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113 lines
2.6 KiB
113 lines
2.6 KiB
<?php
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/**
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* Base 128 varints - decodes and encodes base128 varints to/from decimal
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* @author Nikolai Kordulla
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*/
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class base128varint
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{
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// modus for output
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var $modus = 1;
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/**
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* @param int $modus - 1=Byte 2=String
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*/
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public function __construct($modus)
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{
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$this->modus = $modus;
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}
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/**
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* @param $number - number as decimal
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* Returns the base128 value of an dec value
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*/
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public function set_value($number)
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{
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$string = decbin($number);
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if (strlen($string) < 8)
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{
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$hexstring = dechex(bindec($string));
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if (strlen($hexstring) % 2 == 1)
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$hexstring = '0' . $hexstring;
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if ($this->modus == 1)
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{
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return $this->hex_to_str($hexstring);
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}
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return $hexstring;
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}
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// split it and insert the mb byte
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$string_array = array();
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$pre = '1';
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while (strlen($string) > 0)
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{
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if (strlen($string) < 8)
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{
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$string = substr('00000000', 0, 7 - strlen($string) % 7) . $string;
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$pre = '0';
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}
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$string_array[] = $pre . substr($string, strlen($string) - 7, 7);
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$string = substr($string, 0, strlen($string) - 7);
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$pre = '1';
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if ($string == '0000000')
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break;
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}
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$hexstring = '';
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foreach ($string_array as $string)
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{
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$hexstring .= sprintf('%02X', bindec($string));
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}
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// now format to hexstring in the right format
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if ($this->modus == 1)
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{
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return $this->hex_to_str($hexstring);
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}
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return $hexstring;
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}
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/**
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* Returns the dec value of an base128
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* @param string bstring
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*/
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public function get_value($string)
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{
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// now just drop the msb and reorder it + parse it in own string
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$valuestring = '';
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$string_length = strlen($string);
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$i = 1;
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while ($string_length > $i)
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{
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// unset msb string and reorder it
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$valuestring = substr($string, $i, 7) . $valuestring;
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$i += 8;
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}
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// now interprete it
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return bindec($valuestring);
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}
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/**
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* Converts hex 2 ascii
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* @param String $hex - the hex string
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*/
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public function hex_to_str($hex)
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{
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$str = '';
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for($i = 0; $i < strlen($hex); $i += 2)
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{
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$str .= chr(hexdec(substr($hex, $i, 2)));
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}
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return $str;
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}
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}
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?>
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