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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 /// @file
     19 /// @addtogroup flatbuffers_php_api
     20 /// @{
     21 
     22 namespace Google\FlatBuffers;
     23 
     24 class FlatbufferBuilder
     25 {
     26     /**
     27      * Internal ByteBuffer for the FlatBuffer data.
     28      * @var ByteBuffer $bb
     29      */
     30     public $bb;
     31 
     32     /// @cond FLATBUFFERS_INTERNAL
     33     /**
     34      * @var int $space
     35      */
     36     protected $space;
     37 
     38     /**
     39      * @var int $minalign
     40      */
     41     protected $minalign = 1;
     42 
     43     /**
     44      * @var array $vtable
     45      */
     46     protected $vtable;
     47 
     48     /**
     49      * @var int $vtable_in_use
     50      */
     51     protected $vtable_in_use = 0;
     52 
     53     /**
     54      * @var bool $nested
     55      */
     56     protected $nested = false;
     57 
     58     /**
     59      * @var int $object_start
     60      */
     61     protected $object_start;
     62 
     63     /**
     64      * @var array $vtables
     65      */
     66     protected $vtables = array();
     67 
     68     /**
     69      * @var int $num_vtables
     70      */
     71     protected $num_vtables = 0;
     72 
     73     /**
     74      * @var int $vector_num_elems
     75      */
     76     protected $vector_num_elems = 0;
     77 
     78     /**
     79      * @var bool $force_defaults
     80      */
     81     protected $force_defaults = false;
     82     /// @endcond
     83 
     84     /**
     85      * Create a FlatBufferBuilder with a given initial size.
     86      *
     87      * @param $initial_size initial byte buffer size.
     88      */
     89     public function __construct($initial_size)
     90     {
     91         if ($initial_size <= 0) {
     92             $initial_size = 1;
     93         }
     94         $this->space = $initial_size;
     95         $this->bb = $this->newByteBuffer($initial_size);
     96     }
     97 
     98     /// @cond FLATBUFFERS_INTERNAL
     99     /**
    100      * create new bytebuffer
    101      *
    102      * @param $size
    103      * @return ByteBuffer
    104      */
    105     private function newByteBuffer($size)
    106     {
    107         return new ByteBuffer($size);
    108     }
    109 
    110     /**
    111      * Returns the current ByteBuffer offset.
    112      *
    113      * @return int
    114      */
    115     public function offset()
    116     {
    117         return $this->bb->capacity() - $this->space;
    118     }
    119 
    120     /**
    121      * padding buffer
    122      *
    123      * @param $byte_size
    124      */
    125     public function pad($byte_size)
    126     {
    127         for ($i = 0; $i < $byte_size; $i++) {
    128             $this->bb->putByte(--$this->space, "\0");
    129         }
    130     }
    131 
    132     /**
    133      * prepare bytebuffer
    134      *
    135      * @param $size
    136      * @param $additional_bytes
    137      * @throws \Exception
    138      */
    139     public function prep($size, $additional_bytes)
    140     {
    141         if ($size > $this->minalign) {
    142             $this->minalign = $size;
    143         }
    144 
    145         $align_size = ((~($this->bb->capacity() - $this->space + $additional_bytes)) + 1) & ($size - 1);
    146         while ($this->space < $align_size + $size  + $additional_bytes) {
    147             $old_buf_size = $this->bb->capacity();
    148             $this->bb = $this->growByteBuffer($this->bb);
    149             $this->space += $this->bb->capacity() - $old_buf_size;
    150         }
    151 
    152         $this->pad($align_size);
    153     }
    154 
    155     /**
    156      * @param ByteBuffer $bb
    157      * @return ByteBuffer
    158      * @throws \Exception
    159      */
    160     private static function growByteBuffer(ByteBuffer $bb)
    161     {
    162         $old_buf_size = $bb->capacity();
    163         if (($old_buf_size & 0xC0000000) != 0) {
    164             throw new \Exception("FlatBuffers: cannot grow buffer beyond 2 gigabytes");
    165         }
    166         $new_buf_size = $old_buf_size << 1;
    167 
    168         $bb->setPosition(0);
    169         $nbb = new ByteBuffer($new_buf_size);
    170 
    171         $nbb->setPosition($new_buf_size - $old_buf_size);
    172 
    173         // TODO(chobie): is this little bit faster?
