python-xxhash

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.. HMAC: http://en.wikipedia.org/wiki/Hash-basedmessageauthenticationcode .. _xxHash: https://github.com/Cyan4973/xxHash .. _Cyan4973: https://github.com/Cyan4973

xxhash is a Python binding for the xxHash_ library by Yann Collet__.

_ Cyan4973

Installation

.. code-block:: bash

$ pip install xxhash

As of version 1.0.0, xxhash provides two variants: the original CPython variant, and the new CFFI variant. By default the installation is the CPython variant, setting env variable XXHASH_FORCE_CFFI=1 to install the CFFI variant:

.. code-block:: bash

$ export XXHASHFORCECFFI=1 $ pip install xxhash

Installation Prerequisites ~~~~~~~~~~~~~~~~~~~~~~~~~~~

CPython Variant ^^^^^^^^^^^^^^^^

On Debian/Ubuntu:

.. code-block:: bash

$ apt-get install python-dev gcc

On CentOS/Fedora:

.. code-block:: bash

$ yum install python-devel gcc redhat-rpm-config

CFFI Variant ^^^^^^^^^^^^^

On Debian/Ubuntu:

.. code-block:: bash

$ apt-get install libcffi-dev python-dev gcc

On CentOS/Fedora:

.. code-block:: bash

$ yum install libcffi-devel python-devel gcc redhat-rpm-config

Usage

Module version and its backend xxHash library version can be retrieved using the module properties VERSION AND XXHASH_VERSION respectively.

.. code-block:: python

>>> import xxhash
>>> xxhash.VERSION
'1.0.1'
>>> xxhash.XXHASH_VERSION
'0.6.2'

This module is hashlib-compliant, which means you can use it in the same way as hashlib.md5.

| update() -- update the current digest with an additional string
| digest() -- return the current digest value
| hexdigest() -- return the current digest as a string of hexadecimal digits
| intdigest() -- return the current digest as an integer
| copy() -- return a copy of the current xxhash object
| reset() -- reset state

md5 digest returns bytes, but the original xxh32 and xxh64 C APIs return integers. While this module is made hashlib-compliant, intdigest() is also provided to get the integer digest.

Constructors for hash algorithms provided by this module are xxh32() and xxh64().

For example, to obtain the digest of the byte string b'Nobody inspects the spammish repetition'.

.. code-block:: python

>>> import xxhash
>>> x = xxhash.xxh32()
>>> x.update(b'Nobody inspects')
>>> x.update(b' the spammish repetition')
>>> x.digest()
b'\xe2);/'
>>> x.digest_size
4
>>> x.block_size
16

More condensed.

.. code-block:: python

>>> xxhash.xxh32(b'Nobody inspects the spammish repetition').hexdigest()
'e2293b2f'
>>> xxhash.xxh32(b'Nobody inspects the spammish repetition').digest() == x.digest()
True

An optional seed (default is 0) can be used to alter the result predictably.

.. code-block:: python

>>> import xxhash
>>> xxhash.xxh64('xxhash').hexdigest()
'32dd38952c4bc720'
>>> xxhash.xxh64('xxhash', seed=20141025).hexdigest()
'b559b98d844e0635'
>>> x = xxhash.xxh64(seed=20141025)
>>> x.update('xxhash')
>>> x.hexdigest()
'b559b98d844e0635'
>>> x.intdigest()
13067679811253438005

Be careful that xxh32 takes an unsigned 32-bit integer as seed, while xxh64 takes an unsigned 64-bit integer. Although unsigned integer overflow is defined behavior, it's better to not to let it happen.

.. code-block:: python

>>> xxhash.xxh32('I want an unsigned 32-bit seed!', seed=0).hexdigest()
'f7a35af8'
>>> xxhash.xxh32('I want an unsigned 32-bit seed!', seed=2**32).hexdigest()
'f7a35af8'
>>> xxhash.xxh32('I want an unsigned 32-bit seed!', seed=1).hexdigest()
'd8d4b4ba'
>>> xxhash.xxh32('I want an unsigned 32-bit seed!', seed=2**32+1).hexdigest()
'd8d4b4ba'
>>>
>>> xxhash.xxh64('I want an unsigned 64-bit seed!', seed=0).hexdigest()
'd4cb0a70a2b8c7c1'
>>> xxhash.xxh64('I want an unsigned 64-bit seed!', seed=2**64).hexdigest()
'd4cb0a70a2b8c7c1'
>>> xxhash.xxh64('I want an unsigned 64-bit seed!', seed=1).hexdigest()
'ce5087f12470d961'
>>> xxhash.xxh64('I want an unsigned 64-bit seed!', seed=2**64+1).hexdigest()
'ce5087f12470d961'

digest() returns bytes of the big-endian representation of the integer digest.

