js/public/GCVector.h

   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_GCVector_h
   8 #define js_GCVector_h
   9
  10 #include "mozilla/Assertions.h"       // MOZ_ASSERT
  11 #include "mozilla/Attributes.h"       // MOZ_STACK_CLASS
  12 #include "mozilla/MemoryReporting.h"  // MallocSizeOf
  13 #include "mozilla/Span.h"
  14 #include "mozilla/Vector.h"
  15
  16 #include <stddef.h>  // size_t
  17 #include <utility>   // forward, move
  18
  19 #include "js/AllocPolicy.h"
  20 #include "js/GCPolicyAPI.h"
  21 #include "js/RootingAPI.h"
  22
  23 class JSTracer;
  24 struct JSContext;
  25
  26 namespace JS {
  27
  28 // A GCVector is a Vector with an additional trace method that knows how
  29 // to visit all of the items stored in the Vector. For vectors that contain GC
  30 // things, this is usually more convenient than manually iterating and marking
  31 // the contents.
  32 //
  33 // Most types of GC pointers as keys and values can be traced with no extra
  34 // infrastructure. For structs and non-gc-pointer members, ensure that there is
  35 // a specialization of GCPolicy<T> with an appropriate trace method available
  36 // to handle the custom type. Generic helpers can be found in
  37 // js/public/TracingAPI.h.
  38 //
  39 // Note that although this Vector's trace will deal correctly with moved items,
  40 // it does not itself know when to barrier or trace items. To function properly
  41 // it must either be used with Rooted, or barriered and traced manually.
  42 template <typename T, size_t MinInlineCapacity = 0,
  43           typename AllocPolicy = js::TempAllocPolicy>
  44 class GCVector {
  45   mozilla::Vector<T, MinInlineCapacity, AllocPolicy> vector;
  46
  47  public:
  48   using ElementType = T;
  49
  50   explicit GCVector(AllocPolicy alloc) : vector(std::move(alloc)) {}
  51   GCVector() : GCVector(AllocPolicy()) {}
  52
  53   GCVector(GCVector&& vec) : vector(std::move(vec.vector)) {}
  54
  55   GCVector& operator=(GCVector&& vec) {
  56     vector = std::move(vec.vector);
  57     return *this;
  58   }
  59
  60   size_t length() const { return vector.length(); }
  61   bool empty() const { return vector.empty(); }
  62   size_t capacity() const { return vector.capacity(); }
  63
  64   T* begin() { return vector.begin(); }
  65   const T* begin() const { return vector.begin(); }
  66
  67   T* end() { return vector.end(); }
  68   const T* end() const { return vector.end(); }
  69
  70   T& operator[](size_t i) { return vector[i]; }
  71   const T& operator[](size_t i) const { return vector[i]; }
  72
  73   T& back() { return vector.back(); }
  74   const T& back() const { return vector.back(); }
  75
  76   operator mozilla::Span<T>() { return vector; }
  77   operator mozilla::Span<const T>() const { return vector; }
  78
  79   bool initCapacity(size_t cap) { return vector.initCapacity(cap); }
  80   [[nodiscard]] bool reserve(size_t req) { return vector.reserve(req); }
  81   void shrinkBy(size_t amount) { return vector.shrinkBy(amount); }
  82   void shrinkTo(size_t newLen) { return vector.shrinkTo(newLen); }
  83   [[nodiscard]] bool growBy(size_t amount) { return vector.growBy(amount); }
  84   [[nodiscard]] bool resize(size_t newLen) { return vector.resize(newLen); }
  85
  86   void clear() { return vector.clear(); }
  87   void clearAndFree() { return vector.clearAndFree(); }
  88
  89   template <typename U>
  90   bool append(U&& item) {
  91     return vector.append(std::forward<U>(item));
  92   }
  93
  94   void erase(T* it) { vector.erase(it); }
  95   void erase(T* begin, T* end) { vector.erase(begin, end); }
  96   template <typename Pred>
  97   void eraseIf(Pred pred) {
  98     vector.eraseIf(pred);
  99   }
 100   template <typename U>
 101   void eraseIfEqual(const U& u) {
 102     vector.eraseIfEqual(u);
 103   }
 104
 105   template <typename... Args>
 106   [[nodiscard]] bool emplaceBack(Args&&... args) {
 107     return vector.emplaceBack(std::forward<Args>(args)...);
 108   }
 109
 110   template <typename... Args>
 111   void infallibleEmplaceBack(Args&&... args) {
 112     vector.infallibleEmplaceBack(std::forward<Args>(args)...);
 113   }
 114
 115   template <typename U>
 116   void infallibleAppend(U&& aU) {
 117     return vector.infallibleAppend(std::forward<U>(aU));
 118   }
 119   void infallibleAppendN(const T& aT, size_t aN) {
 120     return vector.infallibleAppendN(aT, aN);
 121   }
 122   template <typename U>
