Java example source code file (CodeCache.java)

This example Java source code file (CodeCache.java) 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, addressfield, codeblob, codecache, codeheap, deoptimizationblob, exceptionblob, internalerror, nmethod, runtimeexception, runtimestub, safepointblob, string, util, virtualconstructor

The CodeCache.java Java example source code

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

package sun.jvm.hotspot.code;

import java.util.*;
import sun.jvm.hotspot.debugger.*;
import sun.jvm.hotspot.memory.*;
import sun.jvm.hotspot.runtime.*;
import sun.jvm.hotspot.types.*;
import sun.jvm.hotspot.utilities.*;

public class CodeCache {
  private static AddressField       heapField;
  private static AddressField       scavengeRootNMethodsField;
  private static VirtualConstructor virtualConstructor;

  private CodeHeap heap;

  static {
    VM.registerVMInitializedObserver(new Observer() {
        public void update(Observable o, Object data) {
          initialize(VM.getVM().getTypeDataBase());
        }
      });
  }

  private static synchronized void initialize(TypeDataBase db) {
    Type type = db.lookupType("CodeCache");

    heapField = type.getAddressField("_heap");
    scavengeRootNMethodsField = type.getAddressField("_scavenge_root_nmethods");

    virtualConstructor = new VirtualConstructor(db);
    // Add mappings for all possible CodeBlob subclasses
    virtualConstructor.addMapping("BufferBlob", BufferBlob.class);
    virtualConstructor.addMapping("nmethod", NMethod.class);
    virtualConstructor.addMapping("RuntimeStub", RuntimeStub.class);
    virtualConstructor.addMapping("AdapterBlob", AdapterBlob.class);
    virtualConstructor.addMapping("MethodHandlesAdapterBlob", MethodHandlesAdapterBlob.class);
    virtualConstructor.addMapping("SafepointBlob", SafepointBlob.class);
    virtualConstructor.addMapping("DeoptimizationBlob", DeoptimizationBlob.class);
    if (VM.getVM().isServerCompiler()) {
      virtualConstructor.addMapping("ExceptionBlob", ExceptionBlob.class);
      virtualConstructor.addMapping("UncommonTrapBlob", UncommonTrapBlob.class);
    }
  }

  public CodeCache() {
    heap = (CodeHeap) VMObjectFactory.newObject(CodeHeap.class, heapField.getValue());
  }

  public NMethod scavengeRootMethods() {
    return (NMethod) VMObjectFactory.newObject(NMethod.class, scavengeRootNMethodsField.getValue());
  }

  public boolean contains(Address p) {
    return getHeap().contains(p);
  }

  /** When VM.getVM().isDebugging() returns true, this behaves like
      findBlobUnsafe */
  public CodeBlob findBlob(Address start) {
    CodeBlob result = findBlobUnsafe(start);
    if (result == null) return null;
    if (VM.getVM().isDebugging()) {
      return result;
    }
    // We could potientially look up non_entrant methods
    // NOTE: this is effectively a "guarantee", and is slightly different from the one in the VM
    if (Assert.ASSERTS_ENABLED) {
      Assert.that(!(result.isZombie() || result.isLockedByVM()), "unsafe access to zombie method");
    }
    return result;
  }

  public CodeBlob findBlobUnsafe(Address start) {
    CodeBlob result = null;

    try {
      result = (CodeBlob) virtualConstructor.instantiateWrapperFor(getHeap().findStart(start));
    }
    catch (WrongTypeException wte) {
      Address cbAddr = null;
      try {
        cbAddr = getHeap().findStart(start);
      }
      catch (Exception findEx) {
        findEx.printStackTrace();
      }

      String message = "Couldn't deduce type of CodeBlob ";
      if (cbAddr != null) {
        message = message + "@" + cbAddr + " ";
      }
      message = message + "for PC=" + start;

      throw new RuntimeException(message, wte);
    }
    if (result == null) return null;
    if (Assert.ASSERTS_ENABLED) {
      // The HeapBlock that contains this blob is outside of the blob
      // but it shouldn't be an error to find a blob based on the
      // pointer to the HeapBlock.
      Assert.that(result.blobContains(start) || result.blobContains(start.addOffsetTo(8)),
                                                                    "found wrong CodeBlob");
    }
    return result;
  }

  public NMethod findNMethod(Address start) {
    CodeBlob cb = findBlob(start);
    if (Assert.ASSERTS_ENABLED) {
      Assert.that(cb == null || cb.isNMethod(), "did not find an nmethod");
    }
    return (NMethod) cb;
  }

  public NMethod findNMethodUnsafe(Address start) {
    CodeBlob cb = findBlobUnsafe(start);
    if (Assert.ASSERTS_ENABLED) {
      Assert.that(cb == null || cb.isNMethod(), "did not find an nmethod");
    }
    return (NMethod) cb;
  }

  /** Routine for instantiating appropriately-typed wrapper for a
      CodeBlob. Used by CodeCache, Runtime1, etc. */
  public CodeBlob createCodeBlobWrapper(Address codeBlobAddr) {
    try {
      return (CodeBlob) virtualConstructor.instantiateWrapperFor(codeBlobAddr);
    }
    catch (Exception e) {
      String message = "Unable to deduce type of CodeBlob from address " + codeBlobAddr +
                       " (expected type nmethod, RuntimeStub, ";
      if (VM.getVM().isClientCompiler()) {
        message = message + " or ";
      }
      message = message + "SafepointBlob";
      if (VM.getVM().isServerCompiler()) {
        message = message + ", DeoptimizationBlob, or ExceptionBlob";
      }
      message = message + ")";
      throw new RuntimeException(message);
    }
  }

  public void iterate(CodeCacheVisitor visitor) {
    CodeHeap heap = getHeap();
    Address ptr = heap.begin();
    Address end = heap.end();

    visitor.prologue(ptr, end);
    CodeBlob lastBlob = null;
    while (ptr != null && ptr.lessThan(end)) {
      try {
        // Use findStart to get a pointer inside blob other findBlob asserts
        CodeBlob blob = findBlobUnsafe(heap.findStart(ptr));
        if (blob != null) {
          visitor.visit(blob);
          if (blob == lastBlob) {
            throw new InternalError("saw same blob twice");
          }
          lastBlob = blob;
        }
      } catch (RuntimeException e) {
        e.printStackTrace();
      }
      Address next = heap.nextBlock(ptr);
      if (next != null && next.lessThan(ptr)) {
        throw new InternalError("pointer moved backwards");
      }
      ptr = next;
    }
    visitor.epilogue();
  }

  //--------------------------------------------------------------------------------
  // Internals only below this point
  //

  private CodeHeap getHeap() {
    return heap;
  }
}