gh-101881: os: support blocking functions on Windows

[RayyanAnsari]

Use the GetNamedPipeHandleState and SetNamedPipeHandleState Win32 API functions to add support for os.get_blocking and os.set_blocking.

• Issue: os: support blocking functions on Windows #101881

[bedevere-bot]

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[ghost]

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[RayyanAnsari]

Tested with this script:

import os
import sys

r, w = os.pipe()

os.set_blocking(r, sys.argv[1] == 'True')
os.set_blocking(w, sys.argv[1] == 'True')

if (os.get_blocking(r) and os.get_blocking(w)):
    print("blocking")
else:
    print("non-blocking")

try:
    while True:
        os.write(w, b'hello')
except BlockingIOError:
    print("blocked")

Output:

PS C:\Users\Rayyan\cpython> PCbuild\amd64\python_d.exe ..\test_blocking.py False
non-blocking
blocked
PS C:\Users\Rayyan\cpython> PCbuild\amd64\python_d.exe ..\test_blocking.py True
blocking
[script hangs]

[RayyanAnsari]

Should now be ready to merge.

[eryksun]

Refer to [MS-FSCC]: FilePipeLocalInformation for details about how the write-quota available depends on whether it's a handle for the server end or client end. Note that it documents the underlying NT API, so the names are different.

WriteQuotaAvailable (4 bytes): A 32-bit unsigned integer that contains the write quota, in bytes, for the named pipe. If the NamedPipeEnd field is set to FILE_PIPE_CLIENT_END, the WriteQuotaAvailable field is the remaining InboundQuota field available. If the NamedPipeEnd field is set to FILE_PIPE_SERVER_END, the WriteQuotaAvailable field is the remaining OutboundQuota field available.

It would be nice if the Windows API exposed WriteQuotaAvailable, which is precisely the value that we need. Limiting a write to exactly what's available would allow more non-blocking writes to succeed.

[bedevere-bot]

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

[RayyanAnsari]

I have made the requested changes; please review again.

[bedevere-bot]

Thanks for making the requested changes!

@zooba: please review the changes made to this pull request.

[zooba]

Thanks for the contribution! Just FYI, there's no need to force push updates to PRs for our project - we always squash merge and edit the commit messages ourselves. All that a force push will do is reset the review status, which makes it hard to see the most recent changes.