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Finally stabilize the unit converter.

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git-svn-id: http://htmlpurifier.org/svnroot/htmlpurifier/trunk@1750 48356398-32a2-884e-a903-53898d9a118a
This commit is contained in:
Edward Z. Yang
2008-05-20 21:23:38 +00:00
parent fda310f1e7
commit d8da5ff406
6 changed files with 160 additions and 41 deletions
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68
library/HTMLPurifier/UnitConverter.php
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@@ -50,6 +50,11 @@ class HTMLPurifier_UnitConverter
/**
* Converts a length object of one unit into another unit.
* @param HTMLPurifier_Length $length
* Instance of HTMLPurifier_Length to convert. You must validate()
* it before passing it here!
* @param string $to_unit
* Unit to convert to.
* @note
* About precision: This conversion function pays very special
* attention to the incoming precision of values and attempts
@@ -60,39 +65,35 @@ class HTMLPurifier_UnitConverter
* - If a number contains less than four sigfigs ($outputPrecision)
* and this causes some decimals to be excluded, those
* decimals will be added on.
* - Significant digits will be ignored for quantities greater
* than one. This is a limitation of BCMath and I don't
* feel like coding around it.
*/
public function convert($length, $to_unit) {
if ($length->n === '0' || $length->unit === false) {
return new HTMLPurifier_Length('0', $unit);
if (!$length->isValid()) return false;
$n = $length->getN();
$unit = $length->getUnit();
if ($n === '0' || $unit === false) {
return new HTMLPurifier_Length('0', false);
}
$state = $dest = false;
$state = $dest_state = false;
foreach (self::$units as $k => $x) {
if (isset($x[$length->unit])) $state = $k;
if (isset($x[$unit])) $state = $k;
if (isset($x[$to_unit])) $dest_state = $k;
}
if (!$state || !$dest_state) return false;
$n = $length->n;
$unit = $length->unit;
// Some calculations about the initial precision of the number;
// this will be useful when we need to do final rounding.
$log = (int) floor(log($n, 10));
if (strpos($n, '.') === false) {
$sigfigs = strlen(trim($n, '0+-'));
} else {
$sigfigs = strlen(ltrim($n, '0+-')) - 1; // eliminate extra decimal character
}
$sigfigs = $this->getSigFigs($n);
if ($sigfigs < $this->outputPrecision) $sigfigs = $this->outputPrecision;
// BCMath's internal precision deals only with decimals. Use
// our default if the initial number has no decimals, or increase
// it by how ever many decimals, thus, the number of guard digits
// will always be greater than or equal to internalPrecision.
$log = (int) floor(log(abs($n), 10));
$cp = ($log < 0) ? $this->internalPrecision - $log : $this->internalPrecision; // internal precision
for ($i = 0; $i < 2; $i++) {
@@ -113,7 +114,7 @@ class HTMLPurifier_UnitConverter
$unit = $dest_unit;
}
// Output was zero, so bail out early
// Output was zero, so bail out early. Shouldn't ever happen.
if ($n === '') {
$n = '0';
$unit = $to_unit;
@@ -148,17 +149,21 @@ class HTMLPurifier_UnitConverter
// Calculate how many decimals we need ($rp)
// Calculations will always be carried to the decimal; this is
// a limitation with BC (we can't set the scale to be negative)
$new_log = (int) floor(log($n, 10));
$new_log = (int) floor(log(abs($n), 10));
$rp = $sigfigs - $new_log - 1;
//echo "----\n";
//echo "$n\nsigfigs = $sigfigs\nnew_log = $new_log\nlog = $log\nrp = $rp\n";
$neg = $n < 0 ? '-' : '';
// Useful for debugging:
//echo "<pre>n";
//echo "$n\nsigfigs = $sigfigs\nnew_log = $new_log\nlog = $log\nrp = $rp\n</pre>\n";
if ($rp >= 0) {
$n = bcadd($n, '0.' . str_repeat('0', $rp) . '5', $rp + 1);
$n = bcadd($n, $neg . '0.' . str_repeat('0', $rp) . '5', $rp + 1);
$n = bcdiv($n, '1', $rp);
} else {
if ($new_log + 1 >= $sigfigs) {
$n = bcadd($n, '5' . str_repeat('0', $new_log - $sigfigs));
$n = substr($n, 0, $sigfigs) . str_repeat('0', $new_log + 1 - $sigfigs);
$n = bcadd($n, $neg . '5' . str_repeat('0', $new_log - $sigfigs));
$n = substr($n, 0, $sigfigs + strlen($neg)) . str_repeat('0', $new_log + 1 - $sigfigs);
}
}
if (strpos($n, '.') !== false) $n = rtrim($n, '0');
@@ -167,4 +172,21 @@ class HTMLPurifier_UnitConverter
return new HTMLPurifier_Length($n, $unit);
}
/**
* Returns the number of significant figures in a string number.
* @param string $n Decimal number
* @return int number of sigfigs
*/
public function getSigFigs($n) {
$n = ltrim($n, '0+-');
$dp = strpos($n, '.'); // decimal position
if ($dp === false) {
$sigfigs = strlen(rtrim($n, '0'));
} else {
$sigfigs = strlen(ltrim($n, '0.')); // eliminate extra decimal character
if ($dp !== 0) $sigfigs--;
}
return $sigfigs;
}
}