fstableindex.java

利用opensource的开源jar实现生成flash文件

/*
 * FSTableIndex.java
 * Transform
 * 
 * Copyright (c) 2001-2006 Flagstone Software Ltd. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, 
 * are permitted provided that the following conditions are met:
 *
 *  * Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *  * Redistributions in binary form must reproduce the above copyright notice, 
 *    this list of conditions and the following disclaimer in the documentation 
 *    and/or other materials provided with the distribution.
 *  * Neither the name of Flagstone Software Ltd. nor the names of its contributors 
 *    may be used to endorse or promote products derived from this software 
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
 * IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE 
 * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package com.flagstone.transform;

/**
FSTableIndex is used with an FSPush action to push a reference to an entry in a table 
of literals onto the stack. 
 
<p>The value is can then be retrieved from the table and used in a subsequent calculation. The data type was extended in Flash 6 to support tables of up to 65535 strings.</p>

<p>In the Macromedia Flash (SWF) File Format Specification all literals used in calculations are stored as strings. When performing a series of actions each time a literal value is used in a calculation it must be pushed onto the stack. Rather than repeatedly pushing the value explicitly using an FSPush action, all the literals are added to a table in the Flash Player's memory using the FSTable action. To retrieve a literal from the table a reference to an entry in the table is pushed onto the stack using an FSTableIndex. The reduces the number of bytes required to perform a given calculation when the values are used repeatedly.</p>

<p>As an example consider the code required to concatenate two strings:</p>

<pre>
ArrayList actions = new ArrayList();
...
// Create the table of literals
FSTable literals = new FSTable();
literals.add("abc");
literals.add("def");
actions.add(literals);
...
// Create references to the string literals
FSPush push = new FSPush();
push.add(new FSTableIndex(0));
push.add(new FSTableIndex(1));
actions.add(push);
...
// concatenate the strings
actions.add(new FSAction(FSAction.Add));
</pre>

<p>An FSTable can store up to 65536 string literals. Using a table index rather 
than specifying the string literal explicitly reduces considerably the number of 
bytes required to represent a sequence of actions.</p>

<h1 class="datasheet">History</h1>

<p>The string literal table was introduced in Flash 5. It was extended in Flash 
6 to support tables of up to 65536 strings.</p>
 */  
public class FSTableIndex extends FSTransformObject
{
    private int index = 0;

    /**
     * Construct an FSTableIndex object, initalizing it with values decoded from
     * an encoded object.
     * 
     * @param coder an FSCoder containing the binary data.
     */
    public FSTableIndex(FSCoder coder)
    {
        decode(coder);
    }
    /** Constructs an FSTableIndex object referencing the value stored in the literal table.

        @param anIndex the index into the literal table.
        */
    public FSTableIndex(int anIndex)
    {
        setIndex(anIndex);
    }
    /**
     * Constructs an FSTableIndex object by copying values from an existing 
     * object.
     *
     * @param obj an FSTableIndex object.
     */
    public FSTableIndex(FSTableIndex obj)
    {
        index = obj.index;
    }    

    /** Gets the index in the table of string literals.

        @return the index into the literal table.
        */
    public int getIndex() 
    {
        return index;
    }

    /** Sets the index in the table of string literals.

        @param anIndex the index into the literal table.
        */
    public void setIndex(int anIndex) 
    {
        index = anIndex;
    }

    /** 
     * Returns true if anObject is equal to this one. Objects are considered 
     * equal if they would generate identical binary data when they are encoded 
     * to a Flash file.
     *
     * @return true if this object would be identical to anObject when encoded.
     */
    public boolean equals(Object anObject)
    {
        boolean result = false;
        
        if (super.equals(anObject))
            result = index == ((FSTableIndex)anObject).getIndex();

        return result;
    }

    public void appendDescription(StringBuffer buffer, int depth)
    {
        buffer.append(name());
        
        if (depth > 0)
        {
            buffer.append(": { ");
            Transform.append(buffer, "index", index);
            buffer.append("}");
        }
    }

    public int length(FSCoder coder)
    { 
        return index < 256 ? 2 : 3;
    }
        
    public void encode(FSCoder coder) 
    {
        int type = index < 256 ? 8 : 9;
        
        coder.writeWord(type, 1);
        coder.writeWord(index, type == 8 ? 1 : 2);
    }
    
    public void decode(FSCoder coder)
    {
        int type = coder.readWord(1, false);
        
        index = coder.readWord(type == 8 ? 1 : 2, false);
    }
}