    174         //$nbb->_buffer = substr_replace($nbb->_buffer, $bb->_buffer, $new_buf_size - $old_buf_size, strlen($bb->_buffer));
    175         for ($i = $new_buf_size - $old_buf_size, $j = 0; $j < strlen($bb->_buffer); $i++, $j++) {
    176             $nbb->_buffer[$i] = $bb->_buffer[$j];
    177         }
    178 
    179         return $nbb;
    180     }
    181 
    182     /**
    183      * @param $x
    184      */
    185     public function putBool($x)
    186     {
    187         $this->bb->put($this->space -= 1, chr((int)(bool)($x)));
    188     }
    189 
    190     /**
    191      * @param $x
    192      */
    193     public function putByte($x)
    194     {
    195         $this->bb->put($this->space -= 1, chr($x));
    196     }
    197 
    198     /**
    199      * @param $x
    200      */
    201     public function putSbyte($x)
    202     {
    203         $this->bb->put($this->space -= 1, chr($x));
    204     }
    205 
    206     /**
    207      * @param $x
    208      */
    209     public function putShort($x)
    210     {
    211         $this->bb->putShort($this->space -= 2, $x);
    212     }
    213 
    214     /**
    215      * @param $x
    216      */
    217     public function putUshort($x)
    218     {
    219         $this->bb->putUshort($this->space -= 2, $x);
    220     }
    221 
    222     /**
    223      * @param $x
    224      */
    225     public function putInt($x)
    226     {
    227         $this->bb->putInt($this->space -= 4, $x);
    228     }
    229 
    230     /**
    231      * @param $x
    232      */
    233     public function putUint($x)
    234     {
    235         if ($x > PHP_INT_MAX) {
    236             throw new \InvalidArgumentException("your platform can't handle uint correctly. use 64bit machine.");
    237         }
    238 
    239         $this->bb->putUint($this->space -= 4, $x);
    240     }
    241 
    242     /**
    243      * @param $x
    244      */
    245     public function putLong($x)
    246     {
    247         if ($x > PHP_INT_MAX) {
    248             throw new \InvalidArgumentException("Your platform can't handle long correctly. Use a 64bit machine.");
    249         }
    250 
    251         $this->bb->putLong($this->space -= 8, $x);
    252     }
    253 
    254     /**
    255      * @param $x
    256      */
    257     public function putUlong($x)
    258     {
    259         if ($x > PHP_INT_MAX) {
    260             throw new \InvalidArgumentException("Your platform can't handle ulong correctly. This is a php limitation. Please wait for the extension release.");
    261         }
    262 
    263         $this->bb->putUlong($this->space -= 8, $x);
    264     }
    265 
    266     /**
    267      * @param $x
    268      */
    269     public function putFloat($x)
    270     {
    271         $this->bb->putFloat($this->space -= 4, $x);
    272     }
    273 
    274     /**
    275      * @param $x
    276      */
    277     public function putDouble($x)
    278     {
    279         $this->bb->putDouble($this->space -= 8, $x);
    280     }
    281     /// @endcond
    282 
    283     /**
    284      * Add a `bool` to the buffer, properly aligned, and grows the buffer (if necessary).
    285      * @param $x The `bool` to add to the buffer.
    286      */
    287     public function addBool($x)
    288     {
    289         $this->prep(1, 0);
    290         $this->putBool($x);
    291     }
    292 
    293     /**
    294      * Add a `byte` to the buffer, properly aligned, and grows the buffer (if necessary).
    295      * @param $x The `byte` to add to the buffer.
    296      */
    297     public function addByte($x)
    298     {
    299         $this->prep(1, 0);
    300         $this->putByte($x);
    301     }
    302 
    303     /**
    304      * Add a `signed byte` to the buffer, properly aligned, and grows the buffer (if necessary).
    305      * @param $x The `signed byte` to add to the buffer.
    306      */
    307     public function addSbyte($x)
    308     {
    309         $this->prep(1, 0);
    310         $this->putSbyte($x);
    311     }
    312 
    313     /**
    314      * Add a `short` to the buffer, properly aligned, and grows the buffer (if necessary).
    315      * @param $x The `short` to add to the buffer.
