libretro.h

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/* Copyright (C) 2010-2018 The RetroArch team
 *
 * ---------------------------------------------------------------------------------------
 * The following license statement only applies to this libretro API header (libretro.h).
 * ---------------------------------------------------------------------------------------
 *
 * Permission is hereby granted, free of charge,
 * to any person obtaining a copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

#ifndef LIBRETRO_H__
#define LIBRETRO_H__

#include <stdint.h>
#include <stddef.h>
#include <limits.h>

#ifdef __cplusplus
extern "C" {
#endif

#ifndef __cplusplus
#if defined(_MSC_VER) && _MSC_VER < 1800 && !defined(SN_TARGET_PS3)
/* Hack applied for MSVC when compiling in C89 mode
 * as it isn't C99-compliant. */
#define bool unsigned char
#define true 1
#define false 0
#else
#include <stdbool.h>
#endif
#endif

#ifndef RETRO_CALLCONV
# if defined(__GNUC__) && defined(__i386__) && !defined(__x86_64__)
# define RETRO_CALLCONV __attribute__((cdecl))
# elif defined(_MSC_VER) && defined(_M_X86) && !defined(_M_X64)
# define RETRO_CALLCONV __cdecl
# else
# define RETRO_CALLCONV /* all other platforms only have one calling convention each */
# endif
#endif

#ifndef RETRO_API
# if defined(_WIN32) || defined(__CYGWIN__) || defined(__MINGW32__)
# ifdef RETRO_IMPORT_SYMBOLS
# ifdef __GNUC__
# define RETRO_API RETRO_CALLCONV __attribute__((__dllimport__))
# else
# define RETRO_API RETRO_CALLCONV __declspec(dllimport)
# endif
# else
# ifdef __GNUC__
# define RETRO_API RETRO_CALLCONV __attribute__((__dllexport__))
# else
# define RETRO_API RETRO_CALLCONV __declspec(dllexport)
# endif
# endif
# else
# if defined(__GNUC__) && __GNUC__ >= 4 && !defined(__CELLOS_LV2__)
# define RETRO_API RETRO_CALLCONV __attribute__((__visibility__("default")))
# else
# define RETRO_API RETRO_CALLCONV
# endif
# endif
#endif

/* Used for checking API/ABI mismatches that can break libretro
 * implementations.
 * It is not incremented for compatible changes to the API.
 */
#define RETRO_API_VERSION 1

/*
 * Libretro's fundamental device abstractions.
 *
 * Libretro's input system consists of some standardized device types,
 * such as a joypad (with/without analog), mouse, keyboard, lightgun
 * and a pointer.
 *
 * The functionality of these devices are fixed, and individual cores
 * map their own concept of a controller to libretro's abstractions.
 * This makes it possible for frontends to map the abstract types to a
 * real input device, and not having to worry about binding input
 * correctly to arbitrary controller layouts.
 */

#define RETRO_DEVICE_TYPE_SHIFT 8
#define RETRO_DEVICE_MASK ((1 << RETRO_DEVICE_TYPE_SHIFT) - 1)
#define RETRO_DEVICE_SUBCLASS(base, id) (((id + 1) << RETRO_DEVICE_TYPE_SHIFT) | base)

/* Input disabled. */
#define RETRO_DEVICE_NONE 0

/* The JOYPAD is called RetroPad. It is essentially a Super Nintendo
 * controller, but with additional L2/R2/L3/R3 buttons, similar to a
 * PS1 DualShock. */
#define RETRO_DEVICE_JOYPAD 1

/* The mouse is a simple mouse, similar to Super Nintendo's mouse.
 * X and Y coordinates are reported relatively to last poll (poll callback).
 * It is up to the libretro implementation to keep track of where the mouse
 * pointer is supposed to be on the screen.
 * The frontend must make sure not to interfere with its own hardware
 * mouse pointer.
 */
#define RETRO_DEVICE_MOUSE 2

/* KEYBOARD device lets one poll for raw key pressed.
 * It is poll based, so input callback will return with the current
 * pressed state.
 * For event/text based keyboard input, see
 * RETRO_ENVIRONMENT_SET_KEYBOARD_CALLBACK.
 */
#define RETRO_DEVICE_KEYBOARD 3

/* LIGHTGUN device is similar to Guncon-2 for PlayStation 2.
 * It reports X/Y coordinates in screen space (similar to the pointer)
 * in the range [-0x8000, 0x7fff] in both axes, with zero being center and
 * -0x8000 being out of bounds.
 * As well as reporting on/off screen state. It features a trigger,
 * start/select buttons, auxiliary action buttons and a
 * directional pad. A forced off-screen shot can be requested for
 * auto-reloading function in some games.
 */
#define RETRO_DEVICE_LIGHTGUN 4

/* The ANALOG device is an extension to JOYPAD (RetroPad).
 * Similar to DualShock2 it adds two analog sticks and all buttons can
 * be analog. This is treated as a separate device type as it returns
 * axis values in the full analog range of [-0x7fff, 0x7fff],
 * although some devices may return -0x8000.
 * Positive X axis is right. Positive Y axis is down.
 * Buttons are returned in the range [0, 0x7fff].
 * Only use ANALOG type when polling for analog values.
 */
#define RETRO_DEVICE_ANALOG 5

/* Abstracts the concept of a pointing mechanism, e.g. touch.
 * This allows libretro to query in absolute coordinates where on the
 * screen a mouse (or something similar) is being placed.
 * For a touch centric device, coordinates reported are the coordinates
 * of the press.
 *
 * Coordinates in X and Y are reported as:
 * [-0x7fff, 0x7fff]: -0x7fff corresponds to the far left/top of the screen,
 * and 0x7fff corresponds to the far right/bottom of the screen.
 * The "screen" is here defined as area that is passed to the frontend and
 * later displayed on the monitor.
 *
 * The frontend is free to scale/resize this screen as it sees fit, however,
 * (X, Y) = (-0x7fff, -0x7fff) will correspond to the top-left pixel of the
 * game image, etc.
 *
 * To check if the pointer coordinates are valid (e.g. a touch display
 * actually being touched), PRESSED returns 1 or 0.
 *
 * If using a mouse on a desktop, PRESSED will usually correspond to the
 * left mouse button, but this is a frontend decision.
 * PRESSED will only return 1 if the pointer is inside the game screen.
 *
 * For multi-touch, the index variable can be used to successively query
 * more presses.
 * If index = 0 returns true for _PRESSED, coordinates can be extracted
 * with _X, _Y for index = 0. One can then query _PRESSED, _X, _Y with
 * index = 1, and so on.
 * Eventually _PRESSED will return false for an index. No further presses
 * are registered at this point. */
#define RETRO_DEVICE_POINTER 6

/* Buttons for the RetroPad (JOYPAD).
 * The placement of these is equivalent to placements on the
 * Super Nintendo controller.
 * L2/R2/L3/R3 buttons correspond to the PS1 DualShock.
 * Also used as id values for RETRO_DEVICE_INDEX_ANALOG_BUTTON */
#define RETRO_DEVICE_ID_JOYPAD_B 0
#define RETRO_DEVICE_ID_JOYPAD_Y 1
#define RETRO_DEVICE_ID_JOYPAD_SELECT 2
#define RETRO_DEVICE_ID_JOYPAD_START 3
#define RETRO_DEVICE_ID_JOYPAD_UP 4
#define RETRO_DEVICE_ID_JOYPAD_DOWN 5
#define RETRO_DEVICE_ID_JOYPAD_LEFT 6
#define RETRO_DEVICE_ID_JOYPAD_RIGHT 7
#define RETRO_DEVICE_ID_JOYPAD_A 8
#define RETRO_DEVICE_ID_JOYPAD_X 9
#define RETRO_DEVICE_ID_JOYPAD_L 10
#define RETRO_DEVICE_ID_JOYPAD_R 11
#define RETRO_DEVICE_ID_JOYPAD_L2 12
#define RETRO_DEVICE_ID_JOYPAD_R2 13
#define RETRO_DEVICE_ID_JOYPAD_L3 14
#define RETRO_DEVICE_ID_JOYPAD_R3 15

/* Index / Id values for ANALOG device. */
#define RETRO_DEVICE_INDEX_ANALOG_LEFT 0
#define RETRO_DEVICE_INDEX_ANALOG_RIGHT 1
#define RETRO_DEVICE_INDEX_ANALOG_BUTTON 2
#define RETRO_DEVICE_ID_ANALOG_X 0
#define RETRO_DEVICE_ID_ANALOG_Y 1

/* Id values for MOUSE. */
#define RETRO_DEVICE_ID_MOUSE_X 0
#define RETRO_DEVICE_ID_MOUSE_Y 1
#define RETRO_DEVICE_ID_MOUSE_LEFT 2
#define RETRO_DEVICE_ID_MOUSE_RIGHT 3
#define RETRO_DEVICE_ID_MOUSE_WHEELUP 4
#define RETRO_DEVICE_ID_MOUSE_WHEELDOWN 5
#define RETRO_DEVICE_ID_MOUSE_MIDDLE 6
#define RETRO_DEVICE_ID_MOUSE_HORIZ_WHEELUP 7
#define RETRO_DEVICE_ID_MOUSE_HORIZ_WHEELDOWN 8
#define RETRO_DEVICE_ID_MOUSE_BUTTON_4 9
#define RETRO_DEVICE_ID_MOUSE_BUTTON_5 10

