1<?php
2
3namespace GuzzleHttp\Psr7;
4
5use Psr\Http\Message\StreamInterface;
6
7/**
8 * Decorator used to return only a subset of a stream.
9 *
10 * @final
11 */
12class LimitStream implements StreamInterface
13{
14    use StreamDecoratorTrait;
15
16    /** @var int Offset to start reading from */
17    private $offset;
18
19    /** @var int Limit the number of bytes that can be read */
20    private $limit;
21
22    /**
23     * @param StreamInterface $stream Stream to wrap
24     * @param int             $limit  Total number of bytes to allow to be read
25     *                                from the stream. Pass -1 for no limit.
26     * @param int             $offset Position to seek to before reading (only
27     *                                works on seekable streams).
28     */
29    public function __construct(
30        StreamInterface $stream,
31        $limit = -1,
32        $offset = 0
33    ) {
34        $this->stream = $stream;
35        $this->setLimit($limit);
36        $this->setOffset($offset);
37    }
38
39    public function eof()
40    {
41        // Always return true if the underlying stream is EOF
42        if ($this->stream->eof()) {
43            return true;
44        }
45
46        // No limit and the underlying stream is not at EOF
47        if ($this->limit == -1) {
48            return false;
49        }
50
51        return $this->stream->tell() >= $this->offset + $this->limit;
52    }
53
54    /**
55     * Returns the size of the limited subset of data
56     * {@inheritdoc}
57     */
58    public function getSize()
59    {
60        if (null === ($length = $this->stream->getSize())) {
61            return null;
62        } elseif ($this->limit == -1) {
63            return $length - $this->offset;
64        } else {
65            return min($this->limit, $length - $this->offset);
66        }
67    }
68
69    /**
70     * Allow for a bounded seek on the read limited stream
71     * {@inheritdoc}
72     */
73    public function seek($offset, $whence = SEEK_SET)
74    {
75        if ($whence !== SEEK_SET || $offset < 0) {
76            throw new \RuntimeException(sprintf(
77                'Cannot seek to offset %s with whence %s',
78                $offset,
79                $whence
80            ));
81        }
82
83        $offset += $this->offset;
84
85        if ($this->limit !== -1) {
86            if ($offset > $this->offset + $this->limit) {
87                $offset = $this->offset + $this->limit;
88            }
89        }
90
91        $this->stream->seek($offset);
92    }
93
94    /**
95     * Give a relative tell()
96     * {@inheritdoc}
97     */
98    public function tell()
99    {
100        return $this->stream->tell() - $this->offset;
101    }
102
103    /**
104     * Set the offset to start limiting from
105     *
106     * @param int $offset Offset to seek to and begin byte limiting from
107     *
108     * @throws \RuntimeException if the stream cannot be seeked.
109     */
110    public function setOffset($offset)
111    {
112        $current = $this->stream->tell();
113
114        if ($current !== $offset) {
115            // If the stream cannot seek to the offset position, then read to it
116            if ($this->stream->isSeekable()) {
117                $this->stream->seek($offset);
118            } elseif ($current > $offset) {
119                throw new \RuntimeException("Could not seek to stream offset $offset");
120            } else {
121                $this->stream->read($offset - $current);
122            }
123        }
124
125        $this->offset = $offset;
126    }
127
128    /**
129     * Set the limit of bytes that the decorator allows to be read from the
130     * stream.
131     *
132     * @param int $limit Number of bytes to allow to be read from the stream.
133     *                   Use -1 for no limit.
134     */
135    public function setLimit($limit)
136    {
137        $this->limit = $limit;
138    }
139
140    public function read($length)
141    {
142        if ($this->limit == -1) {
143            return $this->stream->read($length);
144        }
145
146        // Check if the current position is less than the total allowed
147        // bytes + original offset
148        $remaining = ($this->offset + $this->limit) - $this->stream->tell();
149        if ($remaining > 0) {
150            // Only return the amount of requested data, ensuring that the byte
151            // limit is not exceeded
152            return $this->stream->read(min($remaining, $length));
153        }
154
155        return '';
156    }
157}
158