    316      */
    317     public function addShort($x)
    318     {
    319         $this->prep(2, 0);
    320         $this->putShort($x);
    321     }
    322 
    323     /**
    324      * Add an `unsigned short` to the buffer, properly aligned, and grows the buffer (if necessary).
    325      * @param $x The `unsigned short` to add to the buffer.
    326      */
    327     public function addUshort($x)
    328     {
    329         $this->prep(2, 0);
    330         $this->putUshort($x);
    331     }
    332 
    333     /**
    334      * Add an `int` to the buffer, properly aligned, and grows the buffer (if necessary).
    335      * @param $x The `int` to add to the buffer.
    336      */
    337     public function addInt($x)
    338     {
    339         $this->prep(4, 0);
    340         $this->putInt($x);
    341     }
    342 
    343     /**
    344      * Add an `unsigned int` to the buffer, properly aligned, and grows the buffer (if necessary).
    345      * @param $x The `unsigned int` to add to the buffer.
    346      */
    347     public function addUint($x)
    348     {
    349         $this->prep(4, 0);
    350         $this->putUint($x);
    351     }
    352 
    353     /**
    354      * Add a `long` to the buffer, properly aligned, and grows the buffer (if necessary).
    355      * @param $x The `long` to add to the buffer.
    356      */
    357     public function addLong($x)
    358     {
    359         $this->prep(8, 0);
    360         $this->putLong($x);
    361     }
    362 
    363     /**
    364      * Add an `unsigned long` to the buffer, properly aligned, and grows the buffer (if necessary).
    365      * @param $x The `unsigned long` to add to the buffer.
    366      */
    367     public function addUlong($x)
    368     {
    369         $this->prep(8, 0);
    370         $this->putUlong($x);
    371     }
    372 
    373     /**
    374      * Add a `float` to the buffer, properly aligned, and grows the buffer (if necessary).
    375      * @param $x The `float` to add to the buffer.
    376      */
    377     public function addFloat($x)
    378     {
    379         $this->prep(4, 0);
    380         $this->putFloat($x);
    381     }
    382 
    383     /**
    384      * Add a `double` to the buffer, properly aligned, and grows the buffer (if necessary).
    385      * @param $x The `double` to add to the buffer.
    386      */
    387     public function addDouble($x)
    388     {
    389         $this->prep(8, 0);
    390         $this->putDouble($x);
    391     }
    392 
    393     /// @cond FLATBUFFERS_INTERNAL
    394     /**
    395      * @param $o
    396      * @param $x
    397      * @param $d
    398      */
    399     public function addBoolX($o, $x, $d)
    400     {
    401         if ($this->force_defaults || $x != $d) {
    402             $this->addBool($x);
    403             $this->slot($o);
    404         }
    405     }
    406 
    407     /**
    408      * @param $o
    409      * @param $x
    410      * @param $d
    411      */
    412     public function addByteX($o, $x, $d)
    413     {
    414         if ($this->force_defaults || $x != $d) {
    415             $this->addByte($x);
    416             $this->slot($o);
    417         }
    418     }
    419 
    420     /**
    421      * @param $o
    422      * @param $x
    423      * @param $d
    424      */
    425     public function addSbyteX($o, $x, $d)
    426     {
    427         if ($this->force_defaults || $x != $d) {
    428             $this->addSbyte($x);
    429             $this->slot($o);
    430         }
    431     }
    432 
    433     /**
    434      * @param $o
    435      * @param $x
    436      * @param $d
    437      */
    438     public function addShortX($o, $x, $d)
    439     {
    440         if ($this->force_defaults || $x != $d) {
    441             $this->addShort($x);
    442             $this->slot($o);
    443         }
    444     }
    445 
    446     /**
    447      * @param $o
    448      * @param $x
    449      * @param $d
    450      */
    451     public function addUshortX($o, $x, $d)
    452     {
    453         if ($this->force_defaults || $x != $d) {
    454             $this->addUshort($x);
    455             $this->slot($o);
    456         }
