gecko-dev/dom/bindings/BindingUtils.cpp

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-*/
/* vim: set ts=2 sw=2 et tw=79: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "BindingUtils.h"

namespace mozilla {
namespace dom {

static bool
DefineConstants(JSContext* cx, JSObject* obj, ConstantSpec* cs)
{
  for (; cs->name; ++cs) {
    JSBool ok =
      JS_DefineProperty(cx, obj, cs->name, cs->value, NULL, NULL,
                        JSPROP_ENUMERATE | JSPROP_READONLY | JSPROP_PERMANENT);
    if (!ok) {
      return false;
    }
  }
  return true;
}

// We should use JSFunction objects for interface objects, but we need a custom
// hasInstance hook because we have new interface objects on prototype chains of
// old (XPConnect-based) bindings. Because Function.prototype.toString throws if
// passed a non-Function object we also need to provide our own toString method
// for interface objects.

enum {
  TOSTRING_CLASS_RESERVED_SLOT = 0,
  TOSTRING_NAME_RESERVED_SLOT = 1
};

JSBool
InterfaceObjectToString(JSContext* cx, unsigned argc, JS::Value *vp)
{
  JSObject* callee = JSVAL_TO_OBJECT(JS_CALLEE(cx, vp));

  JSObject* obj = JS_THIS_OBJECT(cx, vp);
  if (!obj) {
    JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL, JSMSG_CANT_CONVERT_TO,
                         "null", "object");
    return false;
  }

  jsval v = js::GetFunctionNativeReserved(callee, TOSTRING_CLASS_RESERVED_SLOT);
  JSClass* clasp = static_cast<JSClass*>(JSVAL_TO_PRIVATE(v));

  v = js::GetFunctionNativeReserved(callee, TOSTRING_NAME_RESERVED_SLOT);
  JSString* jsname = static_cast<JSString*>(JSVAL_TO_STRING(v));
  size_t length;
  const jschar* name = JS_GetInternedStringCharsAndLength(jsname, &length);

  if (js::GetObjectJSClass(obj) != clasp) {
    JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL, JSMSG_INCOMPATIBLE_PROTO,
                         NS_ConvertUTF16toUTF8(name).get(), "toString",
                         "object");
    return false;
  }

  JS::Value* argv = JS_ARGV(cx, vp);
  uint32_t indent = 0;
  if (argc != 0 && !JS_ValueToECMAUint32(cx, argv[0], &indent))
      return false;

  nsAutoString spaces;
  while (indent-- > 0) {
    spaces.Append(PRUnichar(' '));
  }

  nsString str;
  str.Append(spaces);
  str.AppendLiteral("function ");
  str.Append(name, length);
  str.AppendLiteral("() {");
  str.Append('\n');
  str.Append(spaces);
  str.AppendLiteral("    [native code]");
  str.Append('\n');
  str.Append(spaces);
  str.AppendLiteral("}");

  return xpc::NonVoidStringToJsval(cx, str, vp);
}

static JSObject*
CreateInterfaceObject(JSContext* cx, JSObject* global, JSObject* receiver,
                      JSClass* constructorClass, JSNative constructorNative,
                      unsigned ctorNargs, JSObject* proto,
                      JSFunctionSpec* staticMethods, ConstantSpec* constants,
                      const char* name)
{
  JSObject* constructor;
  if (constructorClass) {
    JSObject* functionProto = JS_GetFunctionPrototype(cx, global);
    if (!functionProto) {
      return NULL;
    }
    constructor = JS_NewObject(cx, constructorClass, functionProto, global);
  } else {
    MOZ_ASSERT(constructorNative);
    JSFunction* fun = JS_NewFunction(cx, constructorNative, ctorNargs,
                                     JSFUN_CONSTRUCTOR, global, name);
    if (!fun) {
      return NULL;
    }
    constructor = JS_GetFunctionObject(fun);
  }
  if (!constructor) {
    return NULL;
  }

  if (staticMethods && !JS_DefineFunctions(cx, constructor, staticMethods)) {
    return NULL;
  }

  if (constructorClass) {
    JSFunction* toString = js::DefineFunctionWithReserved(cx, constructor,
                                                          "toString",
                                                          InterfaceObjectToString,
                                                          0, 0);
    if (!toString) {
      return NULL;
    }

