[PR #11139/3dafd4c7 backport][3.12] Fix IOBasePayload reading entire files into memory instead of chunking

[patchback]

This is a backport of PR #11139 as merged into master (3dafd4c).

What do these changes do?

This PR fixes a memory consumption issue where IOBasePayload and TextIOPayload would read entire files into memory when streaming large files. The bug was introduced in #10915 and caused the payload classes to read remaining_content_length bytes at once instead of chunking the reads.

The fix ensures that both payload classes never read more than READ_SIZE (64KB) at a time, regardless of the file size or content length. This prevents out-of-memory errors when uploading large files using file-like objects with the aiohttp client.

Are there changes in behavior for the user?

No behavioral changes for users. The fix is transparent and only affects memory usage during file streaming. Files are still uploaded correctly, but now they're read in 64KB chunks instead of potentially reading gigabytes into memory at once.

Is it a substantial burden for the maintainers to support this?

No, this is a minimal fix that restores the original intended behavior. The changes are:

• Adding READ_SIZE as the first parameter to min() in _read_and_available_len() for both IOBasePayload and TextIOPayload
• Ensuring the _read() method is called with appropriate chunk sizes
• Comprehensive test coverage to prevent regression

The fix is straightforward and maintains backward compatibility while fixing a critical memory issue.

Related issue number

Fixes #11138

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
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      improper undesired behavior that got corrected to match
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    Fixed issue with non-ascii contents in doctest text files
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[codspeed-hq]

CodSpeed Performance Report

Merging #11141 will not alter performance

_{Comparing patchback/backports/3.12/3dafd4c7882b0e82a9f0d5aa82e2130966765d55/pr-11139 (32e54c3) with 3.12 (278fc1e)}

Summary

✅ 59 untouched benchmarks

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.29%. Comparing base (47bc2a4) to head (32e54c3).
Report is 1 commits behind head on 3.12.

Additional details and impacted files

@@            Coverage Diff             @@
##             3.12   #11141      +/-   ##
==========================================
+ Coverage   98.28%   98.29%   +0.01%     
==========================================
  Files         132      132              
  Lines       42908    42990      +82     
  Branches     2357     2367      +10     
==========================================
+ Hits        42173    42258      +85     
+ Misses        560      557       -3     
  Partials      175      175              

Flag	Coverage Δ
CI-GHA	98.18% <100.00%> (+0.01%)	⬆️
OS-Linux	97.93% <100.00%> (+0.01%)	⬆️
OS-Windows	95.59% <100.00%> (-0.01%)	⬇️
OS-macOS	97.16% <100.00%> (+<0.01%)	⬆️
Py-3.10.11	96.93% <100.00%> (+<0.01%)	⬆️
Py-3.10.17	97.40% <100.00%> (-0.03%)	⬇️
Py-3.11.12	97.61% <100.00%> (+<0.01%)	⬆️
Py-3.11.9	97.10% <100.00%> (+<0.01%)	⬆️
Py-3.12.10	97.95% <100.00%> (+0.01%)	⬆️
Py-3.13.3	97.95% <100.00%> (+0.02%)	⬆️
Py-3.9.13	96.82% <100.00%> (-0.01%)	⬇️
Py-3.9.22	97.32% <100.00%> (+<0.01%)	⬆️
Py-pypy7.3.16	90.10% <100.00%> (-0.11%)	⬇️
VM-macos	97.16% <100.00%> (+<0.01%)	⬆️
VM-ubuntu	97.93% <100.00%> (+0.01%)	⬆️
VM-windows	95.59% <100.00%> (-0.01%)	⬇️

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