    457     }
    458 
    459     /**
    460      * @param $o
    461      * @param $x
    462      * @param $d
    463      */
    464     public function addIntX($o, $x, $d)
    465     {
    466         if ($this->force_defaults || $x != $d) {
    467             $this->addInt($x);
    468             $this->slot($o);
    469         }
    470     }
    471 
    472     /**
    473      * @param $o
    474      * @param $x
    475      * @param $d
    476      */
    477     public function addUintX($o, $x, $d)
    478     {
    479         if ($this->force_defaults || $x != $d) {
    480             $this->addUint($x);
    481             $this->slot($o);
    482         }
    483     }
    484 
    485     /**
    486      * @param $o
    487      * @param $x
    488      * @param $d
    489      */
    490     public function addLongX($o, $x, $d)
    491     {
    492         if ($this->force_defaults || $x != $d) {
    493             $this->addLong($x);
    494             $this->slot($o);
    495         }
    496     }
    497 
    498     /**
    499      * @param $o
    500      * @param $x
    501      * @param $d
    502      */
    503     public function addUlongX($o, $x, $d)
    504     {
    505         if ($this->force_defaults || $x != $d) {
    506             $this->addUlong($x);
    507             $this->slot($o);
    508         }
    509     }
    510 
    511 
    512     /**
    513      * @param $o
    514      * @param $x
    515      * @param $d
    516      */
    517     public function addFloatX($o, $x, $d)
    518     {
    519         if ($this->force_defaults || $x != $d) {
    520             $this->addFloat($x);
    521             $this->slot($o);
    522         }
    523     }
    524 
    525     /**
    526      * @param $o
    527      * @param $x
    528      * @param $d
    529      */
    530     public function addDoubleX($o, $x, $d)
    531     {
    532         if ($this->force_defaults || $x != $d) {
    533             $this->addDouble($x);
    534             $this->slot($o);
    535         }
    536     }
    537 
    538     /**
    539      * @param $o
    540      * @param $x
    541      * @param $d
    542      * @throws \Exception
    543      */
    544     public function addOffsetX($o, $x, $d)
    545     {
    546         if ($this->force_defaults || $x != $d) {
    547             $this->addOffset($x);
    548             $this->slot($o);
    549         }
    550     }
    551     /// @endcond
    552 
    553     /**
    554      * Adds on offset, relative to where it will be written.
    555      * @param $off The offset to add to the buffer.
    556      * @throws \Exception Throws an exception if `$off` is greater than the underlying ByteBuffer's
    557      * offest.
    558      */
    559     public function addOffset($off)
    560     {
    561         $this->prep(Constants::SIZEOF_INT, 0); // Ensure alignment is already done
    562         if ($off > $this->offset()) {
    563             throw new \Exception("");
    564         }
    565 
    566         $off = $this->offset() - $off + Constants::SIZEOF_INT;
    567         $this->putInt($off);
    568     }
    569 
    570     /// @cond FLATBUFFERS_INTERNAL
    571     /**
    572      * @param $elem_size
    573      * @param $num_elems
    574      * @param $alignment
    575      * @throws \Exception
    576      */
    577     public function startVector($elem_size, $num_elems, $alignment)
    578     {
    579         $this->notNested();
    580         $this->vector_num_elems = $num_elems;
    581         $this->prep(Constants::SIZEOF_INT, $elem_size * $num_elems);
    582         $this->prep($alignment, $elem_size * $num_elems); // Just in case alignemnt > int;
    583     }
    584 
    585     /**
    586      * @return int
    587      */
    588     public function endVector()
    589     {
    590         $this->putUint($this->vector_num_elems);
    591         return $this->offset();
    592     }
    593 
    594     protected function is_utf8($bytes)
    595     {
    596         if (function_exists('mb_detect_encoding')) {
    597             return (bool) mb_detect_encoding($bytes, 'UTF-8', true);
    598         }
    599 
    600         $len = strlen($bytes);
    601         if ($len < 1) {
