core/java/android/nfc/tech/NfcA.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.tech;

import android.nfc.Tag;
import android.os.Bundle;
import android.os.RemoteException;

import java.io.IOException;

/**
 * Provides access to NFC-A (ISO 14443-3A) properties and I/O operations on a {@link Tag}.
 *
 * <p>Acquire a {@link NfcA} object using {@link #get}.
 * <p>The primary NFC-A I/O operation is {@link #transceive}. Applications must
 * implement their own protocol stack on top of {@link #transceive}.
 */
public final class NfcA extends BasicTagTechnology {
    /** @hide */
    public static final String EXTRA_SAK = "sak";
    /** @hide */
    public static final String EXTRA_ATQA = "atqa";

    private short mSak;
    private byte[] mAtqa;

    /**
     * Get an instance of {@link NfcA} for the given tag.
     * <p>Returns null if {@link NfcA} was not enumerated in {@link Tag#getTechList}.
     * This indicates the tag does not support NFC-A.
     * <p>Does not cause any RF activity and does not block.
     *
     * @param tag an NFC-A compatible tag
     * @return NFC-A object
     */
    public static NfcA get(Tag tag) {
        if (!tag.hasTech(TagTechnology.NFC_A)) return null;
        try {
            return new NfcA(tag);
        } catch (RemoteException e) {
            return null;
        }
    }

    /** @hide */
    public NfcA(Tag tag) throws RemoteException {
        super(tag, TagTechnology.NFC_A);
        Bundle extras = tag.getTechExtras(TagTechnology.NFC_A);
        mSak = extras.getShort(EXTRA_SAK);
        mAtqa = extras.getByteArray(EXTRA_ATQA);
    }

    /**
     * Return the ATQA/SENS_RES bytes from tag discovery.
     *
     * <p>Does not cause any RF activity and does not block.
     *
     * @return ATQA/SENS_RES bytes
     */
    public byte[] getAtqa() {
        return mAtqa;
    }

    /**
     * Return the SAK/SEL_RES bytes from tag discovery.
     *
     * <p>Does not cause any RF activity and does not block.
     *
     * @return SAK bytes
     */
    public short getSak() {
        return mSak;
    }

    /**
     * Send raw NFC-A commands to the tag and receive the response.
     *
     * <p>Applications must not append the EoD (CRC) to the payload,
     * it will be automatically calculated.
     * <p>Applications must only send commands that are complete bytes,
     * for example a SENS_REQ is not possible (these are used to
     * manage tag polling and initialization).
     *
     * <p>This is an I/O operation and will block until complete. It must
     * not be called from the main application thread. A blocked call will be canceled with
     * {@link IOException} if {@link #close} is called from another thread.
     *
     * @param data bytes to send
     * @return bytes received in response
     * @throws TagLostException if the tag leaves the field
     * @throws IOException if there is an I/O failure, or this operation is canceled
     */
    public byte[] transceive(byte[] data) throws IOException {
        return transceive(data, true);
    }
}