http://xmlgraphics.apache.org/fop/: Apache FOP (Formatting Objects Processor) is the world's first print formatter driven by XSL formatting objects (XSL-FO) and the world's first output independent formatter. It is a Java application that reads a formatting object (FO) tree and renders the resulting pages to a specified output. Output formats currently supported include PDF, PCL, PS, AFP, TIFF, PNG, SVG, XML (area tree representation), Print, AWT and TXT. The primary output target is PDF. (Apache Software Foundation) 
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 */

/* $Id: StructuredFieldReader.java 1679676 2015-05-16 02:10:42Z adelmelle $ */

package org.apache.fop.afp.util;

import java.io.IOException;
import java.io.InputStream;


A helper class to read structured fields from a MO:DCA document. Each
component of a mixed object document is explicitly defined and delimited
in the data. This is accomplished through the use of MO:DCA data structures,
called structured fields. Structured fields are used to envelop document
components and to provide commands and information to applications using
the data. Structured fields may contain one or more parameters. Each
parameter provides one value from a set of values defined by the architecture.


MO:DCA structured fields consist of two parts: an introducer that identifies
the length and type of the structured field, and data that provides the
structured field's effect. The data is contained in a set of parameters,
which can consist of other data structures and data elements. The maximum
length of a structured field is 32767 bytes.

/**
 * A helper class to read structured fields from a MO:DCA document. Each
 * component of a mixed object document is explicitly defined and delimited
 * in the data. This is accomplished through the use of MO:DCA data structures,
 * called structured fields. Structured fields are used to envelop document
 * components and to provide commands and information to applications using
 * the data. Structured fields may contain one or more parameters. Each
 * parameter provides one value from a set of values defined by the architecture.
 * <br>
 * MO:DCA structured fields consist of two parts: an introducer that identifies
 * the length and type of the structured field, and data that provides the
 * structured field's effect. The data is contained in a set of parameters,
 * which can consist of other data structures and data elements. The maximum
 * length of a structured field is 32767 bytes.
 */
public class StructuredFieldReader {

    
The input stream to read

/**
     * The input stream to read
     */
    private InputStream inputStream;

    
The constructor for the StructuredFieldReader

Params:
  • inputStream – the input stream to process
/**
     * The constructor for the StructuredFieldReader
     * @param inputStream the input stream to process
     */
    public StructuredFieldReader(InputStream inputStream) {
        this.inputStream = inputStream;
    }

    
Get the next structured field as identified by the identifier
parameter (this must be a valid MO:DCA structured field).
Note: The returned data does not include the field length and identifier!

Params:
  • identifier – the three byte identifier
Throws:
Returns:the next structured field or null when there are no more
/**
     * Get the next structured field as identified by the identifier
     * parameter (this must be a valid MO:DCA structured field).
     * Note: The returned data does not include the field length and identifier!
     * @param identifier the three byte identifier
     * @throws IOException if an I/O exception occurred
     * @return the next structured field or null when there are no more
     */
    public byte[] getNext(byte[] identifier) throws IOException {

        byte[] bytes = AFPResourceUtil.getNext(identifier, this.inputStream);

        if (bytes != null) {
            //Users of this class expect the field data without length and identifier
            int srcPos = 2 + identifier.length;
            byte[] tmp = new byte[bytes.length - srcPos];
            System.arraycopy(bytes, srcPos, tmp, 0, tmp.length);
            bytes = tmp;
        }

        return bytes;

    }

}