/*
 * Copyright (c) 2017, Google 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_RUNTIME_HEAPMONITORING_HPP
#define SHARE_VM_RUNTIME_HEAPMONITORING_HPP

#include "gc/shared/referenceProcessor.hpp"
#include "runtime/sharedRuntime.hpp"

// Support class for sampling heap allocations across the VM.
class HeapMonitoring : AllStatic {
 private:
  // Cheap random number generator
  static uint64_t _rnd;
  static bool _initialized;
  static jint _monitoring_rate;
  static bool _enabled;

  // Statics for the fast log
  static const int _fast_log_num_bits = 10;
  static const int _fast_log_mask = (1 << _fast_log_num_bits) - 1;
  static double _log_table[1<<_fast_log_num_bits];  // Constant

  static void pick_next_sample(JavaThread *t);

  // Returns the next prng value.
  // pRNG is: aX+b mod c with a = 0x5DEECE66D, b =  0xB, c = 1<<48
  // This is the lrand64 generator.
  static inline uint64_t next_random(uint64_t rnd) {
    const uint64_t prng_mult = 0x5DEECE66DLL;
    const uint64_t prng_add = 0xB;
    const uint64_t prng_mod_power = 48;
    const uint64_t prng_mod_mask =
        ~((~static_cast<uint64_t>(0)) << prng_mod_power);
    return (prng_mult * rnd + prng_add) & prng_mod_mask;
  }

  static inline double fast_log2(const double & d) {
    assert(d>0, "bad value passed to assert");
    uint64_t x = 0;
    memcpy(&x, &d, sizeof(uint64_t));
    const uint32_t x_high = x >> 32;
    const uint32_t y = x_high >> (20 - _fast_log_num_bits) & _fast_log_mask;
    const int32_t exponent = ((x_high >> 20) & 0x7FF) - 1023;
    return exponent + _log_table[y];
  }

 public:
  static void pick_next_sample(size_t *ptr);

  static void get_live_traces(jvmtiStackTraces* stack_traces);
  static void get_garbage_traces(jvmtiStackTraces* stack_traces);
  static void get_frequent_garbage_traces(jvmtiStackTraces* stack_traces);
  static void release_traces(jvmtiStackTraces *trace_info);
  static void initialize_profiling(jint monitoring_rate, jint max_storage);
  static void stop_profiling();
  static bool initialized();
  static bool *initialized_address();

  // Called when o is allocated, called by interpreter and C1.
  static void object_alloc_unsized(oopDesc* o);
  static void object_alloc(oopDesc* o, intx byte_size);

  // Called when o is allocated from C2 directly,
  // we know the thread, and we have done the sampling.
  static void object_alloc_do_sample(Thread *t, oopDesc *o, intx size_in_bytes);

  // Called to clean up oops that have been saved by our sampling function,
  // but which no longer have other references in the heap.
  static void weak_oops_do(AbstractRefProcTaskExecutor *task_executor,
                           BoolObjectClosure* is_alive,
                           OopClosure *f,
                           VoidClosure *complete_gc);
  static void weak_oops_do(OopClosure* oop_closure) {
    weak_oops_do(NULL, NULL, oop_closure, NULL);
  }

  static bool enabled() {
    return _enabled;
  }
};

#endif // SHARE_VM_RUNTIME_HEAPMONITORING_HPP