js/public/ValueArray.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 /** GC-safe representations of consecutive JS::Value in memory. */
   8
   9 #ifndef js_ValueArray_h
  10 #define js_ValueArray_h
  11
  12 #include "mozilla/Assertions.h"  // MOZ_ASSERT
  13 #include "mozilla/Attributes.h"  // MOZ_IMPLICIT, MOZ_RAII
  14
  15 #include <stdint.h>  // size_t
  16
  17 #include "js/CallArgs.h"    // JS::CallArgs
  18 #include "js/GCVector.h"    // JS::RootedVector
  19 #include "js/RootingAPI.h"  // JS::AutoGCRooter, JS::{,Mutable}Handle
  20 #include "js/Value.h"       // JS::Value
  21
  22 namespace js {
  23 JS_PUBLIC_API void TraceValueArray(JSTracer* trc, size_t length,
  24                                    JS::Value* elements);
  25 }  // namespace js
  26
  27 namespace JS {
  28
  29 /* A fixed-size array of values, for use inside Rooted<>. */
  30 template <size_t N>
  31 struct ValueArray {
  32   Value elements[N];
  33   void trace(JSTracer* trc) { js::TraceValueArray(trc, N, elements); }
  34 };
  35
  36 /** RootedValueArray roots an internal fixed-size array of Values. */
  37 template <size_t N>
  38 using RootedValueArray = Rooted<ValueArray<N>>;
  39
  40 /**
  41  * A generic handle to an array of rooted values.
  42  *
  43  * The rooted array refernced can take several forms, therfore this is not the
  44  * same as Handle<js::ValueArray>.
  45  */
  46 class HandleValueArray {
  47   const size_t length_;
  48   const Value* const elements_;
  49
  50   HandleValueArray(size_t len, const Value* elements)
  51       : length_(len), elements_(elements) {}
  52
  53  public:
  54   explicit HandleValueArray(Handle<Value> value)
  55       : length_(1), elements_(value.address()) {}
  56
  57   MOZ_IMPLICIT HandleValueArray(const RootedVector<Value>& values)
  58       : length_(values.length()), elements_(values.begin()) {}
  59
  60   MOZ_IMPLICIT HandleValueArray(const PersistentRootedVector<Value>& values)
  61       : length_(values.length()), elements_(values.begin()) {}
  62
  63   template <size_t N>
  64   MOZ_IMPLICIT HandleValueArray(const RootedValueArray<N>& values)
  65       : length_(N), elements_(values.begin()) {}
  66
  67   /** CallArgs must already be rooted somewhere up the stack. */
  68   MOZ_IMPLICIT HandleValueArray(const JS::CallArgs& args)
  69       : length_(args.length()), elements_(args.array()) {}
  70
  71   /** Use with care! Only call this if the data is guaranteed to be marked. */
  72   static HandleValueArray fromMarkedLocation(size_t len,
  73                                              const Value* elements) {
  74     return HandleValueArray(len, elements);
  75   }
  76
  77   static HandleValueArray subarray(const HandleValueArray& values,
  78                                    size_t startIndex, size_t len) {
  79     MOZ_ASSERT(startIndex + len <= values.length());
  80     return HandleValueArray(len, values.begin() + startIndex);
  81   }
  82
  83   static HandleValueArray empty() { return HandleValueArray(0, nullptr); }
  84
  85   size_t length() const { return length_; }
  86   const Value* begin() const { return elements_; }
  87
  88   Handle<Value> operator[](size_t i) const {
  89     MOZ_ASSERT(i < length_);
  90     return Handle<Value>::fromMarkedLocation(&elements_[i]);
  91   }
  92 };
  93
  94 }  // namespace JS
  95
  96 namespace js {
  97
  98 template <size_t N, typename Container>
  99 class WrappedPtrOperations<JS::ValueArray<N>, Container> {
 100   const JS::ValueArray<N>& array() const {
 101     return static_cast<const Container*>(this)->get();
 102   }
 103
 104  public:
 105   size_t length() const { return N; }
 106   const JS::Value* begin() const { return array().elements; }
 107
 108   JS::HandleValue operator[](size_t i) const {
 109     MOZ_ASSERT(i < N);
 110     return JS::HandleValue::fromMarkedLocation(&array().elements[i]);
 111   }
 112 };
 113
 114 template <size_t N, typename Container>
 115 class MutableWrappedPtrOperations<JS::ValueArray<N>, Container>
 116     : public WrappedPtrOperations<JS::ValueArray<N>, Container> {
 117   using Base = WrappedPtrOperations<JS::ValueArray<N>, Container>;
 118   JS::ValueArray<N>& array() { return static_cast<Container*>(this)->get(); }
 119
 120  public:
 121   using Base::begin;
 122   JS::Value* begin() { return array().elements; }
 123
 124   using Base::operator[];
 125   JS::MutableHandleValue operator[](size_t i) {
 126     MOZ_ASSERT(i < N);
 127     return JS::MutableHandleValue::fromMarkedLocation(&array().elements[i]);
 128   }
 129 };
 130
 131 }  // namespace js
 132
 133 #endif  // js_ValueArray_h