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139 lines
3.5 KiB
C++
139 lines
3.5 KiB
C++
//
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// Spectrum.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 07/03/2021.
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// Copyright © 2021 Thomas Harte. All rights reserved.
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//
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#ifndef Storage_Tape_Parsers_Spectrum_hpp
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#define Storage_Tape_Parsers_Spectrum_hpp
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#include "TapeParser.hpp"
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#include <array>
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#include <optional>
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#include <vector>
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namespace Storage {
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namespace Tape {
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namespace ZXSpectrum {
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enum class WaveType {
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// All references to 't-states' below are cycles relative to the
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// ZX Spectrum's 3.5Mhz processor.
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Pilot, // Nominally 2168 t-states.
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Zero, // 855 t-states.
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One, // 1710 t-states.
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Gap,
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};
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// Formally, there are two other types of wave:
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//
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// Sync1, // 667 t-states.
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// Sync2, // 735 t-states.
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//
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// Non-Spectrum machines often just output a plain zero symbol instead of
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// a two-step sync; this parser treats anything close enough to a zero
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// as a sync.
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enum class SymbolType {
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Zero,
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One,
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Pilot,
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Gap,
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};
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/// A block is anything that follows a period of pilot tone; on a Spectrum that might be a
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/// file header or the file contents; on a CPC it might be a file header or a single chunk providing
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/// partial file contents. The Enterprise seems broadly to follow the Spectrum but the internal
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/// byte structure differs.
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struct Block {
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uint8_t type = 0;
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};
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class Parser: public Storage::Tape::PulseClassificationParser<WaveType, SymbolType> {
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public:
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enum class MachineType {
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ZXSpectrum,
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Enterprise,
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SAMCoupe,
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AmstradCPC
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};
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Parser(MachineType);
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/*!
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Calibrates the expected data speed using a value in the CPC's native tape-speed measurement scale.
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*/
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void set_cpc_read_speed(uint8_t);
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/*!
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Finds the next block from the tape, if any.
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Following this call the tape will be positioned immediately after the byte that indicated the block type —
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in Spectrum-world this seems to be called the flag byte. This call can therefore be followed up with one
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of the get_ methods.
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*/
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std::optional<Block> find_block(const std::shared_ptr<Storage::Tape::Tape> &tape);
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/*!
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Reads the contents of the rest of this block, until the next gap.
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*/
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std::vector<uint8_t> get_block_body(const std::shared_ptr<Storage::Tape::Tape> &tape);
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/*!
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Reads a single byte from the tape, if there is one left, updating the internal checksum.
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The checksum is computed as an exclusive OR of all bytes read.
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*/
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std::optional<uint8_t> get_byte(const std::shared_ptr<Storage::Tape::Tape> &tape);
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/*!
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Seeds the internal checksum.
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*/
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void seed_checksum(uint8_t value = 0x00);
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/*!
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Push a pulse; primarily provided for Storage::Tape::PulseClassificationParser but also potentially useful
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for picking up fast loading from an ongoing tape.
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*/
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void process_pulse(const Storage::Tape::Tape::Pulse &pulse) override;
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private:
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const MachineType machine_type_;
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constexpr bool should_flip_bytes() {
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return machine_type_ == MachineType::Enterprise;
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}
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constexpr bool should_detect_speed() {
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return machine_type_ != MachineType::ZXSpectrum;
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}
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void inspect_waves(const std::vector<WaveType> &waves) override;
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uint8_t checksum_ = 0;
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enum class SpeedDetectionPhase {
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WaitingForGap,
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WaitingForPilot,
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CalibratingPilot,
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Done
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} speed_phase_ = SpeedDetectionPhase::Done;
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float too_long_ = 2600.0f;
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float too_short_ = 600.0f;
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float is_pilot_ = 1939.0f;
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float is_one_ = 1282.0f;
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std::array<float, 8> calibration_pulses_;
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size_t calibration_pulse_pointer_ = 0;
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void set_cpc_one_zero_boundary(float);
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};
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}
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}
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}
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#endif /* Spectrum_hpp */
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