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/*
*
* Copyright (c) 2022 Project CHIP Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* @file
* This file defines the SetupDiscriminator type, which is used by
* low-level code (e.g. BLE) in addition to setup payload code.
*/
#pragma once
#include <cstdint>
#include <lib/support/CodeUtils.h>
namespace chip {
class SetupDiscriminator
{
public:
constexpr SetupDiscriminator() : mDiscriminator(0), mIsShortDiscriminator(false) {}
// See section 5.1.2. QR Code in the Matter specification
static constexpr int kLongBits = 12;
// See section 5.1.3. Manual Pairing Code in the Matter specification
static constexpr int kShortBits = 4;
void SetShortValue(uint8_t discriminator)
{
VerifyOrDie(discriminator == (discriminator & kShortMask));
mDiscriminator = (discriminator & kShortMask);
mIsShortDiscriminator = true;
}
void SetLongValue(uint16_t discriminator)
{
VerifyOrDie(discriminator == (discriminator & kLongMask));
mDiscriminator = (discriminator & kLongMask);
mIsShortDiscriminator = false;
}
bool IsShortDiscriminator() const { return mIsShortDiscriminator; }
uint8_t GetShortValue() const
{
if (IsShortDiscriminator())
{
return static_cast<uint8_t>(mDiscriminator);
}
return LongToShortValue(mDiscriminator);
}
uint16_t GetLongValue() const
{
VerifyOrDie(!IsShortDiscriminator());
return mDiscriminator;
}
bool MatchesLongDiscriminator(uint16_t discriminator) const
{
if (!IsShortDiscriminator())
{
return mDiscriminator == discriminator;
}
return mDiscriminator == LongToShortValue(discriminator);
}
bool operator==(const SetupDiscriminator & other) const
{
return mIsShortDiscriminator == other.mIsShortDiscriminator && mDiscriminator == other.mDiscriminator;
}
private:
static constexpr uint16_t kLongMask = (1 << kLongBits) - 1;
static constexpr uint8_t kShortMask = (1 << kShortBits) - 1;
static uint8_t LongToShortValue(uint16_t longValue)
{
// Short value consists of the high bits of the long value.
constexpr int kLongToShortShift = kLongBits - kShortBits;
return static_cast<uint8_t>(longValue >> kLongToShortShift);
}
// If long discriminator, all 12 bits are used. If short discriminator,
// only the low kShortBits bits are used, to store the value of the short
// discriminator (which contains only the high bits of the complete 12-bit
// discriminator).
static_assert(kLongBits == 12, "Unexpected field length");
static_assert(kShortBits <= kLongBits, "Unexpected field length");
uint16_t mDiscriminator;
bool mIsShortDiscriminator;
};
} // namespace chip