// license:BSD-3-Clause
// copyright-holders:Vas Crabb
/***************************************************************************

	ioprocs.h

	I/O interfaces

***************************************************************************/
#ifndef MAME_LIB_UTIL_IOPROCS_H
#define MAME_LIB_UTIL_IOPROCS_H

#pragma once

#include "utilfwd.h"

#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <memory>
#include <system_error>


// FIXME: make a proper place for OSD forward declarations
class osd_file;


namespace util {

	/// \defgroup ioprocs Generic I/O interfaces
	/// \{

	/// \brief Interface to an input stream
	///
	/// Represents a stream producing a sequence of bytes with no further
	/// structure.
	/// \sa write_stream read_write_stream random_read
	class read_stream
	{
	public:
		using ptr = std::unique_ptr<read_stream>;

		virtual ~read_stream() = default;

		/// \brief Read from the current position in the stream
		///
		/// Reads up to the specified number of bytes from the stream into
		/// the supplied buffer.  May read less than the requested number of
		/// bytes if the end of the stream is reached or an error occurs.
		/// If the stream supports seeking, reading starts at the current
		/// position in the stream, and the current position is incremented
		/// by the number of bytes read.
		/// \param [out] buffer Destination buffer.  Must be large enough to
		///   hold the requested number of bytes.
		/// \param [in] length Maximum number of bytes to read.
		/// \param [out] actual Number of bytes actually read.  Will always
		///   be less than or equal to the requested length.
		/// \return An error condition if reading stopped due to an error.
		virtual std::error_condition read(void* buffer, std::size_t length, std::size_t& actual) noexcept = 0;
	};


	/// \brief Interface to an output stream
	///
	/// Represents a stream that accepts a sequence of bytes with no further
	/// structure.
	/// \sa read_stream read_write_stream random_write
	class write_stream
	{
	public:
		using ptr = std::unique_ptr<write_stream>;

		virtual ~write_stream() = default;

		/// \brief Finish writing data
		///
		/// Performs any tasks necessary to finish writing data to the
		/// stream and guarantee that the written data can be read in its
		/// entirety.  Further writes may not be possible.
		/// \return An error condition if the operation fails.
		virtual std::error_condition finalize() noexcept = 0;

		/// \brief Flush application-side caches
		///
		/// Flushes any caches to the underlying stream.  Success does not
		/// guarantee that data has reached persistent storage.
		/// \return An error condition if flushing caches fails.
		virtual std::error_condition flush() noexcept = 0;

		/// \brief Write at the current position in the stream
		///
		/// Writes up to the specified number of bytes from the supplied
		/// buffer to the stream.  May write less than the requested number
		/// of bytes if an error occurs.  If the stream supports seeking,
		/// writing starts at the current position in the stream, and the
		/// current position is incremented by the number of bytes written.
		/// \param [in] buffer Buffer containing the data to write.  Must
		///   contain at least the specified number of bytes.
		/// \param [in] length Number of bytes to write.
		/// \param [out] actual Number of bytes actually written.  Will
		///   always be less than or equal to the requested length.
		/// \return An error condition if writing stopped due to an error.
		virtual std::error_condition write(void const* buffer, std::size_t length, std::size_t& actual) noexcept = 0;
	};


	/// \brief Interface to an I/O stream
	///
	/// Represents an object that acts as both a source of and sink for byte
	/// sequences.
	/// \sa read_stream write_stream random_read_write
	class read_write_stream : public virtual read_stream, public virtual write_stream
	{
	public:
		using ptr = std::unique_ptr<read_write_stream>;
	};


	/// \brief Interface to a byte sequence that supports seeking
	///
	/// Provides an interface for controlling the position within a byte
	/// sequence that supports seeking.
	/// \sa random_read random_write random_read_write
	class random_access
	{
	public:
		virtual ~random_access() = default;

		/// \brief Set the position in the stream
		///
		/// Sets the position for the next read or write operation.  It may
		/// be possible to set the position beyond the end of the stream.
		/// \param [in] offset The offset in bytes, relative to the position
		///   specified by the whence parameter.
		/// \param [in] whence One of SEEK_SET, SEEK_CUR or SEEK_END, to
		///   interpret the offset parameter relative to the beginning of
		///   the stream, the current position in the stream, or the end of
		///   the stream, respectively.
		/// \return An error condition of the operation failed.
		virtual std::error_condition seek(std::int64_t offset, int whence) noexcept = 0;

		/// \brief Get the current position in the stream
		///
		/// Gets the position in the stream for the next read or write
		/// operation.  The position may be beyond the end of the stream.
		/// \param [out] result The position in bytes relative to the
		///   beginning of the stream.  Not valid if the operation fails.
		/// \return An error condition if the operation failed.
		virtual std::error_condition tell(std::uint64_t& result) noexcept = 0;

