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      1 /*
      2  * Copyright (C) 2011 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 
     17 package com.android.nfc.snep;
     18 
     19 import android.nfc.FormatException;
     20 import android.nfc.NdefMessage;
     21 
     22 import java.io.ByteArrayOutputStream;
     23 import java.io.DataOutputStream;
     24 import java.io.IOException;
     25 import java.nio.ByteBuffer;
     26 
     27 public final class SnepMessage {
     28     public static final byte VERSION_MAJOR = (byte) 0x1;
     29     public static final byte VERSION_MINOR = (byte) 0x0;
     30     public static final byte VERSION = (0xF0 & (VERSION_MAJOR << 4)) | (0x0F & VERSION_MINOR);
     31 
     32     public static final byte REQUEST_CONTINUE = (byte) 0x00;
     33     public static final byte REQUEST_GET = (byte) 0x01;
     34     public static final byte REQUEST_PUT = (byte) 0x02;
     35     public static final byte REQUEST_REJECT = (byte) 0x7F;
     36 
     37     public static final byte RESPONSE_CONTINUE = (byte) 0x80;
     38     public static final byte RESPONSE_SUCCESS = (byte) 0x81;
     39     public static final byte RESPONSE_NOT_FOUND = (byte) 0xC0;
     40     public static final byte RESPONSE_EXCESS_DATA = (byte) 0xC1;
     41     public static final byte RESPONSE_BAD_REQUEST = (byte) 0xC2;
     42     public static final byte RESPONSE_NOT_IMPLEMENTED = (byte) 0xE0;
     43     public static final byte RESPONSE_UNSUPPORTED_VERSION = (byte) 0xE1;
     44     public static final byte RESPONSE_REJECT = (byte) 0xFF;
     45 
     46     private static final int HEADER_LENGTH = 6;
     47     private final byte mVersion;
     48     private final byte mField;
     49     private final int mLength;
     50     private final int mAcceptableLength;
     51     private final NdefMessage mNdefMessage;
     52 
     53     public static SnepMessage getGetRequest(int acceptableLength, NdefMessage ndef) {
     54         return new SnepMessage(VERSION, REQUEST_GET, 4 + ndef.toByteArray().length,
     55                 acceptableLength, ndef);
     56     }
     57 
     58     public static SnepMessage getPutRequest(NdefMessage ndef) {
     59         return new SnepMessage(VERSION, REQUEST_PUT, ndef.toByteArray().length, 0, ndef);
     60     }
     61 
     62     public static SnepMessage getMessage(byte field) {
     63         return new SnepMessage(VERSION, field, 0, 0, null);
     64     }
     65 
     66     public static SnepMessage getSuccessResponse(NdefMessage ndef) {
     67         if (ndef == null) {
     68             return new SnepMessage(VERSION, RESPONSE_SUCCESS, 0, 0, null);
     69         } else {
     70             return new SnepMessage(VERSION, RESPONSE_SUCCESS, ndef.toByteArray().length, 0, ndef);
     71         }
     72     }
     73 
     74     public static SnepMessage fromByteArray(byte[] data) throws FormatException {
     75         return new SnepMessage(data);
     76     }
     77 
     78     private SnepMessage(byte[] data) throws FormatException {
     79         ByteBuffer input = ByteBuffer.wrap(data);
     80         int ndefOffset;
     81         int ndefLength;
     82 
     83         mVersion = input.get();
     84         mField = input.get();
     85         mLength = input.getInt();
     86         if (mField == REQUEST_GET) {
     87             mAcceptableLength = input.getInt();
     88             ndefOffset = HEADER_LENGTH + 4;
     89             ndefLength = mLength - 4;
     90         } else {
     91             mAcceptableLength = -1;
     92             ndefOffset = HEADER_LENGTH;
     93             ndefLength = mLength;
     94         }
     95 
     96         if (ndefLength > 0) {
     97             byte[] bytes = new byte[ndefLength];
     98             System.arraycopy(data, ndefOffset, bytes, 0, ndefLength);
     99             mNdefMessage = new NdefMessage(bytes);
    100         } else {
    101             mNdefMessage = null;
    102         }
    103     }
    104 
    105     SnepMessage(byte version, byte field, int length, int acceptableLength,
    106             NdefMessage ndefMessage) {
    107         mVersion = version;
    108         mField = field;
    109         mLength = length;
    110         mAcceptableLength = acceptableLength;
    111         mNdefMessage = ndefMessage;
    112     }
    113 
    114     public byte[] toByteArray() {
    115         byte[] bytes;
    116         if (mNdefMessage != null) {
    117             bytes = mNdefMessage.toByteArray();
    118         } else {
    119             bytes = new byte[0];
    120         }
    121 
    122         ByteArrayOutputStream buffer;
    123         try {
    124             if (mField == REQUEST_GET) {
    125                 buffer = new ByteArrayOutputStream(bytes.length + HEADER_LENGTH + 4);
    126             } else {
    127                 buffer = new ByteArrayOutputStream(bytes.length + HEADER_LENGTH);
    128             }
    129 
    130             DataOutputStream output = new DataOutputStream(buffer);
    131             output.writeByte(mVersion);
    132             output.writeByte(mField);
    133             if (mField == REQUEST_GET) {
    134                 output.writeInt(bytes.length + 4);
    135                 output.writeInt(mAcceptableLength);
    136             } else {
    137                 output.writeInt(bytes.length);
    138             }
    139             output.write(bytes);
    140         } catch(IOException e) {
    141             return null;
    142         }
    143 
    144         return buffer.toByteArray();
    145     }
    146 
    147     public NdefMessage getNdefMessage() {
    148         return mNdefMessage;
    149     }
    150 
    151     public byte getField() {
    152         return mField;
    153     }
    154 
    155     public byte getVersion() {
    156         return mVersion;
    157     }
    158 
    159     public int getLength() {
    160         return mLength;
    161     }
    162 
    163     public int getAcceptableLength() {
    164         if (mField != REQUEST_GET) {
    165             throw new UnsupportedOperationException(
    166                     "Acceptable Length only available on get request messages.");
    167         }
    168         return mAcceptableLength;
    169     }
    170 }
    171