memory-mapped-files

The the client side of a content provider consumer I can do something like this, to get a proper InputStream for reading the picture: InputStream is = getContentResolver().openInputStream(pictureUri); It is a nice API, and will on the server side, the actual content provider result in a call to: public ParcelFileDescriptor openFile(Uri uri, String mode) throws FileNotFoundException { // Open a proper ParcelFileDescriptor, most likely using openFileHelper(uri, mode) } But what if the picture mapped to the URI is not to be found on the filesystem, but as a memory resource, or generated on the

What are the drawbacks (if any) of using memory mapped file to read (regular sized files) over doing the same using CreateFile ReadFile combination? With ReadFile/WriteFile you have deterministic error handling semantics. When you use memory mapped files, errors are returned by throwing an exception. In addition, if the memory mapped file has to hit the disk (or even worse, the network) your memory read may take several seconds (or even minutes) to complete. Depending on your application, this can cause unexpected stalls. If you use ReadFile/WriteFile you can use asynchronous variants of the

Is there any way to use the Interlocked.CompareExchange(); and Interlocked.Increment(); methods against values stored in a memory-mapped file? I'd like to implement a multi-threaded service that will store its data in a memory-mapped file, but since it's multi-threaded I need to prevent conflicting writes, therefore I wonder about the Interlocked operations rather than using explicit locks. I know it's possible with native code, but can it be done in managed code on .NET 4.0? OK, this is how you do it! We had to figure this out, and I figured we could give some back to stackoverflow! class

Here is a code for writing values to memory using memory mapping. When I try to run the code, I get the error "File "MMF.py", line 26, in memcpy(pBuf, szMsg, len(szMsg)) OSError: exception: access violation writing 0xFFFFFFFFFA1C001B" import msvcrt, mmap import ctypes from ctypes import * FILE_MAP_ALL_ACCESS = 0x04 INVALID_HANDLE_VALUE = 0xFFFFFFFF SHMEMSIZE = 256 PAGE_READWRITE = 0x04 szName = ctypes.c_wchar_p("MyFileMappingObject") szMsg = "Message from Python(ctypes) process" hMapObject = windll.kernel32.CreateFileMappingA(INVALID_HANDLE_VALUE,None, PAGE_READWRITE, 0, SHMEMSIZE, szName)