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Java example source code file (javaCalls.cpp)

This example Java source code file (javaCalls.cpp) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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Java - Java tags/keywords

basictype, check, handle, javacallarguments, javacalls\:\:call, javacalls\:\:call_static, javacalls\:\:call_virtual, javathread, klasshandle, one, symbol, t_object, thread, traps

The javaCalls.cpp Java example source code

/*
 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. 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 "classfile/vmSymbols.hpp"
#include "code/nmethod.hpp"
#include "compiler/compileBroker.hpp"
#include "interpreter/interpreter.hpp"
#include "interpreter/linkResolver.hpp"
#include "memory/universe.inline.hpp"
#include "oops/oop.inline.hpp"
#include "prims/jniCheck.hpp"
#include "runtime/compilationPolicy.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/interfaceSupport.hpp"
#include "runtime/javaCalls.hpp"
#include "runtime/mutexLocker.hpp"
#include "runtime/signature.hpp"
#include "runtime/stubRoutines.hpp"
#include "runtime/thread.inline.hpp"

// -----------------------------------------------------
// Implementation of JavaCallWrapper

JavaCallWrapper::JavaCallWrapper(methodHandle callee_method, Handle receiver, JavaValue* result, TRAPS) {
  JavaThread* thread = (JavaThread *)THREAD;
  bool clear_pending_exception = true;

  guarantee(thread->is_Java_thread(), "crucial check - the VM thread cannot and must not escape to Java code");
  assert(!thread->owns_locks(), "must release all locks when leaving VM");
  guarantee(!thread->is_Compiler_thread(), "cannot make java calls from the compiler");
  _result   = result;

  // Allocate handle block for Java code. This must be done before we change thread_state to _thread_in_Java_or_stub,
  // since it can potentially block.
  JNIHandleBlock* new_handles = JNIHandleBlock::allocate_block(thread);

  // After this, we are official in JavaCode. This needs to be done before we change any of the thread local
  // info, since we cannot find oops before the new information is set up completely.
  ThreadStateTransition::transition(thread, _thread_in_vm, _thread_in_Java);

  // Make sure that we handle asynchronous stops and suspends _before_ we clear all thread state
  // in JavaCallWrapper::JavaCallWrapper(). This way, we can decide if we need to do any pd actions
  // to prepare for stop/suspend (flush register windows on sparcs, cache sp, or other state).
  if (thread->has_special_runtime_exit_condition()) {
    thread->handle_special_runtime_exit_condition();
    if (HAS_PENDING_EXCEPTION) {
      clear_pending_exception = false;
    }
  }


  // Make sure to set the oop's after the thread transition - since we can block there. No one is GC'ing
  // the JavaCallWrapper before the entry frame is on the stack.
  _callee_method = callee_method();
  _receiver = receiver();

#ifdef CHECK_UNHANDLED_OOPS
  THREAD->allow_unhandled_oop(&_receiver);
#endif // CHECK_UNHANDLED_OOPS

  _thread       = (JavaThread *)thread;
  _handles      = _thread->active_handles();    // save previous handle block & Java frame linkage

  // For the profiler, the last_Java_frame information in thread must always be in
  // legal state. We have no last Java frame if last_Java_sp == NULL so
  // the valid transition is to clear _last_Java_sp and then reset the rest of
  // the (platform specific) state.

  _anchor.copy(_thread->frame_anchor());
  _thread->frame_anchor()->clear();

  debug_only(_thread->inc_java_call_counter());
  _thread->set_active_handles(new_handles);     // install new handle block and reset Java frame linkage

  assert (_thread->thread_state() != _thread_in_native, "cannot set native pc to NULL");

  // clear any pending exception in thread (native calls start with no exception pending)
  if(clear_pending_exception) {
    _thread->clear_pending_exception();
  }

  if (_anchor.last_Java_sp() == NULL) {
    _thread->record_base_of_stack_pointer();
  }
}


JavaCallWrapper::~JavaCallWrapper() {
  assert(_thread == JavaThread::current(), "must still be the same thread");