/* Id values for LIGHTGUN. */
#define RETRO_DEVICE_ID_LIGHTGUN_SCREEN_X 13 /*Absolute Position*/
#define RETRO_DEVICE_ID_LIGHTGUN_SCREEN_Y 14 /*Absolute*/
#define RETRO_DEVICE_ID_LIGHTGUN_IS_OFFSCREEN 15 /*Status Check*/
#define RETRO_DEVICE_ID_LIGHTGUN_TRIGGER 2
#define RETRO_DEVICE_ID_LIGHTGUN_RELOAD 16 /*Forced off-screen shot*/
#define RETRO_DEVICE_ID_LIGHTGUN_AUX_A 3
#define RETRO_DEVICE_ID_LIGHTGUN_AUX_B 4
#define RETRO_DEVICE_ID_LIGHTGUN_START 6
#define RETRO_DEVICE_ID_LIGHTGUN_SELECT 7
#define RETRO_DEVICE_ID_LIGHTGUN_AUX_C 8
#define RETRO_DEVICE_ID_LIGHTGUN_DPAD_UP 9
#define RETRO_DEVICE_ID_LIGHTGUN_DPAD_DOWN 10
#define RETRO_DEVICE_ID_LIGHTGUN_DPAD_LEFT 11
#define RETRO_DEVICE_ID_LIGHTGUN_DPAD_RIGHT 12
/* deprecated */
#define RETRO_DEVICE_ID_LIGHTGUN_X 0 /*Relative Position*/
#define RETRO_DEVICE_ID_LIGHTGUN_Y 1 /*Relative*/
#define RETRO_DEVICE_ID_LIGHTGUN_CURSOR 3 /*Use Aux:A*/
#define RETRO_DEVICE_ID_LIGHTGUN_TURBO 4 /*Use Aux:B*/
#define RETRO_DEVICE_ID_LIGHTGUN_PAUSE 5 /*Use Start*/

/* Id values for POINTER. */
#define RETRO_DEVICE_ID_POINTER_X 0
#define RETRO_DEVICE_ID_POINTER_Y 1
#define RETRO_DEVICE_ID_POINTER_PRESSED 2

/* Returned from retro_get_region(). */
#define RETRO_REGION_NTSC 0
#define RETRO_REGION_PAL 1

/* Id values for LANGUAGE */
enum retro_language
{
 RETRO_LANGUAGE_ENGLISH = 0,
 RETRO_LANGUAGE_JAPANESE = 1,
 RETRO_LANGUAGE_FRENCH = 2,
 RETRO_LANGUAGE_SPANISH = 3,
 RETRO_LANGUAGE_GERMAN = 4,
 RETRO_LANGUAGE_ITALIAN = 5,
 RETRO_LANGUAGE_DUTCH = 6,
 RETRO_LANGUAGE_PORTUGUESE_BRAZIL = 7,
 RETRO_LANGUAGE_PORTUGUESE_PORTUGAL = 8,
 RETRO_LANGUAGE_RUSSIAN = 9,
 RETRO_LANGUAGE_KOREAN = 10,
 RETRO_LANGUAGE_CHINESE_TRADITIONAL = 11,
 RETRO_LANGUAGE_CHINESE_SIMPLIFIED = 12,
 RETRO_LANGUAGE_ESPERANTO = 13,
 RETRO_LANGUAGE_POLISH = 14,
 RETRO_LANGUAGE_VIETNAMESE = 15,
 RETRO_LANGUAGE_ARABIC = 16,
 RETRO_LANGUAGE_GREEK = 17,
 RETRO_LANGUAGE_LAST,

 /* Ensure sizeof(enum) == sizeof(int) */
 RETRO_LANGUAGE_DUMMY = INT_MAX
};

/* Passed to retro_get_memory_data/size().
 * If the memory type doesn't apply to the
 * implementation NULL/0 can be returned.
 */
#define RETRO_MEMORY_MASK 0xff

/* Regular save RAM. This RAM is usually found on a game cartridge,
 * backed up by a battery.
 * If save game data is too complex for a single memory buffer,
 * the SAVE_DIRECTORY (preferably) or SYSTEM_DIRECTORY environment
 * callback can be used. */
#define RETRO_MEMORY_SAVE_RAM 0

/* Some games have a built-in clock to keep track of time.
 * This memory is usually just a couple of bytes to keep track of time.
 */
#define RETRO_MEMORY_RTC 1

/* System ram lets a frontend peek into a game systems main RAM. */
#define RETRO_MEMORY_SYSTEM_RAM 2

/* Video ram lets a frontend peek into a game systems video RAM (VRAM). */
#define RETRO_MEMORY_VIDEO_RAM 3

/* Keysyms used for ID in input state callback when polling RETRO_KEYBOARD. */
enum retro_key
{
 RETROK_UNKNOWN = 0,
 RETROK_FIRST = 0,
 RETROK_BACKSPACE = 8,
 RETROK_TAB = 9,
 RETROK_CLEAR = 12,
 RETROK_RETURN = 13,
 RETROK_PAUSE = 19,
 RETROK_ESCAPE = 27,
 RETROK_SPACE = 32,
 RETROK_EXCLAIM = 33,
 RETROK_QUOTEDBL = 34,
 RETROK_HASH = 35,
 RETROK_DOLLAR = 36,
 RETROK_AMPERSAND = 38,
 RETROK_QUOTE = 39,
 RETROK_LEFTPAREN = 40,
 RETROK_RIGHTPAREN = 41,
 RETROK_ASTERISK = 42,
 RETROK_PLUS = 43,
 RETROK_COMMA = 44,
 RETROK_MINUS = 45,
 RETROK_PERIOD = 46,
 RETROK_SLASH = 47,
 RETROK_0 = 48,
 RETROK_1 = 49,
 RETROK_2 = 50,
 RETROK_3 = 51,
 RETROK_4 = 52,
 RETROK_5 = 53,
 RETROK_6 = 54,
 RETROK_7 = 55,
 RETROK_8 = 56,
 RETROK_9 = 57,
 RETROK_COLON = 58,
 RETROK_SEMICOLON = 59,
 RETROK_LESS = 60,
 RETROK_EQUALS = 61,
 RETROK_GREATER = 62,
 RETROK_QUESTION = 63,
 RETROK_AT = 64,
 RETROK_LEFTBRACKET = 91,
 RETROK_BACKSLASH = 92,
 RETROK_RIGHTBRACKET = 93,
 RETROK_CARET = 94,
 RETROK_UNDERSCORE = 95,
 RETROK_BACKQUOTE = 96,
 RETROK_a = 97,
 RETROK_b = 98,
 RETROK_c = 99,
 RETROK_d = 100,
 RETROK_e = 101,
 RETROK_f = 102,
 RETROK_g = 103,
 RETROK_h = 104,
 RETROK_i = 105,
 RETROK_j = 106,
 RETROK_k = 107,
 RETROK_l = 108,
 RETROK_m = 109,
 RETROK_n = 110,
 RETROK_o = 111,
 RETROK_p = 112,
 RETROK_q = 113,
 RETROK_r = 114,
 RETROK_s = 115,
 RETROK_t = 116,
 RETROK_u = 117,
 RETROK_v = 118,
 RETROK_w = 119,
 RETROK_x = 120,
 RETROK_y = 121,
 RETROK_z = 122,
 RETROK_LEFTBRACE = 123,
 RETROK_BAR = 124,
 RETROK_RIGHTBRACE = 125,
 RETROK_TILDE = 126,
 RETROK_DELETE = 127,

 RETROK_KP0 = 256,
 RETROK_KP1 = 257,
 RETROK_KP2 = 258,
 RETROK_KP3 = 259,
 RETROK_KP4 = 260,
 RETROK_KP5 = 261,
 RETROK_KP6 = 262,
 RETROK_KP7 = 263,
 RETROK_KP8 = 264,
 RETROK_KP9 = 265,
 RETROK_KP_PERIOD = 266,
 RETROK_KP_DIVIDE = 267,
 RETROK_KP_MULTIPLY = 268,
 RETROK_KP_MINUS = 269,
 RETROK_KP_PLUS = 270,
 RETROK_KP_ENTER = 271,
 RETROK_KP_EQUALS = 272,

 RETROK_UP = 273,
 RETROK_DOWN = 274,
 RETROK_RIGHT = 275,
 RETROK_LEFT = 276,
 RETROK_INSERT = 277,
 RETROK_HOME = 278,
 RETROK_END = 279,
 RETROK_PAGEUP = 280,
 RETROK_PAGEDOWN = 281,

 RETROK_F1 = 282,
 RETROK_F2 = 283,
 RETROK_F3 = 284,
 RETROK_F4 = 285,
 RETROK_F5 = 286,
 RETROK_F6 = 287,
 RETROK_F7 = 288,
 RETROK_F8 = 289,
 RETROK_F9 = 290,
 RETROK_F10 = 291,
 RETROK_F11 = 292,
 RETROK_F12 = 293,
 RETROK_F13 = 294,
 RETROK_F14 = 295,
 RETROK_F15 = 296,

 RETROK_NUMLOCK = 300,
 RETROK_CAPSLOCK = 301,
 RETROK_SCROLLOCK = 302,
 RETROK_RSHIFT = 303,
 RETROK_LSHIFT = 304,
 RETROK_RCTRL = 305,
 RETROK_LCTRL = 306,
 RETROK_RALT = 307,
 RETROK_LALT = 308,
 RETROK_RMETA = 309,
 RETROK_LMETA = 310,
 RETROK_LSUPER = 311,
 RETROK_RSUPER = 312,
 RETROK_MODE = 313,
 RETROK_COMPOSE = 314,

 RETROK_HELP = 315,
 RETROK_PRINT = 316,
 RETROK_SYSREQ = 317,
 RETROK_BREAK = 318,
 RETROK_MENU = 319,
 RETROK_POWER = 320,
 RETROK_EURO = 321,
 RETROK_UNDO = 322,
 RETROK_OEM_102 = 323,

 RETROK_LAST,

 RETROK_DUMMY = INT_MAX /* Ensure sizeof(enum) == sizeof(int) */
};

enum retro_mod
{
 RETROKMOD_NONE = 0x0000,

 RETROKMOD_SHIFT = 0x01,
 RETROKMOD_CTRL = 0x02,
 RETROKMOD_ALT = 0x04,
 RETROKMOD_META = 0x08,

 RETROKMOD_NUMLOCK = 0x10,
 RETROKMOD_CAPSLOCK = 0x20,
 RETROKMOD_SCROLLOCK = 0x40,

 RETROKMOD_DUMMY = INT_MAX /* Ensure sizeof(enum) == sizeof(int) */
};

/* If set, this call is not part of the public libretro API yet. It can
 * change or be removed at any time. */
#define RETRO_ENVIRONMENT_EXPERIMENTAL 0x10000
/* Environment callback to be used internally in frontend. */
#define RETRO_ENVIRONMENT_PRIVATE 0x20000

