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+<?php
+// +----------------------------------------------------------------------+
+// | PHP version 4.0 |
+// +----------------------------------------------------------------------+
+// | Copyright (c) 1997, 1998, 1999, 2000, 2001 The PHP Group |
+// +----------------------------------------------------------------------+
+// | This source file is subject to version 2.0 of the PHP license, |
+// | that is bundled with this package in the file LICENSE, and is |
+// | available at through the world-wide-web at |
+// | http://www.php.net/license/2_02.txt. |
+// | If you did not receive a copy of the PHP license and are unable to |
+// | obtain it through the world-wide-web, please send a note to |
+// | license@php.net so we can mail you a copy immediately. |
+// +----------------------------------------------------------------------+
+// | Authors: Stanislav Okhvat <stanis@ngs.ru> |
+// | Co-authored by : CVH, Chris Hansel <chris@cpi-service.com> |
+// +----------------------------------------------------------------------+
+//
+// $Id: UnitConvertor.php,v 1.00 2002/02/20 11:40:00 stasokhvat Exp $
+
+/**
+* UnitConvertor is able to convert between different units and currencies.
+*
+* @author Stanislav Okhvat <stanis@sibfair.nsk.su, stanis@ngs.ru>
+* @version $Id: UnitConvertor.php,v 1.00 2002/03/01 17:00:00 stasokhvat Exp $
+* @package UnitConvertor
+* @access public
+* @history 01.03.2002 Implemented the code for regular and offset-based
+* conversions
+*
+* 13.12.2004
+* By Chris Hansel (CVH): changed getConvSpecs in order to have it look up
+* intermediary conversions (also see comments in check_key).
+*
+* Intermediary conversions are useful when no conversion ratio is specified
+* between two units when we calculate between the two. For example, we want
+* to convert between Fahrenheit and Kelvin, and we have only
+* specified how to convert Centigrade<->Fahrenheit and
+* Centigrade<->Kelvin. While a direct (Fahrenheit->Kelvin) or
+* reverse (Kelvin->Fahrenheit) lookups fail, looking for an intermediary
+* unit linking the two (Centigrade) helps us do the conversion.
+*
+* 13.12.2004
+* Chris Hansel (CVH): $to_array argument of addConversion method can now
+* contain units as 'unit1/unit2/unit3', when all units stand for the same
+* thing. See examples in unitconv.php
+*/
+class UnitConvertor
+{
+ /**
+ * Stores conversion ratios.
+ *
+ * @var array
+ * @access private
+ */
+ var $conversion_table = array();
+
+ /**
+ * Decimal point character (default is "." - American - set in constructor).
+ *
+ * @var string
+ * @access private
+ */
+ var $decimal_point;
+
+ /**
+ * Thousands separator (default is "," - American - set in constructor).
+ *
+ * @var string
+ * @access private
+ */
+ var $thousand_separator;
+
+ /**
+ * For future use
+ *
+ * @var array
+ * @access private
+ */
+ var $bases = array();
+
+ /**
+ * Constructor. Initializes the UnitConvertor object with the most important
+ * properties.
+ *
+ * @param string decimal point character
+ * @param string thousand separator character
+ * @return void
+ * @access public
+ */
+ function UnitConvertor($dec_point = '.', $thousand_sep = ',')
+ {
+ $this->decimal_point = $dec_point;
+ $this->thousand_separator = $thousand_sep;
+
+ } // end func UnitConvertor
+
+ /**
+ * Adds a conversion ratio to the conversion table.
+ *
+ * @param string the name of unit from which to convert
+ * @param array array(
+ * "pound"=>array("ratio"=>'', "offset"=>'')
+ * )
+ * "pound" - name of unit to set conversion ration to
+ * "ratio" - 'double' conversion ratio which, when
+ * multiplied by the number of $from_unit units produces
+ * the result
+ * "offset" - an offset from 0 which will be added to
+ * the result when converting (needed for temperature
+ * conversions and defaults to 0).
+ * @return boolean true if successful, false otherwise
+ * @access public
+ */
+ function addConversion($from_unit, $to_array)
+ {
+ if (!isset($this->conversion_table[$from_unit])) {
+ while(list($key, $val) = each($to_array))
+ {
+ if (strstr($key, '/'))
+ {
+ $to_units = explode('/', $key);
+ foreach ($to_units as $to_unit)
+ {
+ $this->bases[$from_unit][] = $to_unit;
+
+ if (!is_array($val))
+ {
+ $this->conversion_table[$from_unit."_".$to_unit] = array("ratio"=>$val, "offset"=>0);
+ }
+ else
+ {
+ $this->conversion_table[$from_unit."_".$to_unit] =
+ array(
+ "ratio"=>$val['ratio'],
+ "offset"=>(isset($val['offset']) ? $val['offset'] : 0)
+ );
+ }
+ }
+ }
+ else
+ {
+ $this->bases[$from_unit][] = $key;
+
+ if (!is_array($val))
+ {
+ $this->conversion_table[$from_unit."_".$key] = array("ratio"=>$val, "offset"=>0);
+ }
+ else
+ {
+ $this->conversion_table[$from_unit."_".$key] =
+ array(
+ "ratio"=>$val['ratio'],
+ "offset"=>(isset($val['offset']) ? $val['offset'] : 0)
+ );
+ }
+ }
+ }
+ return true;
+ }
+ return false;
+
+ } // end func addConversion
+
+ /**
+ * Converts from one unit to another using specified precision.
