hphp/runtime/base/ref-data.h

   1 /*
   2    +----------------------------------------------------------------------+
   3    | HipHop for PHP                                                       |
   4    +----------------------------------------------------------------------+
   5    | Copyright (c) 2010-present Facebook, Inc. (http://www.facebook.com)  |
   6    +----------------------------------------------------------------------+
   7    | This source file is subject to version 3.01 of the PHP license,      |
   8    | that is bundled with this package in the file LICENSE, and is        |
   9    | available through the world-wide-web at the following url:           |
  10    | http://www.php.net/license/3_01.txt                                  |
  11    | If you did not receive a copy of the PHP license and are unable to   |
  12    | obtain it through the world-wide-web, please send a note to          |
  13    | license@php.net so we can mail you a copy immediately.               |
  14    +----------------------------------------------------------------------+
  15 */
  16
  17 #ifndef incl_HPHP_REF_DATA_H
  18 #define incl_HPHP_REF_DATA_H
  19
  20 #include "hphp/runtime/base/countable.h"
  21 #include "hphp/runtime/base/memory-manager.h"
  22 #include "hphp/runtime/base/typed-value.h"
  23
  24 namespace HPHP {
  25
  26 struct Variant;
  27
  28 /*
  29  * We heap allocate a RefData when we make a reference to something.
  30  * A Variant or TypedValue can be KindOfRef and point to a RefData,
  31  * but the value held here must not be KindOfRef.
  32  *
  33  * Note that a RefData should never contain KindOfUninit.
  34  */
  35 struct RefData final : Countable, type_scan::MarkScannableCollectable<RefData> {
  36   /*
  37    * Create a RefData, allocated in the request local heap.
  38    */
  39   static RefData* Make(Cell v) {
  40     assertx(cellIsPlausible(v));
  41     return new (tl_heap->objMalloc(sizeof(RefData)))
  42       RefData(v.m_type, v.m_data.num);
  43   }
  44
  45   ~RefData();
  46
  47   /*
  48    * Deallocate a RefData.
  49    */
  50   void release() noexcept {
  51     assertx(kindIsValid());
  52     this->~RefData();
  53     tl_heap->objFree(this, sizeof(RefData));
  54     AARCH64_WALKABLE_FRAME();
  55   }
  56
  57   ALWAYS_INLINE void decRefAndRelease() {
  58     assertx(kindIsValid());
  59     if (decReleaseCheck()) release();
  60   }
  61   bool kindIsValid() const { return m_kind == HeaderKind::Ref; }
  62
  63   /*
  64    * This can never return a non-Cell.
  65    */
  66   const Cell* cell() const {
  67     assertx(kindIsValid());
  68     assertx(cellIsPlausible(m_cell));
  69     return &m_cell;
  70   }
  71
  72   Cell* cell() {
  73     assertx(kindIsValid());
  74     return &m_cell;
  75   }
  76
  77   const Variant* var() const {
  78     return reinterpret_cast<const Variant*>(cell());
  79   }
  80   Variant* var() {
  81     return reinterpret_cast<Variant*>(cell());
  82   }
  83
  84   static constexpr int cellOffset() { return offsetof(RefData, m_cell); }
  85
  86   void assertValid() const { assertx(kindIsValid()); }
  87
  88   bool isReferenced() const {
  89     assertx(kindIsValid());
  90     return hasMultipleRefs();
  91   }
  92
  93 private:
  94   RefData(DataType t, int64_t datum) {
  95     // Initialize this value by laundering uninitNull -> Null.
  96     // count=OneReference
  97     initHeader_16(HeaderKind::Ref, OneReference, 0);
  98     if (!isNullType(t)) {
  99       m_cell.m_type = t;
 100       m_cell.m_data.num = datum;
 101     } else {
 102       m_cell.m_type = KindOfNull;
 103     }
 104   }
 105
 106 private:
 107   Cell m_cell;
 108 };
 109
 110 ALWAYS_INLINE void decRefRef(RefData* ref) {
 111   ref->decRefAndRelease();
 112 }
 113
 114 } // namespace HPHP
 115
 116 #endif //incl_HPHP_REF_DATA_H