1 files changed, 236 insertions, 0 deletions
diff --git a/js/ipc/JavaScriptShared.h b/js/ipc/JavaScriptShared.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sw=4 et tw=80:
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_jsipc_JavaScriptShared_h__
+#define mozilla_jsipc_JavaScriptShared_h__
+
+#include "mozilla/dom/DOMTypes.h"
+#include "mozilla/jsipc/CrossProcessObjectWrappers.h"
+#include "mozilla/jsipc/PJavaScript.h"
+#include "js/GCHashTable.h"
+#include "nsJSUtils.h"
+
+namespace mozilla {
+namespace jsipc {
+
+class ObjectId {
+  public:
+    // Use 47 bits at most, to be safe, since jsval privates are encoded as
+    // doubles. See bug 1065811 comment 12 for an explanation.
+    static const size_t SERIAL_NUMBER_BITS = 47;
+    static const size_t FLAG_BITS = 1;
+    static const uint64_t SERIAL_NUMBER_MAX = (uint64_t(1) << SERIAL_NUMBER_BITS) - 1;
+
+    explicit ObjectId(uint64_t serialNumber, bool hasXrayWaiver)
+      : serialNumber_(serialNumber), hasXrayWaiver_(hasXrayWaiver)
+    {
+        if (MOZ_UNLIKELY(serialNumber == 0 || serialNumber > SERIAL_NUMBER_MAX))
+            MOZ_CRASH("Bad CPOW Id");
+    }
+
+    bool operator==(const ObjectId& other) const {
+        bool equal = serialNumber() == other.serialNumber();
+        MOZ_ASSERT_IF(equal, hasXrayWaiver() == other.hasXrayWaiver());
+        return equal;
+    }
+
+    bool isNull() { return !serialNumber_; }
+
+    uint64_t serialNumber() const { return serialNumber_; }
+    bool hasXrayWaiver() const { return hasXrayWaiver_; }
+    uint64_t serialize() const {
+        MOZ_ASSERT(serialNumber(), "Don't send a null ObjectId over IPC");
+        return uint64_t((serialNumber() << FLAG_BITS) | ((hasXrayWaiver() ? 1 : 0) << 0));
+    }
+
+    static ObjectId nullId() { return ObjectId(); }
+    static ObjectId deserialize(uint64_t data) {
+        return ObjectId(data >> FLAG_BITS, data & 1);
+    }
+
+    // For use with StructGCPolicy.
+    void trace(JSTracer*) const {}
+    bool needsSweep() const { return false; }
+
+  private:
+    ObjectId() : serialNumber_(0), hasXrayWaiver_(false) {}
+
+    uint64_t serialNumber_ : SERIAL_NUMBER_BITS;
+    bool hasXrayWaiver_ : 1;
+};
+
+class JavaScriptShared;
+
+// DefaultHasher<T> requires that T coerce to an integral type. We could make
+// ObjectId do that, but doing so would weaken our type invariants, so we just
+// reimplement it manually.
+struct ObjectIdHasher
+{
+    typedef ObjectId Lookup;
+    static js::HashNumber hash(const Lookup& l) {
+        return l.serialize();
+    }
+    static bool match(const ObjectId& k, const ObjectId& l) {
+        return k == l;
+    }
+    static void rekey(ObjectId& k, const ObjectId& newKey) {
+        k = newKey;
+    }
+};
+
+// Map ids -> JSObjects
+class IdToObjectMap
+{
+    typedef js::HashMap<ObjectId, JS::Heap<JSObject*>, ObjectIdHasher, js::SystemAllocPolicy> Table;
+
+  public:
+    IdToObjectMap();
+
+    bool init();
+    void trace(JSTracer* trc, uint64_t minimumId = 0);
+    void sweep();
+
+    bool add(ObjectId id, JSObject* obj);
+    JSObject* find(ObjectId id);
+    void remove(ObjectId id);
+
+    void clear();
+    bool empty() const;
+
+#ifdef DEBUG
+    bool has(const ObjectId& id, const JSObject* obj) const;
+#endif
+
+  private:
+    Table table_;
+};
+
+// Map JSObjects -> ids
+class ObjectToIdMap
+{
+    using Hasher = js::MovableCellHasher<JS::Heap<JSObject*>>;
+    using Table = JS::GCHashMap<JS::Heap<JSObject*>, ObjectId, Hasher, js::SystemAllocPolicy>;
+
+  public:
+    bool init();
+    void trace(JSTracer* trc);
+    void sweep();
+
+    bool add(JSContext* cx, JSObject* obj, ObjectId id);
+    ObjectId find(JSObject* obj);
+    void remove(JSObject* obj);
+    void clear();
+
+  private:
+    Table table_;
+};
+
+class Logging;
+
+class JavaScriptShared : public CPOWManager
+{
+  public:
+    JavaScriptShared();
