content/browser/android/java/java_method.cc

// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "content/browser/android/java/java_method.h"

#include "base/android/jni_android.h"
#include "base/android/jni_string.h"
#include "content/browser/android/java/jni_reflect.h"

using base::android::AttachCurrentThread;
using base::android::MethodID;
using base::android::ScopedJavaLocalRef;

namespace content {
namespace {

std::string BinaryNameToJNISignature(const std::string& binary_name,
                                     JavaType* type) {
  DCHECK(type);
  *type = JavaType::CreateFromBinaryName(binary_name);
  return type->JNISignature();
}

}  // namespace

JavaMethod::JavaMethod(const base::android::JavaRef<jobject>& method)
    : java_method_(method),
      have_calculated_num_parameters_(false),
      id_(NULL) {
  JNIEnv* env = AttachCurrentThread();
  // On construction, we do nothing except get the name. Everything else is
  // done lazily.
  name_ = GetMethodName(env, java_method_);
}

JavaMethod::~JavaMethod() {
}

size_t JavaMethod::num_parameters() const {
  EnsureNumParametersIsSetUp();
  return num_parameters_;
}

bool JavaMethod::is_static() const {
  EnsureTypesAndIDAreSetUp();
  return is_static_;
}

const JavaType& JavaMethod::parameter_type(size_t index) const {
  EnsureTypesAndIDAreSetUp();
  return parameter_types_[index];
}

const JavaType& JavaMethod::return_type() const {
  EnsureTypesAndIDAreSetUp();
  return return_type_;
}

jmethodID JavaMethod::id() const {
  EnsureTypesAndIDAreSetUp();
  return id_;
}

void JavaMethod::EnsureNumParametersIsSetUp() const {
  if (have_calculated_num_parameters_) {
    return;
  }
  have_calculated_num_parameters_ = true;

  // The number of parameters will be used frequently when determining
  // whether to call this method. We don't get the ID etc until actually
  // required.
  JNIEnv* env = AttachCurrentThread();
  ScopedJavaLocalRef<jobjectArray> parameters(
      GetMethodParameterTypes(env, java_method_));
  num_parameters_ = env->GetArrayLength(parameters.obj());
}

void JavaMethod::EnsureTypesAndIDAreSetUp() const {
  if (id_) {
    return;
  }

  // Get the parameters
  JNIEnv* env = AttachCurrentThread();
  ScopedJavaLocalRef<jobjectArray> parameters(
      GetMethodParameterTypes(env, java_method_));
  // Usually, this will already have been called.
  EnsureNumParametersIsSetUp();
  DCHECK_EQ(num_parameters_,
            static_cast<size_t>(env->GetArrayLength(parameters.obj())));

  // Java gives us the argument type using an extended version of the 'binary
  // name'. See
  // http://download.oracle.com/javase/1.4.2/docs/api/java/lang/Class.html#getName().
  // If we build the signature now, there's no need to store the binary name
  // of the arguments. We just store the simple type.
  std::string signature("(");

  // Form the signature and record the parameter types.
  parameter_types_.resize(num_parameters_);
  for (size_t i = 0; i < num_parameters_; ++i) {
    auto parameter = ScopedJavaLocalRef<jclass>::Adopt(
        env,
        static_cast<jclass>(env->GetObjectArrayElement(parameters.obj(), i)));
    signature += BinaryNameToJNISignature(GetClassName(env, parameter),
                                          &parameter_types_[i]);
    if (parameter_types_[i].type == JavaType::TypeObject) {
      parameter_types_[i].class_ref.Reset(parameter);
    }
  }
  signature += ")";

  // Get the return type
  ScopedJavaLocalRef<jclass> clazz(GetMethodReturnType(env, java_method_));
  signature +=
      BinaryNameToJNISignature(GetClassName(env, clazz), &return_type_);

  // Determine whether the method is static.
  is_static_ = IsMethodStatic(env, java_method_);

  // Get the ID for this method.
  ScopedJavaLocalRef<jclass> declaring_class(
      GetMethodDeclaringClass(env, java_method_));
  id_ = is_static_ ?
      MethodID::Get<MethodID::TYPE_STATIC>(
          env, declaring_class.obj(), name_.c_str(), signature.c_str()) :
      MethodID::Get<MethodID::TYPE_INSTANCE>(
          env, declaring_class.obj(), name_.c_str(), signature.c_str());
  java_method_.Reset();
}

}  // namespace content