44 lines
1.3 KiB
C++
44 lines
1.3 KiB
C++
#include "frontends/common2/speed.h"
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#include "StdAfx.h"
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#include "CPU.h"
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#include "Core.h"
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Speed::Speed(const bool fixedSpeed)
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: myFixedSpeed(fixedSpeed)
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, myStartTime(std::chrono::steady_clock::now())
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, myStartCycles(g_nCumulativeCycles)
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{
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}
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size_t Speed::getCyclesTillNext(const size_t milliseconds) const
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{
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if (myFixedSpeed)
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{
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const size_t cycles = static_cast<uint64_t>(milliseconds * g_fCurrentCLK6502 * 1.0e-3);
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return cycles;
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}
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else
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{
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const uint64_t currentCycles = g_nCumulativeCycles;
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const auto currentTime = std::chrono::steady_clock::now();
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const auto currentDelta = std::chrono::duration_cast<std::chrono::milliseconds>(currentTime - myStartTime).count();
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// target the next time we will be called
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const auto targetDeltaInMillis = currentDelta + milliseconds;
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const uint64_t targetCycles = static_cast<uint64_t>(targetDeltaInMillis * g_fCurrentCLK6502 * 1.0e-3) + myStartCycles;
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if (targetCycles > currentCycles)
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{
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// number of cycles to fill this period
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const uint64_t cyclesToExecute = targetCycles - currentCycles;
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return cyclesToExecute;
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}
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else
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{
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// we got ahead, nothing to do this time
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// CpuExecute will still execute 1 instruction, which does not cause any issues
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return 0;
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}
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}
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}
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