/* Environment commands. */
#define RETRO_ENVIRONMENT_SET_ROTATION 1 /* const unsigned * --
 * Sets screen rotation of graphics.
 * Is only implemented if rotation can be accelerated by hardware.
 * Valid values are 0, 1, 2, 3, which rotates screen by 0, 90, 180,
 * 270 degrees counter-clockwise respectively.
 */
#define RETRO_ENVIRONMENT_GET_OVERSCAN 2 /* bool * --
 * Boolean value whether or not the implementation should use overscan,
 * or crop away overscan.
 */
#define RETRO_ENVIRONMENT_GET_CAN_DUPE 3 /* bool * --
 * Boolean value whether or not frontend supports frame duping,
 * passing NULL to video frame callback.
 */

 /* Environ 4, 5 are no longer supported (GET_VARIABLE / SET_VARIABLES),
 * and reserved to avoid possible ABI clash.
 */

#define RETRO_ENVIRONMENT_SET_MESSAGE 6 /* const struct retro_message * --
 * Sets a message to be displayed in implementation-specific manner
 * for a certain amount of 'frames'.
 * Should not be used for trivial messages, which should simply be
 * logged via RETRO_ENVIRONMENT_GET_LOG_INTERFACE (or as a
 * fallback, stderr).
 */
#define RETRO_ENVIRONMENT_SHUTDOWN 7 /* N/A (NULL) --
 * Requests the frontend to shutdown.
 * Should only be used if game has a specific
 * way to shutdown the game from a menu item or similar.
 */
#define RETRO_ENVIRONMENT_SET_PERFORMANCE_LEVEL 8
 /* const unsigned * --
 * Gives a hint to the frontend how demanding this implementation
 * is on a system. E.g. reporting a level of 2 means
 * this implementation should run decently on all frontends
 * of level 2 and up.
 *
 * It can be used by the frontend to potentially warn
 * about too demanding implementations.
 *
 * The levels are "floating".
 *
 * This function can be called on a per-game basis,
 * as certain games an implementation can play might be
 * particularly demanding.
 * If called, it should be called in retro_load_game().
 */
#define RETRO_ENVIRONMENT_GET_SYSTEM_DIRECTORY 9
 /* const char ** --
 * Returns the "system" directory of the frontend.
 * This directory can be used to store system specific
 * content such as BIOSes, configuration data, etc.
 * The returned value can be NULL.
 * If so, no such directory is defined,
 * and it's up to the implementation to find a suitable directory.
 *
 * NOTE: Some cores used this folder also for "save" data such as
 * memory cards, etc, for lack of a better place to put it.
 * This is now discouraged, and if possible, cores should try to
 * use the new GET_SAVE_DIRECTORY.
 */
#define RETRO_ENVIRONMENT_SET_PIXEL_FORMAT 10
 /* const enum retro_pixel_format * --
 * Sets the internal pixel format used by the implementation.
 * The default pixel format is RETRO_PIXEL_FORMAT_0RGB1555.
 * This pixel format however, is deprecated (see enum retro_pixel_format).
 * If the call returns false, the frontend does not support this pixel
 * format.
 *
 * This function should be called inside retro_load_game() or
 * retro_get_system_av_info().
 */
#define RETRO_ENVIRONMENT_SET_INPUT_DESCRIPTORS 11
 /* const struct retro_input_descriptor * --
 * Sets an array of retro_input_descriptors.
 * It is up to the frontend to present this in a usable way.
 * The array is terminated by retro_input_descriptor::description
 * being set to NULL.
 * This function can be called at any time, but it is recommended
 * to call it as early as possible.
 */
#define RETRO_ENVIRONMENT_SET_KEYBOARD_CALLBACK 12
 /* const struct retro_keyboard_callback * --
 * Sets a callback function used to notify core about keyboard events.
 */
#define RETRO_ENVIRONMENT_SET_DISK_CONTROL_INTERFACE 13
 /* const struct retro_disk_control_callback * --
 * Sets an interface which frontend can use to eject and insert
 * disk images.
 * This is used for games which consist of multiple images and
 * must be manually swapped out by the user (e.g. PSX).
 */
#define RETRO_ENVIRONMENT_SET_HW_RENDER 14
 /* struct retro_hw_render_callback * --
 * Sets an interface to let a libretro core render with
 * hardware acceleration.
 * Should be called in retro_load_game().
 * If successful, libretro cores will be able to render to a
 * frontend-provided framebuffer.
 * The size of this framebuffer will be at least as large as
 * max_width/max_height provided in get_av_info().
 * If HW rendering is used, pass only RETRO_HW_FRAME_BUFFER_VALID or
 * NULL to retro_video_refresh_t.
 */
#define RETRO_ENVIRONMENT_GET_VARIABLE 15
 /* struct retro_variable * --
 * Interface to acquire user-defined information from environment
 * that cannot feasibly be supported in a multi-system way.
 * 'key' should be set to a key which has already been set by
 * SET_VARIABLES.
 * 'data' will be set to a value or NULL.
 */
#define RETRO_ENVIRONMENT_SET_VARIABLES 16
 /* const struct retro_variable * --
 * Allows an implementation to signal the environment
 * which variables it might want to check for later using
 * GET_VARIABLE.
 * This allows the frontend to present these variables to
 * a user dynamically.
 * This should be called the first time as early as
 * possible (ideally in retro_set_environment).
 * Afterward it may be called again for the core to communicate
 * updated options to the frontend, but the number of core
 * options must not change from the number in the initial call.
 *
 * 'data' points to an array of retro_variable structs
 * terminated by a { NULL, NULL } element.
 * retro_variable::key should be namespaced to not collide
 * with other implementations' keys. E.g. A core called
 * 'foo' should use keys named as 'foo_option'.
 * retro_variable::value should contain a human readable
 * description of the key as well as a '|' delimited list
 * of expected values.
 *
 * The number of possible options should be very limited,
 * i.e. it should be feasible to cycle through options
 * without a keyboard.
 *
 * First entry should be treated as a default.
 *
 * Example entry:
 * { "foo_option", "Speed hack coprocessor X; false|true" }
 *
 * Text before first ';' is description. This ';' must be
 * followed by a space, and followed by a list of possible
 * values split up with '|'.
 *
 * Only strings are operated on. The possible values will
 * generally be displayed and stored as-is by the frontend.
 */
#define RETRO_ENVIRONMENT_GET_VARIABLE_UPDATE 17
 /* bool * --
 * Result is set to true if some variables are updated by
 * frontend since last call to RETRO_ENVIRONMENT_GET_VARIABLE.
 * Variables should be queried with GET_VARIABLE.
 */
#define RETRO_ENVIRONMENT_SET_SUPPORT_NO_GAME 18
 /* const bool * --
 * If true, the libretro implementation supports calls to
 * retro_load_game() with NULL as argument.
 * Used by cores which can run without particular game data.
 * This should be called within retro_set_environment() only.
 */
#define RETRO_ENVIRONMENT_GET_LIBRETRO_PATH 19
 /* const char ** --
 * Retrieves the absolute path from where this libretro
 * implementation was loaded.
 * NULL is returned if the libretro was loaded statically
 * (i.e. linked statically to frontend), or if the path cannot be
 * determined.
 * Mostly useful in cooperation with SET_SUPPORT_NO_GAME as assets can
 * be loaded without ugly hacks.
 */

