SourceResource.php

<?php

namespace Jcupitt\Vips;

class SourceResource extends SourceCustom
{
    /**
     * @var resource
     */
    private $resource;

    /**
     * The resource passed in will become "owned" by this class.
     * On destruction of this class, the resource will be closed.
     *
     * @param resource $resource
     */
    public function __construct($resource)
    {
        $this->resource = $resource;
        parent::__construct();

        $this->onRead(static function (int $length) use (&$resource): ?string {
            return (($read = fread($resource, $length)) !== '') ?
                $read :
                null;
        });

        if (stream_get_meta_data($resource)['seekable']) {
            $this->onSeek(static function (int $offset, int $whence) use (&$resource): int {
                return fseek($resource, $offset, $whence) === 0 ?
                    ftell($resource) :
                    -1;
            });
        }
    }

    public function __destruct()
    {
        fclose($this->resource);
        parent::__destruct();
    }
}