/*

 * Copyright (c) 2001, 2019, 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_RUNTIME_PERFMEMORY_HPP

#define SHARE_RUNTIME_PERFMEMORY_HPP

#include "runtime/globals.hpp"

#include "utilities/exceptions.hpp"

/*

 * PerfData Version Constants

 *   - Major Version - change whenever the structure of PerfDataEntry changes

 *   - Minor Version - change whenever the data within the PerfDataEntry

 *                     structure changes. for example, new unit or variability

 *                     values are added or new PerfData subtypes are added.

 */

#define PERFDATA_MAJOR_VERSION 2

#define PERFDATA_MINOR_VERSION 0

/* Byte order of the PerfData memory region. The byte order is exposed in

 * the PerfData memory region as the data in the memory region may have

 * been generated by a little endian JVM implementation. Tracking the byte

 * order in the PerfData memory region allows Java applications to adapt

 * to the native byte order for monitoring purposes. This indicator is

 * also useful when a snapshot of the PerfData memory region is shipped

 * to a machine with a native byte order different from that of the

 * originating machine.

 */

#define PERFDATA_BIG_ENDIAN     0

#define PERFDATA_LITTLE_ENDIAN  1

/*

 * The PerfDataPrologue structure is known by the PerfDataBuffer Java class

 * libraries that read the PerfData memory region. The size and the position

 * of the fields must be changed along with their counterparts in the

 * PerfDataBuffer Java class. The first four bytes of this structure

 * should never change, or compatibility problems between the monitoring

 * applications and HotSpot VMs will result. The reserved fields are

 * available for future enhancements.

 */

typedef struct {

  jint   magic;              // magic number - 0xcafec0c0

  jbyte  byte_order;         // byte order of the buffer

  jbyte  major_version;      // major and minor version numbers

  jbyte  minor_version;

  jbyte  accessible;         // ready to access

  jint   used;               // number of PerfData memory bytes used

  jint   overflow;           // number of bytes of overflow

  jlong  mod_time_stamp;     // time stamp of last structural modification

  jint   entry_offset;       // offset of the first PerfDataEntry

  jint   num_entries;        // number of allocated PerfData entries

} PerfDataPrologue;

/* The PerfDataEntry structure defines the fixed portion of an entry

 * in the PerfData memory region. The PerfDataBuffer Java libraries

 * are aware of this structure and need to be changed when this

 * structure changes.

 */

typedef struct {

  jint entry_length;      // entry length in bytes

  jint name_offset;       // offset of the data item name

  jint vector_length;     // length of the vector. If 0, then scalar

  jbyte data_type;        // type of the data item -

                          // 'B','Z','J','I','S','C','D','F','V','L','['

  jbyte flags;            // flags indicating misc attributes

  jbyte data_units;       // unit of measure for the data type

  jbyte data_variability; // variability classification of data type

  jint  data_offset;      // offset of the data item

/*

  body of PerfData memory entry is variable length

  jbyte[name_length] data_name;        // name of the data item

  jbyte[pad_length] data_pad;          // alignment of data item

  j<data_type>[data_length] data_item; // array of appropriate types.

                                       // data_length is > 1 only when the

                                       // data_type is T_ARRAY.

*/

} PerfDataEntry;

// Prefix of performance data file.

extern const char PERFDATA_NAME[];

// UINT_CHARS contains the number of characters holding a process id

// (i.e. pid). pid is defined as unsigned "int" so the maximum possible pid value

// would be 2^32 - 1 (4294967295) which can be represented as a 10 characters

// string.

static const size_t UINT_CHARS = 10;

/* the PerfMemory class manages creation, destruction,

 * and allocation of the PerfData region.

 */

class PerfMemory : AllStatic {

    friend class VMStructs;

    friend class PerfMemoryTest;

  private:

    static char*  _start;

    static char*  _end;

    static char*  _top;

    static size_t _capacity;

    static PerfDataPrologue*  _prologue;

    static int    _initialized;

    static bool   _destroyed;

    static void create_memory_region(size_t sizep);

    static void delete_memory_region();

  public:

    enum PerfMemoryMode {

      PERF_MODE_RO = 0,

      PERF_MODE_RW = 1

    };

    static char* alloc(size_t size);

    static char* start() { return _start; }

    static char* end() { return _end; }

    static size_t used() { return (size_t) (_top - _start); }

    static size_t capacity() { return _capacity; }

    static bool is_initialized();

    static bool is_destroyed() { return _destroyed; }

    static bool is_usable() { return is_initialized() && !is_destroyed(); }

    static bool contains(char* addr) {

      return ((_start != NULL) && (addr >= _start) && (addr < _end));

    }

    static void mark_updated();

    // methods for attaching to and detaching from the PerfData

    // memory segment of another JVM process on the same system.

    static void attach(const char* user, int vmid, PerfMemoryMode mode,

                       char** addrp, size_t* size, TRAPS);

    static void detach(char* addr, size_t bytes, TRAPS);

    static void initialize();

    static void destroy();

    static void set_accessible(bool value) {

      if (UsePerfData) {

        _prologue->accessible = value;

      }

    }

    // returns the complete file path of hsperfdata.

    // the caller is expected to free the allocated memory.

    static char* get_perfdata_file_path();

};

void perfMemory_init();

void perfMemory_exit();

#endif // SHARE_RUNTIME_PERFMEMORY_HPP