 /* Environment 20 was an obsolete version of SET_AUDIO_CALLBACK.
 * It was not used by any known core at the time,
 * and was removed from the API. */
#define RETRO_ENVIRONMENT_SET_FRAME_TIME_CALLBACK 21
 /* const struct retro_frame_time_callback * --
 * Lets the core know how much time has passed since last
 * invocation of retro_run().
 * The frontend can tamper with the timing to fake fast-forward,
 * slow-motion, frame stepping, etc.
 * In this case the delta time will use the reference value
 * in frame_time_callback..
 */
#define RETRO_ENVIRONMENT_SET_AUDIO_CALLBACK 22
 /* const struct retro_audio_callback * --
 * Sets an interface which is used to notify a libretro core about audio
 * being available for writing.
 * The callback can be called from any thread, so a core using this must
 * have a thread safe audio implementation.
 * It is intended for games where audio and video are completely
 * asynchronous and audio can be generated on the fly.
 * This interface is not recommended for use with emulators which have
 * highly synchronous audio.
 *
 * The callback only notifies about writability; the libretro core still
 * has to call the normal audio callbacks
 * to write audio. The audio callbacks must be called from within the
 * notification callback.
 * The amount of audio data to write is up to the implementation.
 * Generally, the audio callback will be called continously in a loop.
 *
 * Due to thread safety guarantees and lack of sync between audio and
 * video, a frontend can selectively disallow this interface based on
 * internal configuration. A core using this interface must also
 * implement the "normal" audio interface.
 *
 * A libretro core using SET_AUDIO_CALLBACK should also make use of
 * SET_FRAME_TIME_CALLBACK.
 */
#define RETRO_ENVIRONMENT_GET_RUMBLE_INTERFACE 23
 /* struct retro_rumble_interface * --
 * Gets an interface which is used by a libretro core to set
 * state of rumble motors in controllers.
 * A strong and weak motor is supported, and they can be
 * controlled indepedently.
 */
#define RETRO_ENVIRONMENT_GET_INPUT_DEVICE_CAPABILITIES 24
 /* uint64_t * --
 * Gets a bitmask telling which device type are expected to be
 * handled properly in a call to retro_input_state_t.
 * Devices which are not handled or recognized always return
 * 0 in retro_input_state_t.
 * Example bitmask: caps = (1 << RETRO_DEVICE_JOYPAD) | (1 << RETRO_DEVICE_ANALOG).
 * Should only be called in retro_run().
 */
#define RETRO_ENVIRONMENT_GET_SENSOR_INTERFACE (25 | RETRO_ENVIRONMENT_EXPERIMENTAL)
 /* struct retro_sensor_interface * --
 * Gets access to the sensor interface.
 * The purpose of this interface is to allow
 * setting state related to sensors such as polling rate,
 * enabling/disable it entirely, etc.
 * Reading sensor state is done via the normal
 * input_state_callback API.
 */
#define RETRO_ENVIRONMENT_GET_CAMERA_INTERFACE (26 | RETRO_ENVIRONMENT_EXPERIMENTAL)
 /* struct retro_camera_callback * --
 * Gets an interface to a video camera driver.
 * A libretro core can use this interface to get access to a
 * video camera.
 * New video frames are delivered in a callback in same
 * thread as retro_run().
 *
 * GET_CAMERA_INTERFACE should be called in retro_load_game().
 *
 * Depending on the camera implementation used, camera frames
 * will be delivered as a raw framebuffer,
 * or as an OpenGL texture directly.
 *
 * The core has to tell the frontend here which types of
 * buffers can be handled properly.
 * An OpenGL texture can only be handled when using a
 * libretro GL core (SET_HW_RENDER).
 * It is recommended to use a libretro GL core when
 * using camera interface.
 *
 * The camera is not started automatically. The retrieved start/stop
 * functions must be used to explicitly
 * start and stop the camera driver.
 */
#define RETRO_ENVIRONMENT_GET_LOG_INTERFACE 27
 /* struct retro_log_callback * --
 * Gets an interface for logging. This is useful for
 * logging in a cross-platform way
 * as certain platforms cannot use stderr for logging.
 * It also allows the frontend to
 * show logging information in a more suitable way.
 * If this interface is not used, libretro cores should
 * log to stderr as desired.
 */
#define RETRO_ENVIRONMENT_GET_PERF_INTERFACE 28
 /* struct retro_perf_callback * --
 * Gets an interface for performance counters. This is useful
 * for performance logging in a cross-platform way and for detecting
 * architecture-specific features, such as SIMD support.
 */
#define RETRO_ENVIRONMENT_GET_LOCATION_INTERFACE 29
 /* struct retro_location_callback * --
 * Gets access to the location interface.
 * The purpose of this interface is to be able to retrieve
 * location-based information from the host device,
 * such as current latitude / longitude.
 */
#define RETRO_ENVIRONMENT_GET_CONTENT_DIRECTORY 30 /* Old name, kept for compatibility. */
#define RETRO_ENVIRONMENT_GET_CORE_ASSETS_DIRECTORY 30
 /* const char ** --
 * Returns the "core assets" directory of the frontend.
 * This directory can be used to store specific assets that the
 * core relies upon, such as art assets,
 * input data, etc etc.
 * The returned value can be NULL.
 * If so, no such directory is defined,
 * and it's up to the implementation to find a suitable directory.
 */
#define RETRO_ENVIRONMENT_GET_SAVE_DIRECTORY 31
 /* const char ** --
 * Returns the "save" directory of the frontend, unless there is no
 * save directory available. The save directory should be used to
 * store SRAM, memory cards, high scores, etc, if the libretro core
 * cannot use the regular memory interface (retro_get_memory_data()).
 *
 * If the frontend cannot designate a save directory, it will return
 * NULL to indicate that the core should attempt to operate without a
 * save directory set.
 *
 * NOTE: early libretro cores used the system directory for save
 * files. Cores that need to be backwards-compatible can still check
 * GET_SYSTEM_DIRECTORY.
 */
#define RETRO_ENVIRONMENT_SET_SYSTEM_AV_INFO 32
 /* const struct retro_system_av_info * --
 * Sets a new av_info structure. This can only be called from
 * within retro_run().
 * This should *only* be used if the core is completely altering the
 * internal resolutions, aspect ratios, timings, sampling rate, etc.
 * Calling this can require a full reinitialization of video/audio
 * drivers in the frontend,
 *
 * so it is important to call it very sparingly, and usually only with
 * the users explicit consent.
 * An eventual driver reinitialize will happen so that video and
 * audio callbacks
 * happening after this call within the same retro_run() call will
 * target the newly initialized driver.
 *
 * This callback makes it possible to support configurable resolutions
 * in games, which can be useful to
 * avoid setting the "worst case" in max_width/max_height.
 *
 * ***HIGHLY RECOMMENDED*** Do not call this callback every time
 * resolution changes in an emulator core if it's
 * expected to be a temporary change, for the reasons of possible
 * driver reinitialization.
 * This call is not a free pass for not trying to provide
 * correct values in retro_get_system_av_info(). If you need to change
 * things like aspect ratio or nominal width/height,
 * use RETRO_ENVIRONMENT_SET_GEOMETRY, which is a softer variant
 * of SET_SYSTEM_AV_INFO.
 *
 * If this returns false, the frontend does not acknowledge a
 * changed av_info struct.
 */
#define RETRO_ENVIRONMENT_SET_PROC_ADDRESS_CALLBACK 33
 /* const struct retro_get_proc_address_interface * --
 * Allows a libretro core to announce support for the
 * get_proc_address() interface.
 * This interface allows for a standard way to extend libretro where
 * use of environment calls are too indirect,
 * e.g. for cases where the frontend wants to call directly into the core.
 *
 * If a core wants to expose this interface, SET_PROC_ADDRESS_CALLBACK
 * **MUST** be called from within retro_set_environment().
 */
#define RETRO_ENVIRONMENT_SET_SUBSYSTEM_INFO 34
 /* const struct retro_subsystem_info * --
 * This environment call introduces the concept of libretro "subsystems".
 * A subsystem is a variant of a libretro core which supports
 * different kinds of games.
 * The purpose of this is to support e.g. emulators which might
 * have special needs, e.g. Super Nintendo's Super GameBoy, Sufami Turbo.
 * It can also be used to pick among subsystems in an explicit way
 * if the libretro implementation is a multi-system emulator itself.
 *
 * Loading a game via a subsystem is done with retro_load_game_special(),
 * and this environment call allows a libretro core to expose which
 * subsystems are supported for use with retro_load_game_special().
 * A core passes an array of retro_game_special_info which is terminated
 * with a zeroed out retro_game_special_info struct.
 *
 * If a core wants to use this functionality, SET_SUBSYSTEM_INFO
 * **MUST** be called from within retro_set_environment().
 */
#define RETRO_ENVIRONMENT_SET_CONTROLLER_INFO 35
 /* const struct retro_controller_info * --
 * This environment call lets a libretro core tell the frontend
 * which controller subclasses are recognized in calls to
 * retro_set_controller_port_device().
 *
 * Some emulators such as Super Nintendo support multiple lightgun
 * types which must be specifically selected from. It is therefore
 * sometimes necessary for a frontend to be able to tell the core
 * about a special kind of input device which is not specifcally
 * provided by the Libretro API.
 *
 * In order for a frontend to understand the workings of those devices,
 * they must be defined as a specialized subclass of the generic device
 * types already defined in the libretro API.
 *
 * The core must pass an array of const struct retro_controller_info which
 * is terminated with a blanked out struct. Each element of the 
 * retro_controller_info struct corresponds to the ascending port index
 * that is passed to retro_set_controller_port_device() when that function
 * is called to indicate to the core that the frontend has changed the
 * active device subclass. SEE ALSO: retro_set_controller_port_device()
 * 
 * The ascending input port indexes provided by the core in the struct
 * are generally presented by frontends as ascending User # or Player #,
 * such as Player 1, Player 2, Player 3, etc. Which device subclasses are
 * supported can vary per input port.
 *
 * The first inner element of each entry in the retro_controller_info array
 * is a retro_controller_description struct that specifies the names and
 * codes of all device subclasses that are available for the corresponding
 * User or Player, beginning with the generic Libretro device that the
 * subclasses are derived from. The second inner element of each entry is the
 * total number of subclasses that are listed in the retro_controller_description.
 * 
 * NOTE: Even if special device types are set in the libretro core,
 * libretro should only poll input based on the base input device types.
 */
#define RETRO_ENVIRONMENT_SET_MEMORY_MAPS (36 | RETRO_ENVIRONMENT_EXPERIMENTAL)
 /* const struct retro_memory_map * --
 * This environment call lets a libretro core tell the frontend
 * about the memory maps this core emulates.
 * This can be used to implement, for example, cheats in a core-agnostic way.
 *
 * Should only be used by emulators; it doesn't make much sense for
 * anything else.
 * It is recommended to expose all relevant pointers through
 * retro_get_memory_* as well.
 *
 * Can be called from retro_init and retro_load_game.
 */
#define RETRO_ENVIRONMENT_SET_GEOMETRY 37
 /* const struct retro_game_geometry * --
 * This environment call is similar to SET_SYSTEM_AV_INFO for changing
 * video parameters, but provides a guarantee that drivers will not be
 * reinitialized.
 * This can only be called from within retro_run().
 *
 * The purpose of this call is to allow a core to alter nominal
 * width/heights as well as aspect ratios on-the-fly, which can be
 * useful for some emulators to change in run-time.
 *
 * max_width/max_height arguments are ignored and cannot be changed
 * with this call as this could potentially require a reinitialization or a
 * non-constant time operation.
 * If max_width/max_height are to be changed, SET_SYSTEM_AV_INFO is required.
 *
 * A frontend must guarantee that this environment call completes in
 * constant time.
 */
#define RETRO_ENVIRONMENT_GET_USERNAME 38
 /* const char **
 * Returns the specified username of the frontend, if specified by the user.
 * This username can be used as a nickname for a core that has online facilities
 * or any other mode where personalization of the user is desirable.
 * The returned value can be NULL.
 * If this environ callback is used by a core that requires a valid username,
 * a default username should be specified by the core.
 */
#define RETRO_ENVIRONMENT_GET_LANGUAGE 39
 /* unsigned * --
 * Returns the specified language of the frontend, if specified by the user.
 * It can be used by the core for localization purposes.
 */
#define RETRO_ENVIRONMENT_GET_CURRENT_SOFTWARE_FRAMEBUFFER (40 | RETRO_ENVIRONMENT_EXPERIMENTAL)
 /* struct retro_framebuffer * --
 * Returns a preallocated framebuffer which the core can use for rendering
 * the frame into when not using SET_HW_RENDER.
 * The framebuffer returned from this call must not be used
 * after the current call to retro_run() returns.
 *
 * The goal of this call is to allow zero-copy behavior where a core
 * can render directly into video memory, avoiding extra bandwidth cost by copying
 * memory from core to video memory.
 *
 * If this call succeeds and the core renders into it,
 * the framebuffer pointer and pitch can be passed to retro_video_refresh_t.
 * If the buffer from GET_CURRENT_SOFTWARE_FRAMEBUFFER is to be used,
 * the core must pass the exact
 * same pointer as returned by GET_CURRENT_SOFTWARE_FRAMEBUFFER;
 * i.e. passing a pointer which is offset from the
 * buffer is undefined. The width, height and pitch parameters
 * must also match exactly to the values obtained from GET_CURRENT_SOFTWARE_FRAMEBUFFER.
 *
 * It is possible for a frontend to return a different pixel format
 * than the one used in SET_PIXEL_FORMAT. This can happen if the frontend
 * needs to perform conversion.
 *
 * It is still valid for a core to render to a different buffer
 * even if GET_CURRENT_SOFTWARE_FRAMEBUFFER succeeds.
 *
 * A frontend must make sure that the pointer obtained from this function is
 * writeable (and readable).
 */
#define RETRO_ENVIRONMENT_GET_HW_RENDER_INTERFACE (41 | RETRO_ENVIRONMENT_EXPERIMENTAL)
 /* const struct retro_hw_render_interface ** --
 * Returns an API specific rendering interface for accessing API specific data.
 * Not all HW rendering APIs support or need this.
 * The contents of the returned pointer is specific to the rendering API
 * being used. See the various headers like libretro_vulkan.h, etc.
 *
 * GET_HW_RENDER_INTERFACE cannot be called before context_reset has been called.
 * Similarly, after context_destroyed callback returns,
 * the contents of the HW_RENDER_INTERFACE are invalidated.
 */
#define RETRO_ENVIRONMENT_SET_SUPPORT_ACHIEVEMENTS (42 | RETRO_ENVIRONMENT_EXPERIMENTAL)
 /* const bool * --
 * If true, the libretro implementation supports achievements
 * either via memory descriptors set with RETRO_ENVIRONMENT_SET_MEMORY_MAPS
 * or via retro_get_memory_data/retro_get_memory_size.
 *
 * This must be called before the first call to retro_run.
 */
#define RETRO_ENVIRONMENT_SET_HW_RENDER_CONTEXT_NEGOTIATION_INTERFACE (43 | RETRO_ENVIRONMENT_EXPERIMENTAL)
 /* const struct retro_hw_render_context_negotiation_interface * --
 * Sets an interface which lets the libretro core negotiate with frontend how a context is created.
 * The semantics of this interface depends on which API is used in SET_HW_RENDER earlier.
 * This interface will be used when the frontend is trying to create a HW rendering context,
 * so it will be used after SET_HW_RENDER, but before the context_reset callback.
 */
#define RETRO_ENVIRONMENT_SET_SERIALIZATION_QUIRKS 44
 /* uint64_t * --
 * Sets quirk flags associated with serialization. The frontend will zero any flags it doesn't
 * recognize or support. Should be set in either retro_init or retro_load_game, but not both.
 */
#define RETRO_ENVIRONMENT_SET_HW_SHARED_CONTEXT (44 | RETRO_ENVIRONMENT_EXPERIMENTAL)
 /* N/A (null) * --
 * The frontend will try to use a 'shared' hardware context (mostly applicable
 * to OpenGL) when a hardware context is being set up.
 *
 * Returns true if the frontend supports shared hardware contexts and false
 * if the frontend does not support shared hardware contexts.
 *
 * This will do nothing on its own until SET_HW_RENDER env callbacks are
 * being used.
 */
#define RETRO_ENVIRONMENT_GET_VFS_INTERFACE (45 | RETRO_ENVIRONMENT_EXPERIMENTAL)
 /* struct retro_vfs_interface_info * --
 * Gets access to the VFS interface.
 * VFS presence needs to be queried prior to load_game or any
 * get_system/save/other_directory being called to let front end know
 * core supports VFS before it starts handing out paths.
 * It is recomended to do so in retro_set_environment
 */
#define RETRO_ENVIRONMENT_GET_LED_INTERFACE (46 | RETRO_ENVIRONMENT_EXPERIMENTAL)
 /* struct retro_led_interface * --
 * Gets an interface which is used by a libretro core to set
 * state of LEDs.
 */
#define RETRO_ENVIRONMENT_GET_AUDIO_VIDEO_ENABLE (47 | RETRO_ENVIRONMENT_EXPERIMENTAL)
 /* int * --
 * Tells the core if the frontend wants audio or video.
 * If disabled, the frontend will discard the audio or video,
 * so the core may decide to skip generating a frame or generating audio.
 * This is mainly used for increasing performance.
 * Bit 0 (value 1): Enable Video
 * Bit 1 (value 2): Enable Audio
 * Bit 2 (value 4): Use Fast Savestates.
 * Bit 3 (value 8): Hard Disable Audio
 * Other bits are reserved for future use and will default to zero.
 * If video is disabled:
 * * The frontend wants the core to not generate any video,
 * including presenting frames via hardware acceleration.
 * * The frontend's video frame callback will do nothing.
 * * After running the frame, the video output of the next frame should be
 * no different than if video was enabled, and saving and loading state
 * should have no issues.
 * If audio is disabled:
 * * The frontend wants the core to not generate any audio.
 * * The frontend's audio callbacks will do nothing.
 * * After running the frame, the audio output of the next frame should be
 * no different than if audio was enabled, and saving and loading state
 * should have no issues.
 * Fast Savestates:
 * * Guaranteed to be created by the same binary that will load them.
 * * Will not be written to or read from the disk.
 * * Suggest that the core assumes loading state will succeed.
 * * Suggest that the core updates its memory buffers in-place if possible.
 * * Suggest that the core skips clearing memory.
 * * Suggest that the core skips resetting the system.
 * * Suggest that the core may skip validation steps.
 * Hard Disable Audio:
 * * Used for a secondary core when running ahead.
 * * Indicates that the frontend will never need audio from the core.
 * * Suggests that the core may stop synthesizing audio, but this should not
 * compromise emulation accuracy.
 * * Audio output for the next frame does not matter, and the frontend will
 * never need an accurate audio state in the future.
 * * State will never be saved when using Hard Disable Audio.
 */
#define RETRO_ENVIRONMENT_GET_MIDI_INTERFACE (48 | RETRO_ENVIRONMENT_EXPERIMENTAL)
 /* struct retro_midi_interface ** --
 * Returns a MIDI interface that can be used for raw data I/O.
 */

