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<?php |
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/** |
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* This file is part of the ZBateson\StreamDecorators project. |
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* |
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* @license http://opensource.org/licenses/bsd-license.php BSD |
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*/ |
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namespace ZBateson\StreamDecorators; |
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use GuzzleHttp\Psr7\StreamDecoratorTrait; |
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use Psr\Http\Message\StreamInterface; |
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/** |
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* Maintains an internal 'read' position, and seeks to it before reading, then |
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* seeks back to the original position of the underlying stream after reading if |
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* the attached stream supports seeking. |
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* |
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* Although copied form LimitStream, it's not inherited from it since $offset |
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* and $limit are set to private on LimitStream, and most other functions are |
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* re-implemented anyway. This also decouples the implementation from upstream |
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* changes. |
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*/ |
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class SeekingLimitStream implements StreamInterface |
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{ |
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use StreamDecoratorTrait; |
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/** @var int Offset to start reading from */ |
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private int $offset; |
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/** @var int Limit the number of bytes that can be read */ |
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private int $limit; |
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/** |
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* @var int Number of bytes written, and importantly, if non-zero, writes a |
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* final $lineEnding on close (and so maintained instead of using |
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* tell() directly) |
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*/ |
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private int $position = 0; |
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/** |
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* @var StreamInterface $stream |
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*/ |
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private StreamInterface $stream; |
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/** |
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* @param StreamInterface $stream Stream to wrap |
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* @param int $limit Total number of bytes to allow to be read |
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* from the stream. Pass -1 for no limit. |
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* @param int $offset Position to seek to before reading (only |
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* works on seekable streams). |
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*/ |
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public function __construct(StreamInterface $stream, int $limit = -1, int $offset = 0) |
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{ |
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$this->stream = $stream; |
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$this->setLimit($limit); |
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$this->setOffset($offset); |
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} |
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/** |
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* Returns the current relative read position of this stream subset. |
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*/ |
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public function tell() : int |
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{ |
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return $this->position; |
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} |
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/** |
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* Returns the size of the limited subset of data, or null if the wrapped |
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* stream returns null for getSize. |
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*/ |
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public function getSize() : ?int |
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{ |
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$size = $this->stream->getSize(); |
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if ($size === null) { |
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// this shouldn't happen on a seekable stream I don't think... |
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$pos = $this->stream->tell(); |
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$this->stream->seek(0, SEEK_END); |
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$size = $this->stream->tell(); |
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$this->stream->seek($pos); |
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} |
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if ($this->limit === -1) { |
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return $size - $this->offset; |
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} |
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return \min([$this->limit, $size - $this->offset]); |
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} |
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/** |
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* Returns true if the current read position is at the end of the limited |
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* stream |
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*/ |
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public function eof() : bool |
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{ |
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$size = $this->limit; |
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if ($size === -1) { |
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$size = $this->getSize(); |
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} |
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return ($this->position >= $size); |
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} |
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/** |
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* Ensures the seek position specified is within the stream's bounds, and |
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* sets the internal position pointer (doesn't actually seek). |
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*/ |
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private function doSeek(int $pos) : void |
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{ |
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if ($this->limit !== -1) { |
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$pos = \min([$pos, $this->limit]); |
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} |
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$this->position = \max([0, $pos]); |
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} |
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/** |
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* Seeks to the passed position within the confines of the limited stream's |
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* bounds. |
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* |
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* For SeekingLimitStream, no actual seek is performed on the underlying |
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* wrapped stream. Instead, an internal pointer is set, and the stream is |
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* 'seeked' on read operations |
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* |
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* @param int $offset |
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* @param int $whence |
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*/ |
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public function seek($offset, $whence = SEEK_SET) : void |
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{ |
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$pos = $offset; |
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switch ($whence) { |
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case SEEK_CUR: |
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$pos = $this->position + $offset; |
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break; |
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case SEEK_END: |
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$pos = $this->limit + $offset; |
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break; |
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default: |
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break; |
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} |
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$this->doSeek($pos); |
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} |
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/** |
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* Sets the offset to start reading from the wrapped stream. |
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*/ |
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public function setOffset(int $offset) : void |
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{ |
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$this->offset = $offset; |
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$this->position = 0; |
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} |
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/** |
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* Sets the length of the stream to the passed $limit. |
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*/ |
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public function setLimit(int $limit) : void |
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{ |
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$this->limit = $limit; |
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} |
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/** |
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* Seeks to the current position and reads up to $length bytes, or less if |
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* it would result in reading past $this->limit |
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*/ |
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public function seekAndRead(int $length) : string |
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{ |
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$this->stream->seek($this->offset + $this->position); |
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if ($this->limit !== -1) { |
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$length = \min($length, $this->limit - $this->position); |
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if ($length <= 0) { |
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return ''; |
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} |
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} |
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return $this->stream->read($length); |
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} |
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/** |
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* Reads from the underlying stream after seeking to the position within the |
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* bounds set for this limited stream. After reading, the wrapped stream is |
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* 'seeked' back to its position prior to the call to read(). |
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* |
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* @param int $length |
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*/ |
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public function read($length) : string |
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{ |
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$pos = $this->stream->tell(); |
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$ret = $this->seekAndRead($length); |
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$this->position += \strlen($ret); |
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$this->stream->seek($pos); |
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if ($this->limit !== -1 && $this->position > $this->limit) { |
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$ret = \substr($ret, 0, -($this->position - $this->limit)); |
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$this->position = $this->limit; |
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} |
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return $ret; |
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} |
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} |
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zbateson /
stream-decorators
