112 lines
2.7 KiB
C++
112 lines
2.7 KiB
C++
#include "StdAfx.h"
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#include "linux/tape.h"
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#include "Core.h"
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#include "Tape.h"
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#include "Memory.h"
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#include "Pravets.h"
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#include "CPU.h"
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#include <limits>
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namespace
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{
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std::vector<tape_data_t> cassetteTape;
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uint64_t baseCycles;
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int tapeFrequency;
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bool playing = false;
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BYTE lastBit = 1;
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// threshold not needed for https://asciiexpress.net
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// but probably necessary for a real audio file
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constexpr tape_data_t threshold = 5;
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BYTE getBitValue(const tape_data_t val)
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{
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// this has been tested on all formats from https://asciiexpress.net
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//
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// we are extracting the sign bit (set for negative numbers)
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// this is really important for the asymmetric wave in https://asciiexpress.net/diskserver/
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// not so much for the other cases
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if (val > threshold)
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{
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lastBit = 0;
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}
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else if (val < -threshold)
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{
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lastBit = 1;
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}
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// else leave it unchanged to the previous value
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return lastBit;
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}
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tape_data_t getCurrentWave(size_t & pos)
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{
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if (playing && !cassetteTape.empty())
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{
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const double delta = g_nCumulativeCycles - baseCycles;
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const double position = delta / g_fCurrentCLK6502 * tapeFrequency;
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pos = static_cast<size_t>(position);
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if (pos < cassetteTape.size() - 1)
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{
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// linear interpolation
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const double reminder = position - pos;
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const double value = (1.0 - reminder) * cassetteTape[pos] + reminder * cassetteTape[pos + 1];
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return lround(value);
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}
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cassetteTape.clear();
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}
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pos = 0;
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return std::numeric_limits<tape_data_t>::min();
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}
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}
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//---------------------------------------------------------------------------
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BYTE __stdcall TapeRead(WORD pc, WORD address, BYTE, BYTE, ULONG nExecutedCycles) // $C060 TAPEIN
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{
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if (g_Apple2Type == A2TYPE_PRAVETS8A)
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return GetPravets().GetKeycode( MemReadFloatingBus(nExecutedCycles) );
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CpuCalcCycles(nExecutedCycles);
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if (!playing)
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{
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// start play as soon as TAPEIN is read
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playing = true;
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baseCycles = g_nCumulativeCycles;
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}
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size_t pos;
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const tape_data_t val = getCurrentWave(pos); // this has side effects
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const BYTE highBit = getBitValue(val);
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return MemReadFloatingBus(highBit, nExecutedCycles);
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}
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BYTE __stdcall TapeWrite(WORD, WORD address, BYTE, BYTE, ULONG nExecutedCycles) // $C020 TAPEOUT
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{
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return 0;
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}
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void setCassetteTape(const std::vector<tape_data_t> & data, const int frequency)
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{
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playing = false;
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cassetteTape = data;
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tapeFrequency = frequency;
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}
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void getTapeInfo(size_t & size, size_t & pos, int & frequency, uint8_t & bit)
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{
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const tape_data_t val = getCurrentWave(pos); // this has side effects
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bit = lastBit;
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size = cassetteTape.size();
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frequency = tapeFrequency;
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}
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void ejectTape()
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{
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cassetteTape.clear();
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}
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