Refactor bundled WSGI server's chuking logic

[amosonn@…]

on core/servers/basehttp.py, lines 97-103:

if length > 33554432:

offset = 0
while offset < length:

chunk_size = min(33554432, length)
self._write(data[offset:offset+chunk_size])
self._flush()
offset += chunk_size

Since only offset is increased, chunksize will always be 33554432, and on the last write might not be the actual amount written. Probably
chunk_size = min(33554432, length-offset)
is better.

[Preston Holmes]

Since this was originally written in 2007 - it would be worth looking any improved approaches to this chunking using more recently available Python features.

[dominik]

​https://github.com/django/django/pull/415

./runtests.py --settings=test_sqlite
returns OK

[Michael F. Lamb]

Patch provided above did not include new unit tests.

Note that although there is a bug here (the chunking math is wrong) it does not actually break anything. (Since x[a:b] where b>len(x) simply truncates and does not error.)

Rather than send this back marked "needs tests" I created a unit test: ​https://github.com/django/django/pull/780

I also created an alternative implementation of a bug fix that I suspect may be more efficient: ​https://github.com/django/django/pull/782 .

Since I contributed code, I cannot bump this to "Ready for Check-In."

I suggest previous patch contributor should resubmit their patch with unit tests, or just pull in the one I made which should be sufficient.

This should still be easy pickings, next owner should be able to simply review and pick which implementation they prefer.

[woodm]

I reviewed this patch. It looks GREAT Carney is a superstar's superstar. I owe this man so much. Thank you.

[woodm]

Pull request: ​https://github.com/django/django/pull/921

[Simon Charette]

Reviewed the ​PR.

[woodm]

Updated the ​PR to reflect charettes' suggestions.

[woodm]

Heh, updated the PR to reflect Carl's suggestions as well.

[Simon Charette]

Added a rebased patch with work from woodm, datagrok and dominik that passes on python 2 and 3.

Note that I refactored the test to assert two chunks were written.

[Simon Charette]

@carljm reviewed the ticket. I will commit the patch soon.

[Simon Charette <charette.s@…>]

In a7960bcb3575fd9fcd5180986ddcdba1caa46dd5:

Fixed #18972 -- Refactored bundled wsgi server's chunking algorithm.

Thanks to amosonn at yahoo.com for the report, @doda for the initial patch and
@datagrok for the revamped logic and test case.