(PHP ActiveX) Large Persistent Hash Table Stored on Filesystem

Demonstrates how to implement a large, persistent hash table that is stored on the filesystem and allows for quick retrieval using a hash key.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows Note: The php_com_dotnet.dll may need to be enabled inside of php.ini.

<?php

// Let's say we would like to implement a persistent hash table with approximately 200,000 entries.
// We want something simple and straightforward.
// 
// The Chilkat Cache class is a solution that might fit.
// 
// Each hash table entry is a file.  Depending on the number of anticipated hash entries,
// the files can be contained in a single directory, or a collection of 256 directories,
// or a collection of 256x256 directories.

// There are 3 options:
// 
// Level 0: All cache files are in a single directory (the cache root).
// Level 1: Cache files are located in 256 sub-directories numbered 0 .. 255 directly under the cache root.
// Level 2: There are two levels of sub-directories under the cache root. 
//          The 1st level has 256 sub-directories numbered 0 .. 255 directly under the cache root. 
//          The 2nd level allows for up to 256 sub-directories (0..255) under each level-1 directory. 
//          Cache files are stored in the leaf directories. 

// For this example, given that we anticipate a larger number of hash entries, we choose a "level 2" cache.
// For versions of Chilkat < 10.0.0, use new COM('Chilkat_9_5_0.Chilkat.Cache')
$cache = new COM("Chilkat.Cache");

// We can also spread the cache among several root directories, but for this example we'll only use one root directory.
// Call AddRoot once for each root directory.
$cache->AddRoot('c:/temp/myCache');
$cache->Level = 2;

// Add some key/values to the persisted hash table (i.e. the cache).
// The eTag is optional metadata.
$key = 'apple';
$eTag = '';
$itemValue = 'macos';
$success = $cache->SaveTextNoExpire($key,$eTag,$itemValue);

// Add more items..
$success = $cache->SaveTextNoExpire('microsoft','','windows');
$success = $cache->SaveTextNoExpire('google','','android');

// Lookup items:
$key = 'microsoft';
$itemValue = $cache->fetchText($key);
print $key . ': ' . $itemValue . "\n";

$key = 'apple';
$itemValue = $cache->fetchText($key);
print $key . ': ' . $itemValue . "\n";

?>