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124 lines
3.3 KiB
C++
124 lines
3.3 KiB
C++
//
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// Track.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 22/09/2017.
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// Copyright 2017 Thomas Harte. All rights reserved.
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//
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#ifndef Track_h
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#define Track_h
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#include "../../Storage.hpp"
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#include <tuple>
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namespace Storage {
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namespace Disk {
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/*!
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Contains a head position, with some degree of sub-integral precision.
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*/
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class HeadPosition {
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public:
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/// Creates an instance decribing position @c value at a resolution of @c scale ticks per track.
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HeadPosition(int value, int scale) : position_(value * (4/scale)) {}
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explicit HeadPosition(int value) : HeadPosition(value, 1) {}
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HeadPosition() : HeadPosition(0) {}
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/// @returns the whole number part of the position.
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int as_int() const { return position_ >> 2; }
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/// @returns n where n/2 is the head position.
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int as_half() const { return position_ >> 1; }
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/// @returns n where n/4 is the head position.
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int as_quarter() const { return position_; }
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/// @returns the head position at maximal but unspecified precision.
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int as_largest() const { return as_quarter(); }
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HeadPosition &operator +=(const HeadPosition &rhs) {
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position_ += rhs.position_;
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return *this;
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}
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bool operator ==(const HeadPosition &rhs) const {
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return position_ == rhs.position_;
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}
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bool operator !=(const HeadPosition &rhs) const {
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return position_ != rhs.position_;
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}
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bool operator <(const HeadPosition &rhs) const {
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return position_ < rhs.position_;
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}
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bool operator <=(const HeadPosition &rhs) const {
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return position_ <= rhs.position_;
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}
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bool operator >(const HeadPosition &rhs) const {
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return position_ > rhs.position_;
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}
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bool operator >=(const HeadPosition &rhs) const {
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return position_ >= rhs.position_;
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}
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private:
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int position_ = 0;
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};
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/*!
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Models a single track on a disk as a series of events, each event being of arbitrary length
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and resulting in either a flux transition or the sensing of an index hole.
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Subclasses should implement @c get_next_event.
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*/
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class Track {
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public:
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/*!
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Describes the location of a track, implementing < to allow for use as a set key.
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*/
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struct Address {
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int head;
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HeadPosition position;
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bool operator < (const Address &rhs) const {
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int largest_position = position.as_largest();
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int rhs_largest_position = rhs.position.as_largest();
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return std::tie(head, largest_position) < std::tie(rhs.head, rhs_largest_position);
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}
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Address(int head, HeadPosition position) : head(head), position(position) {}
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};
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/*!
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Describes a detectable track event: either a flux transition or the passing of the index hole,
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along with the length of time between the previous event and its occurance.
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The sum of all lengths of time across an entire track should be 1; if an event is said to be
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1/3 away then that means 1/3 of a rotation.
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*/
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struct Event {
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enum {
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IndexHole, FluxTransition
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} type;
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Time length;
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};
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/*!
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@returns the next event that will be detected during rotation of this disk.
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*/
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virtual Event get_next_event() = 0;
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/*!
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Jumps to the event latest offset that is less than or equal to the input time.
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@returns the time jumped to.
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*/
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virtual Time seek_to(const Time &time_since_index_hole) = 0;
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/*!
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The virtual copy constructor pattern; returns a copy of the Track.
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*/
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virtual Track *clone() const = 0;
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};
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}
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}
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#endif /* Track_h */
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