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100 lines
2.1 KiB
C++
100 lines
2.1 KiB
C++
//
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// Bitplanes.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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#pragma once
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#include <cstdint>
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#include "DMADevice.hpp"
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namespace Amiga {
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struct BitplaneData: public std::array<uint16_t, 6> {
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BitplaneData &operator <<= (int c) {
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(*this)[0] <<= c;
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(*this)[1] <<= c;
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(*this)[2] <<= c;
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(*this)[3] <<= c;
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(*this)[4] <<= c;
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(*this)[5] <<= c;
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return *this;
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}
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void clear() {
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std::fill(begin(), end(), 0);
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}
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};
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class Bitplanes: public DMADevice<6, 2> {
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public:
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using DMADevice::DMADevice;
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bool advance_dma(int cycle);
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void do_end_of_line();
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void set_control(uint16_t);
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private:
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bool is_high_res_ = false;
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int plane_count_ = 0;
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BitplaneData next;
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};
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template <typename SourceT> constexpr SourceT bitplane_swizzle(SourceT value) {
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return
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(value&0x21) |
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((value&0x02) << 2) |
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((value&0x04) >> 1) |
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((value&0x08) << 1) |
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((value&0x10) >> 2);
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}
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class BitplaneShifter {
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public:
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/// Installs a new set of output pixels.
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void set(
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const BitplaneData &previous,
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const BitplaneData &next,
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int odd_delay,
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int even_delay);
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/// Shifts either two pixels (in low-res mode) or four pixels (in high-res).
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void shift(bool high_res) {
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constexpr int shifts[] = {16, 32};
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data_[1] = (data_[1] << shifts[high_res]) | (data_[0] >> (64 - shifts[high_res]));
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data_[0] <<= shifts[high_res];
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}
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/// @returns The next four pixels to output; in low-resolution mode only two
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/// of them will be unique.
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///
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/// The value is arranges so that MSB = first pixel to output, LSB = last.
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///
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/// Each byte is swizzled to provide easier playfield separation, being in the form:
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/// b6, b7 = 0;
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/// b3–b5: planes 1, 3 and 5;
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/// b0–b2: planes 0, 2 and 4.
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uint32_t get(bool high_res) {
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if(high_res) {
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return uint32_t(data_[1] >> 32);
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} else {
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uint32_t result = uint16_t(data_[1] >> 48);
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result = ((result & 0xff00) << 8) | (result & 0x00ff);
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result |= result << 8;
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return result;
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}
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}
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private:
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std::array<uint64_t, 2> data_{};
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};
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}
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