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/*
* 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.
*/
/* $Id$ */
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.
* <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
*/
private InputStream inputStream;
/**
* 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!
* @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;
}
}
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