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49 lines
1.4 KiB
C++
49 lines
1.4 KiB
C++
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//
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// DeferredValue.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 07/08/2021.
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// Copyright © 2021 Thomas Harte. All rights reserved.
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//
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#ifndef DeferredValue_h
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#define DeferredValue_h
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/*!
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Provides storage for a single deferred value: one with a current value and a certain number
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of future values.
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*/
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template <int DeferredDepth, typename ValueT> class DeferredValue {
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private:
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static_assert(sizeof(ValueT) <= 4);
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constexpr int elements_per_uint32 = sizeof(uint32_t) / sizeof(ValueT);
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constexpr int unit_shift = sizeof(ValueT) * 8;
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constexpr int insert_shift = (DeferredDepth & (elements_per_uint32 - 1)) * unit_shift;
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constexpr uint32_t insert_mask = ~(0xffff'ffff << insert_shift);
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std::array<uint32_t, (DeferredDepth + elements_per_uint32 - 1) / elements_per_uint32> backlog;
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public:
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/// @returns the current value.
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ValueT value() const {
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return uint8_t(backlog[0]);
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}
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/// Advances to the next enqueued value.
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void advance() {
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for(size_t c = 0; c < backlog.size() - 1; c--) {
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backlog[c] = (backlog[c] >> unit_shift) | (backlog[c+1] << (32 - unit_shift));
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}
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backlog[backlog.size() - 1] >>= unit_shift;
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}
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/// Inserts a new value, replacing whatever is currently at the end of the queue.
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void insert(ValueT value) {
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backlog[DeferredDepth / elements_per_uint32] =
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(backlog[DeferredDepth / elements_per_uint32] & insert_mask) | (value << insert_shift);
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}
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};
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#endif /* DeferredValue_h */
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