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Incorrect behavior of BytesIO.write() when the size of the written data changed during writing #143602

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@serhiy-storchaka

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There is other bug similar to #143378 in the Python implementation of BytesIO.

The buffer is exported twice for the input data. First, to determine the number of bytes, so we can create a slice when overwriting BytesIO data after seeking. Second, to get the data itself. If the number of bytes different, the underlying bytearray object can be shrinked or expanded, with moving bytes after the current position.

Solution -- we need to use the same exported buffer with memoryview() for the whole writing operation. The test will be slightly more complicated variant of the tests added in #143408.

@superboy-zjc, are you interesting to take this issue? It should be easy to you.

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    3.13bugs and security fixes3.14bugs and security fixes3.15pre-release feature fixes, bugs and security fixesstdlibStandard Library Python modules in the Lib/ directorytopic-IOtype-bugAn unexpected behavior, bug, or error

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