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<?php
/*
* Copyright 2016-2017 MongoDB, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
namespace MongoDB\GridFS;
use IteratorIterator;
use MongoDB\Exception\InvalidArgumentException;
use MongoDB\GridFS\Exception\CorruptFileException;
use stdClass;
use function ceil;
use function floor;
use function is_integer;
use function property_exists;
use function sprintf;
use function strlen;
use function substr;
/**
* ReadableStream abstracts the process of reading a GridFS file.
*
* @internal
*/
class ReadableStream
{
/** @var string|null */
private $buffer;
/** @var integer */
private $bufferOffset = 0;
/** @var integer */
private $chunkSize;
/** @var integer */
private $chunkOffset = 0;
/** @var IteratorIterator|null */
private $chunksIterator;
/** @var CollectionWrapper */
private $collectionWrapper;
/** @var float|integer */
private $expectedLastChunkSize = 0;
/** @var stdClass */
private $file;
/** @var integer */
private $length;
/** @var integer */
private $numChunks = 0;
/**
* Constructs a readable GridFS stream.
*
* @param CollectionWrapper $collectionWrapper GridFS collection wrapper
* @param stdClass $file GridFS file document
* @throws CorruptFileException
*/
public function __construct(CollectionWrapper $collectionWrapper, stdClass $file)
{
if (! isset($file->chunkSize) || ! is_integer($file->chunkSize) || $file->chunkSize < 1) {
throw new CorruptFileException('file.chunkSize is not an integer >= 1');
}
if (! isset($file->length) || ! is_integer($file->length) || $file->length < 0) {
throw new CorruptFileException('file.length is not an integer > 0');
}
if (! isset($file->_id) && ! property_exists($file, '_id')) {
throw new CorruptFileException('file._id does not exist');
}
$this->file = $file;
$this->chunkSize = (integer) $file->chunkSize;
$this->length = (integer) $file->length;
$this->collectionWrapper = $collectionWrapper;
if ($this->length > 0) {
$this->numChunks = (integer) ceil($this->length / $this->chunkSize);
$this->expectedLastChunkSize = ($this->length - (($this->numChunks - 1) * $this->chunkSize));
}
}
/**
* Return internal properties for debugging purposes.
*
* @see http://php.net/manual/en/language.oop5.magic.php#language.oop5.magic.debuginfo
* @return array
*/
public function __debugInfo()
{
return [
'bucketName' => $this->collectionWrapper->getBucketName(),
'databaseName' => $this->collectionWrapper->getDatabaseName(),
'file' => $this->file,
];
}
public function close()
{
// Nothing to do
}
/**
* Return the stream's file document.
*
* @return stdClass
*/
public function getFile()
{
return $this->file;
}
/**
* Return the stream's size in bytes.
*
* @return integer
*/
public function getSize()
{
return $this->length;
}
/**
* Return whether the current read position is at the end of the stream.
*
* @return boolean
*/
public function isEOF()
{
if ($this->chunkOffset === $this->numChunks - 1) {
return $this->bufferOffset >= $this->expectedLastChunkSize;
}
return $this->chunkOffset >= $this->numChunks;
}
/**
* Read bytes from the stream.
*
* Note: this method may return a string smaller than the requested length
* if data is not available to be read.
*
* @param integer $length Number of bytes to read
* @return string
* @throws InvalidArgumentException if $length is negative
*/
public function readBytes($length)
{
if ($length < 0) {
throw new InvalidArgumentException(sprintf('$length must be >= 0; given: %d', $length));
}
if ($this->chunksIterator === null) {
$this->initChunksIterator();
}
if ($this->buffer === null && ! $this->initBufferFromCurrentChunk()) {
return '';
}
$data = '';
while (strlen($data) < $length) {
if ($this->bufferOffset >= strlen($this->buffer) && ! $this->initBufferFromNextChunk()) {
break;
}
$initialDataLength = strlen($data);
$data .= substr($this->buffer, $this->bufferOffset, $length - $initialDataLength);
$this->bufferOffset += strlen($data) - $initialDataLength;
}
return $data;
}
/**
* Seeks the chunk and buffer offsets for the next read operation.
*
* @param integer $offset
* @throws InvalidArgumentException if $offset is out of range
*/
public function seek($offset)
{
if ($offset < 0 || $offset > $this->file->length) {
throw new InvalidArgumentException(sprintf('$offset must be >= 0 and <= %d; given: %d', $this->file->length, $offset));
}
/* Compute the offsets for the chunk and buffer (i.e. chunk data) from
* which we will expect to read after seeking. If the chunk offset
* changed, we'll also need to reset the buffer.
*/
$lastChunkOffset = $this->chunkOffset;
$this->chunkOffset = (integer) floor($offset / $this->chunkSize);
$this->bufferOffset = $offset % $this->chunkSize;
if ($lastChunkOffset === $this->chunkOffset) {
return;
}
if ($this->chunksIterator === null) {
return;
}
// Clear the buffer since the current chunk will be changed
$this->buffer = null;
/* If we are seeking to a previous chunk, we need to reinitialize the
* chunk iterator.
*/
if ($lastChunkOffset > $this->chunkOffset) {
$this->chunksIterator = null;
return;
}
/* If we are seeking to a subsequent chunk, we do not need to
* reinitalize the chunk iterator. Instead, we can simply move forward
* to $this->chunkOffset.
*/
$numChunks = $this->chunkOffset - $lastChunkOffset;
for ($i = 0; $i < $numChunks; $i++) {
$this->chunksIterator->next();
}
}
/**
* Return the current position of the stream.
*
* This is the offset within the stream where the next byte would be read.
*
* @return integer
*/
public function tell()
{
return ($this->chunkOffset * $this->chunkSize) + $this->bufferOffset;
}
/**
* Initialize the buffer to the current chunk's data.
*
* @return boolean Whether there was a current chunk to read
* @throws CorruptFileException if an expected chunk could not be read successfully
*/
private function initBufferFromCurrentChunk()
{
if ($this->chunkOffset === 0 && $this->numChunks === 0) {
return false;
}
if (! $this->chunksIterator->valid()) {
throw CorruptFileException::missingChunk($this->chunkOffset);
}
$currentChunk = $this->chunksIterator->current();
if ($currentChunk->n !== $this->chunkOffset) {
throw CorruptFileException::unexpectedIndex($currentChunk->n, $this->chunkOffset);
}
$this->buffer = $currentChunk->data->getData();
$actualChunkSize = strlen($this->buffer);
$expectedChunkSize = $this->chunkOffset === $this->numChunks - 1
? $this->expectedLastChunkSize
: $this->chunkSize;
if ($actualChunkSize !== $expectedChunkSize) {
throw CorruptFileException::unexpectedSize($actualChunkSize, $expectedChunkSize);
}
return true;
}
/**
* Advance to the next chunk and initialize the buffer to its data.
*
* @return boolean Whether there was a next chunk to read
* @throws CorruptFileException if an expected chunk could not be read successfully
*/
private function initBufferFromNextChunk()
{
if ($this->chunkOffset === $this->numChunks - 1) {
return false;
}
$this->bufferOffset = 0;
$this->chunkOffset++;
$this->chunksIterator->next();
return $this->initBufferFromCurrentChunk();
}
/**
* Initializes the chunk iterator starting from the current offset.
*/
private function initChunksIterator()
{
$cursor = $this->collectionWrapper->findChunksByFileId($this->file->_id, $this->chunkOffset);
$this->chunksIterator = new IteratorIterator($cursor);
$this->chunksIterator->rewind();
}
}