| single |
## Motivation
When reading from many possibly large files in a fashion similar to random
access, it is usually the fastest and most efficient to use memory maps.
Although memory maps have many advantages, they represent a very limited
system resource as every map uses one file descriptor, whose amount is
limited per process. On 32 bit systems, the amount of memory you can have
mapped at a time is naturally limited to theoretical 4GB of memory, which
may not be enough for some applications.
## Limitations
* **System resources (file-handles) are likely to be leaked!** This is due
to the library authors reliance on a deterministic `__del__()` destructor.
* The memory access is read-only by design.
## Overview
![Python package]
Smmap wraps an interface around mmap and tracks the mapped files as well as
the amount of clients who use it. If the system runs out of resources, or
if a memory limit is reached, it will automatically unload unused maps to
allow continued operation.
To allow processing large files even on 32 bit systems, it allows only
portions of the file to be mapped. Once the user reads beyond the mapped
region, smmap will automatically map the next required region, unloading
unused regions using a LRU algorithm.
The interface also works around the missing offset parameter in python
implementations up to python 2.5.
Although the library can be used most efficiently with its native
interface, a Buffer implementation is provided to hide these details behind
a simple string-like interface.
For performance critical 64 bit applications, a simplified version of
memory mapping is provided which always maps the whole file, but still
provides the benefit of unloading unused mappings on demand.
## Prerequisites
* Python 2.7 or 3.4+
* OSX, Windows or Linux
The package was tested on all of the previously mentioned configurations.
## Installing smmap
[Documentation Status]
Its easiest to install smmap using the [pip] program:
```bash
$ pip install smmap
```
As the command will install smmap in your respective python distribution,
you will most likely need root permissions to authorize the required
changes.
If you have downloaded the source archive, the package can be installed by
running the `setup.py` script:
```bash
$ python setup.py install
```
It is advised to have a look at the **Usage Guide** for a brief
introduction on the different database implementations.
## Homepage and Links
The project is home on github at
https://github.com/gitpython-developers/smmap .
The latest source can be cloned from github as well:
* git://github.com/gitpython-developers/smmap.git
For support, please use the git-python mailing list:
* http://groups.google.com/group/git-python
Issues can be filed on github:
* https://github.com/gitpython-developers/smmap/issues
A link to the pypi page related to this repository:
* https://pypi.org/project/smmap/
## License Information
*smmap* is licensed under the New BSD License.
|