 123   void infallibleAppend(const U* aBegin, const U* aEnd) {
 124     return vector.infallibleAppend(aBegin, aEnd);
 125   }
 126   template <typename U>
 127   void infallibleAppend(const U* aBegin, size_t aLength) {
 128     return vector.infallibleAppend(aBegin, aLength);
 129   }
 130
 131   template <typename U>
 132   [[nodiscard]] bool appendAll(const U& aU) {
 133     return vector.append(aU.begin(), aU.end());
 134   }
 135   template <typename T2, size_t MinInlineCapacity2, typename AllocPolicy2>
 136   [[nodiscard]] bool appendAll(
 137       GCVector<T2, MinInlineCapacity2, AllocPolicy2>&& aU) {
 138     return vector.appendAll(aU.begin(), aU.end());
 139   }
 140
 141   [[nodiscard]] bool appendN(const T& val, size_t count) {
 142     return vector.appendN(val, count);
 143   }
 144
 145   template <typename U>
 146   [[nodiscard]] bool append(const U* aBegin, const U* aEnd) {
 147     return vector.append(aBegin, aEnd);
 148   }
 149   template <typename U>
 150   [[nodiscard]] bool append(const U* aBegin, size_t aLength) {
 151     return vector.append(aBegin, aLength);
 152   }
 153
 154   void popBack() { return vector.popBack(); }
 155   T popCopy() { return vector.popCopy(); }
 156
 157   size_t sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const {
 158     return vector.sizeOfExcludingThis(mallocSizeOf);
 159   }
 160
 161   size_t sizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) const {
 162     return vector.sizeOfIncludingThis(mallocSizeOf);
 163   }
 164
 165   void trace(JSTracer* trc) {
 166     for (auto& elem : vector) {
 167       GCPolicy<T>::trace(trc, &elem, "vector element");
 168     }
 169   }
 170
 171   bool traceWeak(JSTracer* trc) {
 172     mutableEraseIf(
 173         [trc](T& elem) { return !GCPolicy<T>::traceWeak(trc, &elem); });
 174     return !empty();
 175   }
 176
 177   // Like eraseIf, but may mutate the contents of the vector. Iterates from
 178   // |startIndex| to the last element of the vector.
 179   template <typename Pred>
 180   void mutableEraseIf(Pred pred, size_t startIndex = 0) {
 181     MOZ_ASSERT(startIndex <= length());
 182
 183     T* src = begin() + startIndex;
 184     T* dst = src;
 185     while (src != end()) {
 186       if (!pred(*src)) {
 187         if (src != dst) {
 188           *dst = std::move(*src);
 189         }
 190         dst++;
 191       }
 192       src++;
 193     }
 194
 195     MOZ_ASSERT(dst <= end());
 196     shrinkBy(end() - dst);
 197   }
 198 };
 199
 200 // AllocPolicy is optional. It has a default value declared in TypeDecls.h
 201 template <typename T, typename AllocPolicy>
 202 class MOZ_STACK_CLASS StackGCVector : public GCVector<T, 8, AllocPolicy> {
 203  public:
 204   using Base = GCVector<T, 8, AllocPolicy>;
 205
 206  private:
 207   // Inherit constructor from GCVector.
 208   using Base::Base;
 209 };
 210
 211 }  // namespace JS
 212
 213 namespace js {
 214
 215 template <typename Wrapper, typename T, size_t Capacity, typename AllocPolicy>
 216 class WrappedPtrOperations<JS::GCVector<T, Capacity, AllocPolicy>, Wrapper> {
 217   using Vec = JS::GCVector<T, Capacity, AllocPolicy>;
 218   const Vec& vec() const { return static_cast<const Wrapper*>(this)->get(); }
 219
 220  public:
 221   const AllocPolicy& allocPolicy() const { return vec().allocPolicy(); }
 222   size_t length() const { return vec().length(); }
 223   bool empty() const { return vec().empty(); }
 224   size_t capacity() const { return vec().capacity(); }
 225   const T* begin() const { return vec().begin(); }
 226   const T* end() const { return vec().end(); }
 227   const T& back() const { return vec().back(); }
 228
 229   JS::Handle<T> operator[](size_t aIndex) const {
 230     return JS::Handle<T>::fromMarkedLocation(&vec().operator[](aIndex));
 231   }
 232 };
 233
 234 template <typename Wrapper, typename T, size_t Capacity, typename AllocPolicy>
 235 class MutableWrappedPtrOperations<JS::GCVector<T, Capacity, AllocPolicy>,
 236                                   Wrapper>
 237     : public WrappedPtrOperations<JS::GCVector<T, Capacity, AllocPolicy>,
 238                                   Wrapper> {
 239   using Vec = JS::GCVector<T, Capacity, AllocPolicy>;
 240   const Vec& vec() const { return static_cast<const Wrapper*>(this)->get(); }
 241   Vec& vec() { return static_cast<Wrapper*>(this)->get(); }
 242
 243  public:
 244   const AllocPolicy& allocPolicy() const { return vec().allocPolicy(); }
 245   AllocPolicy& allocPolicy() { return vec().allocPolicy(); }
