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Java example source code file (arena.cpp)

This example Java source code file (arena.cpp) 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

adjust, amalloc, arena, arena\:\:arena, cheapobj::operator, check, chunk, chunk\:\:operator, chunks, get, null, return, save, total

The arena.cpp Java example source code

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

#include "adlc.hpp"

void* Chunk::operator new(size_t requested_size, size_t length) throw() {
  return CHeapObj::operator new(requested_size + length);
}

void  Chunk::operator delete(void* p, size_t length) {
  CHeapObj::operator delete(p);
}

Chunk::Chunk(size_t length) {
  _next = NULL;         // Chain on the linked list
  _len  = length;       // Save actual size
}

//------------------------------chop-------------------------------------------
void Chunk::chop() {
  Chunk *k = this;
  while( k ) {
    Chunk *tmp = k->_next;
    // clear out this chunk (to detect allocation bugs)
    memset(k, 0xBAADBABE, k->_len);
    free(k);                    // Free chunk (was malloc'd)
    k = tmp;
  }
}

void Chunk::next_chop() {
  _next->chop();
  _next = NULL;
}

//------------------------------Arena------------------------------------------
Arena::Arena( size_t init_size ) {
  init_size = (init_size+3) & ~3;
  _first = _chunk = new (init_size) Chunk(init_size);
  _hwm = _chunk->bottom();      // Save the cached hwm, max
  _max = _chunk->top();
  set_size_in_bytes(init_size);
}

Arena::Arena() {
  _first = _chunk = new (Chunk::init_size) Chunk(Chunk::init_size);
  _hwm = _chunk->bottom();      // Save the cached hwm, max
  _max = _chunk->top();
  set_size_in_bytes(Chunk::init_size);
}

Arena::Arena( Arena *a )
: _chunk(a->_chunk), _hwm(a->_hwm), _max(a->_max), _first(a->_first) {
  set_size_in_bytes(a->size_in_bytes());
}

//------------------------------used-------------------------------------------
// Total of all Chunks in arena
size_t Arena::used() const {
  size_t sum = _chunk->_len - (_max-_hwm); // Size leftover in this Chunk
  register Chunk *k = _first;
  while( k != _chunk) {         // Whilst have Chunks in a row
    sum += k->_len;             // Total size of this Chunk
    k = k->_next;               // Bump along to next Chunk
  }
  return sum;                   // Return total consumed space.
}

//------------------------------grow-------------------------------------------
// Grow a new Chunk
void* Arena::grow( size_t x ) {
  // Get minimal required size.  Either real big, or even bigger for giant objs
  size_t len = max(x, Chunk::size);

  register Chunk *k = _chunk;   // Get filled-up chunk address
  _chunk = new (len) Chunk(len);

  if( k ) k->_next = _chunk;    // Append new chunk to end of linked list
  else _first = _chunk;
  _hwm  = _chunk->bottom();     // Save the cached hwm, max
  _max =  _chunk->top();
  set_size_in_bytes(size_in_bytes() + len);
  void* result = _hwm;
  _hwm += x;
  return result;
}

//------------------------------calloc-----------------------------------------
// Allocate zeroed storage in Arena
void *Arena::Acalloc( size_t items, size_t x ) {
  size_t z = items*x;   // Total size needed
  void *ptr = Amalloc(z);       // Get space
  memset( ptr, 0, z );          // Zap space
  return ptr;                   // Return space
}

//------------------------------realloc----------------------------------------
// Reallocate storage in Arena.
void *Arena::Arealloc( void *old_ptr, size_t old_size, size_t new_size ) {
  char *c_old = (char*)old_ptr; // Handy name
  // Stupid fast special case
  if( new_size <= old_size ) {  // Shrink in-place
    if( c_old+old_size == _hwm) // Attempt to free the excess bytes
      _hwm = c_old+new_size;    // Adjust hwm
    return c_old;
  }

  // See if we can resize in-place
  if( (c_old+old_size == _hwm) &&       // Adjusting recent thing
      (c_old+new_size <= _max) ) {      // Still fits where it sits
    _hwm = c_old+new_size;      // Adjust hwm
    return c_old;               // Return old pointer
  }

  // Oops, got to relocate guts
  void *new_ptr = Amalloc(new_size);
  memcpy( new_ptr, c_old, old_size );
  Afree(c_old,old_size);        // Mostly done to keep stats accurate
  return new_ptr;
}

//------------------------------reset------------------------------------------
// Reset this Arena to empty, and return this Arenas guts in a new Arena.
Arena *Arena::reset(void) {
  Arena *a = new Arena(this);   // New empty arena
  _first = _chunk = NULL;       // Normal, new-arena initialization
  _hwm = _max = NULL;
  return a;                     // Return Arena with guts
}

//------------------------------contains---------------------------------------
// Determine if pointer belongs to this Arena or not.
bool Arena::contains( const void *ptr ) const {
  if( (void*)_chunk->bottom() <= ptr && ptr < (void*)_hwm )
    return true;                // Check for in this chunk
  for( Chunk *c = _first; c; c = c->_next )
    if( (void*)c->bottom() <= ptr && ptr < (void*)c->top())
      return true;              // Check for every chunk in Arena
  return false;                 // Not in any Chunk, so not in Arena
}

//-----------------------------------------------------------------------------
// CHeapObj

void* CHeapObj::operator new(size_t size) throw() {
  return (void *) malloc(size);
}

void CHeapObj::operator delete(void* p){
 free(p);
}

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