From 30b71d5e44b00c7bd957830ab0d7a29f0b4c92c5 Mon Sep 17 00:00:00 2001
From: zeromus <zeromus@users.noreply.github.com>
Date: Sat, 26 Mar 2016 01:50:19 -0500
Subject: [PATCH] my small contribution to MemoryBlock: build it on a tempfile
 instead of system pagefile. Couldnt test it because old gpgx.elf and don't
 know how to build?

---
 BizHawk.Emulation.Cores/MemoryBlock.cs | 90 ++++++++++++++++++--------
 1 file changed, 63 insertions(+), 27 deletions(-)

diff --git a/BizHawk.Emulation.Cores/MemoryBlock.cs b/BizHawk.Emulation.Cores/MemoryBlock.cs
index 46d7262ce4..6f7525df24 100644
--- a/BizHawk.Emulation.Cores/MemoryBlock.cs
+++ b/BizHawk.Emulation.Cores/MemoryBlock.cs
@@ -150,40 +150,65 @@ namespace BizHawk.Emulation.Cores
 		}
 
 		/// <summary>
-		/// allocate size bytes starting at a particular address
+		/// Allocates a memory block as a memory-mapped file with the given size (created immediately) which can be Activated and Deactivated only at the given address.
 		/// </summary>
-		/// <param name="start"></param>
-		/// <param name="size"></param>
-		public MemoryBlock(ulong start, ulong size)
-		{
-			if (!Aligned(start))
-				throw new ArgumentOutOfRangeException();
-			if (size == 0)
-				throw new ArgumentOutOfRangeException();
-			size = AlignUp(size);
-
-			_handle = Kernel32.CreateFileMapping(Kernel32.INVALID_HANDLE_VALUE, IntPtr.Zero,
-				Kernel32.FileMapProtection.PageExecuteReadWrite | Kernel32.FileMapProtection.SectionCommit, (uint)(size >> 32), (uint)size, null);
-
-			if (_handle == IntPtr.Zero)
-				throw new InvalidOperationException("CreateFileMapping() returned NULL");
-			Start = start;
-			End = start + size;
-			Size = size;
-			_pageData = new Protection[GetPage(End - 1) + 1];
+		/// <param name="start">Location where this block can be Activated</param>
+		/// <param name="size">Size of the block</param>
+		public MemoryBlock(ulong start, ulong size)
+		{
+			size = 8 * 1024 * 1024 * 1024L;
+			if (!Aligned(start))
+				throw new ArgumentOutOfRangeException();
+			if (size == 0)
+				throw new ArgumentOutOfRangeException();
+			size = AlignUp(size);
+
+			//create a temporary file--the alternative is using the system pagefile(s)
+			//some systems have disabled or too-small files and many systems have a few GBs pagefile and difficulty growing it.
+			//creating a tempfile subverts the user's choice of pagefile locations, but %temp%'s location should be similarly chosen
+			//Could use this as a fallback in case creation on the pagefile fails?
+			var fname = BizHawk.Common.TempFileCleaner.GetTempFilename("MemoryBlock",null,false);
+			IntPtr fhTemp = Kernel32.CreateFile(
+				fname,
+				unchecked((int)(0x80000000 | 0x40000000 | 0x20000000)), //+RWX (protections can later be added with finer granularity)
+				3, //share RW
+				IntPtr.Zero, //security stuff
+				2, //create always
+				0x04000000, //delete on close!
+				IntPtr.Zero //template
+				);
+
+			//create FileMapping around the tempfile
+			//(again, protections can later be added with finer granularity)
+			_handle = Kernel32.CreateFileMapping(fhTemp, IntPtr.Zero,
+				Kernel32.FileMapProtection.PageExecuteReadWrite | Kernel32.FileMapProtection.SectionCommit, (uint)(size >> 32), (uint)size, null);
+
+			//releasing our tempfile handle, essentially yielding the handle to the FileMapping as sole owner
+			new Microsoft.Win32.SafeHandles.SafeFileHandle(fhTemp, true).Dispose();
+
+			if (_handle == IntPtr.Zero)
+				throw new InvalidOperationException("CreateFileMapping() returned NULL");
+			Start = start;
+			End = start + size;
+			Size = size;
+			_pageData = new Protection[GetPage(End - 1) + 1];
 		}
 
+
 		/// <summary>
-		/// activate the memory block, swapping it in at the specified address
+		/// activate the memory block, swapping it in at the predefined address
 		/// </summary>
 		public void Activate()
 		{
 			if (Active)
-				throw new InvalidOperationException("Already active");
-			if (Kernel32.MapViewOfFileEx(_handle, Kernel32.FileMapAccessType.Read | Kernel32.FileMapAccessType.Write | Kernel32.FileMapAccessType.Execute,
-				0, 0, Z.UU(Size), Z.US(Start)) != Z.US(Start))
+				throw new InvalidOperationException("Already active");
+
+			//(again, protections can later be added with finer granularity)
+			IntPtr ptr = Kernel32.MapViewOfFileEx(_handle, Kernel32.FileMapAccessType.Read | Kernel32.FileMapAccessType.Write | Kernel32.FileMapAccessType.Execute,
+				0, 0, Z.UU(Size), Z.US(Start));
+			if (ptr != Z.US(Start))
 			{
-				throw new InvalidOperationException("MapViewOfFileEx() returned NULL");
+				throw new InvalidOperationException("MapViewOfFileEx() returned incorrect starting address");
 			}
 			ProtectAll();
 			Active = true;
@@ -197,7 +222,7 @@ namespace BizHawk.Emulation.Cores
 			if (!Active)
 				throw new InvalidOperationException("Not active");
 			if (!Kernel32.UnmapViewOfFile(Z.US(Start)))
-				throw new InvalidOperationException("UnmapViewOfFile() returned NULL");
+				throw new InvalidOperationException("UnmapViewOfFile() returned false");
 		}
 
 		/// <summary>
@@ -438,7 +463,18 @@ namespace BizHawk.Emulation.Cores
 				GUARD_Modifierflag = 0x100,
 				NOCACHE_Modifierflag = 0x200,
 				WRITECOMBINE_Modifierflag = 0x400
-			}
+			}
+
+			[DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
+			public static extern IntPtr CreateFile(
+				string fileName,
+				int desiredAccess,
+				int shareMode,
+				IntPtr securityAttributes,
+				int creationDisposition,
+				int flagsAndAttributes,
+				IntPtr templateFile);
+
 
 			[DllImport("kernel32.dll", SetLastError = true)]
 			public static extern IntPtr CreateFileMapping(