Line data    Source code

       1             : /*
       2             :  *
       3             :  *    Copyright (c) 2020 Project CHIP Authors
       4             :  *
       5             :  *    Licensed under the Apache License, Version 2.0 (the "License");
       6             :  *    you may not use this file except in compliance with the License.
       7             :  *    You may obtain a copy of the License at
       8             :  *
       9             :  *        http://www.apache.org/licenses/LICENSE-2.0
      10             :  *
      11             :  *    Unless required by applicable law or agreed to in writing, software
      12             :  *    distributed under the License is distributed on an "AS IS" BASIS,
      13             :  *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      14             :  *    See the License for the specific language governing permissions and
      15             :  *    limitations under the License.
      16             :  */
      17             : #include "RecordWriter.h"
      18             : 
      19             : namespace mdns {
      20             : namespace Minimal {
      21             : 
      22       22197 : SerializedQNameIterator RecordWriter::PreviousName(size_t index) const
      23             : {
      24       22197 :     if (index >= kMaxCachedReferences)
      25             :     {
      26           0 :         return SerializedQNameIterator();
      27             :     }
      28             : 
      29       22197 :     uint16_t offset = mPreviousQNames[index];
      30       22197 :     if (offset == kInvalidOffset)
      31             :     {
      32       15761 :         return SerializedQNameIterator();
      33             :     }
      34             : 
      35        6436 :     return SerializedQNameIterator(BytesRange(mOutput->Buffer(), mOutput->Buffer() + mOutput->WritePos()),
      36       12872 :                                    mOutput->Buffer() + offset);
      37             : }
      38             : 
      39        1751 : RecordWriter & RecordWriter::WriteQName(const FullQName & qname)
      40             : {
      41        1751 :     size_t qNameWriteStart = mOutput->WritePos();
      42        1751 :     bool isFullyCompressed = true;
      43             : 
      44        3037 :     for (uint16_t i = 0; i < qname.nameCount; i++)
      45             :     {
      46             : 
      47             :         // find out if the record part remaining already is located somewhere
      48        2821 :         FullQName remaining;
      49        2821 :         remaining.names     = qname.names + i;
      50        2821 :         remaining.nameCount = qname.nameCount - i;
      51             : 
      52             :         // Try to find a valid offset
      53        2821 :         chip::Optional<uint16_t> offset = FindPreviousName(remaining);
      54             : 
      55        2821 :         if (offset.HasValue())
      56             :         {
      57             :             // Pointer to offset: set the highest 2 bits
      58        1535 :             mOutput->Put16(offset.Value() | 0xC000);
      59             : 
      60        1535 :             if (mOutput->Fit() && !isFullyCompressed)
      61             :             {
      62         590 :                 RememberWrittenQnameOffset(qNameWriteStart);
      63             :             }
      64        1535 :             return *this;
      65             :         }
      66             : 
      67        1286 :         mOutput->Put8(static_cast<uint8_t>(strlen(qname.names[i])));
      68        1286 :         mOutput->Put(qname.names[i]);
      69        1286 :         isFullyCompressed = false;
      70        2821 :     }
      71         216 :     mOutput->Put8(0); // end of qnames
      72             : 
      73         216 :     if (mOutput->Fit())
      74             :     {
      75         206 :         RememberWrittenQnameOffset(qNameWriteStart);
      76             :     }
      77         216 :     return *this;
      78             : }
      79             : 
      80         143 : RecordWriter & RecordWriter::WriteQName(const SerializedQNameIterator & qname)
      81             : {
      82         143 :     size_t qNameWriteStart = mOutput->WritePos();
      83         143 :     bool isFullyCompressed = true;
      84             : 
      85         143 :     SerializedQNameIterator copy = qname;
      86             :     while (true)
      87             :     {
      88        1016 :         chip::Optional<uint16_t> offset = FindPreviousName(copy);
      89             : 
      90        1016 :         if (offset.HasValue())
      91             :         {
      92             :             // Pointer to offset: set the highest 2 bits
      93             :             // We guarantee that offsets saved are <= kMaxReuseOffset
      94           0 :             mOutput->Put16(offset.Value() | 0xC000);
      95             : 
      96           0 :             if (mOutput->Fit() && !isFullyCompressed)
      97             :             {
      98           0 :                 RememberWrittenQnameOffset(qNameWriteStart);
      99             :             }
     100           0 :             return *this;
     101             :         }
     102             : 
     103        1016 :         if (!copy.Next())
     104             :         {
     105         143 :             break;
     106             :         }
     107             : 
     108         873 :         if (!copy.IsValid())
     109             :         {
     110           0 :             break;
     111             :         }
     112             : 
     113         873 :         mOutput->Put8(static_cast<uint8_t>(strlen(copy.Value())));
     114         873 :         mOutput->Put(copy.Value());
     115         873 :         isFullyCompressed = false;
     116        1889 :     }
     117         143 :     mOutput->Put8(0); // end of qnames
     118             : 
     119         143 :     if (mOutput->Fit())
     120             :     {
     121         118 :         RememberWrittenQnameOffset(qNameWriteStart);
     122             :     }
     123         143 :     return *this;
     124             : }
     125             : 
     126         914 : void RecordWriter::RememberWrittenQnameOffset(size_t offset)
     127             : {
     128         914 :     if (offset > kMaxReuseOffset)
     129             :     {
     130             :         // cannot represent this offset properly
     131           0 :         return;
     132             :     }
     133             : 
     134        3201 :     for (unsigned short & previousName : mPreviousQNames)
     135             :     {
     136        3139 :         if (previousName == kInvalidOffset)
     137             :         {
     138         852 :             previousName = static_cast<unsigned short>(offset);
     139         852 :             return;
     140             :         }
     141             :     }
     142             : }
     143             : 
     144             : } // namespace Minimal
     145             : } // namespace mdns