 246   const T* begin() const { return vec().begin(); }
 247   T* begin() { return vec().begin(); }
 248   const T* end() const { return vec().end(); }
 249   T* end() { return vec().end(); }
 250   const T& back() const { return vec().back(); }
 251   T& back() { return vec().back(); }
 252
 253   JS::Handle<T> operator[](size_t aIndex) const {
 254     return JS::Handle<T>::fromMarkedLocation(&vec().operator[](aIndex));
 255   }
 256   JS::MutableHandle<T> operator[](size_t aIndex) {
 257     return JS::MutableHandle<T>::fromMarkedLocation(&vec().operator[](aIndex));
 258   }
 259
 260   [[nodiscard]] bool initCapacity(size_t aRequest) {
 261     return vec().initCapacity(aRequest);
 262   }
 263   [[nodiscard]] bool reserve(size_t aRequest) {
 264     return vec().reserve(aRequest);
 265   }
 266   void shrinkBy(size_t aIncr) { vec().shrinkBy(aIncr); }
 267   [[nodiscard]] bool growBy(size_t aIncr) { return vec().growBy(aIncr); }
 268   [[nodiscard]] bool resize(size_t aNewLength) {
 269     return vec().resize(aNewLength);
 270   }
 271   void clear() { vec().clear(); }
 272   void clearAndFree() { vec().clearAndFree(); }
 273   template <typename U>
 274   [[nodiscard]] bool append(U&& aU) {
 275     return vec().append(std::forward<U>(aU));
 276   }
 277   template <typename... Args>
 278   [[nodiscard]] bool emplaceBack(Args&&... aArgs) {
 279     return vec().emplaceBack(std::forward<Args>(aArgs)...);
 280   }
 281   template <typename... Args>
 282   void infallibleEmplaceBack(Args&&... args) {
 283     vec().infallibleEmplaceBack(std::forward<Args>(args)...);
 284   }
 285   template <typename U>
 286   [[nodiscard]] bool appendAll(U&& aU) {
 287     return vec().appendAll(aU);
 288   }
 289   [[nodiscard]] bool appendN(const T& aT, size_t aN) {
 290     return vec().appendN(aT, aN);
 291   }
 292   template <typename U>
 293   [[nodiscard]] bool append(const U* aBegin, const U* aEnd) {
 294     return vec().append(aBegin, aEnd);
 295   }
 296   template <typename U>
 297   [[nodiscard]] bool append(const U* aBegin, size_t aLength) {
 298     return vec().append(aBegin, aLength);
 299   }
 300   template <typename U>
 301   void infallibleAppend(U&& aU) {
 302     vec().infallibleAppend(std::forward<U>(aU));
 303   }
 304   void infallibleAppendN(const T& aT, size_t aN) {
 305     vec().infallibleAppendN(aT, aN);
 306   }
 307   template <typename U>
 308   void infallibleAppend(const U* aBegin, const U* aEnd) {
 309     vec().infallibleAppend(aBegin, aEnd);
 310   }
 311   template <typename U>
 312   void infallibleAppend(const U* aBegin, size_t aLength) {
 313     vec().infallibleAppend(aBegin, aLength);
 314   }
 315   void popBack() { vec().popBack(); }
 316   T popCopy() { return vec().popCopy(); }
 317   void erase(T* aT) { vec().erase(aT); }
 318   void erase(T* aBegin, T* aEnd) { vec().erase(aBegin, aEnd); }
 319   template <typename Pred>
 320   void eraseIf(Pred pred) {
 321     vec().eraseIf(pred);
 322   }
 323   template <typename U>
 324   void eraseIfEqual(const U& u) {
 325     vec().eraseIfEqual(u);
 326   }
 327 };
 328
 329 template <typename Wrapper, typename T, typename AllocPolicy>
 330 class WrappedPtrOperations<JS::StackGCVector<T, AllocPolicy>, Wrapper>
 331     : public WrappedPtrOperations<
 332           typename JS::StackGCVector<T, AllocPolicy>::Base, Wrapper> {};
 333
 334 template <typename Wrapper, typename T, typename AllocPolicy>
 335 class MutableWrappedPtrOperations<JS::StackGCVector<T, AllocPolicy>, Wrapper>
 336     : public MutableWrappedPtrOperations<
 337           typename JS::StackGCVector<T, AllocPolicy>::Base, Wrapper> {};
 338
 339 }  // namespace js
 340
 341 namespace JS {
 342
 343 // An automatically rooted GCVector for stack use.
 344 template <typename T>
 345 class RootedVector : public Rooted<StackGCVector<T>> {
 346   using Vec = StackGCVector<T>;
 347   using Base = Rooted<Vec>;
 348
 349  public:
 350   explicit RootedVector(JSContext* cx) : Base(cx, Vec(cx)) {}
 351 };
 352
 353 // For use in rust code, an analog to RootedVector that doesn't require
 354 // instances to be destroyed in LIFO order.
 355 template <typename T>
 356 class PersistentRootedVector : public PersistentRooted<StackGCVector<T>> {
 357   using Vec = StackGCVector<T>;
 358   using Base = PersistentRooted<Vec>;
 359
 360  public:
 361   explicit PersistentRootedVector(JSContext* cx) : Base(cx, Vec(cx)) {}
 362 };
 363
 364 }  // namespace JS
 365
 366 #endif  // js_GCVector_h