+ *
+ * @param double value to convert
+ * @param string name of the source unit from which to convert
+ * @param string name of the target unit to which we are converting
+ * @param integer double precision of the end result
+ * @return void
+ * @access public
+ */
+ function convert($value, $from_unit, $to_unit, $precision)
+ {
+ if ($this->getConvSpecs($from_unit, $to_unit, $value, $converted ))
+ {
+ return number_format($converted , (int)$precision, $this->decimal_point, $this->thousand_separator);
+ } else {
+ return false;
+ }
+ } // end func
+
+ /**
+ * CVH : changed this Function getConvSpecs in order to have it look up
+ * intermediary Conversions from the
+ * "base" unit being that one that has the highest hierarchical order in one
+ * "logical" Conversion_Array
+ * when taking $conv->addConversion('km',
+ * array('meter'=>1000, 'dmeter'=>10000, 'centimeter'=>100000,
+ * 'millimeter'=>1000000, 'mile'=>0.62137, 'naut.mile'=>0.53996,
+ * 'inch(es)/zoll'=>39370, 'ft/foot/feet'=>3280.8, 'yd/yard'=>1093.6));
+ * "km" would be the logical base unit for all units of dinstance, thus,
+ * if the function fails to find a direct or reverse conversion in the table
+ * it is only logical to suspect that if there is a chance
+ * converting the value it only is via the "base" unit, and so
+ * there is not even a need for a recursive search keeping the perfomance
+ * acceptable and the ressource small...
+ *
+ * CVH check_key checks for a key in the Conversiontable and returns a value
+ */
+ function check_key( $key) {
+ if ( array_key_exists ($key,$this->conversion_table)) {
+ if (! empty($this->conversion_table[$key])) {
+ return $this->conversion_table[$key];
+ }
+ }
+ return false;
+ }
+
+ /**
+ * Key function. Finds the conversion ratio and offset from one unit to another.
+ *
+ * @param string name of the source unit from which to convert
+ * @param string name of the target unit to which we are converting
+ * @param double conversion ratio found. Returned by reference.
+ * @param double offset which needs to be added (or subtracted, if negative)
+ * to the result to convert correctly.
+ * For temperature or some scientific conversions,
+ * i.e. Fahrenheit -> Celcius
+ * @return boolean true if ratio and offset are found for the supplied
+ * units, false otherwise
+ * @access private
+ */
+ function getConvSpecs($from_unit, $to_unit, $value, &$converted)
+ {
+ $key = $from_unit."_".$to_unit;
+ $revkey = $to_unit."_".$from_unit;
+ $found = false;
+ if ($ct_arr = $this->check_key($key)) {
+ // Conversion Specs found directly
+ $ratio = (double)$ct_arr['ratio'];
+ $offset = $ct_arr['offset'];
+ $converted = (double)(($value * $ratio)+ $offset);
+
+ return true;
+ } // not found in direct order, try reverse order
+ elseif ($ct_arr = $this->check_key($revkey)) {
+ $ratio = (double)(1/$ct_arr['ratio']);
+ $offset = -$ct_arr['offset'];
+ $converted = (double)(($value + $offset) * $ratio);
+
+ return true;
+ } // not found test for intermediary conversion
+ else {
+ // return ratio = 1 if keyparts match
+ if ($key == $revkey) {
+ $ratio = 1;
+ $offset = 0;
+ $converted = $value;
+ return true;
+ }
+ // otherwise search intermediary
+ reset($this->conversion_table);
+ while (list($convk, $i1_value) = each($this->conversion_table)) {
+ // split the key into parts
+ $keyparts = preg_split("/_/",$convk);
+ // return ratio = 1 if keyparts match
+
+ // Now test if either part matches the from or to unit
+ if ($keyparts[1] == $to_unit && ($i2_value = $this->check_key($keyparts[0]."_".$from_unit))) {
+ // an intermediary $keyparts[0] was found
+ // now let us put things together intermediary 1 and 2
+ $converted = (double)(((($value - $i2_value['offset']) / $i2_value['ratio']) * $i1_value['ratio'])+ $i1_value['offset']);
+
+ $found = true;
+
+ } elseif ($keyparts[1] == $from_unit && ($i2_value = $this->check_key($keyparts[0]."_".$to_unit))) {
+ // an intermediary $keyparts[0] was found
+ // now let us put things together intermediary 2 and 1
+ $converted = (double)(((($value - $i1_value['offset']) / $i1_value['ratio']) + $i2_value['offset']) * $i2_value['ratio']);
+
+ $found = true;
+ }
+ }
+ return $found;
+ }
+
+ } // end func getConvSpecs
+
+} // end class UnitConvertor
+?> \ No newline at end of file
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