    JSObject* toStringObj = JS_GetFunctionObject(toString);
    js::SetFunctionNativeReserved(toStringObj, TOSTRING_CLASS_RESERVED_SLOT,
                                  PRIVATE_TO_JSVAL(constructorClass));

    JSString *str = ::JS_InternString(cx, name);
    if (!str) {
      return NULL;
    }
    js::SetFunctionNativeReserved(toStringObj, TOSTRING_NAME_RESERVED_SLOT,
                                  STRING_TO_JSVAL(str));
  }

  if (constants && !DefineConstants(cx, constructor, constants)) {
    return NULL;
  }

  if (proto && !JS_LinkConstructorAndPrototype(cx, constructor, proto)) {
    return NULL;
  }

  JSBool alreadyDefined;
  if (!JS_AlreadyHasOwnProperty(cx, receiver, name, &alreadyDefined)) {
    return NULL;
  }

  // This is Enumerable: False per spec.
  if (!alreadyDefined &&
      !JS_DefineProperty(cx, receiver, name, OBJECT_TO_JSVAL(constructor), NULL,
                         NULL, 0)) {
    return NULL;
  }

  return constructor;
}

static JSObject*
CreateInterfacePrototypeObject(JSContext* cx, JSObject* global,
                               JSObject* parentProto, JSClass* protoClass,
                               JSFunctionSpec* methods,
                               JSPropertySpec* properties,
                               ConstantSpec* constants)
{
  JSObject* ourProto = JS_NewObjectWithUniqueType(cx, protoClass, parentProto,
                                                  global);
  if (!ourProto) {
    return NULL;
  }

  if (methods && !JS_DefineFunctions(cx, ourProto, methods)) {
    return NULL;
  }

  if (properties && !JS_DefineProperties(cx, ourProto, properties)) {
    return NULL;
  }

  if (constants && !DefineConstants(cx, ourProto, constants)) {
    return NULL;
  }

  return ourProto;
}

JSObject*
CreateInterfaceObjects(JSContext* cx, JSObject* global, JSObject *receiver,
                       JSObject* protoProto, JSClass* protoClass,
                       JSClass* constructorClass, JSNative constructor,
                       unsigned ctorNargs, JSFunctionSpec* methods,
                       JSPropertySpec* properties, ConstantSpec* constants,
                       JSFunctionSpec* staticMethods, const char* name)
{
  MOZ_ASSERT(protoClass || constructorClass || constructor,
             "Need at least one class or a constructor!");
  MOZ_ASSERT(!(methods || properties) || protoClass,
             "Methods or properties but no protoClass!");
  MOZ_ASSERT(!staticMethods || constructorClass || constructor,
             "Static methods but no constructorClass or constructor!");
  MOZ_ASSERT(bool(name) == bool(constructorClass || constructor),
             "Must have name precisely when we have an interface object");
  MOZ_ASSERT(!constructorClass || !constructor);

  JSObject* proto;
  if (protoClass) {
    proto = CreateInterfacePrototypeObject(cx, global, protoProto, protoClass,
                                           methods, properties, constants);
    if (!proto) {
      return NULL;
    }
  }
  else {
    proto = NULL;
  }

  JSObject* interface;
  if (constructorClass || constructor) {
    interface = CreateInterfaceObject(cx, global, receiver, constructorClass,
                                      constructor, ctorNargs, proto,
                                      staticMethods, constants, name);
    if (!interface) {
      return NULL;
    }
  }

  return protoClass ? proto : interface;
}

static bool
NativeInterface2JSObjectAndThrowIfFailed(XPCLazyCallContext& aLccx,
                                         JSContext* aCx,
                                         JS::Value* aRetval,
                                         xpcObjectHelper& aHelper,
                                         const nsIID* aIID,
                                         bool aAllowNativeWrapper)
{
  nsresult rv;
  if (!XPCConvert::NativeInterface2JSObject(aLccx, aRetval, NULL, aHelper, aIID,
                                            NULL, aAllowNativeWrapper, &rv)) {
    // I can't tell if NativeInterface2JSObject throws JS exceptions
    // or not.  This is a sloppy stab at the right semantics; the
    // method really ought to be fixed to behave consistently.
    if (!JS_IsExceptionPending(aCx)) {
      Throw<true>(aCx, NS_FAILED(rv) ? rv : NS_ERROR_UNEXPECTED);
    }
    return false;
  }
  return true;
}

bool
DoHandleNewBindingWrappingFailure(JSContext* cx, JSObject* scope,
                                  nsISupports* value, JS::Value* vp)
{
  if (JS_IsExceptionPending(cx)) {
    return false;
  }

