Use clearstatcache to avoid wrong filesize

[edpittol]

I was doing some tests and when I tried manipulate a document more than one time, I got an encoding error. Investigating the error, I saw that the function Filesystem::read() use fread() function to read the document content. And is passed the size of the length of the buffer with the function filesize. What happens is that PHP uses a cache to save the file status and this behavior can affect the value of filesize function.

When I add clearstatcache() on Filesystem::read() before the fread($file, filesize($path)), the error doesn't happen anymore.

I tried isolate in a script to prove what is happen on my case, but it just happen on my application. So I create a script that use the PHP library functions used on this project to simulate the error.

 function test_filesize($path, $contents, $clearstatcache) {
    $fp = fopen($path, 'w+');
    if(!flock($fp, LOCK_EX))
    {
        return false;
    }
    $result = fwrite($fp, $contents);
    flock($fp, LOCK_UN);
    fclose($fp);

    if($clearstatcache) {
        clearstatcache();
    }

    $file = fopen($path, 'r');
    $filesize = filesize($path);
    fclose($file);

    echo sprintf('Filesize expected: %d, got: %d', strlen($contents), $filesize) . PHP_EOL;
}

$path = 'some-file-path';
echo 'Not using clearstatcache' . PHP_EOL;
test_filesize( $path, 'a', false);
test_filesize( $path, 'aa', false);
test_filesize( $path, 'aaa', false);

echo 'Using clearstatcache' . PHP_EOL;
test_filesize( $path, 'a', true);
test_filesize( $path, 'aa', true);
test_filesize( $path, 'aaa', true);

This script outputs:

Not using clearstatcache
Filesize expected: 1, got: 1
Filesize expected: 2, got: 1
Filesize expected: 3, got: 1
Using clearstatcache
Filesize expected: 1, got: 1
Filesize expected: 2, got: 2
Filesize expected: 3, got: 3