On Mon, Sep 8, 2008 at 5:44 PM, Kyle Hamilton <[EMAIL PROTECTED]> wrote: > > What is the semantic if someone opens the TCP socket in O_NONBLOCK in > the first place?
The PRFileDesc* returned by PR_ImportTCPSocket is in blocking mode. If the caller intends to use the PRFileDesc* in non-blocking mode, he needs to call PR_SetSocketOption to set the PRFileDesc* in non-blocking mode. The reason that NSPR puts the native file descriptor in non-blocking mode for a PRFileDesc* in blocking mode is to implement the I/O timeout and interrupt of PR_Recv and PR_Send. PR_Recv blocks in poll() instead of recv() because poll() takes a timeout parameter. So, PR_ImportTCPSocket doesn't check if the native file descriptor is already in non-blocking mode. It always sets the O_NONBLOCK flag on the native file descriptor, and the returned PRFileDesc* starts in blocking mode. > (Also, I found http://www.faqs.org/faqs/unix-faq/socket/ section 2.9. > It doesn't exactly help all that much in explaining what goes on, but > does PR_ImportTCPSocket's implementation (and thus the entirety of > NSPR) add something to handle SIGIO? Or is it more of a select() with > a timeout of 0?) NSPR doesn't use SIGIO. NSPR uses poll() (equivalent to select()) because it has a timeout parameter as I explained above. Note that the first paragraph of Section 2.9 of Unix-socket-faq that you cited is misleading. Non-blocking I/O is usually used with select()/poll(). Non-blocking I/O doesn't mean you have to poll the sockets individually. Wan-Teh _______________________________________________ dev-tech-crypto mailing list dev-tech-crypto@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-tech-crypto
