krz/vox-populi

  1<?php
  2namespace GuzzleHttp\Psr7;
  3
  4use Psr\Http\Message\StreamInterface;
  5
  6
  7/**
  8 * Decorator used to return only a subset of a stream
  9 */
 10class LimitStream implements StreamInterface
 11{
 12    use StreamDecoratorTrait;
 13
 14    /** @var int Offset to start reading from */
 15    private $offset;
 16
 17    /** @var int Limit the number of bytes that can be read */
 18    private $limit;
 19
 20    /**
 21     * @param StreamInterface $stream Stream to wrap
 22     * @param int             $limit  Total number of bytes to allow to be read
 23     *                                from the stream. Pass -1 for no limit.
 24     * @param int             $offset Position to seek to before reading (only
 25     *                                works on seekable streams).
 26     */
 27    public function __construct(
 28        StreamInterface $stream,
 29        $limit = -1,
 30        $offset = 0
 31    ) {
 32        $this->stream = $stream;
 33        $this->setLimit($limit);
 34        $this->setOffset($offset);
 35    }
 36
 37    public function eof()
 38    {
 39        // Always return true if the underlying stream is EOF
 40        if ($this->stream->eof()) {
 41            return true;
 42        }
 43
 44        // No limit and the underlying stream is not at EOF
 45        if ($this->limit == -1) {
 46            return false;
 47        }
 48
 49        return $this->stream->tell() >= $this->offset + $this->limit;
 50    }
 51
 52    /**
 53     * Returns the size of the limited subset of data
 54     * {@inheritdoc}
 55     */
 56    public function getSize()
 57    {
 58        if (null === ($length = $this->stream->getSize())) {
 59            return null;
 60        } elseif ($this->limit == -1) {
 61            return $length - $this->offset;
 62        } else {
 63            return min($this->limit, $length - $this->offset);
 64        }
 65    }
 66
 67    /**
 68     * Allow for a bounded seek on the read limited stream
 69     * {@inheritdoc}
 70     */
 71    public function seek($offset, $whence = SEEK_SET)
 72    {
 73        if ($whence !== SEEK_SET || $offset < 0) {
 74            throw new \RuntimeException(sprintf(
 75                'Cannot seek to offset %s with whence %s',
 76                $offset,
 77                $whence
 78            ));
 79        }
 80
 81        $offset += $this->offset;
 82
 83        if ($this->limit !== -1) {
 84            if ($offset > $this->offset + $this->limit) {
 85                $offset = $this->offset + $this->limit;
 86            }
 87        }
 88
 89        $this->stream->seek($offset);
 90    }
 91
 92    /**
 93     * Give a relative tell()
 94     * {@inheritdoc}
 95     */
 96    public function tell()
 97    {
 98        return $this->stream->tell() - $this->offset;
 99    }
100
101    /**
102     * Set the offset to start limiting from
103     *
104     * @param int $offset Offset to seek to and begin byte limiting from
105     *
106     * @throws \RuntimeException if the stream cannot be seeked.
107     */
108    public function setOffset($offset)
109    {
110        $current = $this->stream->tell();
111
112        if ($current !== $offset) {
113            // If the stream cannot seek to the offset position, then read to it
114            if ($this->stream->isSeekable()) {
115                $this->stream->seek($offset);
116            } elseif ($current > $offset) {
117                throw new \RuntimeException("Could not seek to stream offset $offset");
118            } else {
119                $this->stream->read($offset - $current);
120            }
121        }
122
123        $this->offset = $offset;
124    }
125
126    /**
127     * Set the limit of bytes that the decorator allows to be read from the
128     * stream.
129     *
130     * @param int $limit Number of bytes to allow to be read from the stream.
131     *                   Use -1 for no limit.
132     */
133    public function setLimit($limit)
134    {
135        $this->limit = $limit;
136    }
137
138    public function read($length)
139    {
140        if ($this->limit == -1) {
141            return $this->stream->read($length);
142        }
143
144        // Check if the current position is less than the total allowed
145        // bytes + original offset
146        $remaining = ($this->offset + $this->limit) - $this->stream->tell();
147        if ($remaining > 0) {
148            // Only return the amount of requested data, ensuring that the byte
149            // limit is not exceeded
150            return $this->stream->read(min($remaining, $length));
151        }
152
153        return '';
154    }
155}