Product CRC32C in Pure PHP7.4+

crcTest.php

<?php
use Google\CRC32\CRC32;
use GuzzleHttp\Psr7\Utils;

include __DIR__.'/vendor/autoload.php';

$filePath = __DIR__.'/tests/System/data/5mb.txt';

## USAGE:
# Paste the file into https://github.com/googleapis/google-cloud-php/tree/main/Storage
# Run using this command: `php crcTest.php`
# Tests the crc32c hash function for this PR: https://github.com/googleapis/google-cloud-php/pull/6532

$stream = Utils::streamFor(fopen($filePath, 'r'));
$crc32c = CRC32::create(CRC32::CASTAGNOLI);
$crc32c->update((string) $stream);
$hash = ($crc32c->hash(true));
echo $hash.PHP_EOL;

function fileToHash($filePath, $bufferSize = 1048576)
{
    $fp = fopen($filePath, "r");
    $ctx = hash_init('crc32c');
    while (!feof($fp)) {
        $buffer = fgets($fp, $bufferSize);
        hash_update($ctx, $buffer);
    }
    fclose($fp);
    $hash = hash_final($ctx, true);
    return $hash;
}
$hash = fileToHash($filePath);
echo base64_encode($hash).PHP_EOL;

// hash a different buffer window size
$hash = fileToHash($filePath, 65536);
echo base64_encode($hash).PHP_EOL;

// hash full file in one go
$data = file_get_contents($filePath);
$hash = hash('crc32c', $data, true);
echo base64_encode($hash).PHP_EOL;

It printed: egbghQ== (the same hash four times, which means we can safely migrate the hash function)