text: /*
   * Copyright (c) 2001, 2010, 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_RUNTIME_PERFMEMORY_HPP
  #define SHARE_VM_RUNTIME_PERFMEMORY_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;
    private:
      static char*  _start;
      static char*  _end;
      static char*  _top;
      static size_t _capacity;
      static PerfDataPrologue*  _prologue;
      static jint   _initialized;
  
      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() { return _initialized != 0; }
      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;
        }
      }
  
      // filename of backing store or NULL if none.
      static char* backing_store_filename();
  
      // 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_VM_RUNTIME_PERFMEMORY_HPP
  