tor-browser

The Tor Browser
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TraceableFifo.h (3363B)

      1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
      2 * vim: set ts=8 sts=2 et sw=2 tw=80:
      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 js_TraceableFifo_h
      8 #define js_TraceableFifo_h
      9 
     10 #include "ds/Fifo.h"
     11 #include "js/GCVector.h"
     12 #include "js/RootingAPI.h"
     13 #include "js/TracingAPI.h"
     14 
     15 namespace js {
     16 
     17 // A TraceableFifo is a Fifo with an additional trace method that knows how to
     18 // visit all of the items stored in the Fifo. For Fifos that contain GC things,
     19 // this is usually more convenient than manually iterating and marking the
     20 // contents.
     21 //
     22 // Most types of GC pointers as keys and values can be traced with no extra
     23 // infrastructure. For structs and non-gc-pointer members, ensure that there is
     24 // a specialization of GCPolicy<T> with an appropriate trace method available
     25 // to handle the custom type. Generic helpers can be found in
     26 // js/public/TracingAPI.h. Generic helpers can be found in
     27 // js/public/TracingAPI.h.
     28 //
     29 // Note that although this Fifo's trace will deal correctly with moved items, it
     30 // does not itself know when to barrier or trace items. To function properly it
     31 // must either be used with Rooted, or barriered and traced manually.
     32 template <typename T, size_t MinInlineCapacity = 0,
     33          typename AllocPolicy = TempAllocPolicy>
     34 class TraceableFifo
     35    : public js::Fifo<T, MinInlineCapacity, AllocPolicy, JS::GCVector> {
     36  using Base = js::Fifo<T, MinInlineCapacity, AllocPolicy, JS::GCVector>;
     37 
     38 public:
     39  explicit TraceableFifo(AllocPolicy alloc = AllocPolicy())
     40      : Base(std::move(alloc)) {}
     41 
     42  TraceableFifo(TraceableFifo&& rhs) : Base(std::move(rhs)) {}
     43  TraceableFifo& operator=(TraceableFifo&& rhs) = default;
     44 
     45  TraceableFifo(const TraceableFifo&) = delete;
     46  TraceableFifo& operator=(const TraceableFifo&) = delete;
     47 
     48  void trace(JSTracer* trc) {
     49    this->front_.trace(trc);
     50    this->rear_.trace(trc);
     51  }
     52 };
     53 
     54 template <typename Wrapper, typename T, size_t Capacity, typename AllocPolicy>
     55 class WrappedPtrOperations<TraceableFifo<T, Capacity, AllocPolicy>, Wrapper> {
     56  using TF = TraceableFifo<T, Capacity, AllocPolicy>;
     57  const TF& fifo() const { return static_cast<const Wrapper*>(this)->get(); }
     58 
     59 public:
     60  size_t length() const { return fifo().length(); }
     61  bool empty() const { return fifo().empty(); }
     62  const T& front() const { return fifo().front(); }
     63 };
     64 
     65 template <typename Wrapper, typename T, size_t Capacity, typename AllocPolicy>
     66 class MutableWrappedPtrOperations<TraceableFifo<T, Capacity, AllocPolicy>,
     67                                  Wrapper>
     68    : public WrappedPtrOperations<TraceableFifo<T, Capacity, AllocPolicy>,
     69                                  Wrapper> {
     70  using TF = TraceableFifo<T, Capacity, AllocPolicy>;
     71  TF& fifo() { return static_cast<Wrapper*>(this)->get(); }
     72 
     73 public:
     74  T& front() { return fifo().front(); }
     75 
     76  template <typename U>
     77  bool pushBack(U&& u) {
     78    return fifo().pushBack(std::forward<U>(u));
     79  }
     80  template <typename... Args>
     81  bool emplaceBack(Args&&... args) {
     82    return fifo().emplaceBack(std::forward<Args...>(args...));
     83  }
     84 
     85  void popFront() { fifo().popFront(); }
     86  void clear() { fifo().clear(); }
     87 };
     88 
     89 }  // namespace js
     90 
     91 #endif  // js_TraceableFifo_h