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   1  <?php
   2  
   3  namespace GuzzleHttp\Psr7;
   4  
   5  use Psr\Http\Message\StreamInterface;
   6  
   7  /**
   8   * Decorator used to return only a subset of a stream.
   9   *
  10   * @final
  11   */
  12  class LimitStream implements StreamInterface
  13  {
  14      use StreamDecoratorTrait;
  15  
  16      /** @var int Offset to start reading from */
  17      private $offset;
  18  
  19      /** @var int Limit the number of bytes that can be read */
  20      private $limit;
  21  
  22      /**
  23       * @param StreamInterface $stream Stream to wrap
  24       * @param int             $limit  Total number of bytes to allow to be read
  25       *                                from the stream. Pass -1 for no limit.
  26       * @param int             $offset Position to seek to before reading (only
  27       *                                works on seekable streams).
  28       */
  29      public function __construct(
  30          StreamInterface $stream,
  31          $limit = -1,
  32          $offset = 0
  33      ) {
  34          $this->stream = $stream;
  35          $this->setLimit($limit);
  36          $this->setOffset($offset);
  37      }
  38  
  39      public function eof()
  40      {
  41          // Always return true if the underlying stream is EOF
  42          if ($this->stream->eof()) {
  43              return true;
  44          }
  45  
  46          // No limit and the underlying stream is not at EOF
  47          if ($this->limit == -1) {
  48              return false;
  49          }
  50  
  51          return $this->stream->tell() >= $this->offset + $this->limit;
  52      }
  53  
  54      /**
  55       * Returns the size of the limited subset of data
  56       * {@inheritdoc}
  57       */
  58      public function getSize()
  59      {
  60          if (null === ($length = $this->stream->getSize())) {
  61              return null;
  62          } elseif ($this->limit == -1) {
  63              return $length - $this->offset;
  64          } else {
  65              return min($this->limit, $length - $this->offset);
  66          }
  67      }
  68  
  69      /**
  70       * Allow for a bounded seek on the read limited stream
  71       * {@inheritdoc}
  72       */
  73      public function seek($offset, $whence = SEEK_SET)
  74      {
  75          if ($whence !== SEEK_SET || $offset < 0) {
  76              throw new \RuntimeException(sprintf(
  77                  'Cannot seek to offset %s with whence %s',
  78                  $offset,
  79                  $whence
  80              ));
  81          }
  82  
  83          $offset += $this->offset;
  84  
  85          if ($this->limit !== -1) {
  86              if ($offset > $this->offset + $this->limit) {
  87                  $offset = $this->offset + $this->limit;
  88              }
  89          }
  90  
  91          $this->stream->seek($offset);
  92      }
  93  
  94      /**
  95       * Give a relative tell()
  96       * {@inheritdoc}
  97       */
  98      public function tell()
  99      {
 100          return $this->stream->tell() - $this->offset;
 101      }
 102  
 103      /**
 104       * Set the offset to start limiting from
 105       *
 106       * @param int $offset Offset to seek to and begin byte limiting from
 107       *
 108       * @throws \RuntimeException if the stream cannot be seeked.
 109       */
 110      public function setOffset($offset)
 111      {
 112          $current = $this->stream->tell();
 113  
 114          if ($current !== $offset) {
 115              // If the stream cannot seek to the offset position, then read to it
 116              if ($this->stream->isSeekable()) {
 117                  $this->stream->seek($offset);
 118              } elseif ($current > $offset) {
 119                  throw new \RuntimeException("Could not seek to stream offset $offset");
 120              } else {
 121                  $this->stream->read($offset - $current);
 122              }
 123          }
 124  
 125          $this->offset = $offset;
 126      }
 127  
 128      /**
 129       * Set the limit of bytes that the decorator allows to be read from the
 130       * stream.
 131       *
 132       * @param int $limit Number of bytes to allow to be read from the stream.
 133       *                   Use -1 for no limit.
 134       */
 135      public function setLimit($limit)
 136      {
 137          $this->limit = $limit;
 138      }
 139  
 140      public function read($length)
 141      {
 142          if ($this->limit == -1) {
 143              return $this->stream->read($length);
 144          }
 145  
 146          // Check if the current position is less than the total allowed
 147          // bytes + original offset
 148          $remaining = ($this->offset + $this->limit) - $this->stream->tell();
 149          if ($remaining > 0) {
 150              // Only return the amount of requested data, ensuring that the byte
 151              // limit is not exceeded
 152              return $this->stream->read(min($remaining, $length));
 153          }
 154  
 155          return '';
 156      }
 157  }