ARMSX3/rpcs3/dev/block_dev.hpp

#pragma once

#include "Utilities/File.h"
#include <cstddef>
#include <utility>

class block_dev
{
	std::size_t m_block_size = 0;
	std::size_t m_block_count = 0;

public:
	virtual ~block_dev() = default;

	std::size_t block_size() const
	{
		return m_block_size;
	}
	std::size_t block_count() const
	{
		return m_block_count;
	}
	std::size_t size() const
	{
		return block_size() * block_count();
	}

	virtual std::size_t read(std::size_t blockIndex, void* data,
		std::size_t blockCount) = 0;

	virtual std::size_t write(std::size_t blockIndex, const void* data,
		std::size_t blockCount) = 0;

protected:
	void set_block_info(std::size_t size, std::size_t count)
	{
		m_block_size = size;
		m_block_count = count;
	}
};

class file_block_dev final : public block_dev
{
	fs::file m_file;

public:
	explicit file_block_dev(fs::file file, std::size_t blockSize = 2048)
		: m_file(std::move(file))
	{
		set_block_info(blockSize, m_file.size() / blockSize);
	}

	std::size_t read(std::size_t blockIndex, void* data,
		std::size_t blockCount) override
	{
		auto result = m_file.read_at(block_size() * blockIndex, data,
			blockCount * block_size());
		return result / block_size();
	}

	std::size_t write(std::size_t blockIndex, const void* data,
		std::size_t blockCount) override
	{
		// Upstream fs::file has read_at() but no write_at() -- that was an
		// RPCSX addition. Seek + write is the equivalent; ISO mounting is
		// read-only in practice, so this path is not hot.
		m_file.seek(block_size() * blockIndex);
		auto result = m_file.write(data, blockCount * block_size());
		return result / block_size();
	}

	fs::file& file()
	{
		return m_file;
	}
	fs::file release()
	{
		return std::exchange(m_file, {});
	}
};

class file_view_block_dev final : public block_dev
{
	const fs::file* m_file;

public:
	explicit file_view_block_dev(const fs::file& file,
		std::size_t blockSize = 2048)
		: m_file(&file)
	{
		set_block_info(blockSize, m_file->size() / blockSize);
	}

	std::size_t read(std::size_t blockIndex, void* data,
		std::size_t blockCount) override
	{
		auto result = m_file->read_at(block_size() * blockIndex, data,
			blockCount * block_size());
		return result / block_size();
	}

	std::size_t write(std::size_t blockIndex, const void* data,
		std::size_t blockCount) override
	{
		// See the note in file_block_dev::write -- no fs::file::write_at upstream.
		m_file->seek(block_size() * blockIndex);
		auto result = m_file->write(data, blockCount * block_size());
		return result / block_size();
	}
};