LimitStream.php

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<?php
namespace GuzzleHttp\Psr7;

use Psr\Http\Message\StreamInterface;


class LimitStream implements StreamInterface
{
    use StreamDecoratorTrait;

    private $offset;

    private $limit;

    public function __construct(
        StreamInterface $stream,
        $limit = -1,
        $offset = 0
    ) {
        $this->stream = $stream;
        $this->setLimit($limit);
        $this->setOffset($offset);
    }

    public function eof()
    {
        // Always return true if the underlying stream is EOF
        if ($this->stream->eof()) {
            return true;
        }

        // No limit and the underlying stream is not at EOF
        if ($this->limit == -1) {
            return false;
        }

        return $this->stream->tell() >= $this->offset + $this->limit;
    }

    public function getSize()
    {
        if (null === ($length = $this->stream->getSize())) {
            return null;
        } elseif ($this->limit == -1) {
            return $length - $this->offset;
        } else {
            return min($this->limit, $length - $this->offset);
        }
    }

    public function seek($offset, $whence = SEEK_SET)
    {
        if ($whence !== SEEK_SET || $offset < 0) {
            throw new \RuntimeException(sprintf(
                'Cannot seek to offset % with whence %s',
                $offset,
                $whence
            ));
        }

        $offset += $this->offset;

        if ($this->limit !== -1) {
            if ($offset > $this->offset + $this->limit) {
                $offset = $this->offset + $this->limit;
            }
        }

        $this->stream->seek($offset);
    }

    public function tell()
    {
        return $this->stream->tell() - $this->offset;
    }

    public function setOffset($offset)
    {
        $current = $this->stream->tell();

        if ($current !== $offset) {
            // If the stream cannot seek to the offset position, then read to it
            if ($this->stream->isSeekable()) {
                $this->stream->seek($offset);
            } elseif ($current > $offset) {
                throw new \RuntimeException("Could not seek to stream offset $offset");
            } else {
                $this->stream->read($offset - $current);
            }
        }

        $this->offset = $offset;
    }

    public function setLimit($limit)
    {
        $this->limit = $limit;
    }

    public function read($length)
    {
        if ($this->limit == -1) {
            return $this->stream->read($length);
        }

        // Check if the current position is less than the total allowed
        // bytes + original offset
        $remaining = ($this->offset + $this->limit) - $this->stream->tell();
        if ($remaining > 0) {
            // Only return the amount of requested data, ensuring that the byte
            // limit is not exceeded
            return $this->stream->read(min($remaining, $length));
        }

        return '';
    }
}