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      1 <?php
      2 /*
      3  * Copyright 2015 Google Inc.
      4  *
      5  * Licensed under the Apache License, Version 2.0 (the "License");
      6  * you may not use this file except in compliance with the License.
      7  * You may obtain a copy of the License at
      8  *
      9  *     http://www.apache.org/licenses/LICENSE-2.0
     10  *
     11  * Unless required by applicable law or agreed to in writing, software
     12  * distributed under the License is distributed on an "AS IS" BASIS,
     13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     14  * See the License for the specific language governing permissions and
     15  * limitations under the License.
     16  */
     17 
     18 namespace Google\FlatBuffers;
     19 
     20 abstract class Table
     21 {
     22     /**
     23      * @var int $bb_pos
     24      */
     25     protected $bb_pos;
     26     /**
     27      * @var ByteBuffer $bb
     28      */
     29     protected $bb;
     30 
     31     public function __construct()
     32     {
     33     }
     34 
     35     /**
     36      * returns actual vtable offset
     37      *
     38      * @param $vtable_offset
     39      * @return int offset > 0 means exist value. 0 means not exist
     40      */
     41     protected function __offset($vtable_offset)
     42     {
     43         $vtable = $this->bb_pos - $this->bb->getInt($this->bb_pos);
     44         return $vtable_offset < $this->bb->getShort($vtable) ? $this->bb->getShort($vtable + $vtable_offset) : 0;
     45     }
     46 
     47     /**
     48      * @param $offset
     49      * @return mixed
     50      */
     51     protected function __indirect($offset)
     52     {
     53         return $offset + $this->bb->getInt($offset);
     54     }
     55 
     56     /**
     57      * fetch utf8 encoded string.
     58      *
     59      * @param $offset
     60      * @return string
     61      */
     62     protected function __string($offset)
     63     {
     64         $offset += $this->bb->getInt($offset);
     65         $len = $this->bb->getInt($offset);
     66         $startPos = $offset + Constants::SIZEOF_INT;
     67         return substr($this->bb->_buffer, $startPos, $len);
     68     }
     69 
     70     /**
     71      * @param $offset
     72      * @return int
     73      */
     74     protected function __vector_len($offset)
     75     {
     76         $offset += $this->bb_pos;
     77         $offset += $this->bb->getInt($offset);
     78         return $this->bb->getInt($offset);
     79     }
     80 
     81     /**
     82      * @param $offset
     83      * @return int
     84      */
     85     protected function __vector($offset)
     86     {
     87         $offset += $this->bb_pos;
     88         // data starts after the length
     89         return $offset + $this->bb->getInt($offset) + Constants::SIZEOF_INT;
     90     }
     91 
     92     protected function __vector_as_bytes($vector_offset, $elem_size=1)
     93     {
     94         $o = $this->__offset($vector_offset);
     95         if ($o == 0) {
     96             return null;
     97         }
     98 
     99         return substr($this->bb->_buffer, $this->__vector($o), $this->__vector_len($o) * $elem_size);
    100     }
    101 
    102     /**
    103      * @param Table $table
    104      * @param int $offset
    105      * @return Table
    106      */
    107     protected function __union($table, $offset)
    108     {
    109         $offset += $this->bb_pos;
    110         $table->bb_pos = $offset + $this->bb->getInt($offset);
    111         $table->bb = $this->bb;
    112         return $table;
    113     }
    114 
    115     /**
    116      * @param ByteBuffer $bb
    117      * @param string $ident
    118      * @return bool
    119      * @throws \ArgumentException
    120      */
    121     protected static function __has_identifier($bb, $ident)
    122     {
    123         if (strlen($ident) != Constants::FILE_IDENTIFIER_LENGTH) {
    124             throw new \ArgumentException("FlatBuffers: file identifier must be length "  . Constants::FILE_IDENTIFIER_LENGTH);
    125         }
    126 
    127         for ($i = 0; $i < 4; $i++) {
    128             if ($ident[$i] != $bb->get($bb->getPosition() + Constants::SIZEOF_INT + $i)) {
    129                 return false;
    130             }
    131         }
    132 
    133         return true;
    134     }
    135 }
    136