Trivial-MMAP is a Common Lisp library that aims to provide an easy-to-use API for working with memory-mapped files.
The library exports the following symbols:
mmap-filea function that maps a file into memory
munmap-filea function that removes a memory-mapped file from memory
mmap-read-chara helper function that facilitates reading a character from a memory-mapped file
mmap-read-bytea helper function for reading one byte from a memory-mapped file
with-mmap-filea helper macro that ensures that a memory-mapped file is safely unmapped (using
munmap-filefunction) after we are done with it
Trivial-MMAP is based on code snippets in a blog post by Nicolas Martyanoff.
The following code snippet shows how to use Trivial-MMAP's
mmap-read-char to read one character at a time from a file containing Twitter social graph (780 MB uncompressed).
CL-USER> (time (trivial-mmap:with-mmap-file (ptr size "/home/zodmaner/twitter_rv_15066953.net") (loop :for offset :from 0 :to (1- size) :do (characterp (trivial-mmap:mmap-read-char ptr offset))))) Evaluation took: 3.400 seconds of real time 3.400000 seconds of total run time (3.360000 user, 0.040000 system) 100.00% CPU 8,479,536,815 processor cycles 65,952 bytes consed
The little toy benchmark above was run on my laptop (an i5 ThinkPad X230 (Ivy Bridge) with 8 GB of RAM and an SSD). For comparison, reading the same file using
read-char takes around 14 seconds of real time on the same machine.
- Currently, the library only supports reading data from memory-mapped files.
Author & Maintainer
Smith Dhumbumroong ()