js/src/wasm/WasmAnyRef.cpp

   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  *
   4  * Copyright 2023 Mozilla Foundation
   5  *
   6  * Licensed under the Apache License, Version 2.0 (the "License");
   7  * you may not use this file except in compliance with the License.
   8  * You may obtain a copy of the License at
   9  *
  10  *     http://www.apache.org/licenses/LICENSE-2.0
  11  *
  12  * Unless required by applicable law or agreed to in writing, software
  13  * distributed under the License is distributed on an "AS IS" BASIS,
  14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  15  * See the License for the specific language governing permissions and
  16  * limitations under the License.
  17  */
  18
  19 #include "wasm/WasmAnyRef.h"
  20
  21 #include "vm/JSContext.h"
  22 #include "vm/JSObject.h"
  23 #include "vm/NativeObject.h"
  24
  25 #include "vm/JSObject-inl.h"
  26
  27 using namespace js;
  28 using namespace js::wasm;
  29
  30 class WasmValueBox : public NativeObject {
  31  public:
  32   static const unsigned VALUE_SLOT = 0;
  33   static const unsigned RESERVED_SLOTS = 1;
  34   static const JSClass class_;
  35
  36   static WasmValueBox* create(JSContext* cx, HandleValue value);
  37   Value value() const { return getFixedSlot(VALUE_SLOT); }
  38 };
  39
  40 const JSClass WasmValueBox::class_ = {
  41     "WasmValueBox", JSCLASS_HAS_RESERVED_SLOTS(RESERVED_SLOTS)};
  42
  43 WasmValueBox* WasmValueBox::create(JSContext* cx, HandleValue value) {
  44   WasmValueBox* obj = NewObjectWithGivenProto<WasmValueBox>(cx, nullptr);
  45   if (!obj) {
  46     return nullptr;
  47   }
  48   obj->setFixedSlot(VALUE_SLOT, value);
  49   return obj;
  50 }
  51
  52 const JSClass* AnyRef::valueBoxClass() { return &WasmValueBox::class_; }
  53
  54 size_t AnyRef::valueBoxOffsetOfValue() {
  55   return NativeObject::getFixedSlotOffset(WasmValueBox::VALUE_SLOT);
  56 }
  57
  58 bool AnyRef::fromJSValue(JSContext* cx, HandleValue value,
  59                          MutableHandleAnyRef result) {
  60   if (value.isNull()) {
  61     result.set(AnyRef::null());
  62     return true;
  63   }
  64
  65   if (value.isString()) {
  66     JSString* string = value.toString();
  67     result.set(AnyRef::fromJSString(string));
  68     return true;
  69   }
  70
  71   if (value.isObject()) {
  72     JSObject& obj = value.toObject();
  73     MOZ_ASSERT(!obj.is<WasmValueBox>());
  74     MOZ_ASSERT(obj.compartment() == cx->compartment());
  75     result.set(AnyRef::fromJSObject(obj));
  76     return true;
  77   }
  78
  79   if (value.isInt32() && !int32NeedsBoxing(value.toInt32())) {
  80     result.set(AnyRef::fromInt32(value.toInt32()));
  81     return true;
  82   }
  83
  84   if (value.isDouble()) {
  85     double doubleValue = value.toDouble();
  86     int32_t intValue;
  87     if (mozilla::NumberIsInt32(doubleValue, &intValue) &&
  88         !int32NeedsBoxing(intValue)) {
  89       result.set(AnyRef::fromInt32(intValue));
  90       return true;
  91     }
  92   }
  93
  94   JSObject* box = AnyRef::boxValue(cx, value);
  95   if (!box) {
  96     return false;
  97   }
  98   result.set(AnyRef::fromJSObject(*box));
  99   return true;
 100 }
 101
 102 JSObject* AnyRef::boxValue(JSContext* cx, HandleValue value) {
 103   MOZ_ASSERT(AnyRef::valueNeedsBoxing(value));
 104   return WasmValueBox::create(cx, value);
 105 }
 106
 107 Value wasm::AnyRef::toJSValue() const {
 108   // If toJSValue needs to allocate then we need a more complicated API, and
 109   // we need to root the value in the callers, see comments in callExport().
 110   Value value;
 111   if (isNull()) {
 112     value.setNull();
 113   } else if (isJSString()) {
 114     value.setString(toJSString());
 115   } else if (isI31()) {
 116     value.setInt32(toI31());
 117   } else {
 118     JSObject& obj = toJSObject();
 119     if (obj.is<WasmValueBox>()) {
 120       value = obj.as<WasmValueBox>().value();
 121     } else {
 122       value.setObject(obj);
 123     }
 124   }
 125   return value;
 126 }