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<?php
namespace GuzzleHttp\Stream;
use GuzzleHttp\Stream\Exception\SeekException;
/**
* Stream decorator that can cache previously read bytes from a sequentially
* read stream.
*/
class CachingStream implements StreamInterface
{
use StreamDecoratorTrait;
/** @var StreamInterface Stream being wrapped */
private $remoteStream;
/** @var int Number of bytes to skip reading due to a write on the buffer */
private $skipReadBytes = 0;
/**
* We will treat the buffer object as the body of the stream
*
* @param StreamInterface $stream Stream to cache
* @param StreamInterface $target Optionally specify where data is cached
*/
public function __construct(
StreamInterface $stream,
StreamInterface $target = null
) {
$this->remoteStream = $stream;
$this->stream = $target ?: new Stream(fopen('php://temp', 'r+'));
}
public function getSize()
{
return max($this->stream->getSize(), $this->remoteStream->getSize());
}
/**
* {@inheritdoc}
* @throws SeekException When seeking with SEEK_END or when seeking
* past the total size of the buffer stream
*/
public function seek($offset, $whence = SEEK_SET)
{
if ($whence == SEEK_SET) {
$byte = $offset;
} elseif ($whence == SEEK_CUR) {
$byte = $offset + $this->tell();
} else {
return false;
}
// You cannot skip ahead past where you've read from the remote stream
if ($byte > $this->stream->getSize()) {
throw new SeekException(
$this,
$byte,
sprintf('Cannot seek to byte %d when the buffered stream only'
. ' contains %d bytes', $byte, $this->stream->getSize())
);
}
return $this->stream->seek($byte);
}
public function read($length)
{
// Perform a regular read on any previously read data from the buffer
$data = $this->stream->read($length);
$remaining = $length - strlen($data);
// More data was requested so read from the remote stream
if ($remaining) {
// If data was written to the buffer in a position that would have
// been filled from the remote stream, then we must skip bytes on
// the remote stream to emulate overwriting bytes from that
// position. This mimics the behavior of other PHP stream wrappers.
$remoteData = $this->remoteStream->read(
$remaining + $this->skipReadBytes
);
if ($this->skipReadBytes) {
$len = strlen($remoteData);
$remoteData = substr($remoteData, $this->skipReadBytes);
$this->skipReadBytes = max(0, $this->skipReadBytes - $len);
}
$data .= $remoteData;
$this->stream->write($remoteData);
}
return $data;
}
public function write($string)
{
// When appending to the end of the currently read stream, you'll want
// to skip bytes from being read from the remote stream to emulate
// other stream wrappers. Basically replacing bytes of data of a fixed
// length.
$overflow = (strlen($string) + $this->tell()) - $this->remoteStream->tell();
if ($overflow > 0) {
$this->skipReadBytes += $overflow;
}
return $this->stream->write($string);
}
public function eof()
{
return $this->stream->eof() && $this->remoteStream->eof();
}
/**
* Close both the remote stream and buffer stream
*/
public function close()
{
$this->remoteStream->close() && $this->stream->close();
}
}