Create a specific container for HDV files.

Storage/MassStorage/Formats/HDV.cpp

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+//
+//  HDV.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 14/11/2022.
+//  Copyright © 2022 Thomas Harte. All rights reserved.
+//
+
+#include "HDV.hpp"
+
+#include <algorithm>
+
+using namespace Storage::MassStorage;
+
+HDV::HDV(const std::string &file_name, long start, long size):
+	file_(file_name),
+	file_start_(start),
+	image_size_(std::min(size, long(file_.stats().st_size)))
+{
+	mapper_.set_drive_type(
+		Storage::MassStorage::Encodings::Apple::DriveType::SCSI,
+		size_t(size / 512)
+	);
+}
+
+size_t HDV::get_block_size() {
+	return 512;
+}
+
+size_t HDV::get_number_of_blocks() {
+	return mapper_.get_number_of_blocks();
+}
+
+std::vector<uint8_t> HDV::get_block(size_t address) {
+	const auto source_address = mapper_.to_source_address(address);
+	const auto file_offset = offset_for_block(source_address);
+
+	if(source_address >= 0) {
+		file_.seek(file_offset, SEEK_SET);
+		return mapper_.convert_source_block(source_address, file_.read(get_block_size()));
+	} else {
+		return mapper_.convert_source_block(source_address);
+	}
+}
+
+void HDV::set_block(size_t address, const std::vector<uint8_t> &data) {
+	const auto source_address = mapper_.to_source_address(address);
+	const auto file_offset = offset_for_block(source_address);
+
+	if(source_address >= 0 && file_offset >= 0) {
+		file_.seek(file_offset, SEEK_SET);
+		file_.write(data);
+	}
+}
+
+long HDV::offset_for_block(ssize_t address) {
+	if(address < 0) return -1;
+
+	const long offset = 512 * address;
+	if(offset > image_size_ - 512) return -1;
+
+	return file_start_ + offset;
+}

Storage/MassStorage/Formats/HDV.hpp

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+//
+//  HDV.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 14/11/2022.
+//  Copyright © 2022 Thomas Harte. All rights reserved.
+//
+
+#ifndef HDV_hpp
+#define HDV_hpp
+
+#include "../MassStorageDevice.hpp"
+#include "../../FileHolder.hpp"
+#include "../Encodings/AppleIIVolume.hpp"
+
+#include <limits>
+#include <vector>
+
+namespace Storage {
+namespace MassStorage {
+
+/*!
+	Provides a @c MassStorageDevice containing an HDV image, which is a sector dump of
+	the ProDOS volume of an Apple II drive.
+*/
+class HDV: public MassStorageDevice {
+	public:
+		/*!
+			Constructs an HDV with the contents of the file named @c file_name within
+			the range given.
+
+			Raises an exception if the file name doesn't appear to identify a valid
+			Apple II mass storage image.
+		*/
+		HDV(const std::string &file_name, long start = 0, long size = std::numeric_limits<long>::max());
+
+	private:
+		FileHolder file_;
+		long file_start_, image_size_;
+		Storage::MassStorage::Encodings::AppleII::Mapper mapper_;
+
+		/// @returns -1 if @c address is out of range; the offset into the file at which
+		/// the block for @c address resides otherwise.
+		long offset_for_block(ssize_t address);
+
+		/* MassStorageDevices overrides. */
+		size_t get_block_size() final;
+		size_t get_number_of_blocks() final;
+		std::vector<uint8_t> get_block(size_t address) final;
+		void set_block(size_t address, const std::vector<uint8_t> &) final;
+};
+
+}
+}
+
+#endif /* HDV_hpp */