mirror of https://github.com/ShaYmez/xlxd.git
142 lines
3.9 KiB
C++
142 lines
3.9 KiB
C++
/*
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* Copyright (C) 2009-2016 by Jonathan Naylor G4KLX
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include "cysfconvolution.h"
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#include <cstdio>
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#include <cassert>
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#include <cstring>
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const unsigned char BIT_MASK_TABLE[] = {0x80U, 0x40U, 0x20U, 0x10U, 0x08U, 0x04U, 0x02U, 0x01U};
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#define WRITE_BIT1(p,i,b) p[(i)>>3] = (b) ? (p[(i)>>3] | BIT_MASK_TABLE[(i)&7]) : (p[(i)>>3] & ~BIT_MASK_TABLE[(i)&7])
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#define READ_BIT1(p,i) (p[(i)>>3] & BIT_MASK_TABLE[(i)&7])
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const uint8_t BRANCH_TABLE1[] = {0U, 0U, 0U, 0U, 1U, 1U, 1U, 1U};
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const uint8_t BRANCH_TABLE2[] = {0U, 1U, 1U, 0U, 0U, 1U, 1U, 0U};
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const unsigned int NUM_OF_STATES_D2 = 8U;
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const unsigned int NUM_OF_STATES = 16U;
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const uint32_t M = 2U;
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const unsigned int K = 5U;
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CYSFConvolution::CYSFConvolution() :
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m_metrics1(NULL),
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m_metrics2(NULL),
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m_oldMetrics(NULL),
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m_newMetrics(NULL),
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m_decisions(NULL),
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m_dp(NULL)
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{
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m_metrics1 = new uint16_t[16U];
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m_metrics2 = new uint16_t[16U];
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m_decisions = new uint64_t[180U];
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}
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CYSFConvolution::~CYSFConvolution()
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{
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delete[] m_metrics1;
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delete[] m_metrics2;
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delete[] m_decisions;
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}
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void CYSFConvolution::start()
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{
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::memset(m_metrics1, 0x00U, NUM_OF_STATES * sizeof(uint16_t));
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::memset(m_metrics2, 0x00U, NUM_OF_STATES * sizeof(uint16_t));
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m_oldMetrics = m_metrics1;
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m_newMetrics = m_metrics2;
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m_dp = m_decisions;
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}
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void CYSFConvolution::decode(uint8_t s0, uint8_t s1)
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{
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*m_dp = 0U;
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for (uint8_t i = 0U; i < NUM_OF_STATES_D2; i++) {
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uint8_t j = i * 2U;
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uint16_t metric = (BRANCH_TABLE1[i] ^ s0) + (BRANCH_TABLE2[i] ^ s1);
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uint16_t m0 = m_oldMetrics[i] + metric;
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uint16_t m1 = m_oldMetrics[i + NUM_OF_STATES_D2] + (M - metric);
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uint8_t decision0 = (m0 >= m1) ? 1U : 0U;
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m_newMetrics[j + 0U] = decision0 != 0U ? m1 : m0;
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m0 = m_oldMetrics[i] + (M - metric);
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m1 = m_oldMetrics[i + NUM_OF_STATES_D2] + metric;
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uint8_t decision1 = (m0 >= m1) ? 1U : 0U;
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m_newMetrics[j + 1U] = decision1 != 0U ? m1 : m0;
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*m_dp |= (uint64_t(decision1) << (j + 1U)) | (uint64_t(decision0) << (j + 0U));
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}
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++m_dp;
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assert((m_dp - m_decisions) <= 180);
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uint16_t* tmp = m_oldMetrics;
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m_oldMetrics = m_newMetrics;
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m_newMetrics = tmp;
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}
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void CYSFConvolution::chainback(unsigned char* out, unsigned int nBits)
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{
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assert(out != NULL);
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uint32_t state = 0U;
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while (nBits-- > 0) {
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--m_dp;
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uint32_t i = state >> (9 - K);
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uint8_t bit = uint8_t(*m_dp >> i) & 1;
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state = (bit << 7) | (state >> 1);
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WRITE_BIT1(out, nBits, bit != 0U);
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}
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}
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void CYSFConvolution::encode(const unsigned char* in, unsigned char* out, unsigned int nBits) const
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{
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assert(in != NULL);
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assert(out != NULL);
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assert(nBits > 0U);
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uint8_t d1 = 0U, d2 = 0U, d3 = 0U, d4 = 0U;
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uint32_t k = 0U;
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for (unsigned int i = 0U; i < nBits; i++) {
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uint8_t d = READ_BIT1(in, i) ? 1U : 0U;
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uint8_t g1 = (d + d3 + d4) & 1;
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uint8_t g2 = (d + d1 + d2 + d4) & 1;
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d4 = d3;
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d3 = d2;
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d2 = d1;
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d1 = d;
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WRITE_BIT1(out, k, g1 != 0U);
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k++;
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WRITE_BIT1(out, k, g2 != 0U);
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k++;
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}
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}
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