<?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. |
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// +----------------------------------------------------------------------+
// | 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
?>