#define RETRO_ENVIRONMENT_GET_FASTFORWARDING (49 | RETRO_ENVIRONMENT_EXPERIMENTAL)
 /* bool * --
 * Boolean value that indicates whether or not the frontend is in
 * fastforwarding mode.
 */

/* VFS functionality */

/* File paths:
 * File paths passed as parameters when using this api shall be well formed unix-style,
 * using "/" (unquoted forward slash) as directory separator regardless of the platform's native separator.
 * Paths shall also include at least one forward slash ("game.bin" is an invalid path, use "./game.bin" instead).
 * Other than the directory separator, cores shall not make assumptions about path format:
 * "C:/path/game.bin", "http://example.com/game.bin", "#game/game.bin", "./game.bin" (without quotes) are all valid paths.
 * Cores may replace the basename or remove path components from the end, and/or add new components;
 * however, cores shall not append "./", "../" or multiple consecutive forward slashes ("//") to paths they request to front end.
 * The frontend is encouraged to make such paths work as well as it can, but is allowed to give up if the core alters paths too much.
 * Frontends are encouraged, but not required, to support native file system paths (modulo replacing the directory separator, if applicable).
 * Cores are allowed to try using them, but must remain functional if the front rejects such requests.
 * Cores are encouraged to use the libretro-common filestream functions for file I/O,
 * as they seamlessly integrate with VFS, deal with directory separator replacement as appropriate
 * and provide platform-specific fallbacks in cases where front ends do not support VFS. */

/* Opaque file handle
 * Introduced in VFS API v1 */
struct retro_vfs_file_handle;

/* File open flags
 * Introduced in VFS API v1 */
#define RETRO_VFS_FILE_ACCESS_READ (1 << 0) /* Read only mode */
#define RETRO_VFS_FILE_ACCESS_WRITE (1 << 1) /* Write only mode, discard contents and overwrites existing file unless RETRO_VFS_FILE_ACCESS_UPDATE is also specified */
#define RETRO_VFS_FILE_ACCESS_READ_WRITE (RETRO_VFS_FILE_ACCESS_READ | RETRO_VFS_FILE_ACCESS_WRITE) /* Read-write mode, discard contents and overwrites existing file unless RETRO_VFS_FILE_ACCESS_UPDATE is also specified*/
#define RETRO_VFS_FILE_ACCESS_UPDATE_EXISTING (1 << 2) /* Prevents discarding content of existing files opened for writing */

/* These are only hints. The frontend may choose to ignore them. Other than RAM/CPU/etc use,
 and how they react to unlikely external interference (for example someone else writing to that file,
 or the file's server going down), behavior will not change. */
#define RETRO_VFS_FILE_ACCESS_HINT_NONE (0)
/* Indicate that the file will be accessed many times. The frontend should aggressively cache everything. */
#define RETRO_VFS_FILE_ACCESS_HINT_FREQUENT_ACCESS (1 << 0)

/* Seek positions */
#define RETRO_VFS_SEEK_POSITION_START 0
#define RETRO_VFS_SEEK_POSITION_CURRENT 1
#define RETRO_VFS_SEEK_POSITION_END 2

/* Get path from opaque handle. Returns the exact same path passed to file_open when getting the handle
 * Introduced in VFS API v1 */
typedef const char *(RETRO_CALLCONV *retro_vfs_get_path_t)(struct retro_vfs_file_handle *stream);

/* Open a file for reading or writing. If path points to a directory, this will
 * fail. Returns the opaque file handle, or NULL for error.
 * Introduced in VFS API v1 */
typedef struct retro_vfs_file_handle *(RETRO_CALLCONV *retro_vfs_open_t)(const char *path, unsigned mode, unsigned hints);

/* Close the file and release its resources. Must be called if open_file returns non-NULL. Returns 0 on succes, -1 on failure.
 * Whether the call succeeds ot not, the handle passed as parameter becomes invalid and should no longer be used.
 * Introduced in VFS API v1 */
typedef int (RETRO_CALLCONV *retro_vfs_close_t)(struct retro_vfs_file_handle *stream);

/* Return the size of the file in bytes, or -1 for error.
 * Introduced in VFS API v1 */
typedef int64_t (RETRO_CALLCONV *retro_vfs_size_t)(struct retro_vfs_file_handle *stream);

