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Java example source code file (exceptionHandlerTable.hpp)

This example Java source code file (exceptionHandlerTable.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.

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Java - Java tags/keywords

catchnode, growablearray, handlertableentry, implicitexceptiontable, reallocmark, share_vm_code_exceptionhandlertable_hpp, value_obj_class_spec

The exceptionHandlerTable.hpp Java example source code

/*
 * Copyright (c) 1998, 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.
 *
 */

#ifndef SHARE_VM_CODE_EXCEPTIONHANDLERTABLE_HPP
#define SHARE_VM_CODE_EXCEPTIONHANDLERTABLE_HPP

#include "memory/allocation.hpp"
#include "oops/method.hpp"

// A HandlerTableEntry describes an individual entry of a subtable
// of ExceptionHandlerTable. An entry consists of a pair(bci, pco),
// where bci is the exception handler bci, and pco is the pc offset
// relative to the nmethod code start for the compiled exception
// handler corresponding to the (interpreted) exception handler
// starting at bci.
//
// The first HandlerTableEntry of each subtable holds the length
// and catch_pco for the subtable (the length is the number of
// subtable entries w/o header).

class HandlerTableEntry {
 private:
  int _bci;
  int _pco;
  int _scope_depth;

 public:
  HandlerTableEntry(int bci, int pco, int scope_depth) {
    assert( 0 <= pco, "pco must be positive");
    assert( 0 <= scope_depth, "scope_depth must be positive");
    _bci = bci;
    _pco = pco;
    _scope_depth = scope_depth;
  }

  int len() const { return _bci; } // for entry at subtable begin
  int bci() const { return _bci; }
  int pco() const { return _pco; }
  int scope_depth() const { return _scope_depth; }
};


// An ExceptionHandlerTable is an abstraction over a list of subtables
// of exception handlers for CatchNodes. Each subtable has a one-entry
// header holding length and catch_pco of the subtable, followed
// by 'length' entries for each exception handler that can be reached
// from the corresponding CatchNode. The catch_pco is the pc offset of
// the CatchNode in the corresponding nmethod. Empty subtables are dis-
// carded.
//
// Structure of the table:
//
// table    = { subtable }.
// subtable = header entry { entry }.
// header   = a pair (number of subtable entries, catch pc offset, [unused])
// entry    = a pair (handler bci, handler pc offset, scope depth)
//
// An ExceptionHandlerTable can be created from scratch, in which case
// it is possible to add subtables. It can also be created from an
// nmethod (for lookup purposes) in which case the table cannot be
// modified.

class nmethod;
class ExceptionHandlerTable VALUE_OBJ_CLASS_SPEC {
 private:
  HandlerTableEntry* _table;    // the table
  int                _length;   // the current length of the table
  int                _size;     // the number of allocated entries
  ReallocMark        _nesting;  // assertion check for reallocations

  // add the entry & grow the table if needed
  void add_entry(HandlerTableEntry entry);
  HandlerTableEntry* subtable_for(int catch_pco) const;

 public:
  // (compile-time) construction within compiler
  ExceptionHandlerTable(int initial_size = 8);

  // (run-time) construction from nmethod
  ExceptionHandlerTable(const nmethod* nm);

  // (compile-time) add entries
  void add_subtable(
    int                 catch_pco, // the pc offset for the CatchNode
    GrowableArray<intptr_t>* handler_bcis, // the exception handler entry point bcis
    GrowableArray<intptr_t>* scope_depths_from_top_scope,
                                           // if representing exception handlers in multiple
                                           // inlined scopes, indicates which scope relative to
                                           // the youngest/innermost one in which we are performing
                                           // the lookup; zero (or null GrowableArray) indicates
                                           // innermost scope
    GrowableArray<intptr_t>* handler_pcos  // pc offsets for the compiled handlers
  );

  // nmethod support
  int  size_in_bytes() const { return round_to(_length * sizeof(HandlerTableEntry), oopSize); }
  void copy_to(nmethod* nm);

  // lookup
  HandlerTableEntry* entry_for(int catch_pco, int handler_bci, int scope_depth) const;

  // debugging
  void print_subtable(HandlerTableEntry* t) const;
  void print() const;
  void print_subtable_for(int catch_pco) const;
};


// ----------------------------------------------------------------------------
// Implicit null exception tables.  Maps an exception PC offset to a
// continuation PC offset.  During construction it's a variable sized
// array with a max size and current length.  When stored inside an
// nmethod a zero length table takes no space.  This is detected by
// nul_chk_table_size() == 0.  Otherwise the table has a length word
// followed by pairs of <excp-offset, const-offset>.

// Use 32-bit representation for offsets
typedef  uint              implicit_null_entry;

class ImplicitExceptionTable VALUE_OBJ_CLASS_SPEC {
  uint _size;
  uint _len;
  implicit_null_entry *_data;
  implicit_null_entry *adr( uint idx ) const { return &_data[2*idx]; }
  ReallocMark          _nesting;  // assertion check for reallocations
public:
  ImplicitExceptionTable( ) :  _data(0), _size(0), _len(0) { }
  // (run-time) construction from nmethod
  ImplicitExceptionTable( const nmethod *nm );

  void set_size( uint size );
  void append( uint exec_off, uint cont_off );
  uint at( uint exec_off ) const;

  uint len() const { return _len; }
  int size_in_bytes() const { return len() == 0 ? 0 : ((2 * len() + 1) * sizeof(implicit_null_entry)); }

  void copy_to(nmethod* nm);
  void print(address base) const;
  void verify(nmethod *nm) const;
};

#endif // SHARE_VM_CODE_EXCEPTIONHANDLERTABLE_HPP

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