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<?php // $Id: unitsapi.module,v 1.6 2009/02/27 22:54:29 raspberryman Exp $
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/**
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* @file
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* Provides a variety of measurement unit conversions.
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*/
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/**
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* Implementation of hook_help().
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*/
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function unitsapi_help($path, $arg) {
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switch ($path) {
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case 'admin/help#unitsapi':
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$output = '<p>'. t('To use the unitsapi_convert() function, you need the key of the to and from unit. These keys are below.') .'</p>';
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$output .= _unitsapi_key_table();
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return $output;
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}
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}
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/**
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* The API call for all unit conversions.
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*
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* @param $value
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* A number containing the value of the measurement.
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* @param $from
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* A string containing the name of the measurement to convert from.
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* @param $to
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* A string containing the name of the measurement to convert to.
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* @param $details
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* A boolean value. TRUE returns an array with details about the conversion. FALSE returns
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* simply the converted value. Default is FALSE.
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* @return
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* A float containing the result of the conversion. FALSE if an error occured.
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*/
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function unitsapi_convert($value, $from, $to, $details = FALSE) {
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$units = unitsapi_get_units();
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// Only accept numeric values.
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if (!is_numeric($value)) {
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drupal_set_message(t('Unit conversion value must be numeric.'), 'error');
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return FALSE;
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}
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// Check to see if the unit key was found in the array.
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if (!isset($units[$from]) || !isset($units[$to])) {
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drupal_set_message(t('Units API cannot find the specified measurement units.'), 'error');
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return FALSE;
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}
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// Only convert with like kinds
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if ($units[$from]['kind'] != $units[$to]['kind']) {
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drupal_set_message(t('Units API cannot convert between different kinds of measurement units.'), 'error');
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return FALSE;
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}
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// Execute the conversion factors differently based on the kind. For example, temperature needs to be executed differently.
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switch ($units[$from]['kind']) {
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case 'temperature':
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$result = _unitsapi_convert_temperature($value, $units[$to]['factor'][$from]);
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break;
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default:
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$from_si = $units[$from]['factor'];
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$to_si = $units[$to]['factor'];
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$from_convert = $value * $from_si;
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$result = $from_convert / $to_si;
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}
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// Round to the 6 spaces after the decimal.
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$result = round($result, 6);
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$return = array();
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if ($details) {
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$return['result'] = $result;
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$return['from'] = $value == 1 ? t($units[$from]['singular']) : t($units[$from]['plural']);
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$return['to'] = $result == 1 ? t($units[$to]['singular']) : t($units[$to]['plural']);
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}
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else {
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$return = $result;
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}
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return $return;
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}
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/**
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* Fetches the units array, and saved to cache if needed.
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*
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* @return
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* An array of unit data, including conversion factors and labels.
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*/
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function unitsapi_get_units() {
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$cache = cache_get('unitsapi_data');
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if (empty($cache->data) || !is_array($cache->data)) {
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unitsapi_xml_cache();
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$cache = cache_get('unitsapi_data');
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}
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return $cache->data;
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}
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/**
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* Loads units.xml and saves it in the cache as a serialized array.
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*
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* @return
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* TRUE if the cache was successful. FALSE if an error occured.
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*/
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function unitsapi_xml_cache() {
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$file = url(drupal_get_path('module', 'unitsapi'), array('absolute' => TRUE)) .'/units.xml';
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// Load the XML file
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if (!function_exists('simplexml_load_file')) {
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drupal_set_message(t('SimpleXML not found. PHP 5 is required for Units API.'), 'error');
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return FALSE;
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}
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elseif (empty($file)) {
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drupal_set_message(t('The specified Units XML file is empty.'), 'error');
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return FALSE;
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}
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elseif (!$xml = simplexml_load_file($file)) {
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drupal_set_message(t('The Units API XML file could not be loaded by SimpleXML.'), 'error');
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return FALSE;
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}
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// Loop the XML file. It is often easier to force the type of the SimpleXML object to an array.
