add a GC.Collect() call to workaround a .net slow-GC problem, and fix an old bug related to firmware scans occurring several times actually every time you think it should happen once, which probably wasn't helping things

BizHawk.Client.Common/FirmwareManager.cs

@@ -1,4 +1,5 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 
@@ -36,8 +37,10 @@ namespace BizHawk.Client.Common
 			return Resolve(FirmwareDatabase.LookupFirmwareRecord(sysId, firmwareId));
 		}
 
-		public ResolutionInfo Resolve(FirmwareDatabase.FirmwareRecord record)
+		public ResolutionInfo Resolve(FirmwareDatabase.FirmwareRecord record, bool forbidScan = false)
 		{
+			//purpose of forbidScan: sometimes this is called from a loop in Scan(). we dont want to repeatedly DoScanAndResolve in that case, its already been done.
+
 			bool first = true;
 
 		RETRY:
@@ -49,7 +52,7 @@ namespace BizHawk.Client.Common
 			// NOTE: this could result in bad performance in some cases if the scanning happens repeatedly..
 			if (resolved == null && first)
 			{
-				DoScanAndResolve();
+				if(!forbidScan) DoScanAndResolve();
 				first = false;
 				goto RETRY;
 			}
@@ -65,9 +68,15 @@ namespace BizHawk.Client.Common
 			return resolved.FilePath;
 		}
 
-		public class RealFirmwareReader
+		public class RealFirmwareReader : IDisposable
 		{
 			byte[] buffer = new byte[0];
+			System.Security.Cryptography.SHA1 sha1 = System.Security.Cryptography.SHA1.Create();
+			public void Dispose()
+			{
+				sha1.Dispose();
+				sha1 = null;
+			}
 			public RealFirmwareFile Read(FileInfo fi)
 			{
 				var rff = new RealFirmwareFile { FileInfo = fi };
@@ -82,7 +91,11 @@ namespace BizHawk.Client.Common
 					fs.Read(buffer, 0, (int)len);
 				}
 
-				rff.Hash = buffer.HashSHA1(0, (int)len);
+				//without this, the file reading will make bad GC behaviour
+				GC.Collect();
+
+				sha1.ComputeHash(buffer, 0, (int)len);
+				rff.Hash = sha1.Hash.BytesToHexString();
 				dict[rff.Hash] = rff;
 				_files.Add(rff);
 				return rff;
@@ -94,8 +107,8 @@ namespace BizHawk.Client.Common
 
 		public void DoScanAndResolve()
 		{
-			var reader = new RealFirmwareReader();
-
+			using(var reader = new RealFirmwareReader())
+			{
 				// build a list of files under the global firmwares path, and build a hash for each of them while we're at it
 				var todo = new Queue<DirectoryInfo>();
 				todo.Enqueue(new DirectoryInfo(PathManager.MakeAbsolutePath(Global.Config.PathEntries.FirmwaresPathFragment, null)));
@@ -190,7 +203,7 @@ namespace BizHawk.Client.Common
 
 						// check whether it was a known file anyway, and go ahead and bind to the known file, as a perk (the firmwares config doesnt really use this information right now)
 						FirmwareDatabase.FirmwareFile ff;
-					if (FirmwareDatabase.FirmwareFilesByHash.TryGetValue(rff.Hash,out ff))
+						if (FirmwareDatabase.FirmwareFilesByHash.TryGetValue(rff.Hash, out ff))
 						{
 							ri.KnownFirmwareFile = ff;
 
@@ -206,7 +219,11 @@ namespace BizHawk.Client.Common
 							}
 						}
 					}
-			}
-		}
-	}
-}
+
+				} //foreach(firmware record)
+			} //using(new RealFirmwareReader())
+		} //DoScanAndResolve()
+
+	} //class FirmwareManager
+
+} //namespace

BizHawk.Client.EmuHawk/config/FirmwaresConfig.cs

@@ -197,7 +197,7 @@ namespace BizHawk.Client.EmuHawk
 			foreach (ListViewItem lvi in lvFirmwares.Items)
 			{
 				var fr = lvi.Tag as FirmwareDatabase.FirmwareRecord;
-				var ri = Manager.Resolve(fr);
+				var ri = Manager.Resolve(fr, true);
 				for(int i=4;i<=6;i++)
 					lvi.SubItems[i].Text = "";