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   1  <?php
   2  namespace GuzzleHttp\Stream;
   3  
   4  use GuzzleHttp\Stream\Exception\SeekException;
   5  
   6  /**
   7   * Decorator used to return only a subset of a stream
   8   */
   9  class LimitStream implements StreamInterface
  10  {
  11      use StreamDecoratorTrait;
  12  
  13      /** @var int Offset to start reading from */
  14      private $offset;
  15  
  16      /** @var int Limit the number of bytes that can be read */
  17      private $limit;
  18  
  19      /**
  20       * @param StreamInterface $stream Stream to wrap
  21       * @param int             $limit  Total number of bytes to allow to be read
  22       *                                from the stream. Pass -1 for no limit.
  23       * @param int|null        $offset Position to seek to before reading (only
  24       *                                works on seekable streams).
  25       */
  26      public function __construct(
  27          StreamInterface $stream,
  28          $limit = -1,
  29          $offset = 0
  30      ) {
  31          $this->stream = $stream;
  32          $this->setLimit($limit);
  33          $this->setOffset($offset);
  34      }
  35  
  36      public function eof()
  37      {
  38          // Always return true if the underlying stream is EOF
  39          if ($this->stream->eof()) {
  40              return true;
  41          }
  42  
  43          // No limit and the underlying stream is not at EOF
  44          if ($this->limit == -1) {
  45              return false;
  46          }
  47  
  48          $tell = $this->stream->tell();
  49          if ($tell === false) {
  50              return false;
  51          }
  52  
  53          return $tell >= $this->offset + $this->limit;
  54      }
  55  
  56      /**
  57       * Returns the size of the limited subset of data
  58       * {@inheritdoc}
  59       */
  60      public function getSize()
  61      {
  62          if (null === ($length = $this->stream->getSize())) {
  63              return null;
  64          } elseif ($this->limit == -1) {
  65              return $length - $this->offset;
  66          } else {
  67              return min($this->limit, $length - $this->offset);
  68          }
  69      }
  70  
  71      /**
  72       * Allow for a bounded seek on the read limited stream
  73       * {@inheritdoc}
  74       */
  75      public function seek($offset, $whence = SEEK_SET)
  76      {
  77          if ($whence !== SEEK_SET || $offset < 0) {
  78              return false;
  79          }
  80  
  81          $offset += $this->offset;
  82  
  83          if ($this->limit !== -1) {
  84              if ($offset > $this->offset + $this->limit) {
  85                  $offset = $this->offset + $this->limit;
  86              }
  87          }
  88  
  89          return $this->stream->seek($offset);
  90      }
  91  
  92      /**
  93       * Give a relative tell()
  94       * {@inheritdoc}
  95       */
  96      public function tell()
  97      {
  98          return $this->stream->tell() - $this->offset;
  99      }
 100  
 101      /**
 102       * Set the offset to start limiting from
 103       *
 104       * @param int $offset Offset to seek to and begin byte limiting from
 105       *
 106       * @return self
 107       * @throws SeekException
 108       */
 109      public function setOffset($offset)
 110      {
 111          $current = $this->stream->tell();
 112  
 113          if ($current !== $offset) {
 114              // If the stream cannot seek to the offset position, then read to it
 115              if (!$this->stream->seek($offset)) {
 116                  if ($current > $offset) {
 117                      throw new SeekException($this, $offset);
 118                  } else {
 119                      $this->stream->read($offset - $current);
 120                  }
 121              }
 122          }
 123  
 124          $this->offset = $offset;
 125  
 126          return $this;
 127      }
 128  
 129      /**
 130       * Set the limit of bytes that the decorator allows to be read from the
 131       * stream.
 132       *
 133       * @param int $limit Number of bytes to allow to be read from the stream.
 134       *                   Use -1 for no limit.
 135       * @return self
 136       */
 137      public function setLimit($limit)
 138      {
 139          $this->limit = $limit;
 140  
 141          return $this;
 142      }
 143  
 144      public function read($length)
 145      {
 146          if ($this->limit == -1) {
 147              return $this->stream->read($length);
 148          }
 149  
 150          // Check if the current position is less than the total allowed
 151          // bytes + original offset
 152          $remaining = ($this->offset + $this->limit) - $this->stream->tell();
 153          if ($remaining > 0) {
 154              // Only return the amount of requested data, ensuring that the byte
 155              // limit is not exceeded
 156              return $this->stream->read(min($remaining, $length));
 157          } else {
 158              return false;
 159          }
 160      }
 161  }