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<?php
namespace RingCentral\Psr7;
use Psr\Http\Message\StreamInterface;
/**
* Decorator used to return only a subset of a stream
*/
class LimitStream extends StreamDecoratorTrait implements StreamInterface
{
/** @var int Offset to start reading from */
private $offset;
/** @var int Limit the number of bytes that can be read */
private $limit;
/**
* @param StreamInterface $stream Stream to wrap
* @param int $limit Total number of bytes to allow to be read
* from the stream. Pass -1 for no limit.
* @param int|null $offset Position to seek to before reading (only
* works on seekable streams).
*/
public function __construct(
StreamInterface $stream,
$limit = -1,
$offset = 0
) {
parent::__construct($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 + $this->limit;
}
/**
* Returns the size of the limited subset of data
* {@inheritdoc}
*/
public function getSize()
{
if (null === ($length = $this->stream->getSize())) {
return null;
} elseif ($this->limit == -1) {
return $length - $this->offset;
} else {
return min($this->limit, $length - $this->offset);
}
}
/**
* Allow for a bounded seek on the read limited stream
* {@inheritdoc}
*/
public function seek($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);
}
/**
* Give a relative tell()
* {@inheritdoc}
*/
public function tell()
{
return $this->stream->tell() - $this->offset;
}
/**
* Set the offset to start limiting from
*
* @param int $offset Offset to seek to and begin byte limiting from
*
* @throws \RuntimeException if the stream cannot be seeked.
*/
public function setOffset($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;
}
/**
* Set the limit of bytes that the decorator allows to be read from the
* stream.
*
* @param int $limit Number of bytes to allow to be read from the stream.
* Use -1 for no limit.
*/
public function setLimit($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 '';
}
}
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