dcs.c

/* Copyright 2023 Dual Tachyon
 * https://github.com/DualTachyon
 *
 * 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.
 */

#include "dcs.h"

#define ARRAY_SIZE(x) (sizeof(x) / sizeof(x[0]))

const uint16_t CTCSS_Options[50] = {
	0x029E, 0x02B5, 0x02CF, 0x02E8,
	0x0302, 0x031D, 0x0339, 0x0356,
	0x0375, 0x0393, 0x03B4, 0x03CE,
	0x03E8, 0x040B, 0x0430, 0x0455,
	0x047C, 0x04A4, 0x04CE, 0x04F9,
	0x0526, 0x0555, 0x0585, 0x05B6,
	0x05EA, 0x061F, 0x063E, 0x0656,
	0x0677, 0x068F, 0x06B1, 0x06CA,
	0x06ED, 0x0707, 0x072B, 0x0746,
	0x076B, 0x0788, 0x07AE, 0x07CB,
	0x07F3, 0x0811, 0x083B, 0x0885,
	0x08D1, 0x08F3, 0x0920, 0x0972,
	0x09C7, 0x09ED,
};

const uint16_t DCS_Options[104] = {
	0x0013, 0x0015, 0x0016, 0x0019,
	0x001A, 0x001E, 0x0023, 0x0027,
	0x0029, 0x002B, 0x002C, 0x0035,
	0x0039, 0x003A, 0x003B, 0x003C,
	0x004C, 0x004D, 0x004E, 0x0052,
	0x0055, 0x0059, 0x005A, 0x005C,
	0x0063, 0x0065, 0x006A, 0x006D,
	0x006E, 0x0072, 0x0075, 0x007A,
	0x007C, 0x0085, 0x008A, 0x0093,
	0x0095, 0x0096, 0x00A3, 0x00A4,
	0x00A5, 0x00A6, 0x00A9, 0x00AA,
	0x00AD, 0x00B1, 0x00B3, 0x00B5,
	0x00B6, 0x00B9, 0x00BC, 0x00C6,
	0x00C9, 0x00CD, 0x00D5, 0x00D9,
	0x00DA, 0x00E3, 0x00E6, 0x00E9,
	0x00EE, 0x00F4, 0x00F5, 0x00F9,
	0x0109, 0x010A, 0x010B, 0x0113,
	0x0119, 0x011A, 0x0125, 0x0126,
	0x012A, 0x012C, 0x012D, 0x0132,
	0x0134, 0x0135, 0x0136, 0x0143,
	0x0146, 0x014E, 0x0153, 0x0156,
	0x015A, 0x0166, 0x0175, 0x0186,
	0x018A, 0x0194, 0x0197, 0x0199,
	0x019A, 0x01AC, 0x01B2, 0x01B4,
	0x01C3, 0x01CA, 0x01D3, 0x01D9,
	0x01DA, 0x01DC, 0x01E3, 0x01EC,
};

static uint32_t DCS_CalculateGolay(uint32_t CodeWord)
{
	uint32_t Word;
	uint8_t i;

	Word = CodeWord;
	for (i = 0; i < 12; i++) {
		Word <<= 1;
		if (Word & 0x1000) {
			Word ^= 0x08EA;
		}
	}
	return CodeWord | ((Word & 0x0FFE) << 11);
}

uint32_t DCS_GetGolayCodeWord(DCS_CodeType_t CodeType, uint8_t Option)
{
	uint32_t Code;

	Code = DCS_CalculateGolay(DCS_Options[Option] + 0x800U);
	if (CodeType == CODE_TYPE_REVERSE_DIGITAL) {
		Code ^= 0x7FFFFF;
	}

	return Code;
}

uint8_t DCS_GetCdcssCode(uint32_t Code)
{
	uint8_t i;

	for (i = 0; i < 23; i++) {
		uint32_t Shift;

		if (((Code >> 9) & 0x7U) == 4) {
			uint8_t j;

			for (j = 0; j < ARRAY_SIZE(DCS_Options); j++) {
				if (DCS_Options[j] == (Code & 0x1FF)) {
					if (DCS_GetGolayCodeWord(2, j) == Code) {
						return j;
					}
				}
			}
		}
		Shift = Code >> 1;
		if (Code & 1U) {
			Shift |= 0x400000U;
		}
		Code = Shift;
	}

	return 0xFF;
}

uint8_t DCS_GetCtcssCode(uint16_t Code)
{
	uint8_t i;
	int Smallest;
	uint8_t Result = 0xFF;

	Smallest = ARRAY_SIZE(CTCSS_Options);
	for (i = 0; i < ARRAY_SIZE(CTCSS_Options); i++) {
		int Delta;

		Delta = Code - CTCSS_Options[i];
		if (Delta < 0) {
			Delta = -(Code - CTCSS_Options[i]);
		}
		if (Delta < Smallest) {
			Smallest = Delta;
			Result = i;
		}
	}

	return Result;
}