  XPCLazyCallContext lccx(JS_CALLER, cx, scope);

  if (value) {
    xpcObjectHelper helper(value);
    return NativeInterface2JSObjectAndThrowIfFailed(lccx, cx, vp, helper, NULL,
                                                    true);
  }

  return Throw<true>(cx, NS_ERROR_XPC_BAD_CONVERT_JS);
}

// Only set allowNativeWrapper to false if you really know you need it, if in
// doubt use true. Setting it to false disables security wrappers.
bool
XPCOMObjectToJsval(JSContext* cx, JSObject* scope, xpcObjectHelper &helper,
                   const nsIID* iid, bool allowNativeWrapper, JS::Value* rval)
{
  XPCLazyCallContext lccx(JS_CALLER, cx, scope);

  if (!NativeInterface2JSObjectAndThrowIfFailed(lccx, cx, rval, helper, iid,
                                                allowNativeWrapper)) {
    return false;
  }

#ifdef DEBUG
  JSObject* jsobj = JSVAL_TO_OBJECT(*rval);
  if (jsobj && !js::GetObjectParent(jsobj))
    NS_ASSERTION(js::GetObjectClass(jsobj)->flags & JSCLASS_IS_GLOBAL,
                 "Why did we recreate this wrapper?");
#endif

  return true;
}

JSBool
QueryInterface(JSContext* cx, unsigned argc, JS::Value* vp)
{
  JS::Value thisv = JS_THIS(cx, vp);
  if (thisv == JSVAL_NULL)
    return false;

  JSObject* obj = JSVAL_TO_OBJECT(thisv);
  JSClass* clasp = js::GetObjectJSClass(obj);
  if (!IsDOMClass(clasp)) {
    return Throw<true>(cx, NS_ERROR_FAILURE);
  }

  nsISupports* native = UnwrapDOMObject<nsISupports>(obj, clasp);

  if (argc < 1) {
    return Throw<true>(cx, NS_ERROR_XPC_NOT_ENOUGH_ARGS);
  }

  JS::Value* argv = JS_ARGV(cx, vp);
  if (!argv[0].isObject()) {
    return Throw<true>(cx, NS_ERROR_XPC_BAD_CONVERT_JS);
  }

  nsIJSIID* iid;
  xpc_qsSelfRef iidRef;
  if (NS_FAILED(xpc_qsUnwrapArg<nsIJSIID>(cx, argv[0], &iid, &iidRef.ptr,
                                          &argv[0]))) {
    return Throw<true>(cx, NS_ERROR_XPC_BAD_CONVERT_JS);
  }
  MOZ_ASSERT(iid);

  if (iid->GetID()->Equals(NS_GET_IID(nsIClassInfo))) {
    nsresult rv;
    nsCOMPtr<nsIClassInfo> ci = do_QueryInterface(native, &rv);
    if (NS_FAILED(rv)) {
      return Throw<true>(cx, rv);
    }

    return WrapObject(cx, obj, ci, &NS_GET_IID(nsIClassInfo), vp);
  }
  
  // Lie, otherwise we need to check classinfo or QI
  *vp = thisv;
  return true;
}

JSBool
ThrowingConstructor(JSContext* cx, unsigned argc, JS::Value* vp)
{
  return Throw<true>(cx, NS_ERROR_FAILURE);
}

JSBool
ThrowingConstructorWorkers(JSContext* cx, unsigned argc, JS::Value* vp)
{
  return Throw<false>(cx, NS_ERROR_FAILURE);
}

} // namespace dom
} // namespace mozilla