JWebAssembly/src/de/inetsoftware/classparser/Attributes.java

/*
   Copyright 2011 - 2017 Volker Berlin (i-net software)

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.

*/
package de.inetsoftware.classparser;

import java.io.ByteArrayInputStream;
import java.io.DataInputStream;
import java.io.IOException;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;

/**
 * @author Volker Berlin
 */
public class Attributes {

    private final AttributeInfo[] attributes;

    private final ConstantPool    constantPool;

    Attributes( @Nonnull DataInputStream input, @Nonnull ConstantPool constantPool ) throws IOException {
        this.constantPool = constantPool;
        this.attributes = readAttributs( input );
    }

    private AttributeInfo[] readAttributs( @Nonnull DataInputStream input ) throws IOException {
        AttributeInfo[] attrs = new AttributeInfo[input.readUnsignedShort()];
        for( int i = 0; i < attrs.length; i++ ) {
            attrs[i] = new AttributeInfo( input, constantPool );
        }
        return attrs;
    }

    @Nullable
    AttributeInfo get( String name ) {
        for( AttributeInfo attr : attributes ) {
            if( attr.getName().equals( name ) ) {
                return attr;
            }
        }
        return null;
    }

    static class AttributeInfo {

        private final String name;

        private final byte[] info;

        AttributeInfo( @Nonnull DataInputStream input, @Nonnull ConstantPool constantPool ) throws IOException {
            this.name = (String)constantPool.get( input.readUnsignedShort() );
            this.info = new byte[input.readInt()];
            input.readFully( this.info );
        }

        String getName() {
            return name;
        }

        byte[] getData() {
            return info;
        }

        DataInputStream getDataInputStream(){
            return new DataInputStream( new ByteArrayInputStream( info ) );
        }
    }

    /**
     * Get value of SourceFile if available.
     * @return the source file name or null.
     * @throws IOException if an I/O error occurs.
     */
    public String getSourceFile() throws IOException{
        AttributeInfo data = get( "SourceFile" );
        if( data == null ) {
            return null;
        }
        return (String)constantPool.get( data.getDataInputStream().readUnsignedShort() );
    }
}