Hi Paolo,
> here is a version of pipe-filter that works under Win32
> too (tested with Wine), has tests, and so on.
>
> Testing under native Windows would be appreciated.
>
> Bruno, what do you think?
I've added yours under the name 'pipe-filter-gi' and mine under the name
'pipe-filter-ii'. The 'g' stands for the "generator" and the 'i' for the
iterator argument type.
Your code and test suite prompted changes also for pipe-filter-ii:
- argv argument is now 'const char **' instead of 'char **'.
- Handling of write to closed pipe on Woe32: Here errno is EINVAL by
default instead of EPIPE on Unix.
- Handle the case that create_pipe_bidi returns -1.
- Set SIGPIPE handler to SIG_IGN while writing to the subprocess.
- Optim: Initialize readfds and writefds once, outside the loop.
On the side of pipe-filter-gi, I made the following changes:
* Behaviour:
- When the child closes its standard input while the parent is
still writing on it, treat it like an error, with errno = EPIPE.
Normally this situation indicates that the parent and child
don't agree on a protocol, or that the child exited prematurely.
* API:
- Use 2 callback functions for the reader iterator, not just one.
This allows to avoid memcpy in some use cases.
- When there was an error and the child process returns, return
the error code, not the child's exit status.
* Details:
- Don't use assert. Use tests that are always compiled into the code.
- In filter_terminate: Pass finish_reading = true instead of
finish_reading = false when there had been a write error but no
read error.
- Use the same concept of return value in filter_write as in
filter_close. filter_loop no longer leaves a result in errno.
- Handle the case that create_pipe_bidi returns -1.
- Speed up the test suite: fewer bash 'read' calls, but use longer
strings to compensate.
* Details for the Unix implementation:
- Set SIGPIPE handler to SIG_IGN while writing to the subprocess.
- Don't use a 0 timeout for select(); that's a recipe for producing
CPU-burning loops. When select() returns 0, abort.
- Correct the logic in filter_loop: Use the same if() conditions,
not 'if (!f->writer_errno)' in one place and 'if (count)' in another.
- Also in filter_loop, when !HAVE_SELECT: A 'continue' statement
was wrong.
- Also in filter_loop: Terminate the loop when count becomes 0.
- Also in filter_loop: When read() returns 0, don't terminate the
loop. Instead, continue to write the given data.
* Details for the Woe32 implementation:
- For synchronization between the two threads, use a CRITICAL_SECTION
object instead of a mutex HANDLE. It's faster. Mutexes are needed
only when synchronizing threads in different processes.
- In reader_thread_func, don't ignore the errno from the read() call.
- In filter_loop, use write() repeatedly, to protect against short
writes. Also protect against count > INT_MAX.
Bruno
