Metadata-Version: 2.1
Name: cityhash
Version: 0.4.4
Summary: Python bindings for CityHash and FarmHash
Home-page: https://github.com/escherba/python-cityhash
Download-URL: https://github.com/escherba/python-cityhash/tarball/master/0.4.4
Author: Eugene Scherba
Author-email: escherba+cityhash@gmail.com
License: MIT
Keywords: google,hash,hashing,cityhash,farmhash,murmurhash,cython
Classifier: Development Status :: 5 - Production/Stable
Classifier: Intended Audience :: Developers
Classifier: Intended Audience :: Science/Research
Classifier: License :: OSI Approved :: MIT License
Classifier: Operating System :: OS Independent
Classifier: Programming Language :: C++
Classifier: Programming Language :: Cython
Classifier: Programming Language :: Python :: 3.6
Classifier: Programming Language :: Python :: 3.7
Classifier: Programming Language :: Python :: 3.8
Classifier: Programming Language :: Python :: 3.9
Classifier: Programming Language :: Python :: 3.10
Classifier: Programming Language :: Python :: 3.11
Classifier: Topic :: Scientific/Engineering :: Information Analysis
Classifier: Topic :: Software Development :: Libraries
Classifier: Topic :: System :: Distributed Computing
Requires-Python: >=3.6
Description-Content-Type: text/markdown
License-File: LICENSE

# CityHash/FarmHash



Python wrapper for [FarmHash](https://github.com/google/farmhash) and

[CityHash](https://github.com/google/cityhash), a family of fast

non-cryptographic hash functions.



[![Build

Status](https://img.shields.io/github/workflow/status/escherba/python-cityhash/build/master)](https://github.com/escherba/python-cityhash/actions/workflows/build.yml)

[![Latest

Version](https://img.shields.io/pypi/v/cityhash.svg)](https://pypi.python.org/pypi/cityhash)

[![Downloads](https://img.shields.io/pypi/dm/cityhash.svg)](https://pypistats.org/packages/cityhash)

[![License](https://img.shields.io/pypi/l/cityhash.svg)](https://opensource.org/licenses/mit-license)

[![Supported Python

versions](https://img.shields.io/pypi/pyversions/cityhash.svg)](https://pypi.python.org/pypi/cityhash)



## Getting Started



This simplest way to use this package is to install it from PyPI:



``` bash

pip install cityhash

```



This package exposes Python APIs for CityHash and FarmHash under `cityhash` and

`farmhash` namespaces, respectively. Each provides 32-, 64- and 128-bit

implementations.



## Usage Examples



### Stateless hashing



Usage example for FarmHash:



``` python

>>> from farmhash import FarmHash32, FarmHash64, FarmHash128

>>> FarmHash32("abc")

1961358185

>>> FarmHash64("abc")

2640714258260161385

>>> FarmHash128("abc")

76434233956484675513733017140465933893



```



### Hardware-independent fingerprints



Fingerprints are seedless hashes which are guaranteed to be hardware- and

platform-independent. This can be useful for networking applications which

require persisting hashed values.



``` python

>>> from farmhash import Fingerprint128

>>> Fingerprint128("abc")

76434233956484675513733017140465933893



```



### Incremental hashing



CityHash and FarmHash do not support incremental hashing and thus are not ideal

for hashing of streams. If you require incremental hashing feature, use

[MetroHash](https://github.com/escherba/python-metrohash) or

[xxHash](https://github.com/ifduyue/python-xxhash) instead, which do support

it.



### Fast hashing of NumPy arrays



The Python [Buffer Protocol](https://docs.python.org/3/c-api/buffer.html)

allows Python objects to expose their data as raw byte arrays to other objects,

for fast access without copying to a separate location in memory. Among others,

NumPy is a major framework that supports this protocol.



All hashing functions in this packege will read byte arrays from objects that

expose them via the buffer protocol. Here is an example showing hashing of a 4D

NumPy array:



``` python

>>> import numpy as np

>>> from farmhash import FarmHash64

>>> arr = np.zeros((256, 256, 4))

>>> FarmHash64(arr)

1550282412043536862



```



The arrays need to be contiguous for this to work. To convert a non-contiguous

array, use NumPy's `ascontiguousarray()` function.



## SSE4.2 support



For x86-64 platforms, the PyPi repository for this package includes wheels

compiled with SSE4.2 support.  The 32- and 64-bit FarmHash variants

significantly benefit from SSE4.2 instructions. The 128-bit version,

unfortunately, does not exhibit speed up after compiling with SSE4.2 support.



The vanilla CityHash fucntions (under `cityhash` module) do not take advantage

of SSE4.2. Instead, the `cityhashcrc` module provided with this package exposes

128- and 256-bit CRC functions which do harness SSE4.2. These functions are

very fast, and beat `FarmHash128` on speed (FarmHash does not include a 256-bit

function). Since FarmHash is the intended successor of CityHash, I would be

careful before using the CityHash-CRC functions, however, and would verify

whether they provide sufficient randomness for your intended application.



## Development



### Local workflow



For those who want to contribute, here is a quick start using some makefile

commands:



``` bash

git clone https://github.com/escherba/python-cityhash.git

cd python-cityhash

make env           # create a virtual environment

make test          # run Python tests

make cpp-test      # run C++ tests

make shell         # enter IPython shell

```



To find out which Make targets are available, type:



``` bash

make help

```



### Distribution



The wheels are built using [cibuildwheel](https://cibuildwheel.readthedocs.io/)

and are distributed to PyPI using GitHub actions. The wheels contain compiled

binaries and are available for the following platforms: windows-amd64,

ubuntu-x86, linux-x86\_64, linux-aarch64, and macosx-x86\_64.



## See Also



For other fast non-cryptographic hash functions available as Python extensions,

see [MetroHash](https://github.com/escherba/python-metrohash),

[MurmurHash](https://github.com/hajimes/mmh3), and

[xxHash](https://github.com/ifduyue/python-xxhash).



## Authors



The original CityHash Python bindings are due to Alexander \[Amper\] Marshalov.

These were rewritten in Cython by Eugene Scherba, who also added the FarmHash

bindings. The CityHash and FarmHash algorithms and their C++ implementation are

by Google.



## License



This software is licensed under the [MIT

License](http://www.opensource.org/licenses/mit-license). See the included

LICENSE file for details.

