de.berlin.magun.nfcmime.core.NdefMessageBuilder.java Source code

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Here is the source code for de.berlin.magun.nfcmime.core.NdefMessageBuilder.java

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/*
 * 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.berlin.magun.nfcmime.core;

import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.Charset;
import java.util.ArrayList;

import org.apache.commons.io.IOUtils;
import org.apache.commons.lang.ArrayUtils;

import android.nfc.NdefMessage;
import android.nfc.NdefRecord;

/**
 * Provides methods to create NdefMessages. 
 * @author Johannes Bolz
 *
 */
public class NdefMessageBuilder {
    private ArrayList<NdefRecord> recordlist;
    private boolean hasChecksum = false;
    private NdefMessage message;

    public NdefMessageBuilder() {
        this.recordlist = new ArrayList<NdefRecord>();
    }

    /**
     * Stores an NDEF record from an InputStream. Will throw an IOException if the last NDEF record is
     * a checksum added with addChecksum().
     * @param is InputStream that holds the payload data of the NDEF record.
     * @param mimetype MIME type definition, e.g. "text/plain"
     * @throws IOException
     */
    public void addMimeRecord(InputStream is, String mimetype) throws IOException {
        if (!this.hasChecksum) {
            recordlist.add(new NdefRecord(NdefRecord.TNF_MIME_MEDIA, mimetype.getBytes(Charset.forName("US-ASCII")),
                    new byte[0], IOUtils.toByteArray(is)));
        } else {
            throw new IOException("Cannot add record - last record is a checksum.");
        }
    }

    /**
     * Stores an NDEF record containing a URI, using the URI format definition.
     * @param uri the URI to be written
     * @throws IOException
     */
    public void addUriRecord(String uri) throws IOException {
        if (!this.hasChecksum) {
            recordlist.add(new NdefRecord(NdefRecord.TNF_WELL_KNOWN, NdefRecord.RTD_URI, new byte[0],
                    ArrayUtils.addAll(new byte[] { (byte) 0x00 }, uri.getBytes(Charset.forName("UTF-8")))));
        } else {
            throw new IOException("Cannot add record - last record is a checksum.");
        }
    }

    /**
     * Builds an NdefMessage from all stored NDEF records.
     * @return NdefMessage
     */
    public NdefMessage buildMessage() {
        NdefRecord[] records = new NdefRecord[recordlist.size()];
        for (int i = 0; i < recordlist.size(); i++) {
            records[i] = recordlist.get(i);
        }
        this.message = new NdefMessage(records);
        return this.message;
    }

    /**
     * Creates a CRC32 checksum out of all previously added NDEF records and adds it as last record entry. 
     * After that, it will not be possible to add additional records. The record payload will be a String 
     * consisting of the prefix 'crc32:' and a String representation of the checksum long, e.g. 
     * 'crc32:2868450884'. The record will be MIME formatted as 'text/plain'.
     */
    public void addChecksum() {
        CrcGenerator generator = new CrcGenerator();
        NdefRecord[] records = new NdefRecord[recordlist.size()];
        for (int i = 0; i < recordlist.size(); i++) {
            records[i] = recordlist.get(i);
        }
        recordlist.add(new NdefRecord(NdefRecord.TNF_MIME_MEDIA, "text/plain".getBytes(Charset.forName("US-ASCII")),
                new byte[0],
                ("crc32:" + String.valueOf(generator.getChecksum(records))).getBytes(Charset.forName("US-ASCII"))));
    }

    /**
     * @return the overall NdefMessage size.
     */
    public int getDataSize() {
        return buildMessage().toByteArray().length;
    }
}