124     function getData($length = -1)  argument
126         if ($length == -1) {
133         } else if ($length == 0) {
136             $data = gzread($this->gzfile, $length);
146     function skip($length = -1)  argument
148         if($length == -1) {
155             if (@gzseek($this->gzfile, $this->filePos + $length) === -1) {
156                 return parent::skip($length);
158                 $this->filePos += $length;
159                 return $length;
167     function rewind($length = -1)  argument
169         if ($length == -1) {
171                 return parent::rewind($length);
178             $length = min($length, $this->filePos);
179             if (@gzseek($this->gzfile, $this->filePos - $length) === -1) {
180                 return parent::rewind($length);
182                 $this->filePos -= $length;
183                 return $length;
235         foreach ($blocks as $length) {
237                 $expectedPos = $this->filePos + $length;
243                 $this->skip($length);