Reading OpenEXRs sequentially from a Pipe

Question

I am trying to read a stream of EXRs from one pipe, process them and write the results into a different pipe. This this case they are named pipes but they could just as well be stdin and stdout.

My problem occurs when the pipe runs dry. OpenEXR doesn't like trying to read nothing and crashes with the following stack trace.

(gdb) run in.exr out.exr
Starting program: /Users/jon/Library/Developer/Xcode/DerivedData/compressor-abhdftqzleulxsfkpidvcazfowwo/Build/Products/Debug/compressor in.exr out.exr
Reading symbols for shared libraries +++++++++......................................................................................................... done
Reading symbols for shared libraries ............ done
Reading symbols for shared libraries . done
Reading symbols for shared libraries . done
terminate called throwing an exception
Program received signal SIGABRT, Aborted.
0x00007fff90957ce2 in __pthread_kill ()
(gdb) backtrace
#0  0x00007fff90957ce2 in __pthread_kill ()
#1  0x00007fff866f27d2 in pthread_kill ()
#2  0x00007fff866e3a7a in abort ()
#3  0x00007fff8643c7bc in abort_message ()
#4  0x00007fff86439fcf in default_terminate ()
#5  0x00007fff844d61cd in _objc_terminate ()
#6  0x00007fff8643a001 in safe_handler_caller ()
#7  0x00007fff86439fed in unexpected_defaults_to_terminate ()
#8  0x00007fff8643a040 in __cxxabiv1::__unexpected ()
#9  0x00007fff8643aefe in __cxa_call_unexpected ()
#10 0x0000000100008cfb in exr::ReadEXR (pixelBuffer=@0x7fff5fbfee00, is=@0x7fff5fbfeef8) at /Users/jon/Development/compressor/compressor/exr.cpp:47
#11 0x0000000100001c39 in main (argc=4, argv=0x7fff5fbffaa8) at /Users/jon/Development/compressor/compressor/main.cpp:79

I would really like OpenEXR to block the thread until more data becomes available but if there was some method of checking manually to see whether there is more data that would do, so long as it was somewhat robust.

Thanks.

After some more investigation it appears that the solution is to write a custom Imf::IStream which will block instead of throwing an exception when the pipe runs dry. — Jonathan Hatchett, Jul 17 '12 at 10:47

score 0 · Accepted Answer · answered Jul 18 '12 at 11:52

The solution to this problem is indeed to extend Imf::Istream and implement it to block when the input pipe runs dry.

For this specific problem some considerations need to be made like pipes aren't seekable and d o not know their position, they can be worked around however.

Reading OpenEXRs sequentially from a Pipe

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