		/// \brief Get the length of the stream
		///
		/// Gets the current length of the stream.
		/// \param [out] result The length of the stream in bytes.  Not
		///   valid if the operation fails.
		/// \return An error condtion if the operation failed.
		virtual std::error_condition length(std::uint64_t& result) noexcept = 0;
	};


	/// \brief Interface to a random-access byte input sequence
	///
	/// Provides an interface for reading from arbitrary positions within a
	/// byte sequence.  No further structure is provided.
	/// \sa read_stream random_write random_read_write
	class random_read : public virtual read_stream, public virtual random_access
	{
	public:
		using ptr = std::unique_ptr<random_read>;

		/// \brief Read from specified position
		///
		/// Reads up to the specified number of bytes into the supplied
		/// buffer.  If seeking is supported, reading starts at the
		/// specified position and the current position is unaffected.  May
		/// read less than the requested number of bytes if the end of the
		/// stream is encountered or an error occurs.
		/// \param [in] offset The position to start reading from, specified
		///   as a number of bytes from the beginning of the stream.
		/// \param [out] buffer Destination buffer.  Must be large enough to
		///   hold the requested number of bytes.
		/// \param [in] length Maximum number of bytes to read.
		/// \param [out] actual Number of bytes actually read.  Will always
		///   be less than or equal to the requested length.
		/// \return An error condition if seeking failed or reading stopped
		///   due to an error.
		virtual std::error_condition read_at(std::uint64_t offset, void* buffer, std::size_t length, std::size_t& actual) noexcept = 0;
	};


	/// \brief Interface to a random-access byte output sequence
	///
	/// Provides an interface for writing to arbitrary positions within a
	/// byte sequence.  No further structure is provided.
	/// \sa write_stream random_read random_read_write
	class random_write : public virtual write_stream, public virtual random_access
	{
	public:
		using ptr = std::unique_ptr<random_write>;

		/// \brief Write at specified position
		///
		/// Writes up to the specified number of bytes from the supplied
		/// buffer.  If seeking is supported, writing starts at the
		/// specified position and the current position is unaffected.   May
		/// write less than the requested number of bytes if an error
		/// occurs.
		/// \param [in] offset The position to start writing at, specified
		///   as a number of bytes from the beginning of the stream.
		/// \param [in] buffer Buffer containing the data to write.  Must
		///   contain at least the specified number of bytes.
		/// \param [in] length Number of bytes to write.
		/// \param [out] actual Number of bytes actually written.  Will
		///   always be less than or equal to the requested length.
		/// \return An error condition if seeking failed or writing stopped
		///   due to an error.
		virtual std::error_condition write_at(std::uint64_t offset, void const* buffer, std::size_t length, std::size_t& actual) noexcept = 0;
	};


	/// \brief Interface to a random-access read/write byte sequence
	///
	/// Provides an interface for reading from and writing to arbitrary
	/// positions within a byte sequence.  No further structure is provided.
	/// \sa random_read random_write read_write_stream
	class random_read_write : public read_write_stream, public virtual random_read, public virtual random_write
	{
	public:
		using ptr = std::unique_ptr<random_read_write>;
	};

	/// \}


	random_read::ptr ram_read(void const* data, std::size_t size) noexcept;
	random_read::ptr ram_read(void const* data, std::size_t size, std::uint8_t filler) noexcept;
	random_read::ptr ram_read_copy(void const* data, std::size_t size) noexcept;
	random_read::ptr ram_read_copy(void const* data, std::size_t size, std::uint8_t filler) noexcept;

	random_read::ptr stdio_read(FILE* file) noexcept;
	random_read::ptr stdio_read(FILE* file, std::uint8_t filler) noexcept;
	random_read::ptr stdio_read_noclose(FILE* file) noexcept;
	random_read::ptr stdio_read_noclose(FILE* file, std::uint8_t filler) noexcept;

	random_read_write::ptr stdio_read_write(FILE* file) noexcept;
	random_read_write::ptr stdio_read_write(FILE* file, std::uint8_t filler) noexcept;
	random_read_write::ptr stdio_read_write_noclose(FILE* file) noexcept;
	random_read_write::ptr stdio_read_write_noclose(FILE* file, std::uint8_t filler) noexcept;

	random_read::ptr osd_file_read(std::unique_ptr<osd_file>&& file) noexcept;
	random_read::ptr osd_file_read(osd_file& file) noexcept;

	random_read_write::ptr osd_file_read_write(std::unique_ptr<osd_file>&& file) noexcept;
	random_read_write::ptr osd_file_read_write(osd_file& file) noexcept;

} // namespace util

#endif // MAME_LIB_UTIL_IOPROCS_H
