Author: Robert Hyatt
Date: 14:53:02 11/04/02
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On November 04, 2002 at 17:19:30, Severi Salminen wrote: >I try to get the WinBoard interface working without disabling input buffering. >Disabling the buffer by setbuf(stdin, NULL) causes problems with WB. But I have >also a problem _without_ disabling the buffer: > >These are send to engine: > >7360 >first : time 5794 >otim 5935 >7360 >first : usermove 7360 >first : g1f3 > >PeekNamedPipe reports 34 bytes in pipe. After 1st fget() I get only the first >command (time 5694) but after that PeekNamedPipe tells that 0 bytes available in >pipe. When doing a fget() after this I can, however, read the next command. So, >the question: how can I fetch these commands so that PeekNamedPipe doesn't get >confused -> after first fget(), PeeknamedPipe should give 24 bytes available, >not 0. fget clearly is not the right function, but others seem to behave >identically. > >Severi If you don't disable buffering, it simply won't work correctly. You need to be able to ask the question "is there any unread input that I need to process?" You can only do this at the system level, checking on system buffers. Unfortunately, when you do a buffered I/O read, the C library reads in _everything_ in the system buffer, and gives the first piece of it to you. If you ask "is there more input" the answer is "no" because the system buffer is empty. you get way out of sync with things. If you do another read, you will get the next piece of data, but if there is none, you block, which you don't want to do. You have two choices: (1) disable buffering or else use unbuffered I/O (read/write). I do the latter and it works perfectly; (2) use a separate I/O thread so that blocking waiting on input is perfectly OK, since the engine thread can continue to execute as it should....
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