/* Truncate file to specified size. Returns 0 on success or -1 on error
 * Introduced in VFS API v2 */
typedef int64_t (RETRO_CALLCONV *retro_vfs_truncate_t)(struct retro_vfs_file_handle *stream, int64_t length);

/* Get the current read / write position for the file. Returns - 1 for error.
 * Introduced in VFS API v1 */
typedef int64_t (RETRO_CALLCONV *retro_vfs_tell_t)(struct retro_vfs_file_handle *stream);

/* Set the current read/write position for the file. Returns the new position, -1 for error.
 * Introduced in VFS API v1 */
typedef int64_t (RETRO_CALLCONV *retro_vfs_seek_t)(struct retro_vfs_file_handle *stream, int64_t offset, int seek_position);

/* Read data from a file. Returns the number of bytes read, or -1 for error.
 * Introduced in VFS API v1 */
typedef int64_t (RETRO_CALLCONV *retro_vfs_read_t)(struct retro_vfs_file_handle *stream, void *s, uint64_t len);

/* Write data to a file. Returns the number of bytes written, or -1 for error.
 * Introduced in VFS API v1 */
typedef int64_t (RETRO_CALLCONV *retro_vfs_write_t)(struct retro_vfs_file_handle *stream, const void *s, uint64_t len);

/* Flush pending writes to file, if using buffered IO. Returns 0 on sucess, or -1 on failure.
 * Introduced in VFS API v1 */
typedef int (RETRO_CALLCONV *retro_vfs_flush_t)(struct retro_vfs_file_handle *stream);

/* Delete the specified file. Returns 0 on success, -1 on failure
 * Introduced in VFS API v1 */
typedef int (RETRO_CALLCONV *retro_vfs_remove_t)(const char *path);

/* Rename the specified file. Returns 0 on success, -1 on failure
 * Introduced in VFS API v1 */
typedef int (RETRO_CALLCONV *retro_vfs_rename_t)(const char *old_path, const char *new_path);

struct retro_vfs_interface
{
 /* VFS API v1 */
 retro_vfs_get_path_t get_path;
 retro_vfs_open_t open;
 retro_vfs_close_t close;
 retro_vfs_size_t size;
 retro_vfs_tell_t tell;
 retro_vfs_seek_t seek;
 retro_vfs_read_t read;
 retro_vfs_write_t write;
 retro_vfs_flush_t flush;
 retro_vfs_remove_t remove;
 retro_vfs_rename_t rename;
 /* VFS API v2 */
 retro_vfs_truncate_t truncate;
};

struct retro_vfs_interface_info
{
 /* Set by core: should this be higher than the version the front end supports,
 * front end will return false in the RETRO_ENVIRONMENT_GET_VFS_INTERFACE call
 * Introduced in VFS API v1 */
 uint32_t required_interface_version;

 /* Frontend writes interface pointer here. The frontend also sets the actual
 * version, must be at least required_interface_version.
 * Introduced in VFS API v1 */
 struct retro_vfs_interface *iface;
};

enum retro_hw_render_interface_type
{
 RETRO_HW_RENDER_INTERFACE_VULKAN = 0,
 RETRO_HW_RENDER_INTERFACE_D3D9 = 1,
 RETRO_HW_RENDER_INTERFACE_D3D10 = 2,
 RETRO_HW_RENDER_INTERFACE_D3D11 = 3,
 RETRO_HW_RENDER_INTERFACE_D3D12 = 4,
 RETRO_HW_RENDER_INTERFACE_DUMMY = INT_MAX
};

/* Base struct. All retro_hw_render_interface_* types
 * contain at least these fields. */
struct retro_hw_render_interface
{
 enum retro_hw_render_interface_type interface_type;
 unsigned interface_version;
};

typedef void (RETRO_CALLCONV *retro_set_led_state_t)(int led, int state);
struct retro_led_interface
{
 retro_set_led_state_t set_led_state;
};

/* Retrieves the current state of the MIDI input.
 * Returns true if it's enabled, false otherwise. */
typedef bool (RETRO_CALLCONV *retro_midi_input_enabled_t)(void);

/* Retrieves the current state of the MIDI output.
 * Returns true if it's enabled, false otherwise */
typedef bool (RETRO_CALLCONV *retro_midi_output_enabled_t)(void);

/* Reads next byte from the input stream.
 * Returns true if byte is read, false otherwise. */
typedef bool (RETRO_CALLCONV *retro_midi_read_t)(uint8_t *byte);

/* Writes byte to the output stream.
 * 'delta_time' is in microseconds and represent time elapsed since previous write.
 * Returns true if byte is written, false otherwise. */
typedef bool (RETRO_CALLCONV *retro_midi_write_t)(uint8_t byte, uint32_t delta_time);

/* Flushes previously written data.
 * Returns true if successful, false otherwise. */
typedef bool (RETRO_CALLCONV *retro_midi_flush_t)(void);

struct retro_midi_interface
{
 retro_midi_input_enabled_t input_enabled;
 retro_midi_output_enabled_t output_enabled;
 retro_midi_read_t read;
 retro_midi_write_t write;
 retro_midi_flush_t flush;
};

enum retro_hw_render_context_negotiation_interface_type
{
 RETRO_HW_RENDER_CONTEXT_NEGOTIATION_INTERFACE_VULKAN = 0,
 RETRO_HW_RENDER_CONTEXT_NEGOTIATION_INTERFACE_DUMMY = INT_MAX
};

/* Base struct. All retro_hw_render_context_negotiation_interface_* types
 * contain at least these fields. */
struct retro_hw_render_context_negotiation_interface
{
 enum retro_hw_render_context_negotiation_interface_type interface_type;
 unsigned interface_version;
};

/* Serialized state is incomplete in some way. Set if serialization is
 * usable in typical end-user cases but should not be relied upon to
 * implement frame-sensitive frontend features such as netplay or
 * rerecording. */
#define RETRO_SERIALIZATION_QUIRK_INCOMPLETE (1 << 0)
/* The core must spend some time initializing before serialization is
 * supported. retro_serialize() will initially fail; retro_unserialize()
 * and retro_serialize_size() may or may not work correctly either. */
#define RETRO_SERIALIZATION_QUIRK_MUST_INITIALIZE (1 << 1)
/* Serialization size may change within a session. */
#define RETRO_SERIALIZATION_QUIRK_CORE_VARIABLE_SIZE (1 << 2)
/* Set by the frontend to acknowledge that it supports variable-sized
 * states. */
#define RETRO_SERIALIZATION_QUIRK_FRONT_VARIABLE_SIZE (1 << 3)
/* Serialized state can only be loaded during the same session. */
#define RETRO_SERIALIZATION_QUIRK_SINGLE_SESSION (1 << 4)
/* Serialized state cannot be loaded on an architecture with a different
 * endianness from the one it was saved on. */
#define RETRO_SERIALIZATION_QUIRK_ENDIAN_DEPENDENT (1 << 5)
/* Serialized state cannot be loaded on a different platform from the one it
 * was saved on for reasons other than endianness, such as word size
 * dependence */
#define RETRO_SERIALIZATION_QUIRK_PLATFORM_DEPENDENT (1 << 6)

#define RETRO_MEMDESC_CONST (1 << 0) /* The frontend will never change this memory area once retro_load_game has returned. */
#define RETRO_MEMDESC_BIGENDIAN (1 << 1) /* The memory area contains big endian data. Default is little endian. */
#define RETRO_MEMDESC_SYSTEM_RAM (1 << 2) /* The memory area is system RAM. This is main RAM of the gaming system. */
#define RETRO_MEMDESC_SAVE_RAM (1 << 3) /* The memory area is save RAM. This RAM is usually found on a game cartridge, backed up by a battery. */
#define RETRO_MEMDESC_VIDEO_RAM (1 << 4) /* The memory area is video RAM (VRAM) */
#define RETRO_MEMDESC_ALIGN_2 (1 << 16) /* All memory access in this area is aligned to their own size, or 2, whichever is smaller. */
#define RETRO_MEMDESC_ALIGN_4 (2 << 16)
#define RETRO_MEMDESC_ALIGN_8 (3 << 16)
#define RETRO_MEMDESC_MINSIZE_2 (1 << 24) /* All memory in this region is accessed at least 2 bytes at the time. */
#define RETRO_MEMDESC_MINSIZE_4 (2 << 24)
#define RETRO_MEMDESC_MINSIZE_8 (3 << 24)
struct retro_memory_descriptor
{
 uint64_t flags;

 /* Pointer to the start of the relevant ROM or RAM chip.
 * It's strongly recommended to use 'offset' if possible, rather than
 * doing math on the pointer.
 *
 * If the same byte is mapped my multiple descriptors, their descriptors
 * must have the same pointer.
 * If 'start' does not point to the first byte in the pointer, put the
 * difference in 'offset' instead.
 *
 * May be NULL if there's nothing usable here (e.g. hardware registers and
 * open bus). No flags should be set if the pointer is NULL.
 * It's recommended to minimize the number of descriptors if possible,
 * but not mandatory. */
 void *ptr;
 size_t offset;

 /* This is the location in the emulated address space
 * where the mapping starts. */
 size_t start;

 /* Which bits must be same as in 'start' for this mapping to apply.
 * The first memory descriptor to claim a certain byte is the one
 * that applies.
 * A bit which is set in 'start' must also be set in this.
 * Can be zero, in which case each byte is assumed mapped exactly once.
 * In this case, 'len' must be a power of two. */
 size_t select;

 /* If this is nonzero, the set bits are assumed not connected to the
 * memory chip's address pins. */
 size_t disconnect;

 /* This one tells the size of the current memory area.
 * If, after start+disconnect are applied, the address is higher than
 * this, the highest bit of the address is cleared.
 *
 * If the address is still too high, the next highest bit is cleared.
 * Can be zero, in which case it's assumed to be infinite (as limited
 * by 'select' and 'disconnect'). */
 size_t len;

 /* To go from emulated address to physical address, the following
 * order applies:
 * Subtract 'start', pick off 'disconnect', apply 'len', add 'offset'. */

