From c6f77c8a3dd991ccf788d82336fd403cc63d7b66 Mon Sep 17 00:00:00 2001
From: Souryo <mesenemu@gmail.com>
Date: Tue, 12 Sep 2017 20:52:12 -0400
Subject: [PATCH] Startup: Only overwrite existing files on disks if they don't
 match the embedded file

---
 GUI.NET/Forms/frmUpdatePrompt.cs | 15 +-----------
 GUI.NET/ResourceManager.cs       | 42 ++++++++++++++++++++++++++------
 2 files changed, 36 insertions(+), 21 deletions(-)

diff --git a/GUI.NET/Forms/frmUpdatePrompt.cs b/GUI.NET/Forms/frmUpdatePrompt.cs
index dd129681..41e2b7af 100644
--- a/GUI.NET/Forms/frmUpdatePrompt.cs
+++ b/GUI.NET/Forms/frmUpdatePrompt.cs
@@ -72,7 +72,7 @@ namespace Mesen.GUI.Forms
 				frmDownloadProgress frmDownload = new frmDownloadProgress("http://www.mesen.ca/Services/GetLatestVersion.php?a=download&p=win&v=" + InteropEmu.GetMesenVersion(), srcFilePath);
 				if(frmDownload.ShowDialog() == DialogResult.OK) {
 					FileInfo fileInfo = new FileInfo(srcFilePath);
-					if(fileInfo.Length > 0 && GetSha1Hash(srcFilePath) == _fileHash) {
+					if(fileInfo.Length > 0 && ResourceManager.GetSha1Hash(File.ReadAllBytes(srcFilePath)) == _fileHash) {
 						if(Program.IsMono) {
 							Process.Start("mono", string.Format("\"{0}\" \"{1}\" \"{2}\" \"{3}\"", updateHelper, srcFilePath, destFilePath, backupFilePath));
 						} else {
@@ -88,19 +88,6 @@ namespace Mesen.GUI.Forms
 #endif
 		}
 
-		private string GetSha1Hash(string filename)
-		{
-			using(SHA1Managed sha1 = new SHA1Managed()) {
-				byte[] hash = sha1.ComputeHash(File.ReadAllBytes(filename));
-
-				var sb = new StringBuilder(hash.Length * 2);
-				foreach(byte b in hash) {
-					sb.Append(b.ToString("x2"));
-				}
-				return sb.ToString();
-			}
-		}
-
 		private void picDonate_Click(object sender, EventArgs e)
 		{
 			Process.Start("http://www.mesen.ca/Donate.php?l=" + ResourceHelper.GetLanguageCode());
diff --git a/GUI.NET/ResourceManager.cs b/GUI.NET/ResourceManager.cs
index 6dbd80e3..6bc80414 100644
--- a/GUI.NET/ResourceManager.cs
+++ b/GUI.NET/ResourceManager.cs
@@ -7,24 +7,52 @@ using System.Text;
 using System.Threading.Tasks;
 using Mesen.GUI.Config;
 using System.IO.Compression;
+using System.Security.Cryptography;
 
 namespace Mesen.GUI
 {
 	class ResourceManager
 	{
+		public static string GetSha1Hash(byte[] fileData)
+		{
+			using(SHA1Managed sha1 = new SHA1Managed()) {
+				byte[] hash = sha1.ComputeHash(fileData);
+
+				var sb = new StringBuilder(hash.Length * 2);
+				foreach(byte b in hash) {
+					sb.Append(b.ToString("x2"));
+				}
+				return sb.ToString();
+			}
+		}
+
 		private static void ExtractFile(ZipArchiveEntry entry, string outputFilename)
 		{
 			if(File.Exists(outputFilename)) {
+				byte[] zipFileData = new byte[entry.Length];
+				using(Stream fileStream = entry.Open()) {
+					fileStream.Read(zipFileData, 0, (int)entry.Length);
+				}
+
+				string diskFileSha1 = GetSha1Hash(File.ReadAllBytes(outputFilename));
+				string zipFileSha1 = GetSha1Hash(zipFileData);
+
+				if(diskFileSha1 != zipFileSha1) {
+					try {
+						File.Delete(outputFilename);
+					} catch { }
+					try {
+						File.WriteAllBytes(outputFilename, zipFileData);
+					} catch { }
+				}
+			} else {
 				try {
-					File.Delete(outputFilename);
+					//On Mono, using overwrite = true for ExtractToFile crashes/kills any currently running instance that uses the file.
+					//This is probably a Mono bug?
+					//Better to attempt a delete & then extract, like now (and like it used to be) 
+					entry.ExtractToFile(outputFilename);
 				} catch { }
 			}
-			try {
-				//On Mono, using overwrite = true for ExtractToFile crashes/kills any currently running instance that uses the file.
-				//This is probably a Mono bug?
-				//Better to attempt a delete & then extract, like now (and like it used to be) 
-				entry.ExtractToFile(outputFilename);
-			} catch { }
 		}
 
 		public static Stream GetZippedResource(string filename)