js/src/jscompartmentinlines.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 jscompartmentinlines_h
   8 #define jscompartmentinlines_h
   9
  10 #include "jscompartment.h"
  11
  12 #include "gc/Barrier.h"
  13
  14 #include "jscntxtinlines.h"
  15
  16 inline void
  17 JSCompartment::initGlobal(js::GlobalObject& global)
  18 {
  19     MOZ_ASSERT(global.compartment() == this);
  20     MOZ_ASSERT(!global_);
  21     global_.set(&global);
  22 }
  23
  24 js::GlobalObject*
  25 JSCompartment::maybeGlobal() const
  26 {
  27     MOZ_ASSERT_IF(global_, global_->compartment() == this);
  28     return global_;
  29 }
  30
  31 js::GlobalObject*
  32 JSCompartment::unsafeUnbarrieredMaybeGlobal() const
  33 {
  34     return *global_.unsafeGet();
  35 }
  36
  37 js::AutoCompartment::AutoCompartment(ExclusiveContext* cx, JSObject* target)
  38   : cx_(cx),
  39     origin_(cx->compartment_)
  40 {
  41     cx_->enterCompartment(target->compartment());
  42 }
  43
  44 js::AutoCompartment::AutoCompartment(ExclusiveContext* cx, JSCompartment* target)
  45   : cx_(cx),
  46     origin_(cx_->compartment_)
  47 {
  48     cx_->enterCompartment(target);
  49 }
  50
  51 js::AutoCompartment::~AutoCompartment()
  52 {
  53     cx_->leaveCompartment(origin_);
  54 }
  55
  56 inline bool
  57 JSCompartment::wrap(JSContext* cx, JS::MutableHandleValue vp, JS::HandleObject existing)
  58 {
  59     MOZ_ASSERT_IF(existing, vp.isObject());
  60
  61     /* Only GC things have to be wrapped or copied. */
  62     if (!vp.isMarkable())
  63         return true;
  64
  65     /*
  66      * Symbols are GC things, but never need to be wrapped or copied because
  67      * they are always allocated in the atoms compartment.
  68      */
  69     if (vp.isSymbol())
  70         return true;
  71
  72     /* Handle strings. */
  73     if (vp.isString()) {
  74         JS::RootedString str(cx, vp.toString());
  75         if (!wrap(cx, &str))
  76             return false;
  77         vp.setString(str);
  78         return true;
  79     }
  80
  81     MOZ_ASSERT(vp.isObject());
  82
  83     /*
  84      * All that's left are objects.
  85      *
  86      * Object wrapping isn't the fastest thing in the world, in part because
  87      * we have to unwrap and invoke the prewrap hook to find the identity
  88      * object before we even start checking the cache. Neither of these
  89      * operations are needed in the common case, where we're just wrapping
  90      * a plain JS object from the wrappee's side of the membrane to the
  91      * wrapper's side.
  92      *
  93      * To optimize this, we note that the cache should only ever contain
  94      * identity objects - that is to say, objects that serve as the
  95      * canonical representation for a unique object identity observable by
  96      * script. Unwrap and prewrap are both steps that we take to get to the
  97      * identity of an incoming objects, and as such, they shuld never map
  98      * one identity object to another object. This means that we can safely
  99      * check the cache immediately, and only risk false negatives. Do this
 100      * in opt builds, and do both in debug builds so that we can assert
 101      * that we get the same answer.
 102      */
 103 #ifdef DEBUG
 104     JS::RootedObject cacheResult(cx);
 105 #endif
 106     JS::RootedValue v(cx, vp);
 107     if (js::WrapperMap::Ptr p = crossCompartmentWrappers.lookup(js::CrossCompartmentKey(v))) {
 108 #ifdef DEBUG
 109         cacheResult = &p->value().get().toObject();
 110 #else
 111         vp.set(p->value());
 112         return true;
 113 #endif
 114     }
 115
 116     JS::RootedObject obj(cx, &vp.toObject());
 117     if (!wrap(cx, &obj, existing))
 118         return false;
 119     vp.setObject(*obj);
 120     MOZ_ASSERT_IF(cacheResult, obj == cacheResult);
 121     return true;
 122 }
 123
 124 #endif /* jscompartmentinlines_h */