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Compressed Deque

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Copyright (c) 2016, Pedro Lopes

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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Description: Compressed Deque
================

A deque which compresses its items for a decreased volatile and persistent memory footprint.

Installation
------------

.. code-block:: bash

$ pip install compressed-deque


How to Use it
-------------

.. code-block:: python

from compdeque import CompressedDeque

# Instantiate the Deque
collection = CompressedDeque()

# Use it as a normal deque
collection.append(1)

# Persist to a file
CompressedDeque.save_to_file(collection, file_path="/path/to/collection.dat")

# ...

# and load it when you need it later
loaded_collection = CompressedDeque.load_from_file("/path/to/collection.dat")

Tests and documentation
-----------------------

On the project's root folder:

.. code-block:: bash

# Run all tests
$ make test

# Generate documentation
$ make docs

Structure
---------

Compressed Deque inherits from `deque <https://docs.python.org/2/library/collections.html#collections.deque>`_ and stores its items as zlib compressed pickles. The middle pickle layer only serves as a generic serialization method which can provide a serialized object string for zlib to compress. Although pickle can compress objects, its compression rate does not match zlib's, even using `higher protocols <https://docs.python.org/2/library/pickle.html#data-stream-format>`_.

.. image:: docs/images/value_layers.png

``save_to_file()`` and ``load_from_file()`` static methods are provided to persist the collection directly into disk in its compressed representation, without much overhead.

The persisted file contains a sequence of header/compressed_value pairs: the header is a 4 byte integer description of the compressed value's length and the compressed value is similiar to its in-memory representation.

.. image:: docs/images/persisted_values.png
Keywords: compressed deque zipped zlib
Platform: UNKNOWN
Classifier: Development Status :: 3 - Alpha
Classifier: Intended Audience :: Developers
Classifier: Topic :: Software Development :: Build Tools
Classifier: License :: OSI Approved :: MIT License
Classifier: Programming Language :: Python :: 2
Classifier: Programming Language :: Python :: 2.6
Classifier: Programming Language :: Python :: 2.7

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