Tuesday, October 14, 2008

TDM Rerun #11: Shared Pools

Sometimes we run into problems because of a Windows feature, and most of the time this is a very good feature, that a file mapping (an essential part of my shared memory implementation) cannot exist on its own. A file mapping, like mutexes, events, and other Windows primitives, must have an owner. If all processes associated with a given file mapping die, the file mapping will be destroyed. Because in my shared memory implementation this file mapping is backed with a page file, its contents won’t be preserved on an accessible part of the disk.

- Shared Pools, The Delphi Magazine 95, July 2003

Shared pool architectureThe shared pool was one of my more baroque creations. In fact, it was so complicated that it was never used in a deployed application. Basically, the article described an architecture to implement a pool of shared memory objects, which multiple Writers could use to send data to one Reader (typically sitting in another process). The system also handled cleanup when a Reader task died and other management details.

You really should not be playing with this code. There are better solutions.

Links: article (PDF, 193 KB), source code (ZIP, 1.9 MB)

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