codeattribute.java

已经移植好的java虚拟机

/*
 *	CodeAttribute.java	1.8	02/09/27
 *
 * Copyright (c) 1997 Sun Microsystems, Inc. All Rights Reserved.
 *
 * This software is the confidential and proprietary information of Sun
 * Microsystems, Inc. ("Confidential Information").  You shall not
 * disclose such Confidential Information and shall use it only in
 * accordance with the terms of the license agreement you entered into
 * with Sun.
 *
 * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
 * SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
 * PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR ANY DAMAGES
 * SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING
 * THIS SOFTWARE OR ITS DERIVATIVES.
 * Use is subject to license terms.
 */

package components;
import java.io.DataOutput;
import java.io.DataInput;
import java.io.IOException;
import util.DataFormatException;
import java.util.Hashtable;

/*
 * A class to represent the Code Attribute
 * of a method
 */

public
class CodeAttribute extends Attribute
{
    public int		  stack;
    public int		  locals;
    public byte		  code[];
    public ExceptionEntry exceptionTable[];
    public Attribute	  codeAttributes[];

    public
    CodeAttribute( UnicodeConstant name, int l, int ns, int nl, byte c[],
	ExceptionEntry et[], Attribute ca[] ){
	super( name, l );
	stack  = ns;
	locals = nl;
	code   = c;
	exceptionTable = et;
	codeAttributes = ca;
    }

    public void
    externalize( ConstantPool p ){
	super.externalize( p );
	Attribute.externalizeAttributes( codeAttributes, p );
    }

    public void
    countConstantReferences( boolean isRelocatable ){
	super.countConstantReferences( isRelocatable );
	if ( exceptionTable != null ){
	    for( int i = 0; i < exceptionTable.length; i++ ){
		exceptionTable[i].countConstantReferences();
	    }
	}
	Attribute.countConstantReferences( codeAttributes, isRelocatable );
    }

    protected int
    writeData( DataOutput o ) throws IOException{
	int trueLength = 8 + code.length;
	o.writeShort( stack );
	o.writeShort( locals );
	o.writeInt( code.length );
	o.write( code, 0, code.length );
	if ( exceptionTable == null ){
	    o.writeShort( 0 );
	    trueLength += 2;
	} else {
	    o.writeShort( exceptionTable.length );
	    for ( int i = 0; i < exceptionTable.length ; i ++ ){
		exceptionTable[i].write( o );
	    }
	    trueLength += 2 + exceptionTable.length*ExceptionEntry.size;
	}
	if ( codeAttributes == null ){
	    o.writeShort(0);
	    trueLength += 2;
	} else {
	    Attribute.writeAttributes( codeAttributes, o, false );
	    trueLength += Attribute.length( codeAttributes );
	}
	return trueLength;
    }

    /*
     * This hashtable is for use when reading code attributes.
     * The only code attribute we're interested in is
     * the LineNumberTableAttribute.
     * Other stuff we ignore.
     */
    static private Hashtable codeAttributeTypes = new Hashtable();
    static{
	codeAttributeTypes.put( "LineNumberTable", LineNumberTableAttributeFactory.instance );
	codeAttributeTypes.put( "LocalVariableTable", LocalVariableTableAttributeFactory.instance );
	codeAttributeTypes.put( "StackMap", StackMapAttributeFactory.instance );
    }

    public static Attribute
    readAttribute( DataInput i, ConstantObject locals[], ConstantObject globals[] ) throws IOException{
	UnicodeConstant name;

	name = (UnicodeConstant)globals[i.readUnsignedShort()];
	return finishReadAttribute( i, name, locals, globals );
    }

    //
    // for those cases where we already read the name index
    // and know that its not something requiring special handling.
    //
    public static Attribute
    finishReadAttribute( DataInput in, UnicodeConstant name, ConstantObject locals[], ConstantObject globals[] ) throws IOException {
	int l;
	int nstack;
	int nlocals;
	ConstantObject d;
	ExceptionEntry exceptionTable[];

	l       = in.readInt();
	nstack  = in.readUnsignedShort();
	nlocals = in.readUnsignedShort();

	int codesize = in.readInt();
	byte code[] = new byte[ codesize ];
	in.readFully( code );

	int tableSize = in.readUnsignedShort();
	exceptionTable = new ExceptionEntry[tableSize];
	for (int j = 0; j < tableSize; j++) {
	    int sPC = in.readUnsignedShort();
	    int e = in.readUnsignedShort();
	    int h = in.readUnsignedShort();
	    int catchTypeIndex = in.readUnsignedShort();
	    ClassConstant ctype;
	    if ( catchTypeIndex == 0 ){
		ctype = null;
	    } else {
		ctype = (ClassConstant)locals[ catchTypeIndex ];
	    }
	    exceptionTable[j] = new ExceptionEntry( 
		sPC, e, h, ctype );
	}

	Attribute a[] = Attribute.readAttributes( in, locals, globals, codeAttributeTypes, false );
	return new CodeAttribute(
	    name, l, nstack, nlocals, code, exceptionTable, a );
    }

}