SystemK/Protocols/Test.c

/*
 * This program source code file is part of SystemK, a library in the KTag project.
 *
 * 🛡️ <https://ktag.clubk.club> 🃞
 *
 * Copyright © 2016-2025 Joseph P. Kearney and the KTag developers.
 *
 * This program is free software: you can redistribute it and/or modify it under
 * the terms of the GNU Affero General Public License as published by the Free
 * Software Foundation, either version 3 of the License, or (at your option) any
 * later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE.  See the GNU Affero General Public License for more
 * details.
 *
 * There should be a copy of the GNU Affero General Public License in the LICENSE
 * file in the root of this repository.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <stdbool.h>
#include <stdio.h>

#include "SystemK.h"

static const char *KLOG_TAG = "Test Protocol";

#define TEST_PULSE_SUBTRAHEND_IN_us 300
//! The shortest test packet is a two marks, the first of duration (3 * TEST_PULSE_SUBTRAHEND_IN_us), and the second of duration TEST_PULSE_SUBTRAHEND_IN_us.
#define TEST_MINIMUM_LONGEST_PULSE_DURATION_IN_us (3 * TEST_PULSE_SUBTRAHEND_IN_us)
#define TEST_TOLERANCE_IN_us ((TEST_PULSE_SUBTRAHEND_IN_us / 2) - 1)

static TimedPulseTrain_T Tag_Send_Buffer;
static DecodedPacket_T Test_Tag_Received_Buffers[3] =
    {
        {.Tag.type = DECODED_PACKET_TYPE_BUFFER_FREE},
        {.Tag.type = DECODED_PACKET_TYPE_BUFFER_FREE},
        {.Tag.type = DECODED_PACKET_TYPE_BUFFER_FREE}};

static inline DecodedPacket_T *Get_Tag_Packet_Buffer(void)
{
    if (Test_Tag_Received_Buffers[0].Tag.type == DECODED_PACKET_TYPE_BUFFER_FREE)
    {
        return &Test_Tag_Received_Buffers[0];
    }
    else if (Test_Tag_Received_Buffers[1].Tag.type == DECODED_PACKET_TYPE_BUFFER_FREE)
    {
        return &Test_Tag_Received_Buffers[1];
    }
    else
    {
        // Just use it.
        return &Test_Tag_Received_Buffers[2];
    }
}

static inline void PackPulseTrain(TimedPulseTrain_T *pulsetrain, uint32_t longest_pulse_duration_in_us)
{
    uint_fast8_t index = 0;
    uint32_t next_pulse_duration_in_us = longest_pulse_duration_in_us;
    TimedBit_T next_bit;

    if (next_pulse_duration_in_us < TEST_MINIMUM_LONGEST_PULSE_DURATION_IN_us)
    {
        next_pulse_duration_in_us = TEST_MINIMUM_LONGEST_PULSE_DURATION_IN_us;
    }

    while ((next_pulse_duration_in_us >= TEST_PULSE_SUBTRAHEND_IN_us) && (index < MAX_PULSES))
    {
        // Even indicies are marks.
        if ((index % 2) == 0)
        {
            next_bit.symbol = MARK;
        }
        // Odd indicies are spaces.
        else
        {
            next_bit.symbol = SPACE;
        }
        next_bit.duration = next_pulse_duration_in_us;
        pulsetrain->bitstream[index] = next_bit;

        next_pulse_duration_in_us = next_pulse_duration_in_us - TEST_PULSE_SUBTRAHEND_IN_us;
        index++;
    }

    // Mark the end of the train.
    next_bit.symbol = SPACE;
    next_bit.duration = LAST_PULSE;
    pulsetrain->bitstream[index] = next_bit;
    pulsetrain->count = index;
}

TimedPulseTrain_T *TEST_EncodePacket(TagPacket_T *packet)
{
    uint32_t packed_data = 2100;

    PackPulseTrain(&Tag_Send_Buffer, packed_data);

    return &Tag_Send_Buffer;
}

DecodedPacket_T *TEST_MaybeDecodePacket(TimedPulseTrain_T *packet)
{
    // packet->bitstream[0] is the longest pulse--assume it was received correctly.
    uint32_t longest_pulse_duration_in_us = packet->bitstream[0].duration;

    if ((longest_pulse_duration_in_us - TEST_TOLERANCE_IN_us) < TEST_MINIMUM_LONGEST_PULSE_DURATION_IN_us)
    {
        // The first pulse is too short!
        return NULL;
    }

    for (uint_fast8_t index = 1; index < packet->count; index++)
    {
        uint32_t expected_pulse_duration_in_us = longest_pulse_duration_in_us - (index * TEST_PULSE_SUBTRAHEND_IN_us);

        if (packet->bitstream[index].duration < (expected_pulse_duration_in_us - TEST_TOLERANCE_IN_us))
        {
            KLOG_WARN(KLOG_TAG, "Pulse %u is too short! Expected %lu; received %u.", index, expected_pulse_duration_in_us, packet->bitstream[index].duration);
            return NULL;
        }
        if (packet->bitstream[index].duration > (expected_pulse_duration_in_us + TEST_TOLERANCE_IN_us))
        {
            KLOG_WARN(KLOG_TAG, "Pulse %u is too long! Expected %lu; received %u.", index, expected_pulse_duration_in_us, packet->bitstream[index].duration);
            return NULL;
        }
    }

    DecodedPacket_T *Command_Rx_Buffer = Get_Tag_Packet_Buffer();
    Command_Rx_Buffer->Command.type = DECODED_PACKET_TYPE_COMMAND_RECEIVED;
    Command_Rx_Buffer->Command.protocol = TEST_PROTOCOL;
    Command_Rx_Buffer->Command.data = longest_pulse_duration_in_us;
    return Command_Rx_Buffer;
}

color_t TEST_GetTeamColor(__attribute__((unused)) uint8_t team_ID)
{
    color_t result = COLOR_WHITE;

    return result;
}