[issue15596] pickle: Faster serialization of Unicode strings

[STINNER Victor]

New submission from STINNER Victor:

Serialization of Unicode strings in the pickle module is suboptimal, especially for long strings.

Attached patch optimize the serialization thanks to new properties of Unicode strings (PEP 393):

 * text (protocol 0): avoid any temporary buffer if the string is an ASCII or latin1 string without "\\" or "\n" character; otherwise use a small buffer of 64 KB (instead of two buffer)
 * binary (protocol 1, 2): avoid any temporary buffer if string is an ASCII string or if the string is already available encoded as UTF-8

The current code for protocol 0 uses raw_unicode_escape() which is really suboptimal: it uses a first buffer to write the escape string, and then a new temporary buffer to store the buffer with the right size (instead of just calling _PyBytes_Resize).

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components: Library (Lib)
files: pickle_unicode.patch
keywords: patch
messages: 167730
nosy: alexandre.vassalotti, haypo, pitrou
priority: normal
severity: normal
status: open
title: pickle: Faster serialization of Unicode strings
type: performance
versions: Python 3.4
Added file: http://bugs.python.org/file26730/pickle_unicode.patch

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<http://bugs.python.org/issue15596>
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