  // restore previous handle block & Java frame linkage
  JNIHandleBlock *_old_handles = _thread->active_handles();
  _thread->set_active_handles(_handles);

  _thread->frame_anchor()->zap();

  debug_only(_thread->dec_java_call_counter());

  if (_anchor.last_Java_sp() == NULL) {
    _thread->set_base_of_stack_pointer(NULL);
  }


  // Old thread-local info. has been restored. We are not back in the VM.
  ThreadStateTransition::transition_from_java(_thread, _thread_in_vm);

  // State has been restored now make the anchor frame visible for the profiler.
  // Do this after the transition because this allows us to put an assert
  // the Java->vm transition which checks to see that stack is not walkable
  // on sparc/ia64 which will catch violations of the reseting of last_Java_frame
  // invariants (i.e. _flags always cleared on return to Java)

  _thread->frame_anchor()->copy(&_anchor);

  // Release handles after we are marked as being inside the VM again, since this
  // operation might block
  JNIHandleBlock::release_block(_old_handles, _thread);
}


void JavaCallWrapper::oops_do(OopClosure* f) {
  f->do_oop((oop*)&_receiver);
  handles()->oops_do(f);
}


// Helper methods
static BasicType runtime_type_from(JavaValue* result) {
  switch (result->get_type()) {
    case T_BOOLEAN: // fall through
    case T_CHAR   : // fall through
    case T_SHORT  : // fall through
    case T_INT    : // fall through
#ifndef _LP64
    case T_OBJECT : // fall through
    case T_ARRAY  : // fall through
#endif
    case T_BYTE   : // fall through
    case T_VOID   : return T_INT;
    case T_LONG   : return T_LONG;
    case T_FLOAT  : return T_FLOAT;
    case T_DOUBLE : return T_DOUBLE;
#ifdef _LP64
    case T_ARRAY  : // fall through
    case T_OBJECT:  return T_OBJECT;
#endif
  }
  ShouldNotReachHere();
  return T_ILLEGAL;
}

// ===== object constructor calls =====

void JavaCalls::call_default_constructor(JavaThread* thread, methodHandle method, Handle receiver, TRAPS) {
  assert(method->name() == vmSymbols::object_initializer_name(),    "Should only be called for default constructor");
  assert(method->signature() == vmSymbols::void_method_signature(), "Should only be called for default constructor");

  InstanceKlass* ik = method->method_holder();
  if (ik->is_initialized() && ik->has_vanilla_constructor()) {
    // safe to skip constructor call
  } else {
    static JavaValue result(T_VOID);
    JavaCallArguments args(receiver);
    call(&result, method, &args, CHECK);
  }
}

// ============ Virtual calls ============

void JavaCalls::call_virtual(JavaValue* result, KlassHandle spec_klass, Symbol* name, Symbol* signature, JavaCallArguments* args, TRAPS) {
  CallInfo callinfo;
  Handle receiver = args->receiver();
  KlassHandle recvrKlass(THREAD, receiver.is_null() ? (Klass*)NULL : receiver->klass());
  LinkResolver::resolve_virtual_call(
          callinfo, receiver, recvrKlass, spec_klass, name, signature,
          KlassHandle(), false, true, CHECK);
  methodHandle method = callinfo.selected_method();
  assert(method.not_null(), "should have thrown exception");

  // Invoke the method
  JavaCalls::call(result, method, args, CHECK);
}


void JavaCalls::call_virtual(JavaValue* result, Handle receiver, KlassHandle spec_klass, Symbol* name, Symbol* signature, TRAPS) {
  JavaCallArguments args(receiver); // One oop argument
  call_virtual(result, spec_klass, name, signature, &args, CHECK);
}


void JavaCalls::call_virtual(JavaValue* result, Handle receiver, KlassHandle spec_klass, Symbol* name, Symbol* signature, Handle arg1, TRAPS) {
  JavaCallArguments args(receiver); // One oop argument
  args.push_oop(arg1);
  call_virtual(result, spec_klass, name, signature, &args, CHECK);
}



void JavaCalls::call_virtual(JavaValue* result, Handle receiver, KlassHandle spec_klass, Symbol* name, Symbol* signature, Handle arg1, Handle arg2, TRAPS) {
  JavaCallArguments args(receiver); // One oop argument
  args.push_oop(arg1);
  args.push_oop(arg2);
  call_virtual(result, spec_klass, name, signature, &args, CHECK);
}


