/*

 * Copyright (c) 1997, 2012, 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.

 *

 */

#ifndef SHARE_VM_UTILITIES_EVENTS_HPP

#define SHARE_VM_UTILITIES_EVENTS_HPP

#include "memory/allocation.hpp"

#include "runtime/mutexLocker.hpp"

#include "runtime/thread.hpp"

#include "utilities/top.hpp"

#include "utilities/vmError.hpp"

// Events and EventMark provide interfaces to log events taking place in the vm.

// This facility is extremly useful for post-mortem debugging. The eventlog

// often provides crucial information about events leading up to the crash.

//

// Abstractly the logs can record whatever they way but normally they

// would record at least a timestamp and the current Thread, along

// with whatever data they need in a ring buffer.  Commonly fixed

// length text messages are recorded for simplicity but other

// strategies could be used.  Several logs are provided by default but

// new instances can be created as needed.

// The base event log dumping class that is registered for dumping at

// crash time.  This is a very generic interface that is mainly here

// for completeness.  Normally the templated EventLogBase would be

// subclassed to provide different log types.

  friend class Events;

 private:

  EventLog* _next;

  EventLog* next() const { return _next; }

 public:

  // Automatically registers the log so that it will be printed during

  // crashes.

  EventLog();

  virtual void print_log_on(outputStream* out) = 0;

};

// A templated subclass of EventLog that provides basic ring buffer

// functionality.  Most event loggers should subclass this, possibly

// providing a more featureful log function if the existing copy

// semantics aren't appropriate.  The name is used as the label of the

// log when it is dumped during a crash.

template <class T> class EventLogBase : public EventLog {

  template <class X> class EventRecord {

   public:

    double  timestamp;

    Thread* thread;

    X       data;

  };

 protected:

  Mutex           _mutex;

  const char*     _name;

  int             _length;

  int             _index;

  int             _count;

  EventRecord<T>* _records;

 public:

  EventLogBase<T>(const char* name, int length = LogEventsBufferEntries):

    _name(name),

    _length(length),

    _count(0),

    _index(0),

    _mutex(Mutex::event, name) {

    _records = new EventRecord<T>[length];

  }

  double fetch_timestamp() {

    return os::elapsedTime();

  }

  // move the ring buffer to next open slot and return the index of

  // the slot to use for the current message.  Should only be called

  // while mutex is held.

  int compute_log_index() {

    int index = _index;

    if (_count < _length) _count++;

    _index++;

    if (_index >= _length) _index = 0;

    return index;

  }

  bool should_log() {

    // Don't bother adding new entries when we're crashing.  This also

    // avoids mutating the ring buffer when printing the log.

    return !VMError::fatal_error_in_progress();

  }

  // Print the contents of the log

  void print_log_on(outputStream* out);

 private:

  void print_log_impl(outputStream* out);

  // Print a single element.  A templated implementation might need to

  // be declared by subclasses.

  void print(outputStream* out, T& e);

  void print(outputStream* out, EventRecord<T>& e) {

    out->print("Event: %.3f ", e.timestamp);

    if (e.thread != NULL) {

      out->print("Thread " INTPTR_FORMAT " ", e.thread);

    }

    print(out, e.data);

  }

};

// A simple wrapper class for fixed size text messages.

class StringLogMessage : public FormatBuffer<132> {

 public:

  // Wrap this buffer in a stringStream.

  stringStream stream() {

    return stringStream(_buf, sizeof(_buf));

  }

};

// A simple ring buffer of fixed size text messages.

class StringEventLog : public EventLogBase<StringLogMessage> {

 public:

  StringEventLog(const char* name, int count = LogEventsBufferEntries) : EventLogBase<StringLogMessage>(name, count) {}

  void logv(Thread* thread, const char* format, va_list ap) {

    if (!should_log()) return;

    double timestamp = fetch_timestamp();

    MutexLockerEx ml(&_mutex, Mutex::_no_safepoint_check_flag);

    int index = compute_log_index();

    _records[index].thread = thread;

    _records[index].timestamp = timestamp;

    _records[index].data.printv(format, ap);

  }

  void log(Thread* thread, const char* format, ...) {

    va_list ap;

    va_start(ap, format);

    logv(thread, format, ap);

    va_end(ap);

  }

};

class Events : AllStatic {

  friend class EventLog;

 private:

  static EventLog* _logs;

  // A log for generic messages that aren't well categorized.

  static StringEventLog* _messages;

  // A log for internal exception related messages, like internal

  // throws and implicit exceptions.

  static StringEventLog* _exceptions;

  // Deoptization related messages

  static StringEventLog* _deopt_messages;

 public:

  static void print_all(outputStream* out);

  // Dump all events to the tty

  static void print();

  // Logs a generic message with timestamp and format as printf.

  static void log(Thread* thread, const char* format, ...);

  // Log exception related message

  static void log_exception(Thread* thread, const char* format, ...);

  static void log_deopt_message(Thread* thread, const char* format, ...);

  // Register default loggers

  static void init();

};

inline void Events::log(Thread* thread, const char* format, ...) {

  if (LogEvents) {

    va_list ap;

    va_start(ap, format);

    _messages->logv(thread, format, ap);

    va_end(ap);

  }

}

inline void Events::log_exception(Thread* thread, const char* format, ...) {

  if (LogEvents) {

    va_list ap;

    va_start(ap, format);

    _exceptions->logv(thread, format, ap);

    va_end(ap);

  }

}

inline void Events::log_deopt_message(Thread* thread, const char* format, ...) {

  if (LogEvents) {

    va_list ap;

    va_start(ap, format);

    _deopt_messages->logv(thread, format, ap);

    va_end(ap);

  }

}

template <class T>

inline void EventLogBase<T>::print_log_on(outputStream* out) {

  if (ThreadLocalStorage::get_thread_slow() == NULL) {

    // Not a regular Java thread so don't bother locking

    print_log_impl(out);

  } else {

    MutexLockerEx ml(&_mutex, Mutex::_no_safepoint_check_flag);

    print_log_impl(out);

  }

}

// Dump the ring buffer entries that current have entries.

template <class T>

inline void EventLogBase<T>::print_log_impl(outputStream* out) {

  out->print_cr("%s (%d events):", _name, _count);

  if (_count == 0) {

    out->print_cr("No events");

    out->cr();

    return;

  }

  if (_count < _length) {

    for (int i = 0; i < _count; i++) {

      print(out, _records[i]);

    }

  } else {

    for (int i = _index; i < _length; i++) {

      print(out, _records[i]);

    }

    for (int i = 0; i < _index; i++) {

      print(out, _records[i]);

    }

  }

  out->cr();

}

// Implement a printing routine for the StringLogMessage

template <>

inline void EventLogBase<StringLogMessage>::print(outputStream* out, StringLogMessage& lm) {

  out->print_raw(lm);

  out->cr();

}

// Place markers for the beginning and end up of a set of events.

// These end up in the default log.

class EventMark : public StackObj {

  StringLogMessage _buffer;

 public:

  // log a begin event, format as printf

  EventMark(const char* format, ...);

  // log an end event

  ~EventMark();

};

#endif // SHARE_VM_UTILITIES_EVENTS_HPP