SockTP reconstructor

parse.php

<?php
$lines = explode("\n", file_get_contents('out.txt'));
$user = '1';
$contexts = [];

class STPCTX {
    public $blocks = [];
    public $fileName = '';
    public $streamHash = '';
    public $sender = 0;

    public function __construct(string $hash, string $fileName, int $blocks, int $sender = 0) {
        $this->fileName = base64_decode($fileName);
        $this->streamHash = $hash;
        $this->blocks = array_fill(0, $blocks, 0);
        $this->sender = 0;
    }
    
    public function verifySender(int $sender): bool {
        return $sender < 1 || $this->sender === $sender;
    }

    public function appendBlock(int $num, string $data): void {
        $this->blocks[$num] = base64_decode($data);
    }

    public function save(): bool {
        $data = '';

        for ($i = 0; $i < count($this->blocks); $i++)
            $data .= $this->blocks[$i];

        if (hash('sha256', $data) !== $this->streamHash)
            return false;

        file_put_contents($this->fileName, gzdecode($data));
        return true;
    }
}

foreach ($lines as $line) {
    $sc = explode("\t", $line);

    if (count($sc) < 3)
        continue;

    $csv = explode(',', $sc[2]);

    switch ($csv[0]) {
        case 'STPv1OPN':
            if (array_key_exists($csv[1], $contexts)) {
                echo 'Context is already active?', PHP_EOL;
                break;
            }

            echo "N[{$csv[1]}] H[{$csv[2]}] F[{$csv[3]}] B[{$csv[4]}] Opened new SockTP context", PHP_EOL;
            $contexts[$csv[1]] = new STPCTX($csv[2], $csv[3], $csv[4], (int)$sc[1]);
            break;

        case 'STPv1BLK':
            if (!array_key_exists($csv[1], $contexts)) {
                echo 'Invalid context.', PHP_EOL;
                break;
            }

            if ($contexts[$csv[1]]->verifySender((int)$sc[1])) {
                echo 'Someone pretended to be the sender, packet ignored.', PHP_EOL;
                break;
            }

            echo "N[{$csv[1]}] I[{$csv[2]}] Received block", PHP_EOL;

            $contexts[$csv[1]]->appendBlock($csv[2], $csv[3]);
            break;

        case 'STPv1FIN':
            if (!array_key_exists($csv[1], $contexts)) {
                echo 'Invalid context.', PHP_EOL;
                break;
            }

            if ($contexts[$csv[1]]->verifySender((int)$sc[1])) {
                echo 'Someone pretended to be the sender, packet ignored.', PHP_EOL;
                break;
            }

            echo "N[{$csv[1]}] Transfer finished!", PHP_EOL;

            if (!$contexts[$csv[1]]->save())
                echo 'Stream hash mismatch, transfer failed.', PHP_EOL;
            break;
    }
}