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       , originalGcNumber(cx->zone()->gcNumber())
  29     {}
  30
  31     template <class KeyInput, class ValueInput>
  32     bool add(const ExclusiveContext* cx, T& table, const KeyInput& key, const ValueInput& value) {
  33         bool gcHappened = originalGcNumber != cx->zone()->gcNumber();
  34         if (gcHappened)
  35             addPtr = table.lookupForAdd(key);
  36         return table.relookupOrAdd(addPtr, key, value);
  37     }
  38
  39     typedef void (DependentAddPtr::* ConvertibleToBool)();
  40     void nonNull() {}
  41
  42     bool found() const                 { return addPtr.found(); }
  43     operator ConvertibleToBool() const { return found() ? &DependentAddPtr::nonNull : 0; }
  44     const Entry& operator*() const     { return *addPtr; }
  45     const Entry* operator->() const    { return &*addPtr; }
  46
  47   private:
  48     AddPtr addPtr ;
  49     const uint64_t originalGcNumber;
  50
  51     DependentAddPtr() = delete;
  52     DependentAddPtr(const DependentAddPtr&) = delete;
  53     DependentAddPtr& operator=(const DependentAddPtr&) = delete;
  54 };
  55
  56 } // namespace js
  57
  58 #endif