    602             /* NOTE: always return 1 when passed string is null */
    603             return true;
    604         }
    605 
    606         for ($j = 0, $i = 0; $i < $len; $i++) {
    607             // check ACII
    608             if ($bytes[$j] == "\x09" ||
    609                 $bytes[$j] == "\x0A" ||
    610                 $bytes[$j] == "\x0D" ||
    611                 ($bytes[$j] >= "\x20" && $bytes[$j] <= "\x7E")) {
    612                 $j++;
    613                 continue;
    614             }
    615 
    616             /* non-overlong 2-byte */
    617             if ((($i+1) <= $len) &&
    618                 ($bytes[$j] >= "\xC2" && $bytes[$j] <= "\xDF" &&
    619                     ($bytes[$j+1] >= "\x80" && $bytes[$j+1] <= "\xBF"))) {
    620                 $j += 2;
    621                 $i++;
    622                 continue;
    623             }
    624 
    625             /* excluding overlongs */
    626             if ((($i + 2) <= $len) &&
    627                 $bytes[$j] == "\xE0" &&
    628                 ($bytes[$j+1] >= "\xA0" && $bytes[$j+1] <= "\xBF" &&
    629                     ($bytes[$j+2] >= "\x80" && $bytes[$j+2] <= "\xBF"))) {
    630                 $bytes += 3;
    631                 $i +=2;
    632                 continue;
    633             }
    634 
    635             /* straight 3-byte */
    636             if ((($i+2) <= $len) &&
    637                 (($bytes[$j] >= "\xE1" && $bytes[$j] <= "\xEC") ||
    638                     $bytes[$j] == "\xEE" ||
    639                     $bytes[$j] = "\xEF") &&
    640                 ($bytes[$j+1] >= "\x80" && $bytes[$j+1] <= "\xBF") &&
    641                 ($bytes[$j+2] >= "\x80" && $bytes[$j+2] <= "\xBF")) {
    642                 $j += 3;
    643                 $i += 2;
    644                 continue;
    645             }
    646 
    647             /* excluding surrogates */
    648             if ((($i+2) <= $len) &&
    649                 $bytes[$j] == "\xED" &&
    650                 ($bytes[$j+1] >= "\x80" && $bytes[$j+1] <= "\x9f" &&
    651                     ($bytes[$j+2] >= "\x80" && $bytes[$j+2] <= "\xBF"))) {
    652                 $j += 3;
    653                 $i += 2;
    654                 continue;
    655             }
    656 
    657             /* planes 1-3 */
    658             if ((($i + 3) <= $len) &&
    659                 $bytes[$j] == "\xF0" &&
    660                 ($bytes[$j+1] >= "\x90" && $bytes[$j+1] <= "\xBF") &&
    661                 ($bytes[$j+2] >= "\x80" && $bytes[$j+2] <= "\xBF") &&
    662                 ($bytes[$j+3] >= "\x80" && $bytes[$j+3] <= "\xBF")) {
    663                 $j += 4;
    664                 $i += 3;
    665                 continue;
    666             }
    667 
    668 
    669             /* planes 4-15 */
    670             if ((($i+3) <= $len) &&
    671                 $bytes[$j] >= "\xF1" && $bytes[$j] <= "\xF3" &&
    672                 $bytes[$j+1] >= "\x80" && $bytes[$j+1] <= "\xBF" &&
    673                 $bytes[$j+2] >= "\x80" && $bytes[$j+2] <= "\xBF" &&
    674                 $bytes[$j+3] >= "\x80" && $bytes[$j+3] <= "\xBF"
    675             ) {
    676                 $j += 4;
    677                 $i += 3;
    678                 continue;
    679             }
    680 
    681             /* plane 16 */
    682             if ((($i+3) <= $len) &&
    683                 $bytes[$j] == "\xF4" &&
    684                 ($bytes[$j+1] >= "\x80" && $bytes[$j+1] <= "\x8F") &&
    685                 ($bytes[$j+2] >= "\x80" && $bytes[$j+2] <= "\xBF") &&
    686                 ($bytes[$j+3] >= "\x80" && $bytes[$j+3] <= "\xBF")
    687             ) {
    688                 $bytes += 4;
    689                 $i += 3;
    690                 continue;
    691             }
    692 
    693 
    694             return false;
    695         }
    696 
    697         return true;
    698     }
    699     /// @endcond
    700 
    701     /**
    702      * Encode the string `$s` in the buffer using UTF-8.
    703      * @param string $s The string to encode.
    704      * @return int The offset in the buffer where the encoded string starts.
    705      * @throws InvalidArgumentException Thrown if the input string `$s` is not
    706      *     UTF-8.