 /* The address space name must consist of only a-zA-Z0-9_-,
 * should be as short as feasible (maximum length is 8 plus the NUL),
 * and may not be any other address space plus one or more 0-9A-F
 * at the end.
 * However, multiple memory descriptors for the same address space is
 * allowed, and the address space name can be empty. NULL is treated
 * as empty.
 *
 * Address space names are case sensitive, but avoid lowercase if possible.
 * The same pointer may exist in multiple address spaces.
 *
 * Examples:
 * blank+blank - valid (multiple things may be mapped in the same namespace)
 * 'Sp'+'Sp' - valid (multiple things may be mapped in the same namespace)
 * 'A'+'B' - valid (neither is a prefix of each other)
 * 'S'+blank - valid ('S' is not in 0-9A-F)
 * 'a'+blank - valid ('a' is not in 0-9A-F)
 * 'a'+'A' - valid (neither is a prefix of each other)
 * 'AR'+blank - valid ('R' is not in 0-9A-F)
 * 'ARB'+blank - valid (the B can't be part of the address either, because
 * there is no namespace 'AR')
 * blank+'B' - not valid, because it's ambigous which address space B1234
 * would refer to.
 * The length can't be used for that purpose; the frontend may want
 * to append arbitrary data to an address, without a separator. */
 const char *addrspace;

 /* TODO: When finalizing this one, add a description field, which should be
 * "WRAM" or something roughly equally long. */

 /* TODO: When finalizing this one, replace 'select' with 'limit', which tells
 * which bits can vary and still refer to the same address (limit = ~select).
 * TODO: limit? range? vary? something else? */

 /* TODO: When finalizing this one, if 'len' is above what 'select' (or
 * 'limit') allows, it's bankswitched. Bankswitched data must have both 'len'
 * and 'select' != 0, and the mappings don't tell how the system switches the
 * banks. */

 /* TODO: When finalizing this one, fix the 'len' bit removal order.
 * For len=0x1800, pointer 0x1C00 should go to 0x1400, not 0x0C00.
 * Algorithm: Take bits highest to lowest, but if it goes above len, clear
 * the most recent addition and continue on the next bit.
 * TODO: Can the above be optimized? Is "remove the lowest bit set in both
 * pointer and 'len'" equivalent? */

 /* TODO: Some emulators (MAME?) emulate big endian systems by only accessing
 * the emulated memory in 32-bit chunks, native endian. But that's nothing
 * compared to Darek Mihocka <http://www.emulators.com/docs/nx07_vm101.htm>
 * (section Emulation 103 - Nearly Free Byte Reversal) - he flips the ENTIRE
 * RAM backwards! I'll want to represent both of those, via some flags.
 *
 * I suspect MAME either didn't think of that idea, or don't want the #ifdef.
 * Not sure which, nor do I really care. */

 /* TODO: Some of those flags are unused and/or don't really make sense. Clean
 * them up. */
};

/* The frontend may use the largest value of 'start'+'select' in a
 * certain namespace to infer the size of the address space.
 *
 * If the address space is larger than that, a mapping with .ptr=NULL
 * should be at the end of the array, with .select set to all ones for
 * as long as the address space is big.
 *
 * Sample descriptors (minus .ptr, and RETRO_MEMFLAG_ on the flags):
 * SNES WRAM:
 * .start=0x7E0000, .len=0x20000
 * (Note that this must be mapped before the ROM in most cases; some of the
 * ROM mappers
 * try to claim $7E0000, or at least $7E8000.)
 * SNES SPC700 RAM:
 * .addrspace="S", .len=0x10000
 * SNES WRAM mirrors:
 * .flags=MIRROR, .start=0x000000, .select=0xC0E000, .len=0x2000
 * .flags=MIRROR, .start=0x800000, .select=0xC0E000, .len=0x2000
 * SNES WRAM mirrors, alternate equivalent descriptor:
 * .flags=MIRROR, .select=0x40E000, .disconnect=~0x1FFF
 * (Various similar constructions can be created by combining parts of
 * the above two.)
 * SNES LoROM (512KB, mirrored a couple of times):
 * .flags=CONST, .start=0x008000, .select=0x408000, .disconnect=0x8000, .len=512*1024
 * .flags=CONST, .start=0x400000, .select=0x400000, .disconnect=0x8000, .len=512*1024
 * SNES HiROM (4MB):
 * .flags=CONST, .start=0x400000, .select=0x400000, .len=4*1024*1024
 * .flags=CONST, .offset=0x8000, .start=0x008000, .select=0x408000, .len=4*1024*1024
 * SNES ExHiROM (8MB):
 * .flags=CONST, .offset=0, .start=0xC00000, .select=0xC00000, .len=4*1024*1024
 * .flags=CONST, .offset=4*1024*1024, .start=0x400000, .select=0xC00000, .len=4*1024*1024
 * .flags=CONST, .offset=0x8000, .start=0x808000, .select=0xC08000, .len=4*1024*1024
 * .flags=CONST, .offset=4*1024*1024+0x8000, .start=0x008000, .select=0xC08000, .len=4*1024*1024
 * Clarify the size of the address space:
 * .ptr=NULL, .select=0xFFFFFF
 * .len can be implied by .select in many of them, but was included for clarity.
 */

struct retro_memory_map
{
 const struct retro_memory_descriptor *descriptors;
 unsigned num_descriptors;
};

struct retro_controller_description
{
 /* Human-readable description of the controller. Even if using a generic
 * input device type, this can be set to the particular device type the
 * core uses. */
 const char *desc;

 /* Device type passed to retro_set_controller_port_device(). If the device
 * type is a sub-class of a generic input device type, use the
 * RETRO_DEVICE_SUBCLASS macro to create an ID.
 *
 * E.g. RETRO_DEVICE_SUBCLASS(RETRO_DEVICE_JOYPAD, 1). */
 unsigned id;
};

struct retro_controller_info
{
 const struct retro_controller_description *types;
 unsigned num_types;
};

struct retro_subsystem_memory_info
{
 /* The extension associated with a memory type, e.g. "psram". */
 const char *extension;

 /* The memory type for retro_get_memory(). This should be at
 * least 0x100 to avoid conflict with standardized
 * libretro memory types. */
 unsigned type;
};

struct retro_subsystem_rom_info
{
 /* Describes what the content is (SGB BIOS, GB ROM, etc). */
 const char *desc;

 /* Same definition as retro_get_system_info(). */
 const char *valid_extensions;

 /* Same definition as retro_get_system_info(). */
 bool need_fullpath;

 /* Same definition as retro_get_system_info(). */
 bool block_extract;

 /* This is set if the content is required to load a game.
 * If this is set to false, a zeroed-out retro_game_info can be passed. */
 bool required;

 /* Content can have multiple associated persistent
 * memory types (retro_get_memory()). */
 const struct retro_subsystem_memory_info *memory;
 unsigned num_memory;
};

struct retro_subsystem_info
{
 /* Human-readable string of the subsystem type, e.g. "Super GameBoy" */
 const char *desc;

 /* A computer friendly short string identifier for the subsystem type.
 * This name must be [a-z].
 * E.g. if desc is "Super GameBoy", this can be "sgb".
 * This identifier can be used for command-line interfaces, etc.
 */
 const char *ident;

 /* Infos for each content file. The first entry is assumed to be the
 * "most significant" content for frontend purposes.
 * E.g. with Super GameBoy, the first content should be the GameBoy ROM,
 * as it is the most "significant" content to a user.
 * If a frontend creates new file paths based on the content used
 * (e.g. savestates), it should use the path for the first ROM to do so. */
 const struct retro_subsystem_rom_info *roms;

 /* Number of content files associated with a subsystem. */
 unsigned num_roms;

 /* The type passed to retro_load_game_special(). */
 unsigned id;
};

typedef void (RETRO_CALLCONV *retro_proc_address_t)(void);

/* libretro API extension functions:
 * (None here so far).
 *
 * Get a symbol from a libretro core.
 * Cores should only return symbols which are actual
 * extensions to the libretro API.
 *
 * Frontends should not use this to obtain symbols to standard
 * libretro entry points (static linking or dlsym).
 *
 * The symbol name must be equal to the function name,
 * e.g. if void retro_foo(void); exists, the symbol must be called "retro_foo".
 * The returned function pointer must be cast to the corresponding type.
 */
typedef retro_proc_address_t (RETRO_CALLCONV *retro_get_proc_address_t)(const char *sym);

struct retro_get_proc_address_interface
{
 retro_get_proc_address_t get_proc_address;
};

enum retro_log_level
{
 RETRO_LOG_DEBUG = 0,
 RETRO_LOG_INFO,
 RETRO_LOG_WARN,
 RETRO_LOG_ERROR,

 RETRO_LOG_DUMMY = INT_MAX
};

/* Logging function. Takes log level argument as well. */
typedef void (RETRO_CALLCONV *retro_log_printf_t)(enum retro_log_level level,
 const char *fmt, ...);

struct retro_log_callback
{
 retro_log_printf_t log;
};

/* Performance related functions */

/* ID values for SIMD CPU features */
#define RETRO_SIMD_SSE (1 << 0)
#define RETRO_SIMD_SSE2 (1 << 1)
#define RETRO_SIMD_VMX (1 << 2)
#define RETRO_SIMD_VMX128 (1 << 3)
#define RETRO_SIMD_AVX (1 << 4)
#define RETRO_SIMD_NEON (1 << 5)
#define RETRO_SIMD_SSE3 (1 << 6)
#define RETRO_SIMD_SSSE3 (1 << 7)
#define RETRO_SIMD_MMX (1 << 8)
#define RETRO_SIMD_MMXEXT (1 << 9)
#define RETRO_SIMD_SSE4 (1 << 10)
#define RETRO_SIMD_SSE42 (1 << 11)
#define RETRO_SIMD_AVX2 (1 << 12)
#define RETRO_SIMD_VFPU (1 << 13)
#define RETRO_SIMD_PS (1 << 14)
#define RETRO_SIMD_AES (1 << 15)
#define RETRO_SIMD_VFPV3 (1 << 16)
#define RETRO_SIMD_VFPV4 (1 << 17)
#define RETRO_SIMD_POPCNT (1 << 18)
#define RETRO_SIMD_MOVBE (1 << 19)
#define RETRO_SIMD_CMOV (1 << 20)
#define RETRO_SIMD_ASIMD (1 << 21)

typedef uint64_t retro_perf_tick_t;
typedef int64_t retro_time_t;

struct retro_perf_counter
{
 const char *ident;
 retro_perf_tick_t start;
 retro_perf_tick_t total;
 retro_perf_tick_t call_cnt;

 bool registered;
};

