Pascal StdIn/StdOut pipes -


i'm trying write pascal (lazarus/fpc) program started program process. caller (the arena chess gui) talks program using stdin , stdout.

first used readln in program text commands sent gui , writeln reply them. worked except program stop doing if readln had wait input gui. since wanted program carry on working , deal commands arrived had change this.

so changed code use:

... var   inpstream        : tinputpipestream; ... inpstream := tinputpipestream.create(stdinputhandle); ... if inpstream.numbytesavailable > 0 begin     setlength(s_buffer, inpstream.numbytesavailable);     inpstream.read(s_buffer[1], length(s_buffer)); end; ...

that worked no longer paused read. writeln stopped working: nothing gets sent gui. thought maybe help:

... var inpstream        : tinputpipestream;     outstream        : toutputpipestream; ... inpstream := tinputpipestream.create(stdinputhandle); outstream := toutputpipestream.create(stdoutputhandle); ... if inpstream.numbytesavailable > 0 begin     setlength(s_buffer, inpstream.numbytesavailable);     inpstream.read(s_buffer[1], length(s_buffer)); end; ... outstream.write(s_buffer, length(s_buffer));

but makes worse doesn't read or write anything. how can have non-blocked input on stdin while maintaining ability write stdout?

assuming use windows, means program reads output doesn't read enough (it lets mass up), , when total size of pipes reaches size (typically several mbs) windows stops processing.

this new situation require digging deeping windows pipes , job control. in fpc 3.x tprocess bugs fixed, , similar (pipe processing stalled if stderr wasn't regularly processed too, see intruncommand code).

if receiving program doesn't process stderr, don't use it.


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