Fast file search algorithm for IP addresses

Posted by Dave Jarvis on Stack Overflow See other posts from Stack Overflow or by Dave Jarvis
Published on 2010-04-18T00:05:07Z Indexed on 2010/04/18 0:13 UTC
Read the original article Hit count: 527

Filed under:

php

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algorithm

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text-search

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ip-address

Question

What is the fastest way to find if an IP address exists in a file that contains IP addresses sorted as:

219.93.88.62
219.94.181.87
219.94.193.96
220.1.72.201
220.110.162.50
220.126.52.187
220.126.52.247

Constraints

No database (e.g., MySQL, PostgreSQL, Oracle, etc.).
Infrequent pre-processing is allowed (see possibilities section)
Would be nice not to have to load the file each query (131Kb)
Uses under 5 megabytes of disk space

File Details

One IP address per line
9500+ lines

Possible Solutions

Create a directory hierarchy (radix tree?) then use is_dir() (sadly, this uses 87 megabytes)

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