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77 lines
1.5 KiB
C++
77 lines
1.5 KiB
C++
//
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// Sprites.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 26/11/2021.
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// Copyright © 2021 Thomas Harte. All rights reserved.
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//
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#ifndef Sprites_hpp
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#define Sprites_hpp
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#include <cstdint>
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#include "DMADevice.hpp"
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namespace Amiga {
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class Sprite: public DMADevice<1> {
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public:
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using DMADevice::DMADevice;
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void set_start_position(uint16_t value);
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void set_stop_and_control(uint16_t value);
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void set_image_data(int slot, uint16_t value);
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void advance_line(int y, bool is_end_of_blank);
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bool advance_dma(int offset);
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uint16_t data[2]{};
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bool attached = false;
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bool visible = false;
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uint16_t h_start = 0;
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private:
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uint16_t v_start_ = 0, v_stop_ = 0;
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enum class DMAState {
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FetchControl,
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FetchImage
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} dma_state_ = DMAState::FetchControl;
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};
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class TwoSpriteShifter {
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public:
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/// Installs new pixel data for @c sprite (either 0 or 1),
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/// with @c delay being either 0 or 1 to indicate whether
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/// output should begin now or in one pixel's time.
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template <int sprite> void load(
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uint16_t lsb,
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uint16_t msb,
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int delay);
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/// Shifts two pixels.
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void shift() {
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data_ <<= 8;
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data_ |= overflow_;
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overflow_ = 0;
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}
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/// @returns The next two pixels to output, formulated as
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/// abcd efgh where ab and ef are two pixels of the first sprite
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/// and cd and gh are two pixels of the second. In each case the
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/// more significant two are output first.
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uint8_t get() {
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return uint8_t(data_ >> 56);
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}
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private:
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uint64_t data_;
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uint8_t overflow_;
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};
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}
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#endif /* Sprites_hpp */
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