streamBase64EncodeFilter.php

<?php

class Base64Encode extends \php_user_filter
{
    private $bufferHandle;

    private $tail = '';

    public function filter($in, $out, &$consumed, $closing)
    {
        $data = $this->tail;

        while ($bucket = stream_bucket_make_writeable($in)) {
            $data .= $bucket->data;
            $consumed += $bucket->datalen;
        }

        $buck = stream_bucket_new($this->bufferHandle, '');

        if (false === $buck) {
            return PSFS_ERR_FATAL;
        }

        if (!$closing) {
            $dataLen = strlen($data);
            $this->tail = substr($data, -1 * ($dataLen % 3));
            $buck->data = base64_encode(substr($data, 0, $dataLen - strlen($this->tail)));
        } else {
            $buck->data = base64_encode($data);
        }

        stream_bucket_append($out, $buck);
        return PSFS_PASS_ON;
    }

    public function onCreate()
    {
        $this->bufferHandle = @fopen('php://temp', 'wb+');

        return false !== $this->bufferHandle;
    }

    public function onClose()
    {
        @fclose($this->bufferHandle);
    }
}

stream_filter_register('base64streamEncode', Base64Encode::class);

$filename = '/Volumes/work/LKIM/web/_files/image/da6951bbdf767fef0fd55c869b0cd65d.jpg';

$f = fopen($filename, 'rb+');
stream_filter_append($f, 'base64streamEncode');
$b = '';
while ('' !== $part = stream_get_contents($f, 8192)) {
    $b .= $part;
}
fclose($f);

var_dump(number_format(memory_get_peak_usage()));