// ============ Special calls ============

void JavaCalls::call_special(JavaValue* result, KlassHandle klass, Symbol* name, Symbol* signature, JavaCallArguments* args, TRAPS) {
  CallInfo callinfo;
  LinkResolver::resolve_special_call(callinfo, klass, name, signature, KlassHandle(), false, CHECK);
  methodHandle method = callinfo.selected_method();
  assert(method.not_null(), "should have thrown exception");

  // Invoke the method
  JavaCalls::call(result, method, args, CHECK);
}


void JavaCalls::call_special(JavaValue* result, Handle receiver, KlassHandle klass, Symbol* name, Symbol* signature, TRAPS) {
  JavaCallArguments args(receiver); // One oop argument
  call_special(result, klass, name, signature, &args, CHECK);
}


void JavaCalls::call_special(JavaValue* result, Handle receiver, KlassHandle klass, Symbol* name, Symbol* signature, Handle arg1, TRAPS) {
  JavaCallArguments args(receiver); // One oop argument
  args.push_oop(arg1);
  call_special(result, klass, name, signature, &args, CHECK);
}


void JavaCalls::call_special(JavaValue* result, Handle receiver, KlassHandle klass, Symbol* name, Symbol* signature, Handle arg1, Handle arg2, TRAPS) {
  JavaCallArguments args(receiver); // One oop argument
  args.push_oop(arg1);
  args.push_oop(arg2);
  call_special(result, klass, name, signature, &args, CHECK);
}


// ============ Static calls ============

void JavaCalls::call_static(JavaValue* result, KlassHandle klass, Symbol* name, Symbol* signature, JavaCallArguments* args, TRAPS) {
  CallInfo callinfo;
  LinkResolver::resolve_static_call(callinfo, klass, name, signature, KlassHandle(), false, true, CHECK);
  methodHandle method = callinfo.selected_method();
  assert(method.not_null(), "should have thrown exception");

  // Invoke the method
  JavaCalls::call(result, method, args, CHECK);
}


void JavaCalls::call_static(JavaValue* result, KlassHandle klass, Symbol* name, Symbol* signature, TRAPS) {
  JavaCallArguments args; // No argument
  call_static(result, klass, name, signature, &args, CHECK);
}


void JavaCalls::call_static(JavaValue* result, KlassHandle klass, Symbol* name, Symbol* signature, Handle arg1, TRAPS) {
  JavaCallArguments args(arg1); // One oop argument
  call_static(result, klass, name, signature, &args, CHECK);
}


void JavaCalls::call_static(JavaValue* result, KlassHandle klass, Symbol* name, Symbol* signature, Handle arg1, Handle arg2, TRAPS) {
  JavaCallArguments args; // One oop argument
  args.push_oop(arg1);
  args.push_oop(arg2);
  call_static(result, klass, name, signature, &args, CHECK);
}


// -------------------------------------------------
// Implementation of JavaCalls (low level)


void JavaCalls::call(JavaValue* result, methodHandle method, JavaCallArguments* args, TRAPS) {
  // Check if we need to wrap a potential OS exception handler around thread
  // This is used for e.g. Win32 structured exception handlers
  assert(THREAD->is_Java_thread(), "only JavaThreads can make JavaCalls");
  // Need to wrap each and everytime, since there might be native code down the
  // stack that has installed its own exception handlers
  os::os_exception_wrapper(call_helper, result, &method, args, THREAD);
}

void JavaCalls::call_helper(JavaValue* result, methodHandle* m, JavaCallArguments* args, TRAPS) {
  methodHandle method = *m;
  JavaThread* thread = (JavaThread*)THREAD;
  assert(thread->is_Java_thread(), "must be called by a java thread");
  assert(method.not_null(), "must have a method to call");
  assert(!SafepointSynchronize::is_at_safepoint(), "call to Java code during VM operation");
  assert(!thread->handle_area()->no_handle_mark_active(), "cannot call out to Java here");


