android/nfc/NdefRecord.java

/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * 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 android.nfc;

import android.os.Parcel;
import android.os.Parcelable;

import java.lang.UnsupportedOperationException;

/**
 * Represents a logical (unchunked) NDEF (NFC Data Exchange Format) record.
 * <p>An NDEF record always contains:
 * <ul>
 * <li>3-bit TNF (Type Name Format) field: Indicates how to interpret the type field
 * <li>Variable length type: Describes the record format
 * <li>Variable length ID: A unique identifier for the record
 * <li>Variable length payload: The actual data payload
 * </ul>
 * <p>The underlying record
 * representation may be chunked across several NDEF records when the payload is
 * large.
 * <p>This is an immutable data class.
 */
public final class NdefRecord implements Parcelable {
    /**
     * Indicates no type, id, or payload is associated with this NDEF Record.
     * <p>
     * Type, id and payload fields must all be empty to be a valid TNF_EMPTY
     * record.
     */
    public static final short TNF_EMPTY = 0x00;

    /**
     * Indicates the type field uses the RTD type name format.
     * <p>
     * Use this TNF with RTD types such as RTD_TEXT, RTD_URI.
     */
    public static final short TNF_WELL_KNOWN = 0x01;

    /**
     * Indicates the type field contains a value that follows the media-type BNF
     * construct defined by RFC 2046.
     */
    public static final short TNF_MIME_MEDIA = 0x02;

    /**
     * Indicates the type field contains a value that follows the absolute-URI
     * BNF construct defined by RFC 3986.
     */
    public static final short TNF_ABSOLUTE_URI = 0x03;

    /**
     * Indicates the type field contains a value that follows the RTD external
     * name specification.
     * <p>
     * Note this TNF should not be used with RTD_TEXT or RTD_URI constants.
     * Those are well known RTD constants, not external RTD constants.
     */
    public static final short TNF_EXTERNAL_TYPE = 0x04;

    /**
     * Indicates the payload type is unknown.
     * <p>
     * This is similar to the "application/octet-stream" MIME type. The payload
     * type is not explicitly encoded within the NDEF Message.
     * <p>
     * The type field must be empty to be a valid TNF_UNKNOWN record.
     */
    public static final short TNF_UNKNOWN = 0x05;

    /**
     * Indicates the payload is an intermediate or final chunk of a chunked
     * NDEF Record.
     * <p>
     * The payload type is specified in the first chunk, and subsequent chunks
     * must use TNF_UNCHANGED with an empty type field. TNF_UNCHANGED must not
     * be used in any other situation.
     */
    public static final short TNF_UNCHANGED = 0x06;

    /**
     * Reserved TNF type.
     * <p>
     * The NFC Forum NDEF Specification v1.0 suggests for NDEF parsers to treat this
     * value like TNF_UNKNOWN.
     * @hide
     */
    public static final short TNF_RESERVED = 0x07;

    /**
     * RTD Text type. For use with TNF_WELL_KNOWN.
     */
    public static final byte[] RTD_TEXT = {0x54};  // "T"

    /**
     * RTD URI type. For use with TNF_WELL_KNOWN.
     */
    public static final byte[] RTD_URI = {0x55};   // "U"

    /**
     * RTD Smart Poster type. For use with TNF_WELL_KNOWN.
     */
    public static final byte[] RTD_SMART_POSTER = {0x53, 0x70};  // "Sp"

    /**
     * RTD Alternative Carrier type. For use with TNF_WELL_KNOWN.
     */
    public static final byte[] RTD_ALTERNATIVE_CARRIER = {0x61, 0x63};  // "ac"

    /**
     * RTD Handover Carrier type. For use with TNF_WELL_KNOWN.
     */
    public static final byte[] RTD_HANDOVER_CARRIER = {0x48, 0x63};  // "Hc"

    /**
     * RTD Handover Request type. For use with TNF_WELL_KNOWN.
     */
    public static final byte[] RTD_HANDOVER_REQUEST = {0x48, 0x72};  // "Hr"

    /**
     * RTD Handover Select type. For use with TNF_WELL_KNOWN.
     */
    public static final byte[] RTD_HANDOVER_SELECT = {0x48, 0x73}; // "Hs"

    private static final byte FLAG_MB = (byte) 0x80;
    private static final byte FLAG_ME = (byte) 0x40;
    private static final byte FLAG_CF = (byte) 0x20;
    private static final byte FLAG_SR = (byte) 0x10;
    private static final byte FLAG_IL = (byte) 0x08;

    private final byte mFlags;
    private final short mTnf;
    private final byte[] mType;
    private final byte[] mId;
    private final byte[] mPayload;

