Java example source code file (CmdIDList.cpp)

This example Java source code file (CmdIDList.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

array_initial_size, array_maximum_size, array_size_increment, awtcmdidlist, awtcmdidlist\:\:add, awtcmdidlist\:\:lookup, buildfreelist, cmdidentry, criticalsection::lock, dassert, null, safe_size_array_alloc, safe_size_array_realloc, uint

The CmdIDList.cpp Java example source code

/*
 * Copyright (c) 1996, 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.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * 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 "CmdIDList.h"

// How much space to allocate initially
static const UINT ARRAY_INITIAL_SIZE = 1024;

// Array expansion increment when need more free space
static const UINT ARRAY_SIZE_INCREMENT = 1024;

// It seems that Win95 can not handle ids greater than 2**16
static const UINT ARRAY_MAXIMUM_SIZE = 32768;


AwtCmdIDList::AwtCmdIDList()
{
    m_capacity = ARRAY_INITIAL_SIZE;
    m_first_free = -1;
    m_array = (CmdIDEntry *)SAFE_SIZE_ARRAY_ALLOC(safe_Malloc, m_capacity, sizeof(AwtObject*));
    BuildFreeList(0);
}

AwtCmdIDList::~AwtCmdIDList()
{
    free(m_array);
}


// Build a new free list from a newly allocated memory.  This only
// happens after malloc/realloc, and new free entries are contiguous
// from first_index to m_capacity-1
INLINE void AwtCmdIDList::BuildFreeList(UINT first_index)
{
    DASSERT(m_first_free == -1);
    for (UINT i = first_index; i < m_capacity-1; ++i)
        m_array[i].next_free_index = i+1;
    m_array[m_capacity-1].next_free_index = -1; // nil
    m_first_free = first_index; // head of the free list
}

// Assign an id to the object.  Recycle the first free entry from the
// head of the free list or allocate more memory for a new free list.
UINT AwtCmdIDList::Add(AwtObject* obj)
{
    CriticalSection::Lock l(m_lock);

    if (m_first_free == -1) {   // out of free ids
        if (m_capacity == ARRAY_MAXIMUM_SIZE) {
            // Really bad - out of ids.  Since we hardly can have *so*
            // many items simultaneously in existence, we have an id
            // leak somewhere.
            DASSERT(FALSE);
            return 0;
        }
        else {                  // snarf a bigger arena
            UINT old_capacity = m_capacity; // will be the first free entry
            m_capacity += ARRAY_SIZE_INCREMENT;
            if (m_capacity > ARRAY_MAXIMUM_SIZE)
                m_capacity = ARRAY_MAXIMUM_SIZE;
            m_array = (CmdIDEntry *)SAFE_SIZE_ARRAY_REALLOC(safe_Realloc, m_array,
                                        m_capacity, sizeof(CmdIDEntry*));
            BuildFreeList(old_capacity);
        }
    }

    DASSERT(m_first_free != -1);
    UINT newid = m_first_free;  // use the entry from the head of the list
    m_first_free = m_array[newid].next_free_index; // advance free pointer
    m_array[newid].obj = obj;

    return newid;
}

// Return the object associated with this id..
AwtObject* AwtCmdIDList::Lookup(UINT id)
{
    CriticalSection::Lock l(m_lock);
    DASSERT(id < m_capacity);
    if (m_array[id].next_free_index <= ARRAY_MAXIMUM_SIZE) {
        return NULL;
    }
    return m_array[id].obj;
}

// Return this id to the head of the free list.
void AwtCmdIDList::Remove(UINT id)
{
    CriticalSection::Lock l(m_lock);
    DASSERT(id < m_capacity);
    DASSERT(m_array[id].next_free_index > ARRAY_MAXIMUM_SIZE); // it's a pointer
    m_array[id].next_free_index = m_first_free;
    m_first_free = id;
}