[Summary view]

   1  <?php
   2  
   3  declare(strict_types=1);
   4  
   5  namespace GuzzleHttp\Psr7;
   6  
   7  use Psr\Http\Message\StreamInterface;
   8  
   9  /**
  10   * Decorator used to return only a subset of a stream.
  11   */
  12  final 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      /** @var StreamInterface */
  23      private $stream;
  24  
  25      /**
  26       * @param StreamInterface $stream Stream to wrap
  27       * @param int             $limit  Total number of bytes to allow to be read
  28       *                                from the stream. Pass -1 for no limit.
  29       * @param int             $offset Position to seek to before reading (only
  30       *                                works on seekable streams).
  31       */
  32      public function __construct(
  33          StreamInterface $stream,
  34          int $limit = -1,
  35          int $offset = 0
  36      ) {
  37          $this->stream = $stream;
  38          $this->setLimit($limit);
  39          $this->setOffset($offset);
  40      }
  41  
  42      public function eof(): bool
  43      {
  44          // Always return true if the underlying stream is EOF
  45          if ($this->stream->eof()) {
  46              return true;
  47          }
  48  
  49          // No limit and the underlying stream is not at EOF
  50          if ($this->limit === -1) {
  51              return false;
  52          }
  53  
  54          return $this->stream->tell() >= $this->offset + $this->limit;
  55      }
  56  
  57      /**
  58       * Returns the size of the limited subset of data
  59       */
  60      public function getSize(): ?int
  61      {
  62          if (null === ($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 - $this->offset);
  68          }
  69      }
  70  
  71      /**
  72       * Allow for a bounded seek on the read limited stream
  73       */
  74      public function seek($offset, $whence = SEEK_SET): void
  75      {
  76          if ($whence !== SEEK_SET || $offset < 0) {
  77              throw new \RuntimeException(sprintf(
  78                  'Cannot seek to offset %s with whence %s',
  79                  $offset,
  80                  $whence
  81              ));
  82          }
  83  
  84          $offset += $this->offset;
  85  
  86          if ($this->limit !== -1) {
  87              if ($offset > $this->offset + $this->limit) {
  88                  $offset = $this->offset + $this->limit;
  89              }
  90          }
  91  
  92          $this->stream->seek($offset);
  93      }
  94  
  95      /**
  96       * Give a relative tell()
  97       */
  98      public function tell(): int
  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(int $offset): void
 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(int $limit): void
 136      {
 137          $this->limit = $limit;
 138      }
 139  
 140      public function read($length): string
 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  }