NdefMessage.java revision c9f7890a203a013646650a695157277df81b6a17 
1/*
2 * Copyright (C) 2010 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package android.nfc;
18
19import android.nfc.NdefRecord;
20import android.os.Parcel;
21import android.os.Parcelable;
22
23/**
24 * Represents an NDEF (NFC Data Exchange Format) data message that contains one or more {@link
25 * NdefRecord}s.
26 * <p>An NDEF message includes "records" that can contain different sets of data, such as
27 * MIME-type media, a URI, or one of the supported RTD types (see {@link NdefRecord}). An NDEF
28 * message always contains zero or more NDEF records.</p>
29 * <p>This is an immutable data class.
30 */
31public class NdefMessage implements Parcelable {
32    private static final byte FLAG_MB = (byte) 0x80;
33    private static final byte FLAG_ME = (byte) 0x40;
34
35    private final NdefRecord[] mRecords;
36
37    //TODO(npelly) FormatException
38    /**
39     * Create an NDEF message from raw bytes.
40     * <p>
41     * Validation is performed to make sure the Record format headers are valid,
42     * and the ID + TYPE + PAYLOAD fields are of the correct size.
43     * @throws FormatException
44     *
45     * @hide
46     */
47    public NdefMessage(byte[] data) throws FormatException {
48        mRecords = null;  // stop compiler complaints about final field
49        if (parseNdefMessage(data) == -1) {
50            throw new FormatException("Error while parsing NDEF message");
51        }
52    }
53
54    /**
55     * Create an NDEF message from NDEF records.
56     */
57    public NdefMessage(NdefRecord[] records) {
58        mRecords = new NdefRecord[records.length];
59        System.arraycopy(records, 0, mRecords, 0, records.length);
60    }
61
62    /**
63     * Get the NDEF records inside this NDEF message.
64     *
65     * @return array of zero or more NDEF records.
66     */
67    public NdefRecord[] getRecords() {
68        return mRecords.clone();
69    }
70
71    /**
72     * Get a byte array representation of this NDEF message.
73     *
74     * @return byte array
75     * @hide
76     */
77    public byte[] toByteArray() {
78        //TODO(nxp): do not return null
79        //TODO(nxp): allocate the byte array once, copy each record once
80        //TODO(nxp): process MB and ME flags outside loop
81        if ((mRecords == null) || (mRecords.length == 0))
82            return null;
83
84        byte[] msg = {};
85
86        for (int i = 0; i < mRecords.length; i++) {
87            byte[] record = mRecords[i].toByteArray();
88            byte[] tmp = new byte[msg.length + record.length];
89
90            /* Make sure the Message Begin flag is set only for the first record */
91            if (i == 0) {
92                record[0] |= FLAG_MB;
93            } else {
94                record[0] &= ~FLAG_MB;
95            }
96
97            /* Make sure the Message End flag is set only for the last record */
98            if (i == (mRecords.length - 1)) {
99                record[0] |= FLAG_ME;
100            } else {
101                record[0] &= ~FLAG_ME;
102            }
103
104            System.arraycopy(msg, 0, tmp, 0, msg.length);
105            System.arraycopy(record, 0, tmp, msg.length, record.length);
106
107            msg = tmp;
108        }
109
110        return msg;
111    }
112
113    public int describeContents() {
114        return 0;
115    }
116
117    public void writeToParcel(Parcel dest, int flags) {
118        dest.writeInt(mRecords.length);
119        dest.writeTypedArray(mRecords, flags);
120    }
121
122    public static final Parcelable.Creator<NdefMessage> CREATOR =
123            new Parcelable.Creator<NdefMessage>() {
124        public NdefMessage createFromParcel(Parcel in) {
125            int recordsLength = in.readInt();
126            NdefRecord[] records = new NdefRecord[recordsLength];
127            in.readTypedArray(records, NdefRecord.CREATOR);
128            return new NdefMessage(records);
129        }
130        public NdefMessage[] newArray(int size) {
131            return new NdefMessage[size];
132        }
133    };
134
135    private native int parseNdefMessage(byte[] data);
136}