The Tor Browser: js/src/jscompartmentinlines.h@b8a032363ba2

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

     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/. */

     7 #ifndef jscompartmentinlines_h

     8 #define jscompartmentinlines_h

    10 #include "jscompartment.h"

    12 #include "gc/Barrier-inl.h"

    14 inline void

    15 JSCompartment::initGlobal(js::GlobalObject &global)

    16 {

    17     JS_ASSERT(global.compartment() == this);

    18     JS_ASSERT(!global_);

    19     global_ = &global;

    20 }

    22 js::GlobalObject *

    23 JSCompartment::maybeGlobal() const

    24 {

    25     JS_ASSERT_IF(global_, global_->compartment() == this);

    26     return global_;

    27 }

    29 js::AutoCompartment::AutoCompartment(ExclusiveContext *cx, JSObject *target)

    30   : cx_(cx),

    31     origin_(cx->compartment_)

    32 {

    33     cx_->enterCompartment(target->compartment());

    34 }

    36 js::AutoCompartment::AutoCompartment(ExclusiveContext *cx, JSCompartment *target)

    37   : cx_(cx),

    38     origin_(cx_->compartment_)

    39 {

    40     cx_->enterCompartment(target);

    41 }

    43 js::AutoCompartment::~AutoCompartment()

    44 {

    45     cx_->leaveCompartment(origin_);

    46 }

    48 inline bool

    49 JSCompartment::wrap(JSContext *cx, JS::MutableHandleValue vp, JS::HandleObject existing)

    50 {

    51     JS_ASSERT_IF(existing, vp.isObject());

    53     /* Only GC things have to be wrapped or copied. */

    54     if (!vp.isMarkable())

    55         return true;

    57     /* Handle strings. */

    58     if (vp.isString()) {

    59         JS::RootedString str(cx, vp.toString());

    60         if (!wrap(cx, str.address()))

    61             return false;

    62         vp.setString(str);

    63         return true;

    64     }

    66     JS_ASSERT(vp.isObject());

    68     /*

    69      * All that's left are objects.

    70      *

    71      * Object wrapping isn't the fastest thing in the world, in part because

    72      * we have to unwrap and invoke the prewrap hook to find the identity

    73      * object before we even start checking the cache. Neither of these

    74      * operations are needed in the common case, where we're just wrapping

    75      * a plain JS object from the wrappee's side of the membrane to the

    76      * wrapper's side.

    77      *

    78      * To optimize this, we note that the cache should only ever contain

    79      * identity objects - that is to say, objects that serve as the

    80      * canonical representation for a unique object identity observable by

    81      * script. Unwrap and prewrap are both steps that we take to get to the

    82      * identity of an incoming objects, and as such, they shuld never map

    83      * one identity object to another object. This means that we can safely

    84      * check the cache immediately, and only risk false negatives. Do this

    85      * in opt builds, and do both in debug builds so that we can assert

    86      * that we get the same answer.

    87      */

    88 #ifdef DEBUG

    89     JS::RootedObject cacheResult(cx);

    90 #endif

    91     JS::RootedValue v(cx, vp);

    92     if (js::WrapperMap::Ptr p = crossCompartmentWrappers.lookup(v)) {

    93 #ifdef DEBUG

    94         cacheResult = &p->value().get().toObject();

    95 #else

    96         vp.set(p->value());

    97         return true;

    98 #endif

    99     }

   101     JS::RootedObject obj(cx, &vp.toObject());

   102     if (!wrap(cx, &obj, existing))

   103         return false;

   104     vp.setObject(*obj);

   105     JS_ASSERT_IF(cacheResult, obj == cacheResult);

   106     return true;

   107 }

   109 #endif /* jscompartmentinlines_h */

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