the match object.  Based on patch by WGH.

the match object.  Based on patch by WGH.

the match object.  Based on patch by WGH.

Patch by Chi Hsuan Yen.

Decreased density gives better collision statistics (average of 2.5 probes in a
full table versus 3.0 previously) and fewer occurences of starting a second
possibly overlapping sequence of 10 linear probes.  Makes resizes a little more
frequent but each with less work (fewer insertions and fewer collisions).

Based on patch by Georg Brandl.

Original patch by Georg Brandl.

using PySlice_GetIndicesEx() in debug builds.

using PySlice_GetIndicesEx() in debug builds.

using PySlice_GetIndicesEx() in debug builds.

Patch by Jelle Zijlstra.

Patch by Jelle Zijlstra.

Calling builtin method is at most 10% faster.

* so->used never gets changed during a resize
* so->filled only changes when dummies are present and being eliminated

(10-20% for small integers).

Issue #29300: Rename struct.unpack() second parameter from "inputstr" to
"buffer", and use the Py_buffer type.

Fix also unit tests on struct.unpack() which passed a Unicode string instead of
a bytes string as struct.unpack() second parameter. The purpose of
test_trailing_counter() is to test invalid format strings, not to test the
buffer parameter.

Add an unit test on the _struct.Struct.unpack_from() method to test passing
arguments as keywords.

* The struct module now requires contiguous buffers.
* Convert most functions and methods of the _struct module to Argument Clinic
* Use "Py_buffer" type for the "buffer" argument. Argument Clinic is
  responsible to create and release the Py_buffer object.
* Use "PyStructObject *" type for self to avoid explicit conversions.
* Add an unit test on the _struct.Struct.unpack_from() method to test passing
  arguments as keywords.
* Rephrase docstrings.
* Rename "fmt" argument to "format" in docstrings and the documentation.

As a side effect, functions and methods which used METH_VARARGS calling
convention like struct.pack() now use the METH_FASTCALL calling convention
which avoids the creation of temporary tuple to pass positional arguments and
so is faster. For example, struct.pack("i", 1) becomes 1.56x faster (-36%)::

    $ ./python -m perf timeit \
        -s 'import struct; pack=struct.pack' 'pack("i", 1)' \
        --compare-to=../default-ref/python
    Median +- std dev: 119 ns +- 1 ns -> 76.8 ns +- 0.4 ns: 1.56x faster (-36%)
    Significant (t=295.91)

Patch co-written with Serhiy Storchaka.

_Pickle_FastCall() has a surprising API: it decrements the reference counter of
its second argument.

method when unpickle collections.deque and other list-like objects.
This can speed up unpickling to 2 times.