  CHECK_UNHANDLED_OOPS_ONLY(thread->clear_unhandled_oops();)

  // Verify the arguments

  if (CheckJNICalls)  {
    args->verify(method, result->get_type(), thread);
  }
  else debug_only(args->verify(method, result->get_type(), thread));

  // Ignore call if method is empty
  if (method->is_empty_method()) {
    assert(result->get_type() == T_VOID, "an empty method must return a void value");
    return;
  }


#ifdef ASSERT
  { InstanceKlass* holder = method->method_holder();
    // A klass might not be initialized since JavaCall's might be used during the executing of
    // the <clinit>. For example, a Thread.start might start executing on an object that is
    // not fully initialized! (bad Java programming style)
    assert(holder->is_linked(), "rewritting must have taken place");
  }
#endif


  assert(!thread->is_Compiler_thread(), "cannot compile from the compiler");
  if (CompilationPolicy::must_be_compiled(method)) {
    CompileBroker::compile_method(method, InvocationEntryBci,
                                  CompilationPolicy::policy()->initial_compile_level(),
                                  methodHandle(), 0, "must_be_compiled", CHECK);
  }

  // Since the call stub sets up like the interpreter we call the from_interpreted_entry
  // so we can go compiled via a i2c. Otherwise initial entry method will always
  // run interpreted.
  address entry_point = method->from_interpreted_entry();
  if (JvmtiExport::can_post_interpreter_events() && thread->is_interp_only_mode()) {
    entry_point = method->interpreter_entry();
  }

  // Figure out if the result value is an oop or not (Note: This is a different value
  // than result_type. result_type will be T_INT of oops. (it is about size)
  BasicType result_type = runtime_type_from(result);
  bool oop_result_flag = (result->get_type() == T_OBJECT || result->get_type() == T_ARRAY);

  // NOTE: if we move the computation of the result_val_address inside
  // the call to call_stub, the optimizer produces wrong code.
  intptr_t* result_val_address = (intptr_t*)(result->get_value_addr());

  // Find receiver
  Handle receiver = (!method->is_static()) ? args->receiver() : Handle();

  // When we reenter Java, we need to reenable the yellow zone which
  // might already be disabled when we are in VM.
  if (thread->stack_yellow_zone_disabled()) {
    thread->reguard_stack();
  }

  // Check that there are shadow pages available before changing thread state
  // to Java
  if (!os::stack_shadow_pages_available(THREAD, method)) {
    // Throw stack overflow exception with preinitialized exception.
    Exceptions::throw_stack_overflow_exception(THREAD, __FILE__, __LINE__, method);
    return;
  } else {
    // Touch pages checked if the OS needs them to be touched to be mapped.
    os::bang_stack_shadow_pages();
  }

  // do call
  { JavaCallWrapper link(method, receiver, result, CHECK);
    { HandleMark hm(thread);  // HandleMark used by HandleMarkCleaner

      StubRoutines::call_stub()(
        (address)&link,
        // (intptr_t*)&(result->_value), // see NOTE above (compiler problem)
        result_val_address,          // see NOTE above (compiler problem)
        result_type,
        method(),
        entry_point,
        args->parameters(),
        args->size_of_parameters(),
        CHECK
      );

      result = link.result();  // circumvent MS C++ 5.0 compiler bug (result is clobbered across call)
      // Preserve oop return value across possible gc points
      if (oop_result_flag) {
        thread->set_vm_result((oop) result->get_jobject());
      }
    }
  } // Exit JavaCallWrapper (can block - potential return oop must be preserved)

  // Check if a thread stop or suspend should be executed
  // The following assert was not realistic.  Thread.stop can set that bit at any moment.
  //assert(!thread->has_special_runtime_exit_condition(), "no async. exceptions should be installed");

