8427E";
+
 #if NET6_0
 		public static byte[] Compute(ReadOnlySpan<byte> data)
 			=> MD5.HashData(data);
diff --git a/src/BizHawk.Common/checksums/SHA1Checksum.cs b/src/BizHawk.Common/checksums/SHA1Checksum.cs
index 671dbf00c4..f67a3f34e7 100644
--- a/src/BizHawk.Common/checksums/SHA1Checksum.cs
+++ b/src/BizHawk.Common/checksums/SHA1Checksum.cs
@@ -17,6 +17,12 @@ namespace BizHawk.Common
 
 		internal const string PREFIX = "SHA1";
 
+		public /*static readonly*/const string Dummy = "EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE";
+
+		public /*static readonly*/const string EmptyFile = "DA39A3EE5E6B4B0D3255BFEF95601890AFD80709";
+
+		public /*static readonly*/const string Zero = "0000000000000000000000000000000000000000";
+
 #if NET6_0
 		public static byte[] Compute(ReadOnlySpan<byte> data)
 			=> SHA1.HashData(data);
diff --git a/src/BizHawk.Emulation.Common/Database/Database.cs b/src/BizHawk.Emulation.Common/Database/Database.cs
index 6007d5d81a..32a459d861 100644
--- a/src/BizHawk.Emulation.Common/Database/Database.cs
+++ b/src/BizHawk.Emulation.Common/Database/Database.cs
@@ -152,7 +152,7 @@ namespace BizHawk.Emulation.Common
 						Region = items.Length >= 7 ? items[6] : "",
 						ForcedCore = items.Length >= 8 ? items[7].ToLowerInvariant() : ""
 					};
-					if (game.Hash is "DA39A3EE5E6B4B0D3255BFEF95601890AFD80709" or "D41D8CD98F00B204E9800998ECF8427E")
+					if (game.Hash is SHA1Checksum.EmptyFile or MD5Checksum.EmptyFile)
 					{
 						Console.WriteLine($"WARNING: gamedb {path} contains entry for empty rom as \"{game.Name}\"!");
 					}
diff --git a/src/BizHawk.Emulation.Common/Database/FirmwareDatabase.cs b/src/BizHawk.Emulation.Common/Database/FirmwareDatabase.cs
index ad5b6919c2..f892d557ea 100644
--- a/src/BizHawk.Emulation.Common/Database/FirmwareDatabase.cs
+++ b/src/BizHawk.Emulation.Common/Database/FirmwareDatabase.cs
@@ -3,6 +3,8 @@
 using System.Collections.Generic;
 using System.Linq;
 
+using BizHawk.Common;
+
 // ReSharper disable IdentifierTypo
 // ReSharper disable InconsistentNaming
 // ReSharper disable StringLiteralTypo
@@ -114,8 +116,8 @@ namespace BizHawk.Emulation.Common
 
 			FirmwareAndOption("24F67BDEA115A2C847C8813A262502EE1607B7DF", 16384, "NDS", "bios7", "NDS_Bios7.bin", "ARM7 BIOS");
 			FirmwareAndOption("BFAAC75F101C135E32E2AAF541DE6B1BE4C8C62D", 4096, "NDS", "bios9", "NDS_Bios9.bin", "ARM9 BIOS");
-			FirmwareAndOption("0000000000000000000000000000000000000000", 65536, "NDS", "bios7i", "NDS_Bios7i.bin", "ARM7i BIOS");
-			FirmwareAndOption("0000000000000000000000000000000000000000", 65536, "NDS", "bios9i", "NDS_Bios9i.bin", "ARM9i BIOS");
+			FirmwareAndOption(SHA1Checksum.Dummy, 65536, "NDS", "bios7i", "NDS_Bios7i.bin", "ARM7i BIOS");
+			FirmwareAndOption(SHA1Checksum.Dummy, 65536, "NDS", "bios9i", "NDS_Bios9i.bin", "ARM9i BIOS");
 			Firmware("NDS", "firmware", "NDS Firmware");
 			// throwing a ton of hashes from the interwebs
 			var knownhack1 = File("22A7547DBC302BCBFB4005CFB5A2D426D3F85AC6", 262144, "NDS_Firmware [b1].bin", "NDS Firmware", "known hack", true);
@@ -131,8 +133,8 @@ namespace BizHawk.Emulation.Common
 			Option("NDS", "firmware", in likelygood2);
 			Option("NDS", "firmware", in likelygood3);
 
-			FirmwareAndOption("0000000000000000000000000000000000000000", 131072, "NDS", "firmwarei", "DSi_Firmware.bin", "DSi Firmware");
-			FirmwareAndOption("0000000000000000000000000000000000000000", 251658304, "NDS", "nand", "DSi_Nand.bin", "DSi NAND");
+			FirmwareAndOption(SHA1Checksum.Dummy, 131072, "NDS", "firmwarei", "DSi_Firmware.bin", "DSi Firmware");
+			FirmwareAndOption(SHA1Checksum.Dummy, 251658304, "NDS", "nand", "DSi_Nand.bin", "DSi NAND");
 
 			FirmwareAndOption("E4ED47FAE31693E016B081C6BDA48DA5B70D7CCB", 512, "Lynx", "Boot", "LYNX_boot.img", "Boot Rom");