.. code-block:: python

>>> import xxhash
>>> h = xxhash.xxh64()
>>> h.digest()
b'\xefF\xdb7Q\xd8\xe9\x99'
>>> h.intdigest().to_bytes(8, 'big')
b'\xefF\xdb7Q\xd8\xe9\x99'
>>> h.hexdigest()
'ef46db3751d8e999'
>>> format(h.intdigest(), '016x')
'ef46db3751d8e999'
>>> h.intdigest()
17241709254077376921
>>> int(h.hexdigest(), 16)
17241709254077376921

Besides xxh32/xxh64 mentioned above, oneshot functions are also provided. By using oneshot functions we can avoid creating XXH32/64_state on heap.

| xxh32_digest(bytes, seed)
| xxh32_intdigest(bytes, seed)
| xxh32_hexdigest(bytes, seed)
| xxh64_digest(bytes, seed)
| xxh64_intdigest(bytes, seed)
| xxh64_hexdigest(bytes, seed)

.. code-block:: python

>>> import xxhash
>>> xxhash.xxh64('a').digest == xxhash.xxh64_digest('a')
False
>>> xxhash.xxh64('a').digest() == xxhash.xxh64_digest('a')
True
>>> xxhash.xxh64('a').intdigest() == xxhash.xxh64_intdigest('a')
True
>>> xxhash.xxh64('a').hexdigest() == xxhash.xxh64_hexdigest('a')
True
>>> xxhash.xxh64_hexdigest('xxhash', seed=20141025)
'b559b98d844e0635'
>>> xxhash.xxh64_intdigest('xxhash', seed=20141025)
13067679811253438005L
>>> xxhash.xxh64_digest('xxhash', seed=20141025)
'\xb5Y\xb9\x8d\x84N\x065'

Caveats

SEED OVERFLOW ~~~~~~~~~~~~~~

xxh32 takes an unsigned 32-bit integer as seed, and xxh64 takes an unsigned 64-bit integer as seed. Make sure that the seed is greater than or equal to 0.

ENDIANNESS ~~~~~~~~~~~

As of python-xxhash 0.3.0, digest() returns bytes of the big-endian representation of the integer digest. It used to be little-endian.

DONT USE XXHASH IN HMAC ~~~~~~~~~~~~~~~~~~~~~~~ Though you can use xxhash as an HMAC_ hash function, but it's highly recommended not to.

xxhash is NOT a cryptographic hash function, it is a non-cryptographic hash algorithm aimed at speed and quality. Do not put xxhash in any position where cryptographic hash functions are required.

Copyright and License

Copyright (c) 2014-2018 Yue Du - https://github.com/ifduyue

Licensed under BSD 2-Clause License <http://opensource.org/licenses/BSD-2-Clause>_

CHANGELOG

v1.2.0 2018-07-13 ~~~~~~~~~~~~~~~~~

Add oneshot functions xxh{32,64}_{,int,hex}digest

v1.1.0 2018-07-05 ~~~~~~~~~~~~~~~~~

Allow input larger than 2GB
Release the GIL on sufficiently large input
Drop support for Python 3.2

v1.0.1 2017-03-02 ~~~~~~~~~~~~~~~~~~

Free state actively, instead of delegating it to ffi.gc

v1.0.0 2017-02-10 ~~~~~~~~~~~~~~~~~~

Fixed copy() segfault
Added CFFI variant

v0.6.3 2017-02-10 ~~~~~~~~~~~~~~~~~~

Fixed copy() segfault

v0.6.2 2017-02-10 ~~~~~~~~~~~~~~~~~~

Upgrade xxHash to v0.6.2

v0.6.1 2016-06-26 ~~~~~~~~~~~~~~~~~~

Upgrade xxHash to v0.6.1

v0.5.0 2016-03-02 ~~~~~~~~~~~~~~~~~~

Upgrade xxHash to v0.5.0

v0.4.3 2015-08-21 ~~~~~~~~~~~~~~~~~~

Upgrade xxHash to r42

v0.4.1 2015-08-16 ~~~~~~~~~~~~~~~~~~

Upgrade xxHash to r41

v0.4.0 2015-08-05 ~~~~~~~~~~~~~~~~~~

Added method reset
Upgrade xxHash to r40

v0.3.2 2015-01-27 ~~~~~~~~~~~~~~~~~~

Fixed some typos in docstrings

v0.3.1 2015-01-24 ~~~~~~~~~~~~~~~~~~

Upgrade xxHash to r39

v0.3.0 2014-11-11 ~~~~~~~~~~~~~~~~~~

Change digest() from little-endian representation to big-endian representation of the integer digest. This change breaks compatibility (digest() results are different).

v0.2.0 2014-10-25 ~~~~~~~~~~~~~~~~~~

Make this package hashlib-compliant

v0.1.3 2014-10-23 ~~~~~~~~~~~~~~~~~~

Update xxHash to r37

v0.1.2 2014-10-19 ~~~~~~~~~~~~~~~~~~

Improve: Check XXHnn_init() return value.
Update xxHash to r36

v0.1.1 2014-08-07 ~~~~~~~~~~~~~~~~~~

Improve: Can now be built with Visual C++ Compiler.

v0.1.0 2014-08-05 ~~~~~~~~~~~~~~~~~~

New: XXH32 and XXH64 type, which support partially update.
Fix: build under Python 3.4

v0.0.2 2014-08-03 ~~~~~~~~~~~~~~~~~~

NEW: Support Python 3

v0.0.1 2014-07-30 ~~~~~~~~~~~~~~~~~~

NEW: xxh32 and xxh64

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