[issue22003] BytesIO copy-on-write

[David Wilson]

David Wilson added the comment:

Stefan,

Thanks for digging here. As much as I'd love to follow this interpretation, it simply doesn't match existing buffer implementations, including within the standard library.

For example, mmap.mmap(..., flags=mmap.MAP_SHARED, prot=mmap.PROT_READ) will produce a read-only buffer, yet mutability is entirely at the whim of the operating system. In this case, "immutability" may be apparent for years, until some machine has memory pressure, causing the shared mapping to be be flushed, and refreshed from (say, incoherent NFS storage) on next access.

I thought it would be worth auditing some of the most popular types of buffer just to check your interpretation, and this was the first, most obvious candidate.

Any thoughts? I'm leaning heavily toward the Bytes specialization approach

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<http://bugs.python.org/issue22003>
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