+    virtual ~JavaScriptShared();
+
+    bool init();
+
+    void decref();
+    void incref();
+
+    bool Unwrap(JSContext* cx, const InfallibleTArray<CpowEntry>& aCpows, JS::MutableHandleObject objp);
+    bool Wrap(JSContext* cx, JS::HandleObject aObj, InfallibleTArray<CpowEntry>* outCpows);
+
+  protected:
+    bool toVariant(JSContext* cx, JS::HandleValue from, JSVariant* to);
+    bool fromVariant(JSContext* cx, const JSVariant& from, JS::MutableHandleValue to);
+
+    bool toJSIDVariant(JSContext* cx, JS::HandleId from, JSIDVariant* to);
+    bool fromJSIDVariant(JSContext* cx, const JSIDVariant& from, JS::MutableHandleId to);
+
+    bool toSymbolVariant(JSContext* cx, JS::Symbol* sym, SymbolVariant* symVarp);
+    JS::Symbol* fromSymbolVariant(JSContext* cx, const SymbolVariant& symVar);
+
+    bool fromDescriptor(JSContext* cx, JS::Handle<JS::PropertyDescriptor> desc,
+                        PPropertyDescriptor* out);
+    bool toDescriptor(JSContext* cx, const PPropertyDescriptor& in,
+                      JS::MutableHandle<JS::PropertyDescriptor> out);
+
+    bool toObjectOrNullVariant(JSContext* cx, JSObject* obj, ObjectOrNullVariant* objVarp);
+    JSObject* fromObjectOrNullVariant(JSContext* cx, const ObjectOrNullVariant& objVar);
+
+    bool convertIdToGeckoString(JSContext* cx, JS::HandleId id, nsString* to);
+    bool convertGeckoStringToId(JSContext* cx, const nsString& from, JS::MutableHandleId id);
+
+    virtual bool toObjectVariant(JSContext* cx, JSObject* obj, ObjectVariant* objVarp) = 0;
+    virtual JSObject* fromObjectVariant(JSContext* cx, const ObjectVariant& objVar) = 0;
+
+    static void ConvertID(const nsID& from, JSIID* to);
+    static void ConvertID(const JSIID& from, nsID* to);
+
+    JSObject* findCPOWById(const ObjectId& objId) {
+        return cpows_.find(objId);
+    }
+    JSObject* findObjectById(JSContext* cx, const ObjectId& objId);
+
+#ifdef DEBUG
+    bool hasCPOW(const ObjectId& objId, const JSObject* obj) {
+        return cpows_.has(objId, obj);
+    }
+#endif
+
+    static bool LoggingEnabled() { return sLoggingEnabled; }
+    static bool StackLoggingEnabled() { return sStackLoggingEnabled; }
+
+    friend class Logging;
+
+    virtual bool isParent() = 0;
+
+    virtual JSObject* scopeForTargetObjects() = 0;
+
+  protected:
+    uintptr_t refcount_;
+
+    IdToObjectMap objects_;
+    IdToObjectMap cpows_;
+
+    uint64_t nextSerialNumber_;
+
+    // nextCPOWNumber_ should be the value of nextSerialNumber_ in the other
+    // process. The next new CPOW we get should have this serial number.
+    uint64_t nextCPOWNumber_;
+
+    // CPOW references can be weak, and any object we store in a map may be
+    // GCed (at which point the CPOW will report itself "dead" to the owner).
+    // This means that we don't want to store any js::Wrappers in the CPOW map,
+    // because CPOW will die if the wrapper is GCed, even if the underlying
+    // object is still alive.
+    //
+    // This presents a tricky situation for Xray waivers, since they're normally
+    // represented as a special same-compartment wrapper. We have to strip them
+    // off before putting them in the id-to-object and object-to-id maps, so we
+    // need a way of distinguishing them at lookup-time.
+    //
+    // For the id-to-object map, we encode waiver-or-not information into the id
+    // itself, which lets us do the right thing when accessing the object.
+    //
+    // For the object-to-id map, we just keep two maps, one for each type.
+    ObjectToIdMap unwaivedObjectIds_;
+    ObjectToIdMap waivedObjectIds_;
+    ObjectToIdMap& objectIdMap(bool waiver) {
+        return waiver ? waivedObjectIds_ : unwaivedObjectIds_;
+    }
+
+    static bool sLoggingInitialized;
+    static bool sLoggingEnabled;
+    static bool sStackLoggingEnabled;
+};
+
+} // namespace jsipc
+} // namespace mozilla
+
+#endif