private unsafe void Initialize(string fileMappingName, int fileMappingSize, int initialOffset) {
string mappingName = fileMappingName;
SharedUtils.CheckEnvironment();
SafeLocalMemHandle securityDescriptorPointer = null;
new SecurityPermission(SecurityPermissionFlag.UnmanagedCode).Assert();
try {
// The sddl string consists of these parts:
// D: it's a DACL
// (A; this is an allow ACE
// OICI; object inherit and container inherit
// FRFWGRGW;;; allow file read, file write, generic read and generic write
// AU) granted to Authenticated Users
// ;S-1-5-33) the same permission granted to AU is also granted to restricted services
string sddlString = "D:(A;OICI;FRFWGRGW;;;AU)(A;OICI;FRFWGRGW;;;S-1-5-33)";
if (!SafeLocalMemHandle.ConvertStringSecurityDescriptorToSecurityDescriptor(sddlString, NativeMethods.SDDL_REVISION_1,
out securityDescriptorPointer, IntPtr.Zero))
throw new InvalidOperationException(SR.GetString(SR.SetSecurityDescriptorFailed));
NativeMethods.SECURITY_ATTRIBUTES securityAttributes = new NativeMethods.SECURITY_ATTRIBUTES();
securityAttributes.lpSecurityDescriptor = securityDescriptorPointer;
securityAttributes.bInheritHandle = false;
//
//
// Here we call CreateFileMapping to create the memory mapped file. When CreateFileMapping fails
// with ERROR_ACCESS_DENIED, we know the file mapping has been created and we then open it with OpenFileMapping.
//
// There is chance of a race condition between CreateFileMapping and OpenFileMapping; The memory mapped file
// may actually be closed in between these two calls. When this happens, OpenFileMapping returns ERROR_FILE_NOT_FOUND.
// In this case, we need to loop back and retry creating the memory mapped file.
//
// This loop will timeout in approximately 1.4 minutes. An InvalidOperationException is thrown in the timeout case.
//
//
int waitRetries = 14; //((2^13)-1)*10ms == approximately 1.4mins
int waitSleep = 0;
bool created = false;
while (!created && waitRetries > 0) {
fileMappingHandle = NativeMethods.CreateFileMapping((IntPtr)(-1), securityAttributes,
NativeMethods.PAGE_READWRITE, 0, fileMappingSize, mappingName);
if ((Marshal.GetLastWin32Error() != NativeMethods.ERROR_ACCESS_DENIED) || !fileMappingHandle.IsInvalid) {
created = true;
}
else {
// Invalidate the old safehandle before we get rid of it. This prevents it from trying to finalize
fileMappingHandle.SetHandleAsInvalid();
fileMappingHandle = NativeMethods.OpenFileMapping(NativeMethods.FILE_MAP_WRITE, false, mappingName);
if ((Marshal.GetLastWin32Error() != NativeMethods.ERROR_FILE_NOT_FOUND) || !fileMappingHandle.IsInvalid) {
created = true;
}
else {
--waitRetries;
if (waitSleep == 0) {
waitSleep = 10;
}
else {
System.Threading.Thread.Sleep(waitSleep);
waitSleep *= 2;
}
}
}
}
if (fileMappingHandle.IsInvalid) {
throw new InvalidOperationException(SR.GetString(SR.CantCreateFileMapping));
}
fileViewAddress = SafeFileMapViewHandle.MapViewOfFile(fileMappingHandle, NativeMethods.FILE_MAP_WRITE, 0,0, UIntPtr.Zero);
if (fileViewAddress.IsInvalid)
throw new InvalidOperationException(SR.GetString(SR.CantMapFileView));
// figure out what size the share memory really is.
NativeMethods.MEMORY_BASIC_INFORMATION meminfo = new NativeMethods.MEMORY_BASIC_INFORMATION();
if (NativeMethods.VirtualQuery(fileViewAddress, ref meminfo, (IntPtr) sizeof(NativeMethods.MEMORY_BASIC_INFORMATION)) == IntPtr.Zero)
throw new InvalidOperationException(SR.GetString(SR.CantGetMappingSize));
FileMappingSize = (int) meminfo.RegionSize;
}
finally {
if (securityDescriptorPointer != null) securityDescriptorPointer.Close();
SecurityPermission.RevertAssert();
}
SafeNativeMethods.InterlockedCompareExchange(fileViewAddress.DangerousGetHandle(), initialOffset, 0);
}