    /**
     * Construct an NDEF Record.
     * <p>
     * Applications should not attempt to manually chunk NDEF Records - the
     * implementation of android.nfc will automatically chunk an NDEF Record
     * when necessary (and only present a single logical NDEF Record to the
     * application). So applications should not use TNF_UNCHANGED.
     *
     * @param tnf  a 3-bit TNF constant
     * @param type byte array, containing zero to 255 bytes, must not be null
     * @param id   byte array, containing zero to 255 bytes, must not be null
     * @param payload byte array, containing zero to (2 ** 32 - 1) bytes,
     *                must not be null
     */
    public NdefRecord(short tnf, byte[] type, byte[] id, byte[] payload) {
        /* New NDEF records created by applications will have FLAG_MB|FLAG_ME
         * set by default; when multiple records are stored in a
         * {@link NdefMessage}, these flags will be corrected when the {@link NdefMessage}
         * is serialized to bytes.
         */
        this(tnf, type, id, payload, (byte)(FLAG_MB|FLAG_ME));
    }

    /**
     * @hide
     */
    /*package*/ NdefRecord(short tnf, byte[] type, byte[] id, byte[] payload, byte flags) {
        /* check arguments */
        if ((type == null) || (id == null) || (payload == null)) {
            throw new IllegalArgumentException("Illegal null argument");
        }

        if (tnf < 0 || tnf > 0x07) {
            throw new IllegalArgumentException("TNF out of range " + tnf);
        }

        /* Determine if it is a short record */
        if(payload.length < 0xFF) {
            flags |= FLAG_SR;
        }

        /* Determine if an id is present */
        if(id.length != 0) {
            flags |= FLAG_IL;
        }

        mFlags = flags;
        mTnf = tnf;
        mType = type.clone();
        mId = id.clone();
        mPayload = payload.clone();
    }

    /**
     * Construct an NDEF Record from raw bytes.
     * <p>
     * Validation is performed to make sure the header is valid, and that
     * the id, type and payload sizes appear to be valid.
     *
     * @throws FormatException if the data is not a valid NDEF record
     */
    public NdefRecord(byte[] data) throws FormatException {
        /* Prevent compiler to complain about unassigned final fields */
        mFlags = 0;
        mTnf = 0;
        mType = null;
        mId = null;
        mPayload = null;
        /* Perform actual parsing */
        if (parseNdefRecord(data) == -1) {
            throw new FormatException("Error while parsing NDEF record");
        }
    }

    /**
     * Returns the 3-bit TNF.
     * <p>
     * TNF is the top-level type.
     */
    public short getTnf() {
        return mTnf;
    }

    /**
     * Returns the variable length Type field.
     * <p>
     * This should be used in conjunction with the TNF field to determine the
     * payload format.
     */
    public byte[] getType() {
        return mType.clone();
    }

    /**
     * Returns the variable length ID.
     */
    public byte[] getId() {
        return mId.clone();
    }

    /**
     * Returns the variable length payload.
     */
    public byte[] getPayload() {
        return mPayload.clone();
    }

    /**
     * Returns this entire NDEF Record as a byte array.
     */
    public byte[] toByteArray() {
        return generate(mFlags, mTnf, mType, mId, mPayload);
    }

    public int describeContents() {
        return 0;
    }

    public void writeToParcel(Parcel dest, int flags) {
        dest.writeInt(mFlags);
        dest.writeInt(mTnf);
        dest.writeInt(mType.length);
        dest.writeByteArray(mType);
        dest.writeInt(mId.length);
        dest.writeByteArray(mId);
        dest.writeInt(mPayload.length);
        dest.writeByteArray(mPayload);
    }

    public static final Parcelable.Creator<NdefRecord> CREATOR =
            new Parcelable.Creator<NdefRecord>() {
        public NdefRecord createFromParcel(Parcel in) {
            byte flags = (byte)in.readInt();
            short tnf = (short)in.readInt();
            int typeLength = in.readInt();
            byte[] type = new byte[typeLength];
            in.readByteArray(type);
            int idLength = in.readInt();
            byte[] id = new byte[idLength];
            in.readByteArray(id);
            int payloadLength = in.readInt();
            byte[] payload = new byte[payloadLength];
            in.readByteArray(payload);

            return new NdefRecord(tnf, type, id, payload, flags);
        }
        public NdefRecord[] newArray(int size) {
            return new NdefRecord[size];
        }
    };

    private native int parseNdefRecord(byte[] data);
    private native byte[] generate(short flags, short tnf, byte[] type, byte[] id, byte[] data);
}