CLK/Storage/Disk/Encodings/AppleGCR.hpp

//
//  AppleGCR.hpp
//  Clock Signal
//
//  Created by Thomas Harte on 21/04/2018.
//  Copyright © 2018 Thomas Harte. All rights reserved.
//

#ifndef AppleGCR_hpp
#define AppleGCR_hpp

#include <cstdint>
#include "../../Disk/Track/PCMSegment.hpp"

namespace Storage {
namespace Encodings {

namespace AppleGCR {

	/*!
		@returns the eight-bit 13-sector GCR encoding for the low five bits of @c value.
	*/
//	unsigned int five_and_three_encoding_for_value(int value);

	/*!
		@returns the eight-bit 16-sector GCR encoding for the low six bits of @c value.
	*/
//	unsigned int six_and_two_encoding_for_value(int value);

	/*!
		A block is defined to be five source bytes, which encodes to eight GCR bytes.
	*/
//	void encode_five_and_three_block(uint8_t *destination, uint8_t *source);

	/*!
		A block is defined to be three source bytes, which encodes to four GCR bytes.
	*/
//	void encode_six_and_two_block(uint8_t *destination, uint8_t *source);

	/*!
		@returns the four bit nibble for the five-bit GCR @c quintet if a valid GCR value; INT_MAX otherwise.
	*/
//	unsigned int decoding_from_quintet(unsigned int quintet);

	/*!
		@returns the byte composed by splitting the dectet into two qintets, decoding each and composing the resulting nibbles.
	*/
//	unsigned int decoding_from_dectet(unsigned int dectet);

	/// Describes the standard three-byte prologue that begins a header.
	const uint8_t header_prologue[3] = {0xd5, 0xaa, 0x96};
	/// Describes the standard three-byte prologue that begins a data section.
	const uint8_t data_prologue[3] = {0xd5, 0xaa, 0xad};
	/// Describes the epilogue that ends both data sections and headers.
	const uint8_t epilogue[3] = {0xde, 0xaa, 0xeb};

	/*!
		Produces the Apple-standard '4 and 4' per-sector header. This is the same
		for both the 13- and 16-sector formats, and is 112 bits long.
	*/
	Storage::Disk::PCMSegment header(uint8_t volume, uint8_t track, uint8_t sector);

	Storage::Disk::PCMSegment six_and_two_data(const uint8_t *source);
	Storage::Disk::PCMSegment six_and_two_sync(int length);

	Storage::Disk::PCMSegment five_and_three_data(const uint8_t *source);
	Storage::Disk::PCMSegment five_and_three_sync(int length);
}

}
}

#endif /* AppleGCR_hpp */