js/src/jshashutil.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
   2  * vim: set ts=8 sts=4 et sw=4 tw=99:
   3  * This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef jshashutil_h
   8 #define jshashutil_h
   9
  10 #include "jscntxt.h"
  11
  12 namespace js {
  13
  14 /*
  15  * Used to add entries to a js::HashMap or HashSet where the key depends on a GC
  16  * thing that may be moved by generational or compacting GC between the call to
  17  * lookupForAdd() and relookupOrAdd().
  18  */
  19 template <class T>
  20 struct DependentAddPtr
  21 {
  22     typedef typename T::AddPtr AddPtr;
  23     typedef typename T::Entry Entry;
  24
  25     template <class Lookup>
  26     DependentAddPtr(const ExclusiveContext *cx, const T &table, const Lookup &lookup)
  27       : addPtr(table.lookupForAdd(lookup))
  28 #ifdef JSGC_GENERATIONAL
  29       , originalGcNumber(cx->zone()->gcNumber())
  30 #endif
  31         {}
  32
  33     template <class KeyInput, class ValueInput>
  34     bool add(const ExclusiveContext *cx, T &table, const KeyInput &key, const ValueInput &value) {
  35 #ifdef JSGC_GENERATIONAL
  36         bool gcHappened = originalGcNumber != cx->zone()->gcNumber();
  37         if (gcHappened)
  38             addPtr = table.lookupForAdd(key);
  39 #endif
  40         return table.relookupOrAdd(addPtr, key, value);
  41     }
  42
  43     typedef void (DependentAddPtr::* ConvertibleToBool)();
  44     void nonNull() {}
  45
  46     bool found() const                 { return addPtr.found(); }
  47     operator ConvertibleToBool() const { return found() ? &DependentAddPtr::nonNull : 0; }
  48     const Entry &operator*() const     { return *addPtr; }
  49     const Entry *operator->() const    { return &*addPtr; }
  50
  51   private:
  52     AddPtr addPtr ;
  53 #ifdef JSGC_GENERATIONAL
  54     const uint64_t originalGcNumber;
  55 #endif
  56
  57     DependentAddPtr() MOZ_DELETE;
  58     DependentAddPtr(const DependentAddPtr&) MOZ_DELETE;
  59     DependentAddPtr& operator=(const DependentAddPtr&) MOZ_DELETE;
  60 };
  61
  62 } // namespace js
  63
  64 #endif