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File: hexarray.php

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  Classes of Auslarrie Popier  >  Binary Array  >  hexarray.php  >  Download  
File: hexarray.php
Role: Class source
Content type: text/plain
Description: Stores integer array internall as hex-string data.
Class: Binary Array
Manipulate compact arrays of integers with strings
Author: By
Last change:
Date: 4 years ago
Size: 1,749 bytes
 

Contents

Class file image Download
<?php

/**
 * Memory-efficient integer storage class.
 * Behaves like a normal array.
 *
 * This one uses: a HEX-STRING
 * and stores: 16 BIT integer.
 *
 *
 * For example: 32768 entries use
 * - 132056 bytes for HexArray
 * - but 6817000 bytes for a PHP array()
 * - which is almost 50 times as much
 *
 *
 */
class HexArray IMPLEMENTS ArrayAccess {

    var
$data = "0000";
    const
LEN = 4; // 4 characters = 16 bit

    /**
     * Initialize data.
     *
     * @param integer/string create either a fixed size empty array,
     * or use source data (hexstring)
     */
   
function __construct($from=NULL) {
        if (
is_string($from)) {
           
$this->data = $from;
        }
        elseif (
is_int($from)) {
           
$this->data = str_repeat("0", self::LEN * $from);
        }
    }

   
/**
     * Compare array index against data size.
     *
     */
   
function offsetExists ( $offset ) {
        return (
strlen($this->data) / self::LEN) - 1 >= $offset;
    }

   
/**
     * Retrieve value.
     *
     */
   
function offsetGet ( $offset ) {
        return
hexdec(substr($this->data, $offset * self::LEN, self::LEN));
    }

   
/**
     * Update value.
     *
     */
   
function offsetSet ( $offset , $value ) {

       
$hex = dechex($value);
        if (
$fill = self::LEN - strlen($hex)) {
           
$hex = str_repeat("0", $fill) . $hex;
        }

        for (
$i=0; $i<self::LEN; $i++) {
           
$this->data[$offset * self::LEN + $i] = $hex[$i];
        }
    }

   
/**
     * Unsetting not supported.
     *
     */
   
function offsetUnset ( $offset ) {
       
assert(false);
    }

}


?>