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https://github.com/patchzyy/wiicompiled
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patchzyy
51 lines
2.0 KiB
C++
51 lines
2.0 KiB
C++
#pragma once
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#include <chrono>
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#include <cstdint>
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namespace TimeBaseContract {
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// Broadway's time base runs at one quarter of the 243 MHz Wii bus clock.
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// Reduced against one billion nanoseconds per second, that is exactly
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// 243 time-base ticks per 4000 nanoseconds (60.75 MHz).
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inline constexpr uint64_t kBusClockHz = 243'000'000u;
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inline constexpr uint64_t kTimeBaseDivider = 4u;
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inline constexpr uint64_t kTicksPerSecond = kBusClockHz / kTimeBaseDivider;
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inline constexpr uint64_t kNanosecondsPerSecond = 1'000'000'000u;
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inline constexpr uint64_t kTickRatioNumerator = 243u;
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inline constexpr uint64_t kTickRatioDenominator = 4'000u;
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static_assert(kTicksPerSecond == 60'750'000u);
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static_assert(kTicksPerSecond * kTickRatioDenominator ==
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kNanosecondsPerSecond * kTickRatioNumerator);
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// Split the rational conversion around the division so the intermediate
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// product cannot overflow. The result is floor(nanoseconds * 243 / 4000).
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constexpr uint64_t NanosecondsToTicks(uint64_t nanoseconds) noexcept
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{
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return (nanoseconds / kTickRatioDenominator) * kTickRatioNumerator +
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((nanoseconds % kTickRatioDenominator) * kTickRatioNumerator) /
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kTickRatioDenominator;
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}
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// Convert guest ticks to a host duration without applying scheduling policy.
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// Oversized durations retain the existing zero-duration failure behavior.
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constexpr std::chrono::nanoseconds TicksToDuration(uint64_t ticks) noexcept
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{
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constexpr uint64_t kMaxNanoseconds =
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static_cast<uint64_t>(std::chrono::nanoseconds::max().count());
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constexpr uint64_t kMaxTicks = NanosecondsToTicks(kMaxNanoseconds);
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if (ticks == 0 || ticks > kMaxTicks) {
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return std::chrono::nanoseconds::zero();
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}
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const uint64_t nanoseconds =
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(ticks / kTickRatioNumerator) * kTickRatioDenominator +
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((ticks % kTickRatioNumerator) * kTickRatioDenominator) /
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kTickRatioNumerator;
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return std::chrono::nanoseconds(static_cast<int64_t>(nanoseconds));
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}
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} // namespace TimeBaseContract
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