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   template <size_t N>
  61   MOZ_IMPLICIT HandleValueArray(const RootedValueArray<N>& values)
  62       : length_(N), elements_(values.begin()) {}
  63
  64   /** CallArgs must already be rooted somewhere up the stack. */
  65   MOZ_IMPLICIT HandleValueArray(const JS::CallArgs& args)
  66       : length_(args.length()), elements_(args.array()) {}
  67
  68   /** Use with care! Only call this if the data is guaranteed to be marked. */
  69   static HandleValueArray fromMarkedLocation(size_t len,
  70                                              const Value* elements) {
  71     return HandleValueArray(len, elements);
  72   }
  73
  74   static HandleValueArray subarray(const HandleValueArray& values,
  75                                    size_t startIndex, size_t len) {
  76     MOZ_ASSERT(startIndex + len <= values.length());
  77     return HandleValueArray(len, values.begin() + startIndex);
  78   }
  79
  80   static HandleValueArray empty() { return HandleValueArray(0, nullptr); }
  81
  82   size_t length() const { return length_; }
  83   const Value* begin() const { return elements_; }
  84
  85   Handle<Value> operator[](size_t i) const {
  86     MOZ_ASSERT(i < length_);
  87     return Handle<Value>::fromMarkedLocation(&elements_[i]);
  88   }
  89 };
  90
  91 }  // namespace JS
  92
  93 namespace js {
  94
  95 template <size_t N, typename Container>
  96 class WrappedPtrOperations<JS::ValueArray<N>, Container> {
  97   const JS::ValueArray<N>& array() const {
  98     return static_cast<const Container*>(this)->get();
  99   }
 100
 101  public:
 102   size_t length() const { return N; }
 103   const JS::Value* begin() const { return array().elements; }
 104
 105   JS::HandleValue operator[](size_t i) const {
 106     MOZ_ASSERT(i < N);
 107     return JS::HandleValue::fromMarkedLocation(&array().elements[i]);
 108   }
 109 };
 110
 111 template <size_t N, typename Container>
 112 class MutableWrappedPtrOperations<JS::ValueArray<N>, Container>
 113     : public WrappedPtrOperations<JS::ValueArray<N>, Container> {
 114   using Base = WrappedPtrOperations<JS::ValueArray<N>, Container>;
 115   JS::ValueArray<N>& array() { return static_cast<Container*>(this)->get(); }
 116
 117  public:
 118   using Base::begin;
 119   JS::Value* begin() { return array().elements; }
 120
 121   using Base::operator[];
 122   JS::MutableHandleValue operator[](size_t i) {
 123     MOZ_ASSERT(i < N);
 124     return JS::MutableHandleValue::fromMarkedLocation(&array().elements[i]);
 125   }
 126 };
 127
 128 }  // namespace js
 129
 130 #endif  // js_ValueArray_h