    707      */
    708     public function createString($s)
    709     {
    710         if (!$this->is_utf8($s)) {
    711             throw new \InvalidArgumentException("string must be utf-8 encoded value.");
    712         }
    713 
    714         $this->notNested();
    715         $this->addByte(0); // null terminated
    716         $this->startVector(1, strlen($s), 1);
    717         $this->space -= strlen($s);
    718         for ($i =  $this->space, $j = 0 ; $j < strlen($s) ; $i++, $j++) {
    719             $this->bb->_buffer[$i] = $s[$j];
    720         }
    721         return $this->endVector();
    722     }
    723 
    724     /// @cond FLATBUFFERS_INTERNAL
    725     /**
    726      * @throws \Exception
    727      */
    728     public function notNested()
    729     {
    730         if ($this->nested) {
    731             throw new \Exception("FlatBuffers; object serialization must not be nested");
    732         }
    733     }
    734 
    735     /**
    736      * @param $obj
    737      * @throws \Exception
    738      */
    739     public function nested($obj)
    740     {
    741         if ($obj != $this->offset()) {
    742             throw new \Exception("FlatBuffers: struct must be serialized inline");
    743         }
    744     }
    745 
    746     /**
    747      * @param $numfields
    748      * @throws \Exception
    749      */
    750     public function startObject($numfields)
    751     {
    752         $this->notNested();
    753         if ($this->vtable == null || count($this->vtable) < $numfields) {
    754             $this->vtable = array();
    755         }
    756 
    757         $this->vtable_in_use = $numfields;
    758         for ($i = 0; $i < $numfields; $i++) {
    759             $this->vtable[$i] = 0;
    760         }
    761 
    762         $this->nested = true;
    763         $this->object_start = $this->offset();
    764     }
    765 
    766     /**
    767      * @param $voffset
    768      * @param $x
    769      * @param $d
    770      * @throws \Exception
    771      */
    772     public function addStructX($voffset, $x, $d)
    773     {
    774         if ($x != $d) {
    775             $this->nested($x);
    776             $this->slot($voffset);
    777         }
    778     }
    779 
    780     /**
    781      * @param $voffset
    782      * @param $x
    783      * @param $d
    784      * @throws \Exception
    785      */
    786     public function addStruct($voffset, $x, $d)
    787     {
    788         if ($x != $d) {
    789             $this->nested($x);
    790             $this->slot($voffset);
    791         }
    792     }
    793 
    794     /**
    795      * @param $voffset
    796      */
    797     public function slot($voffset)
    798     {
    799         $this->vtable[$voffset] = $this->offset();
    800     }
    801 
    802     /**
    803      * @return int
    804      * @throws \Exception
    805      */
    806     public function endObject()
    807     {
    808         if ($this->vtable == null || !$this->nested) {
    809             throw new \Exception("FlatBuffers: endObject called without startObject");
    810         }
    811 
    812         $this->addInt(0);
    813         $vtableloc = $this->offset();
    814 
    815         $i = $this->vtable_in_use -1;
    816         // Trim trailing zeroes.
    817         for (; $i >= 0 && $this->vtable[$i] == 0; $i--) {}
    818         $trimmed_size = $i + 1;
    819         for (; $i >= 0; $i--) {
    820             $off = ($this->vtable[$i] != 0) ? $vtableloc - $this->vtable[$i] : 0;
    821             $this->addShort($off);
    822         }
    823 
    824         $standard_fields = 2; // the fields below
    825         $this->addShort($vtableloc - $this->object_start);
    826         $this->addShort(($trimmed_size + $standard_fields) * Constants::SIZEOF_SHORT);
    827 
    828         // search for an existing vtable that matches the current one.
