Metadata-Version: 2.1
Name: cityhash
Version: 0.3.5.post4
Summary: Python bindings for CityHash and FarmHash
Home-page: https://github.com/escherba/python-cityhash
Author: Eugene Scherba
Author-email: escherba+cityhash@gmail.com
License: MIT
Download-URL: https://github.com/escherba/python-cityhash/tarball/master/0.3.5.post4
Keywords: google,hash,hashing,cityhash,farmhash,murmurhash,cython
Platform: UNKNOWN
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: Topic :: Scientific/Engineering :: Information Analysis
Classifier: Topic :: Software Development :: Libraries
Classifier: Topic :: System :: Distributed Computing
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://github.com/escherba/python-cityhash/actions/workflows/build.yml/badge.svg?branch=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://pypi.python.org/pypi/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



To use this package in your program, simply type



``` 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 Mac and Linux x86-64 platforms, the PyPi repository for this package

includes wheels compiled with SSE4.2 support. Although it also includes wheels

that work on Windows, the Windows wheels were not compiled with SSE4.2

support---pull requests that address this are welcome!



The 32- and 64-bit FarmHash variants both 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 (Mac

and Linux platforms only) 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 Python virtualenv

make test          # run Python tests

make cpp-test      # run C++ tests

make shell         # enter IPython shell

```



The Makefiles provided have self-documenting targets. To find out which 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 using [this

workflow](.github/workflows/publish.yml). 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.



