alvinalexander.com | career | drupal | java | mac | mysql | perl | scala | uml | unix  

Java example source code file (vmStructs.hpp)

This example Java source code file (vmStructs.hpp) 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.

Learn more about this Java project at its project page.

Java - Java tags/keywords

address, does, klass, method, name, share_vm_runtime_vmstructs_hpp, size, superclass, the, value, vmintconstantentry, vmlongconstantentry, vmstructentry, vmtypeentry

The vmStructs.hpp Java example source code

/*
 * Copyright (c) 2000, 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.
 *
 */

#ifndef SHARE_VM_RUNTIME_VMSTRUCTS_HPP
#define SHARE_VM_RUNTIME_VMSTRUCTS_HPP

#include "utilities/debug.hpp"
#ifdef COMPILER1
#include "c1/c1_Runtime1.hpp"
#endif

// This table encapsulates the debugging information required by the
// serviceability agent in order to run. Specifically, we need to
// understand the layout of certain C data structures (offsets, in
// bytes, of their fields.)
//
// There are alternatives for the design of this mechanism, including
// parsing platform-specific debugging symbols from a debug build into
// a program database. While this current mechanism can be considered
// to be a workaround for the inability to debug arbitrary C and C++
// programs at the present time, it does have certain advantages.
// First, it is platform-independent, which will vastly simplify the
// initial bringup of the system both now and on future platforms.
// Second, it is embedded within the VM, as opposed to being in a
// separate program database; experience has shown that whenever
// portions of a system are decoupled, version skew is problematic.
// Third, generating a program database, for example for a product
// build, would probably require two builds to be done: the desired
// product build as well as an intermediary build with the PRODUCT
// flag turned on but also compiled with -g, leading to a doubling of
// the time required to get a serviceability agent-debuggable product
// build. Fourth, and very significantly, this table probably
// preserves more information about field types than stabs do; for
// example, it preserves the fact that a field is a "jlong" rather
// than transforming the type according to the typedef in jni_md.h,
// which allows the Java-side code to identify "Java-sized" fields in
// C++ data structures. If the symbol parsing mechanism was redone
// using stabs, it might still be necessary to have a table somewhere
// containing this information.
//
// Do not change the sizes or signedness of the integer values in
// these data structures; they are fixed over in the serviceability
// agent's Java code (for bootstrapping).

typedef struct {
  const char* typeName;            // The type name containing the given field (example: "Klass")
  const char* fieldName;           // The field name within the type           (example: "_name")
  const char* typeString;          // Quoted name of the type of this field (example: "Symbol*";
                                   // parsed in Java to ensure type correctness
  int32_t  isStatic;               // Indicates whether following field is an offset or an address
  uint64_t offset;                 // Offset of field within structure; only used for nonstatic fields
  void* address;                   // Address of field; only used for static fields
                                   // ("offset" can not be reused because of apparent SparcWorks compiler bug
                                   // in generation of initializer data)
} VMStructEntry;

typedef struct {
  const char* typeName;            // Type name (example: "Method")
  const char* superclassName;      // Superclass name, or null if none (example: "oopDesc")
  int32_t isOopType;               // Does this type represent an oop typedef? (i.e., "Method*" or
                                   // "Klass*", but NOT "Method")
  int32_t isIntegerType;           // Does this type represent an integer type (of arbitrary size)?
  int32_t isUnsigned;              // If so, is it unsigned?
  uint64_t size;                   // Size, in bytes, of the type
} VMTypeEntry;

typedef struct {
  const char* name;                // Name of constant (example: "_thread_in_native")
  int32_t value;                   // Value of constant
} VMIntConstantEntry;

typedef struct {
  const char* name;                // Name of constant (example: "_thread_in_native")
  uint64_t value;                  // Value of constant
} VMLongConstantEntry;

// This class is a friend of most classes, to be able to access
// private fields
class VMStructs {
public:
  // The last entry is identified over in the serviceability agent by
  // the fact that it has a NULL fieldName
  static VMStructEntry localHotSpotVMStructs[];

  // The last entry is identified over in the serviceability agent by
  // the fact that it has a NULL typeName
  static VMTypeEntry   localHotSpotVMTypes[];

  // Table of integer constants required by the serviceability agent.
  // The last entry is identified over in the serviceability agent by
  // the fact that it has a NULL typeName
  static VMIntConstantEntry localHotSpotVMIntConstants[];

  // Table of long constants required by the serviceability agent.
  // The last entry is identified over in the serviceability agent by
  // the fact that it has a NULL typeName
  static VMLongConstantEntry localHotSpotVMLongConstants[];

  // This is used to run any checking code necessary for validation of
  // the data structure (debug build only)
  static void init();

#ifndef PRODUCT
  // Execute unit tests
  static void test();
#endif

private:
  // Look up a type in localHotSpotVMTypes using strcmp() (debug build only).
  // Returns 1 if found, 0 if not.
  //  debug_only(static int findType(const char* typeName);)
  static int findType(const char* typeName);
};

#endif // SHARE_VM_RUNTIME_VMSTRUCTS_HPP

Other Java examples (source code examples)

Here is a short list of links related to this Java vmStructs.hpp source code file:

... this post is sponsored by my books ...

#1 New Release!

FP Best Seller

 

new blog posts

 

Copyright 1998-2021 Alvin Alexander, alvinalexander.com
All Rights Reserved.

A percentage of advertising revenue from
pages under the /java/jwarehouse URI on this website is
paid back to open source projects.