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      1 /*
      2  * Copyright (C) 2006 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.internal.telephony.cat;
     18 
     19 import java.util.List;
     20 
     21 /**
     22  * Class for representing BER-TLV objects.
     23  *
     24  * @see "ETSI TS 102 223 Annex C" for more information.
     25  *
     26  * {@hide}
     27  */
     28 class BerTlv {
     29     private int mTag = BER_UNKNOWN_TAG;
     30     private List<ComprehensionTlv> mCompTlvs = null;
     31     private boolean mLengthValid = true;
     32 
     33     public static final int BER_UNKNOWN_TAG             = 0x00;
     34     public static final int BER_PROACTIVE_COMMAND_TAG   = 0xd0;
     35     public static final int BER_MENU_SELECTION_TAG      = 0xd3;
     36     public static final int BER_EVENT_DOWNLOAD_TAG      = 0xd6;
     37 
     38     private BerTlv(int tag, List<ComprehensionTlv> ctlvs, boolean lengthValid) {
     39         mTag = tag;
     40         mCompTlvs = ctlvs;
     41         mLengthValid = lengthValid;
     42     }
     43 
     44     /**
     45      * Gets a list of ComprehensionTlv objects contained in this BER-TLV object.
     46      *
     47      * @return A list of COMPREHENSION-TLV object
     48      */
     49     public List<ComprehensionTlv> getComprehensionTlvs() {
     50         return mCompTlvs;
     51     }
     52 
     53     /**
     54      * Gets a tag id of the BER-TLV object.
     55      *
     56      * @return A tag integer.
     57      */
     58     public int getTag() {
     59         return mTag;
     60     }
     61 
     62     /**
     63      * Gets if the length of the BER-TLV object is valid
     64      *
     65      * @return if length valid
     66      */
     67      public boolean isLengthValid() {
     68          return mLengthValid;
     69      }
     70 
     71     /**
     72      * Decodes a BER-TLV object from a byte array.
     73      *
     74      * @param data A byte array to decode from
     75      * @return A BER-TLV object decoded
     76      * @throws ResultException
     77      */
     78     public static BerTlv decode(byte[] data) throws ResultException {
     79         int curIndex = 0;
     80         int endIndex = data.length;
     81         int tag, length = 0;
     82         boolean isLengthValid = true;
     83 
     84         try {
     85             /* tag */
     86             tag = data[curIndex++] & 0xff;
     87             if (tag == BER_PROACTIVE_COMMAND_TAG) {
     88                 /* length */
     89                 int temp = data[curIndex++] & 0xff;
     90                 if (temp < 0x80) {
     91                     length = temp;
     92                 } else if (temp == 0x81) {
     93                     temp = data[curIndex++] & 0xff;
     94                     if (temp < 0x80) {
     95                         throw new ResultException(
     96                                 ResultCode.CMD_DATA_NOT_UNDERSTOOD,
     97                                 "length < 0x80 length=" + Integer.toHexString(length) +
     98                                 " curIndex=" + curIndex + " endIndex=" + endIndex);
     99 
    100                     }
    101                     length = temp;
    102                 } else {
    103                     throw new ResultException(
    104                             ResultCode.CMD_DATA_NOT_UNDERSTOOD,
    105                             "Expected first byte to be length or a length tag and < 0x81" +
    106                             " byte= " + Integer.toHexString(temp) + " curIndex=" + curIndex +
    107                             " endIndex=" + endIndex);
    108                 }
    109             } else {
    110                 if (ComprehensionTlvTag.COMMAND_DETAILS.value() == (tag & ~0x80)) {
    111                     tag = BER_UNKNOWN_TAG;
    112                     curIndex = 0;
    113                 }
    114             }
    115         } catch (IndexOutOfBoundsException e) {
    116             throw new ResultException(ResultCode.REQUIRED_VALUES_MISSING,
    117                     "IndexOutOfBoundsException " +
    118                     " curIndex=" + curIndex + " endIndex=" + endIndex);
    119         } catch (ResultException e) {
    120             throw new ResultException(ResultCode.CMD_DATA_NOT_UNDERSTOOD, e.explanation());
    121         }
    122 
    123         /* COMPREHENSION-TLVs */
    124         if (endIndex - curIndex < length) {
    125             throw new ResultException(ResultCode.CMD_DATA_NOT_UNDERSTOOD,
    126                     "Command had extra data endIndex=" + endIndex + " curIndex=" + curIndex +
    127                     " length=" + length);
    128         }
    129 
    130         List<ComprehensionTlv> ctlvs = ComprehensionTlv.decodeMany(data,
    131                 curIndex);
    132 
    133         if (tag == BER_PROACTIVE_COMMAND_TAG) {
    134             int totalLength = 0;
    135             for (ComprehensionTlv item : ctlvs) {
    136                 int itemLength = item.getLength();
    137                 if (itemLength >= 0x80 && itemLength <= 0xFF) {
    138                     totalLength += itemLength + 3; //3: 'tag'(1 byte) and 'length'(2 bytes).
    139                 } else if (itemLength >= 0 && itemLength < 0x80) {
    140                     totalLength += itemLength + 2; //2: 'tag'(1 byte) and 'length'(1 byte).
    141                 } else {
    142                     isLengthValid = false;
    143                     break;
    144                 }
    145             }
    146 
    147             // According to 3gpp11.14, chapter 6.10.6 "Length errors",
    148 
    149             // If the total lengths of the SIMPLE-TLV data objects are not
    150             // consistent with the length given in the BER-TLV data object,
    151             // then the whole BER-TLV data object shall be rejected. The
    152             // result field in the TERMINAL RESPONSE shall have the error
    153             // condition "Command data not understood by ME".
    154             if (length != totalLength) {
    155                 isLengthValid = false;
    156             }
    157         }
    158 
    159         return new BerTlv(tag, ctlvs, isLengthValid);
    160     }
    161 }
    162