    829         $existing_vtable = 0;
    830 
    831         for ($i = 0; $i < $this->num_vtables; $i++) {
    832             $vt1 = $this->bb->capacity() - $this->vtables[$i];
    833             $vt2 = $this->space;
    834 
    835             $len = $this->bb->getShort($vt1);
    836 
    837             if ($len == $this->bb->getShort($vt2)) {
    838                 for ($j = Constants::SIZEOF_SHORT; $j < $len; $j += Constants::SIZEOF_SHORT) {
    839                     if ($this->bb->getShort($vt1 + $j) != $this->bb->getShort($vt2 + $j)) {
    840                         continue 2;
    841                     }
    842                 }
    843                 $existing_vtable = $this->vtables[$i];
    844                 break;
    845             }
    846         }
    847 
    848         if ($existing_vtable != 0) {
    849             // Found a match:
    850             // Remove the current vtable
    851             $this->space = $this->bb->capacity() - $vtableloc;
    852             $this->bb->putInt($this->space, $existing_vtable - $vtableloc);
    853         } else {
    854             // No Match:
    855             // Add the location of the current vtable to the list of vtables
    856             if ($this->num_vtables == count($this->vtables)) {
    857                 $vtables = $this->vtables;
    858                 $this->vtables = array();
    859                 // copy of
    860                 for ($i = 0; $i < count($vtables) * 2; $i++) {
    861                     $this->vtables[$i] = ($i < count($vtables)) ? $vtables[$i] : 0;
    862                 }
    863             }
    864             $this->vtables[$this->num_vtables++] = $this->offset();
    865             $this->bb->putInt($this->bb->capacity() - $vtableloc, $this->offset() - $vtableloc);
    866         }
    867 
    868         $this->nested = false;
    869         $this->vtable = null;
    870         return $vtableloc;
    871     }
    872 
    873     /**
    874      * @param $table
    875      * @param $field
    876      * @throws \Exception
    877      */
    878     public function required($table, $field)
    879     {
    880         $table_start = $this->bb->capacity() - $table;
    881         $vtable_start = $table_start - $this->bb->getInt($table_start);
    882         $ok = $this->bb->getShort($vtable_start + $field) != 0;
    883 
    884         if (!$ok) {
    885             throw new \Exception("FlatBuffers: field "  . $field  .  " must be set");
    886         }
    887     }
    888     /// @endcond
    889 
    890     /**
    891      * Finalize a buffer, pointing to the given `$root_table`.
    892      * @param $root_table An offest to be added to the buffer.
    893      * @param $file_identifier A FlatBuffer file identifier to be added to the
    894      *     buffer before `$root_table`. This defaults to `null`.
    895      * @throws InvalidArgumentException Thrown if an invalid `$identifier` is
    896      *     given, where its length is not equal to
    897      *    `Constants::FILE_IDENTIFIER_LENGTH`.
    898      */
    899     public function finish($root_table, $identifier = null)
    900     {
    901         if ($identifier == null) {
    902             $this->prep($this->minalign, Constants::SIZEOF_INT);
    903             $this->addOffset($root_table);
    904             $this->bb->setPosition($this->space);
    905         } else {
    906             $this->prep($this->minalign, Constants::SIZEOF_INT + Constants::FILE_IDENTIFIER_LENGTH);
    907             if (strlen($identifier) != Constants::FILE_IDENTIFIER_LENGTH) {
    908                 throw new \InvalidArgumentException(
    909                     sprintf("FlatBuffers: file identifier must be length %d",
    910                         Constants::FILE_IDENTIFIER_LENGTH));
    911             }
    912 
    913             for ($i = Constants::FILE_IDENTIFIER_LENGTH - 1; $i >= 0;
    914                   $i--) {
    915                 $this->addByte(ord($identifier[$i]));
    916             }
    917             $this->finish($root_table);
    918         }
    919     }
    920 
    921     /**
    922      * In order to save space, fields that are set to their default value don't
    923      * get serialized into the buffer.
    924      * @param bool $forceDefaults When set to `true`, always serializes default
    925      *     values.
    926      */
    927     public function forceDefaults($forceDefaults)
    928     {
    929         $this->force_defaults = $forceDefaults;
    930     }
    931 
    932     /**
    933      * Get the ByteBuffer representing the FlatBuffer.
    934      * @return ByteBuffer The ByteBuffer containing the FlatBuffer data.
    935      */
    936     public function dataBuffer()
    937     {
    938         return $this->bb;
    939     }
    940 
    941     /// @cond FLATBUFFERS_INTERNAL
    942     /**
    943      * @return int
    944      */
    945     public function dataStart()
    946     {
    947         return $this->space;
    948     }
    949     /// @endcond
    950 
    951     /**
    952      * Utility function to copy and return the FlatBuffer data from the
    953      * underlying ByteBuffer.
    954      * @return string A string (representing a byte[]) that contains a copy
    955      * of the FlatBuffer data.
    956      */
    957     public function sizedByteArray()
    958     {
    959         $start = $this->space;
    960         $length = $this->bb->capacity() - $this->space;
    961 
    962         $result = str_repeat("\0", $length);
    963         $this->bb->setPosition($start);
    964         $this->bb->getX($result);
    965 
    966         return $result;
    967     }
    968 }
    969 
    970 /// @}
    971