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
17package com.android.nfc.snep;
18
19import android.nfc.FormatException;
20import android.nfc.NdefMessage;
21
22import java.io.ByteArrayOutputStream;
23import java.io.DataOutputStream;
24import java.io.IOException;
25import java.nio.ByteBuffer;
26
27public 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) 0x07;
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