/*

 * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.

 * Copyright (c) 2018, SAP SE. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

#include "precompiled.hpp"

#include "classfile/systemDictionary.hpp"

#include "memory/resourceArea.hpp"

#include "oops/constantPool.hpp"

#include "oops/reflectionAccessorImplKlassHelper.hpp"

#include "utilities/constantTag.hpp"

#include "utilities/debug.hpp"

#include "utilities/globalDefinitions.hpp"

// This code extracts name of target class, method and signature from the constant pool of a class

// assumed to be of type jdk/internal/reflect/Generated{SerializationConstructor|Constructor|Method}AccessorXXX.

// Since this may be affected by bitrot if these classes change, extra care is taken to make the

// release build of this coding robust.

// We extract target class name, method name and sig from the constant pool of the Accessor class.

// This is an excerpt of the Constant pool (see jdk/internal/reflect/MethodAccessorGenerator.java:)

// (^  = Only present if generating SerializationConstructorAccessor)

// 1    [UTF-8] [This class's name]

// 2    [CONSTANT_Class_info] for above

// 3    [UTF-8] "jdk/internal/reflect/{MethodAccessorImpl,ConstructorAccessorImpl,SerializationConstructorAccessorImpl}"

// 4    [CONSTANT_Class_info] for above

// 5    [UTF-8] [Target class's name]

// 6    [CONSTANT_Class_info] for above

// 7^   [UTF-8] [Serialization: Class's name in which to invoke constructor]

// 8^   [CONSTANT_Class_info] for above

// 9    [UTF-8] target method or constructor name

// 10   [UTF-8] target method or constructor signature

// Note that these strings are found at slightly different slots depending on the class type:

// - MethodAccessorImpl, ConstructoreAccessorImpl: slots 5, 7 and 8.

// - SerializationConstructorAccessorImpl: slots 5, 9 and 10.

// Unfortunately SerializationConstructorAccessorImpl is a child of ConstructoreAccessorImpl and there

//  is no easy way to tell them apart. So we examine parent class name.

enum cpi_slots {

  cpi_slot_parent_class_name = 3,

  cpi_slot_target_class_name = 5,

  cpi_slot_target_method_name = 7,

  cpi_slot_target_method_name_sca = 9, // SerializationConstructorAccessor case, see above

  cpi_slot_target_method_sig = 8,

  cpi_slot_target_method_sig_sca = 10  // SerializationConstructorAccessor case, see above

};

// Returns a string, resource-area allocated, from an UTF8 slot in the constant pool in the

// given Klass*.

static const char* get_string_from_cp_with_checks(const InstanceKlass* k, int cpi) {

  const char* s = NULL;

  const ConstantPool* const cp = k->constants();

  assert(cp != NULL, "No cp?");

  assert(cp->is_within_bounds(cpi), "Unexpected constant pool layout for \"%s\", child class of Generated{Method|Constructor}AccessorImplXXX"

         " (cpi %d out of bounds for [0..%d)).", k->external_name(), cpi, cp->length());

  assert(cp->tag_at(cpi).is_utf8(), "Unexpected constant pool layout for \"%s\", child class of Generated{Method|Constructor}AccessorImplXXX"

         " (no UTF8 at cpi %d (%u)).", k->external_name(), cpi, cp->tag_at(cpi).value());

  // Be nice in release: lets not crash, just return NULL.

  if (cp != NULL && cp->is_within_bounds(cpi) && cp->tag_at(cpi).is_utf8()) {

    s = cp->symbol_at(cpi)->as_C_string();

  }

  return s;

}

// helper, returns true if class name of given class matches a given prefix

static bool classname_matches_prefix(const Klass* k, const char* prefix) {

  const char* classname = k->external_name();

  if (classname != NULL) {

    if (::strncmp(classname, prefix, strlen(prefix)) == 0) {

      return true;

    }

  }

  return false;

}

// Returns true if k is of type jdk/internal/reflect/GeneratedMethodAccessorXXX.

bool ReflectionAccessorImplKlassHelper::is_generated_method_accessor(const InstanceKlass* k) {

  return k->super() == SystemDictionary::reflect_MethodAccessorImpl_klass() &&

         classname_matches_prefix(k, "jdk.internal.reflect.GeneratedMethodAccessor");

}

// Returns true if k is of type jdk/internal/reflect/GeneratedConstructorAccessorXXX.

bool ReflectionAccessorImplKlassHelper::is_generated_constructor_accessor(const InstanceKlass* k) {

  return k->super() == SystemDictionary::reflect_ConstructorAccessorImpl_klass() &&

         classname_matches_prefix(k, "jdk.internal.reflect.GeneratedConstructorAccessor");

}

// Returns true if k is of type jdk/internal/reflect/GeneratedSerializationConstructorAccessorXXX.

bool ReflectionAccessorImplKlassHelper::is_generated_method_serialization_constructor_accessor(const InstanceKlass* k) {

  // GeneratedSerializationConstructorAccessor is not a direct subclass of ConstructorAccessorImpl

  const Klass* sk = k->super();

  if (sk != NULL && sk->super() == SystemDictionary::reflect_ConstructorAccessorImpl_klass() &&

      classname_matches_prefix(k, "jdk.internal.reflect.GeneratedSerializationConstructorAccessor")) {

    return true;

  }

  return false;

}

const char* ReflectionAccessorImplKlassHelper::get_target_class_name(const InstanceKlass* k) {

  return get_string_from_cp_with_checks(k, cpi_slot_target_class_name);

}

const char* ReflectionAccessorImplKlassHelper::get_target_method_name(const InstanceKlass* k) {

  const int target_method_name_cpi =

      is_generated_method_serialization_constructor_accessor(k) ? cpi_slot_target_method_name_sca : cpi_slot_target_method_name;

  return get_string_from_cp_with_checks(k, target_method_name_cpi);

}

const char* ReflectionAccessorImplKlassHelper::get_target_method_signature(const InstanceKlass* k) {

  const int target_method_name_cpi =

      is_generated_method_serialization_constructor_accessor(k) ? cpi_slot_target_method_sig_sca : cpi_slot_target_method_sig;

  return get_string_from_cp_with_checks(k, target_method_name_cpi);

}

// Returns true if this is either one of jdk/internal/reflect/Generated{SerializationConstructor|Constructor|Method}AccessorXXX

// and it is safe to call print_invocation_target(k)

bool ReflectionAccessorImplKlassHelper::is_generated_accessor(const Klass* k) {

  if (k != NULL && k->is_instance_klass()) {

    const InstanceKlass* ik = InstanceKlass::cast(k);

    if (ik->is_initialized()) {

      return is_generated_method_accessor(ik) ||

             is_generated_constructor_accessor(ik) ||

             is_generated_method_serialization_constructor_accessor(ik);

    }

  }

  return false;

}

void ReflectionAccessorImplKlassHelper::print_invocation_target(outputStream* out, Klass* k) {

  assert(ReflectionAccessorImplKlassHelper::is_generated_accessor(k), "Invariant");

  InstanceKlass* ik = InstanceKlass::cast(k);

  ResourceMark rm;

  const char* target_class_name = ReflectionAccessorImplKlassHelper::get_target_class_name(ik);

  const char* target_method_name = ReflectionAccessorImplKlassHelper::get_target_method_name(ik);

  const char* target_method_signature = ReflectionAccessorImplKlassHelper::get_target_method_signature(ik);

  out->print("%s::%s %s",

      target_class_name != NULL ? target_class_name : "?",

      target_method_name != NULL ? target_method_name : "?",

      target_method_signature != NULL ? target_method_signature : "?");

}