Line data    Source code

       1              : /*
       2              :  *
       3              :  *    Copyright (c) 2022 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              : 
      18              : /**
      19              :  *    @file
      20              :  *      This file defines the SetupDiscriminator type, which is used by
      21              :  *      low-level code (e.g. BLE) in addition to setup payload code.
      22              :  */
      23              : 
      24              : #pragma once
      25              : 
      26              : #include <cstdint>
      27              : 
      28              : #include <lib/support/CodeUtils.h>
      29              : 
      30              : namespace chip {
      31              : 
      32              : class SetupDiscriminator
      33              : {
      34              : public:
      35            2 :     constexpr SetupDiscriminator() : mDiscriminator(0), mIsShortDiscriminator(false) {}
      36              : 
      37              :     // See section 5.1.2. QR Code in the Matter specification
      38              :     static constexpr int kLongBits = 12;
      39              : 
      40              :     // See section 5.1.3. Manual Pairing Code in the Matter specification
      41              :     static constexpr int kShortBits = 4;
      42              : 
      43            2 :     void SetShortValue(uint8_t discriminator)
      44              :     {
      45            2 :         VerifyOrDie(discriminator == (discriminator & kShortMask));
      46            2 :         mDiscriminator        = (discriminator & kShortMask);
      47            2 :         mIsShortDiscriminator = true;
      48            2 :     }
      49              : 
      50            4 :     void SetLongValue(uint16_t discriminator)
      51              :     {
      52            4 :         VerifyOrDie(discriminator == (discriminator & kLongMask));
      53            4 :         mDiscriminator        = (discriminator & kLongMask);
      54            4 :         mIsShortDiscriminator = false;
      55            4 :     }
      56              : 
      57           39 :     bool IsShortDiscriminator() const { return mIsShortDiscriminator; }
      58              : 
      59            0 :     uint8_t GetShortValue() const
      60              :     {
      61            0 :         if (IsShortDiscriminator())
      62              :         {
      63            0 :             return static_cast<uint8_t>(mDiscriminator);
      64              :         }
      65              : 
      66            0 :         return LongToShortValue(mDiscriminator);
      67              :     }
      68              : 
      69           12 :     uint16_t GetLongValue() const
      70              :     {
      71           12 :         VerifyOrDie(!IsShortDiscriminator());
      72           12 :         return mDiscriminator;
      73              :     }
      74              : 
      75            0 :     bool MatchesLongDiscriminator(uint16_t discriminator) const
      76              :     {
      77            0 :         if (!IsShortDiscriminator())
      78              :         {
      79            0 :             return mDiscriminator == discriminator;
      80              :         }
      81              : 
      82            0 :         return mDiscriminator == LongToShortValue(discriminator);
      83              :     }
      84              : 
      85           35 :     bool operator==(const SetupDiscriminator & other) const
      86              :     {
      87           35 :         return mIsShortDiscriminator == other.mIsShortDiscriminator && mDiscriminator == other.mDiscriminator;
      88              :     }
      89              : 
      90              : private:
      91              :     static constexpr uint16_t kLongMask = (1 << kLongBits) - 1;
      92              :     static constexpr uint8_t kShortMask = (1 << kShortBits) - 1;
      93              : 
      94            0 :     static uint8_t LongToShortValue(uint16_t longValue)
      95              :     {
      96              :         // Short value consists of the high bits of the long value.
      97            0 :         constexpr int kLongToShortShift = kLongBits - kShortBits;
      98            0 :         return static_cast<uint8_t>(longValue >> kLongToShortShift);
      99              :     }
     100              : 
     101              :     // If long discriminator, all 12 bits are used.  If short discriminator,
     102              :     // only the low kShortBits bits are used, to store the value of the short
     103              :     // discriminator (which contains only the high bits of the complete 12-bit
     104              :     // discriminator).
     105              :     static_assert(kLongBits == 12, "Unexpected field length");
     106              :     static_assert(kShortBits <= kLongBits, "Unexpected field length");
     107              :     uint16_t mDiscriminator;
     108              :     bool mIsShortDiscriminator;
     109              : };
     110              : 
     111              : } // namespace chip