Formats the percent completion for a batch set.

**$total**:
The total number of operations.

**$current**:
The number of the current operation. This may be a floating point number
rather than an integer in the case of a multi-step operation that is not
yet complete; in that case, the fractional part of $current represents the
fraction of the operation that has been completed.

The properly formatted percentage, as a string. We output percentages using the correct number of decimal places so that we never print "100%" until we are finished, but we also never print more decimal places than are meaningful.

2 calls to _batch_api_percentage()

- BatchPercentagesUnitTestCase::testBatchPercentages in drupal/
modules/ simpletest/ tests/ batch.test - Test the _batch_api_percentage() function.
- _batch_process in drupal/
includes/ batch.inc - Processes sets in a batch.

- drupal/
includes/ batch.inc, line 391 - Batch processing API for processes to run in multiple HTTP requests.

```
function _batch_api_percentage($total, $current) {
if (!$total || $total == $current) {
// If $total doesn't evaluate as true or is equal to the current set, then
// we're finished, and we can return "100".
$percentage = "100";
}
else {
// We add a new digit at 200, 2000, etc. (since, for example, 199/200
// would round up to 100% if we didn't).
$decimal_places = max(0, floor(log10($total / 2.0)) - 1);
do {
// Calculate the percentage to the specified number of decimal places.
$percentage = sprintf('%01.' . $decimal_places . 'f', round($current / $total * 100, $decimal_places));
// When $current is an integer, the above calculation will always be
// correct. However, if $current is a floating point number (in the case
// of a multi-step batch operation that is not yet complete), $percentage
// may be erroneously rounded up to 100%. To prevent that, we add one
// more decimal place and try again.
$decimal_places++;
} while ($percentage == '100');
}
return $percentage;
}
```