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foreach ((array) $xml as $kind => $units) {
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foreach ($units->unit as $unit) {
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$unitarray = (array) $unit;
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// If this unit has multiple factors, set them in $unitsarray according to their kind
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if (isset($unit->factors)) {
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unset($unitarray['factors']);
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foreach ($unit->factors->factor as $factor) {
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$factor = (array) $factor;
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switch ($kind) {
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case 'temperature':
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$unitarray['factor'][$factor['@attributes']['from']] = $factor[0];
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break;
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}
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}
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}
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$units_cache[$unitarray['key']] = array(
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'singular' => $unitarray['singular'],
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'plural' => $unitarray['plural'],
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'symbol' => $unitarray['symbol'],
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'factor' => _unitsapi_factor_set($unitarray['factor']),
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'kind' => $kind,
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'source' => $unitarray['source'],
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);
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}
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}
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$data = module_invoke_all('unitsapi');
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// Loop through the $data array and make changes to the $units collection
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if (!empty($data) && is_array($data)) {
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foreach ($data as $key => $unit) {
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if (!empty($unit) && is_array($unit) && isset($units_cache[$key])) {
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foreach ($unit as $parameter => $value) {
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if (isset($units_cache[$key][$parameter])) {
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$units_cache[check_plain($key)][check_plain($parameter)] = check_plain($value);
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}
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}
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}
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}
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}
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cache_set('unitsapi_data', $units_cache);
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return TRUE;
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}
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/**
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* Helper function to format the conversion factor.
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*
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* @param $si
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* A string or array containing the conversion factor equation.
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* @return
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* A string or array that contains equations that are formatted for execution.
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*/
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function _unitsapi_factor_set($si) {
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$si = str_replace(' ', '', $si);
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$si = str_replace(array('—', '−', '–'), '-', $si);
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return $si;
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}
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/**
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* Executes the temperature conversion equation.
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*
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* @param $value
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* A number containing the value of the temperature.
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* @param $factor
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* A string containing the conversion equation.
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* @return
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* A float containing the result of the conversion. FALSE if an error occured.
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*/
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function _unitsapi_convert_temperature($value, $factor) {
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// Security note: Execute a variety of checks to make sure the equation is not something mischievous
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$equation = str_replace(array('t/°C', 't/°F', 'T/K'), $value, $factor);
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$equation = preg_replace("/[^0-9+\-.*\/()%]/", "", $equation);
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$equation = preg_replace("/([+-])([0-9]+)(%)/", "*(1\$1.\$2)", $equation);
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$equation = preg_replace("/([0-9]+)(%)/", ".\$1", $equation);
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if ($equation == "") {
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$return = FALSE;
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}
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else {
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eval("\$return=". $equation .";");
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}
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return $return;
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}
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/**
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* Helper function to generate a table of unit keys, symbols, and conversion factors. Used in hook_help()
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*
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* @return
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* A themed table of unit keys, symbols, and conversion factors.
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*/
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function _unitsapi_key_table() {
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$units = unitsapi_get_units();
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$header = array(
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t('KEY'),
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t('UNIT NAME'),
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t('CONVERSION FACTOR'),
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);
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if (!empty($units) && is_array($units)) {
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foreach ($units as $key => $unit) {
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if ($curr_kind != $unit['kind']) {
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$curr_kind = $unit['kind'];
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$row = array(
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'data' => array(array('data' => '<strong>'. drupal_ucfirst(t($curr_kind)) .'</strong>', 'colspan' => 4)),
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);
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$rows[] = $row;
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}
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if ($curr_kind == 'temperature') {
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$output_factor = '';
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foreach ($unit['factor'] as $factor_key => $factor) {
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$output_factor .= t('from @factor-key: <a href="@source-url">@factor</a>', array('@factor-key' => $factor_key, '@source-url' => url($unit['source']), '@factor' => $factor)) .'<br />';
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}
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$row = array(
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check_plain($key),
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t('@singular (@symbol)', array('@singular' => $unit['singular'], '@symbol' => $unit['symbol'])),
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$output_factor,
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);
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}
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else {
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$row = array(
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check_plain($key),
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t('@singular (@symbol)', array('@singular' => $unit['singular'], '@symbol' => $unit['symbol'])),
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t('<a href="@source-url">@factor</a>', array('@source-url' => url($unit['source']), '@factor' => $unit['factor'])),
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);
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}
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$rows[] = $row;
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}
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}
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return theme('table', $header, $rows);
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}
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