Dr. Dobb's Journal - December 2008 - (Page 44) d12babk_p4db 10/10/08 10:53 AM Page 44 State of the Art FILE DESCRIPTORS AND MULTITHREADED PROGRAMS This approach is not limited to sockets this thread check a flag after each accepted connection, whether it’s requested to exit. Then at exit time, set this flag and connect a new socket from your own program to the listening socket, and immediately close the new connection. Accepting this connection makes the listening thread wake up, and it would then check the exit flag and exit. This select() solution is pretty robust and should be used whenever the extra overhead is acceptable. But what about another obvious option: What if we just close the file descriptor? It is not that different from the socket being closed from the other side by the peer, and the application should already be able to handle that! Yes, it’s a pretty efficient way. And it limits the intrusion into the library. You will need to get direct access to the OS file descriptor, but the other changes are smaller. Still, it’s not entirely simple. The trouble is with the synchronization. There is an inherent race. The reader thread works generally as in Listing One. The close() call not only stops communications but also frees the OS-level file descriptor. When the reader thread makes a call to read() or close(), it’s using the value of state.fd that is no longer valid. In the best case, this value would still be invalid and the calls would return an error, with the only consequence being a spurious error message. In the worst case, another thread might open some file in the meantime, and the OS would reuse this value for its file Get data right AddressObject API Prevent errors before they occur to ensure the integrity of your database. Use AddressObject API to verify, cleanse and format customer data at the point of entry or in batch. Address Object easily integrates with Perl, PHP Java and .NET. , - offering a better way to build-in data validation. right from the start Get a FREE demo at: MelissaData.com/dobbs 44 1.800.MELISSA Dr. Dobb’s Journal l www.ddj.com l December 2008 http://www.mcobject.com http://www.mcobject.com/enterprise http://www.MelissaData.com/dobbs http://www.MelissaData.com/dobbs http://www.ddj.com
Table of Contents Feed for the Digital Edition of Dr. Dobb's Journal - December 2008 Dr. Dobb's Journal - December 2008 Contents Friday Night Fish Fry Alia Vox Developer Diaries Conversations The Man Who Sold the Sky Performance on Rails LINQ-to-SQL and T-SQL A Remote Java RMI Registry Beyond B-Trees File Descriptors and Multithreaded Programs Effective Concurrency The Agile Edge Swaine's Flames Dr. Dobb's Journal - December 2008 Dr. Dobb's Journal - December 2008 - Dr. Dobb's Journal - December 2008 (Page Cover1) Dr. Dobb's Journal - December 2008 - Dr. Dobb's Journal - December 2008 (Page Cover2) Dr. Dobb's Journal - December 2008 - Dr. Dobb's Journal - December 2008 (Page 1) Dr. Dobb's Journal - December 2008 - Dr. Dobb's Journal - December 2008 (Page 2) Dr. Dobb's Journal - December 2008 - Dr. Dobb's Journal - December 2008 (Page 3) Dr. Dobb's Journal - December 2008 - Contents (Page 4) Dr. Dobb's Journal - December 2008 - Contents (Page 5) Dr. Dobb's Journal - December 2008 - Friday Night Fish Fry (Page 6) Dr. Dobb's Journal - December 2008 - Friday Night Fish Fry (Page 7) Dr. Dobb's Journal - December 2008 - Friday Night Fish Fry (Page 8) Dr. Dobb's Journal - December 2008 - Friday Night Fish Fry (Page 9) Dr. Dobb's Journal - December 2008 - Alia Vox (Page 10) Dr. Dobb's Journal - December 2008 - Alia Vox (Page 11) Dr. Dobb's Journal - December 2008 - Developer Diaries (Page 12) Dr. Dobb's Journal - December 2008 - Developer Diaries (Page 13) Dr. Dobb's Journal - December 2008 - Conversations (Page 14) Dr. Dobb's Journal - December 2008 - Conversations (Page 15) Dr. Dobb's Journal - December 2008 - The Man Who Sold the Sky (Page 16) Dr. Dobb's Journal - December 2008 - The Man Who Sold the Sky (Page 17) Dr. Dobb's Journal - December 2008 - The Man Who Sold the Sky (Page 18) Dr. Dobb's Journal - December 2008 - The Man Who Sold the Sky (Page 19) Dr. Dobb's Journal - December 2008 - Performance on Rails (Page 20) Dr. Dobb's Journal - December 2008 - Performance on Rails (Page 21) Dr. Dobb's Journal - December 2008 - Performance on Rails (Page 22) Dr. Dobb's Journal - December 2008 - Performance on Rails (Page 23) Dr. Dobb's Journal - December 2008 - Performance on Rails (Page 24) Dr. Dobb's Journal - December 2008 - Performance on Rails (Page 25) Dr. Dobb's Journal - December 2008 - Performance on Rails (Page 26) Dr. Dobb's Journal - December 2008 - Performance on Rails (Page 27) Dr. Dobb's Journal - December 2008 - Performance on Rails (Page 28) Dr. Dobb's Journal - December 2008 - LINQ-to-SQL and T-SQL (Page 29) Dr. Dobb's Journal - December 2008 - LINQ-to-SQL and T-SQL (Page 30) Dr. Dobb's Journal - December 2008 - LINQ-to-SQL and T-SQL (Page 31) Dr. Dobb's Journal - December 2008 - LINQ-to-SQL and T-SQL (Page 32) Dr. Dobb's Journal - December 2008 - LINQ-to-SQL and T-SQL (Page 33) Dr. Dobb's Journal - December 2008 - LINQ-to-SQL and T-SQL (Page 34) Dr. Dobb's Journal - December 2008 - A Remote Java RMI Registry (Page 35) Dr. Dobb's Journal - December 2008 - A Remote Java RMI Registry (Page 36) Dr. Dobb's Journal - December 2008 - A Remote Java RMI Registry (Page 37) Dr. Dobb's Journal - December 2008 - A Remote Java RMI Registry (Page 38) Dr. Dobb's Journal - December 2008 - A Remote Java RMI Registry (Page 39) Dr. Dobb's Journal - December 2008 - Beyond B-Trees (Page 40) Dr. Dobb's Journal - December 2008 - Beyond B-Trees (Page 41) Dr. Dobb's Journal - December 2008 - File Descriptors and Multithreaded Programs (Page 42) Dr. Dobb's Journal - December 2008 - File Descriptors and Multithreaded Programs (Page 43) Dr. Dobb's Journal - December 2008 - File Descriptors and Multithreaded Programs (Page 44) Dr. Dobb's Journal - December 2008 - File Descriptors and Multithreaded Programs (Page 45) Dr. Dobb's Journal - December 2008 - Effective Concurrency (Page 46) Dr. Dobb's Journal - December 2008 - Effective Concurrency (Page 47) Dr. Dobb's Journal - December 2008 - Effective Concurrency (Page 48) Dr. Dobb's Journal - December 2008 - The Agile Edge (Page 49) Dr. Dobb's Journal - December 2008 - The Agile Edge (Page 50) Dr. Dobb's Journal - December 2008 - The Agile Edge (Page 51) Dr. Dobb's Journal - December 2008 - Swaine's Flames (Page 52) Dr. Dobb's Journal - December 2008 - Swaine's Flames (Page Cover3) Dr. Dobb's Journal - December 2008 - Swaine's Flames (Page Cover4)
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