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bpo-43612: Add wbits parameter to zlib.compress #25011

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2c600de
Add test for zlib.compress wbits
rhpvorderman Mar 24, 2021
b15bd48
Add wbits argument to zlib.compress
rhpvorderman Mar 24, 2021
ea55f57
Use clinic to generate input
rhpvorderman Mar 24, 2021
ff24df3
Update documentation for zlib
rhpvorderman Mar 24, 2021
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Add blurb news entry for zlib.compress wbits parameter
rhpvorderman Mar 24, 2021
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Fix doc typo
rhpvorderman Mar 24, 2021
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Remove unnecessary whitespace, add punctionation and complete sentences.
rhpvorderman Jun 1, 2021
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Break line to comply with PEP-7
rhpvorderman Jun 1, 2021
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Update blurb to include :func: reference
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Update documentation for zlib
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@rhpvorderman
rhpvorderman committed Mar 24, 2021
commit ff24df370f9b78140078672401e421b7c438d496
48 changes: 29 additions & 19 deletions Doc/library/zlib.rst
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Expand Up @@ -47,19 +47,43 @@ The available exception and functions in this module are:
platforms, use ``adler32(data) & 0xffffffff``.


.. function:: compress(data, /, level=-1)
.. function:: compress(data, /, level=-1, wbits=MAX_WBITS)

Compresses the bytes in *data*, returning a bytes object containing compressed data.
*level* is an integer from ``0`` to ``9`` or ``-1`` controlling the level of compression;

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*level* is an integer from ``0`` to ``9`` or ``-1`` controlling the level of compression;
``1`` (Z_BEST_SPEED) is fastest and produces the least compression, ``9`` (Z_BEST_COMPRESSION)
is slowest and produces the most. ``0`` (Z_NO_COMPRESSION) is no compression.
The default value is ``-1`` (Z_DEFAULT_COMPRESSION). Z_DEFAULT_COMPRESSION represents a default
compromise between speed and compression (currently equivalent to level 6).

.. _compress-wbits:

The *wbits* argument controls the size of the history buffer (or the
"window size") used when compressing data, and whether a header and
trailer is included in the output. It can take several ranges of values,
defaulting to ``15`` (MAX_WBITS):

* +9 to +15: The base-two logarithm of the window size, which
therefore ranges between 512 and 32768. Larger values produce
better compression at the expense of greater memory usage. The
resulting output will include a zlib-specific header and trailer.

* −9 to −15: Uses the absolute value of *wbits* as the
window size logarithm, while producing a raw output stream with no
header or trailing checksum.

* +25 to +31 = 16 + (9 to 15): Uses the low 4 bits of the value as the
window size logarithm, while including a basic :program:`gzip` header
and trailing checksum in the output.

Raises the :exc:`error` exception if any error occurs.

.. versionchanged:: 3.6
*level* can now be used as a keyword parameter.

.. versionchanged:: 3.10
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*wbits* parameter added.
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.. function:: compressobj(level=-1, method=DEFLATED, wbits=MAX_WBITS, memLevel=DEF_MEM_LEVEL, strategy=Z_DEFAULT_STRATEGY[, zdict])

Expand All @@ -76,23 +100,9 @@ The available exception and functions in this module are:
*method* is the compression algorithm. Currently, the only supported value is
:const:`DEFLATED`.

The *wbits* argument controls the size of the history buffer (or the
"window size") used when compressing data, and whether a header and
trailer is included in the output. It can take several ranges of values,
defaulting to ``15`` (MAX_WBITS):

* +9 to +15: The base-two logarithm of the window size, which
therefore ranges between 512 and 32768. Larger values produce
better compression at the expense of greater memory usage. The
resulting output will include a zlib-specific header and trailer.

* −9 to −15: Uses the absolute value of *wbits* as the
window size logarithm, while producing a raw output stream with no
header or trailing checksum.

* +25 to +31 = 16 + (9 to 15): Uses the low 4 bits of the value as the
window size logarithm, while including a basic :program:`gzip` header
and trailing checksum in the output.
The *wbits* parameter controls the size of the history buffer (or the
"window size"), and what header and trailer format will be used It has
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the same meaning as `described for compress() <#compress-wbits>`__.

The *memLevel* argument controls the amount of memory used for the
internal compression state. Valid values range from ``1`` to ``9``.
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