  // Restore possible oop return
  if (oop_result_flag) {
    result->set_jobject((jobject)thread->vm_result());
    thread->set_vm_result(NULL);
  }
}


//--------------------------------------------------------------------------------------
// Implementation of JavaCallArguments

intptr_t* JavaCallArguments::parameters() {
  // First convert all handles to oops
  for(int i = 0; i < _size; i++) {
    if (_is_oop[i]) {
      // Handle conversion
      _value[i] = cast_from_oop<intptr_t>(Handle::raw_resolve((oop *)_value[i]));
    }
  }
  // Return argument vector
  return _value;
}


class SignatureChekker : public SignatureIterator {
 private:
   bool *_is_oop;
   int   _pos;
   BasicType _return_type;
   intptr_t*   _value;
   Thread* _thread;

 public:
  bool _is_return;

  SignatureChekker(Symbol* signature, BasicType return_type, bool is_static, bool* is_oop, intptr_t* value, Thread* thread) : SignatureIterator(signature) {
    _is_oop = is_oop;
    _is_return = false;
    _return_type = return_type;
    _pos = 0;
    _value = value;
    _thread = thread;

    if (!is_static) {
      check_value(true); // Receiver must be an oop
    }
  }

  void check_value(bool type) {
    guarantee(_is_oop[_pos++] == type, "signature does not match pushed arguments");
  }

  void check_doing_return(bool state) { _is_return = state; }

  void check_return_type(BasicType t) {
    guarantee(_is_return && t == _return_type, "return type does not match");
  }

  void check_int(BasicType t) {
    if (_is_return) {
      check_return_type(t);
      return;
    }
    check_value(false);
  }

  void check_double(BasicType t) { check_long(t); }

  void check_long(BasicType t) {
    if (_is_return) {
      check_return_type(t);
      return;
    }

    check_value(false);
    check_value(false);
  }

  void check_obj(BasicType t) {
    if (_is_return) {
      check_return_type(t);
      return;
    }

    // verify handle and the oop pointed to by handle
    int p = _pos;
    bool bad = false;
    // If argument is oop
    if (_is_oop[p]) {
      intptr_t v = _value[p];
      if (v != 0 ) {
        size_t t = (size_t)v;
        bad = (t < (size_t)os::vm_page_size() ) || !Handle::raw_resolve((oop *)v)->is_oop_or_null(true);
        if (CheckJNICalls && bad) {
          ReportJNIFatalError((JavaThread*)_thread, "Bad JNI oop argument");
        }
      }
      // for the regular debug case.
      assert(!bad, "Bad JNI oop argument");
    }

    check_value(true);
  }

  void do_bool()                       { check_int(T_BOOLEAN);       }
  void do_char()                       { check_int(T_CHAR);          }
  void do_float()                      { check_int(T_FLOAT);         }
  void do_double()                     { check_double(T_DOUBLE);     }
  void do_byte()                       { check_int(T_BYTE);          }
  void do_short()                      { check_int(T_SHORT);         }
  void do_int()                        { check_int(T_INT);           }
  void do_long()                       { check_long(T_LONG);         }
  void do_void()                       { check_return_type(T_VOID);  }
  void do_object(int begin, int end)   { check_obj(T_OBJECT);        }
  void do_array(int begin, int end)    { check_obj(T_OBJECT);        }
};


void JavaCallArguments::verify(methodHandle method, BasicType return_type,
  Thread *thread) {
  guarantee(method->size_of_parameters() == size_of_parameters(), "wrong no. of arguments pushed");

  // Treat T_OBJECT and T_ARRAY as the same
  if (return_type == T_ARRAY) return_type = T_OBJECT;

  // Check that oop information is correct
  Symbol* signature = method->signature();

  SignatureChekker sc(signature, return_type, method->is_static(),_is_oop, _value, thread);
  sc.iterate_parameters();
  sc.check_doing_return(true);
  sc.iterate_returntype();
}

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