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86 lines
2.4 KiB
C++
86 lines
2.4 KiB
C++
//
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// ROMSlotHandler.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 03/01/2018.
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// Copyright 2018 Thomas Harte. All rights reserved.
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//
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#ifndef ROMSlotHandler_hpp
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#define ROMSlotHandler_hpp
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#include "../../ClockReceiver/ClockReceiver.hpp"
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#include "../../Analyser/Dynamic/ConfidenceCounter.hpp"
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#include <cstddef>
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#include <cstdint>
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#include <string>
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/*
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Design assumptions:
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- to-ROM writes and paging events are 'rare', so virtual call costs aren't worrisome;
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- ROM type variety is sufficiently slender that most of it can be built into the MSX.
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Part of the motivation is also that the MSX has four logical slots, the ROM, RAM plus two
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things plugged in. So even if the base class were templated to remove the virtual call,
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there'd just be a switch on what to call.
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*/
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namespace MSX {
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class MemoryMap {
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public:
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/*!
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Maps source data from the ROM's source to the given address range.
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*/
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virtual void map(int slot, std::size_t source_address, uint16_t destination_address, std::size_t length) = 0;
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/*!
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Unmaps source data from the given address range; the slot handler's read function will be used
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to respond to queries in that range.
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*/
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virtual void unmap(int slot, uint16_t destination_address, std::size_t length) = 0;
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};
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class ROMSlotHandler {
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public:
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virtual ~ROMSlotHandler() {}
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/*! Advances time by @c half_cycles. */
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virtual void run_for([[maybe_unused]] HalfCycles half_cycles) {}
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/*! Announces an attempt to write @c value to @c address. */
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virtual void write(uint16_t address, uint8_t value, bool pc_is_outside_bios) = 0;
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/*! Seeks the result of a read at @c address; this is used only if the area is unmapped. */
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virtual uint8_t read([[maybe_unused]] uint16_t address) { return 0xff; }
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enum class WrappingStrategy {
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/// Repeat causes all accesses to be modulo the size of the ROM.
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Repeat,
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/// Empty causes all out-of-bounds accesses to read a vacant bus.
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Empty
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};
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/*! @returns The wrapping strategy to apply to mapping requests from this ROM slot. */
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virtual WrappingStrategy wrapping_strategy() const {
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return WrappingStrategy::Repeat;
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}
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/*! @returns The probability that this handler is correct for the data it owns. */
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float get_confidence() {
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return confidence_counter_.get_confidence();
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}
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virtual std::string debug_type() {
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return "";
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}
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protected:
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Analyser::Dynamic::ConfidenceCounter confidence_counter_;
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};
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}
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#endif /* ROMSlotHandler_hpp */
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