/* Returns current time in microseconds.
 * Tries to use the most accurate timer available.
 */
typedef retro_time_t (RETRO_CALLCONV *retro_perf_get_time_usec_t)(void);

/* A simple counter. Usually nanoseconds, but can also be CPU cycles.
 * Can be used directly if desired (when creating a more sophisticated
 * performance counter system).
 * */
typedef retro_perf_tick_t (RETRO_CALLCONV *retro_perf_get_counter_t)(void);

/* Returns a bit-mask of detected CPU features (RETRO_SIMD_*). */
typedef uint64_t (RETRO_CALLCONV *retro_get_cpu_features_t)(void);

/* Asks frontend to log and/or display the state of performance counters.
 * Performance counters can always be poked into manually as well.
 */
typedef void (RETRO_CALLCONV *retro_perf_log_t)(void);

/* Register a performance counter.
 * ident field must be set with a discrete value and other values in
 * retro_perf_counter must be 0.
 * Registering can be called multiple times. To avoid calling to
 * frontend redundantly, you can check registered field first. */
typedef void (RETRO_CALLCONV *retro_perf_register_t)(struct retro_perf_counter *counter);

/* Starts a registered counter. */
typedef void (RETRO_CALLCONV *retro_perf_start_t)(struct retro_perf_counter *counter);

/* Stops a registered counter. */
typedef void (RETRO_CALLCONV *retro_perf_stop_t)(struct retro_perf_counter *counter);

/* For convenience it can be useful to wrap register, start and stop in macros.
 * E.g.:
 * #ifdef LOG_PERFORMANCE
 * #define RETRO_PERFORMANCE_INIT(perf_cb, name) static struct retro_perf_counter name = {#name}; if (!name.registered) perf_cb.perf_register(&(name))
 * #define RETRO_PERFORMANCE_START(perf_cb, name) perf_cb.perf_start(&(name))
 * #define RETRO_PERFORMANCE_STOP(perf_cb, name) perf_cb.perf_stop(&(name))
 * #else
 * ... Blank macros ...
 * #endif
 *
 * These can then be used mid-functions around code snippets.
 *
 * extern struct retro_perf_callback perf_cb; * Somewhere in the core.
 *
 * void do_some_heavy_work(void)
 * {
 * RETRO_PERFORMANCE_INIT(cb, work_1;
 * RETRO_PERFORMANCE_START(cb, work_1);
 * heavy_work_1();
 * RETRO_PERFORMANCE_STOP(cb, work_1);
 *
 * RETRO_PERFORMANCE_INIT(cb, work_2);
 * RETRO_PERFORMANCE_START(cb, work_2);
 * heavy_work_2();
 * RETRO_PERFORMANCE_STOP(cb, work_2);
 * }
 *
 * void retro_deinit(void)
 * {
 * perf_cb.perf_log(); * Log all perf counters here for example.
 * }
 */

struct retro_perf_callback
{
 retro_perf_get_time_usec_t get_time_usec;
 retro_get_cpu_features_t get_cpu_features;

 retro_perf_get_counter_t get_perf_counter;
 retro_perf_register_t perf_register;
 retro_perf_start_t perf_start;
 retro_perf_stop_t perf_stop;
 retro_perf_log_t perf_log;
};

/* FIXME: Document the sensor API and work out behavior.
 * It will be marked as experimental until then.
 */
enum retro_sensor_action
{
 RETRO_SENSOR_ACCELEROMETER_ENABLE = 0,
 RETRO_SENSOR_ACCELEROMETER_DISABLE,

 RETRO_SENSOR_DUMMY = INT_MAX
};

/* Id values for SENSOR types. */
#define RETRO_SENSOR_ACCELEROMETER_X 0
#define RETRO_SENSOR_ACCELEROMETER_Y 1
#define RETRO_SENSOR_ACCELEROMETER_Z 2

typedef bool (RETRO_CALLCONV *retro_set_sensor_state_t)(unsigned port,
 enum retro_sensor_action action, unsigned rate);

typedef float (RETRO_CALLCONV *retro_sensor_get_input_t)(unsigned port, unsigned id);

struct retro_sensor_interface
{
 retro_set_sensor_state_t set_sensor_state;
 retro_sensor_get_input_t get_sensor_input;
};

enum retro_camera_buffer
{
 RETRO_CAMERA_BUFFER_OPENGL_TEXTURE = 0,
 RETRO_CAMERA_BUFFER_RAW_FRAMEBUFFER,

 RETRO_CAMERA_BUFFER_DUMMY = INT_MAX
};

/* Starts the camera driver. Can only be called in retro_run(). */
typedef bool (RETRO_CALLCONV *retro_camera_start_t)(void);

/* Stops the camera driver. Can only be called in retro_run(). */
typedef void (RETRO_CALLCONV *retro_camera_stop_t)(void);

/* Callback which signals when the camera driver is initialized
 * and/or deinitialized.
 * retro_camera_start_t can be called in initialized callback.
 */
typedef void (RETRO_CALLCONV *retro_camera_lifetime_status_t)(void);

/* A callback for raw framebuffer data. buffer points to an XRGB8888 buffer.
 * Width, height and pitch are similar to retro_video_refresh_t.
 * First pixel is top-left origin.
 */
typedef void (RETRO_CALLCONV *retro_camera_frame_raw_framebuffer_t)(const uint32_t *buffer,
 unsigned width, unsigned height, size_t pitch);

/* A callback for when OpenGL textures are used.
 *
 * texture_id is a texture owned by camera driver.
 * Its state or content should be considered immutable, except for things like
 * texture filtering and clamping.
 *
 * texture_target is the texture target for the GL texture.
 * These can include e.g. GL_TEXTURE_2D, GL_TEXTURE_RECTANGLE, and possibly
 * more depending on extensions.
 *
 * affine points to a packed 3x3 column-major matrix used to apply an affine
 * transform to texture coordinates. (affine_matrix * vec3(coord_x, coord_y, 1.0))
 * After transform, normalized texture coord (0, 0) should be bottom-left
 * and (1, 1) should be top-right (or (width, height) for RECTANGLE).
 *
 * GL-specific typedefs are avoided here to avoid relying on gl.h in
 * the API definition.
 */
typedef void (RETRO_CALLCONV *retro_camera_frame_opengl_texture_t)(unsigned texture_id,
 unsigned texture_target, const float *affine);

struct retro_camera_callback
{
 /* Set by libretro core.
 * Example bitmask: caps = (1 << RETRO_CAMERA_BUFFER_OPENGL_TEXTURE) | (1 << RETRO_CAMERA_BUFFER_RAW_FRAMEBUFFER).
 */
 uint64_t caps;

 /* Desired resolution for camera. Is only used as a hint. */
 unsigned width;
 unsigned height;

 /* Set by frontend. */
 retro_camera_start_t start;
 retro_camera_stop_t stop;

 /* Set by libretro core if raw framebuffer callbacks will be used. */
 retro_camera_frame_raw_framebuffer_t frame_raw_framebuffer;

 /* Set by libretro core if OpenGL texture callbacks will be used. */
 retro_camera_frame_opengl_texture_t frame_opengl_texture;

 /* Set by libretro core. Called after camera driver is initialized and
 * ready to be started.
 * Can be NULL, in which this callback is not called.
 */
 retro_camera_lifetime_status_t initialized;

 /* Set by libretro core. Called right before camera driver is
 * deinitialized.
 * Can be NULL, in which this callback is not called.
 */
 retro_camera_lifetime_status_t deinitialized;
};

/* Sets the interval of time and/or distance at which to update/poll
 * location-based data.
 *
 * To ensure compatibility with all location-based implementations,
 * values for both interval_ms and interval_distance should be provided.
 *
 * interval_ms is the interval expressed in milliseconds.
 * interval_distance is the distance interval expressed in meters.
 */
typedef void (RETRO_CALLCONV *retro_location_set_interval_t)(unsigned interval_ms,
 unsigned interval_distance);

/* Start location services. The device will start listening for changes to the
 * current location at regular intervals (which are defined with
 * retro_location_set_interval_t). */
typedef bool (RETRO_CALLCONV *retro_location_start_t)(void);

/* Stop location services. The device will stop listening for changes
 * to the current location. */
typedef void (RETRO_CALLCONV *retro_location_stop_t)(void);

/* Get the position of the current location. Will set parameters to
 * 0 if no new location update has happened since the last time. */
typedef bool (RETRO_CALLCONV *retro_location_get_position_t)(double *lat, double *lon,
 double *horiz_accuracy, double *vert_accuracy);

/* Callback which signals when the location driver is initialized
 * and/or deinitialized.
 * retro_location_start_t can be called in initialized callback.
 */
typedef void (RETRO_CALLCONV *retro_location_lifetime_status_t)(void);

struct retro_location_callback
{
 retro_location_start_t start;
 retro_location_stop_t stop;
 retro_location_get_position_t get_position;
 retro_location_set_interval_t set_interval;

 retro_location_lifetime_status_t initialized;
 retro_location_lifetime_status_t deinitialized;
};

enum retro_rumble_effect
{
 RETRO_RUMBLE_STRONG = 0,
 RETRO_RUMBLE_WEAK = 1,

 RETRO_RUMBLE_DUMMY = INT_MAX
};

/* Sets rumble state for joypad plugged in port 'port'.
 * Rumble effects are controlled independently,
 * and setting e.g. strong rumble does not override weak rumble.
 * Strength has a range of [0, 0xffff].
 *
 * Returns true if rumble state request was honored.
 * Calling this before first retro_run() is likely to return false. */
typedef bool (RETRO_CALLCONV *retro_set_rumble_state_t)(unsigned port,
 enum retro_rumble_effect effect, uint16_t strength);

struct retro_rumble_interface
{
 retro_set_rumble_state_t set_rumble_state;
};

/* Notifies libretro that audio data should be written. */
typedef void (RETRO_CALLCONV *retro_audio_callback_t)(void);

/* True: Audio driver in frontend is active, and callback is
 * expected to be called regularily.
 * False: Audio driver in frontend is paused or inactive.
 * Audio callback will not be called until set_state has been
 * called with true.
 * Initial state is false (inactive).
 */
typedef void (RETRO_CALLCONV *retro_audio_set_state_callback_t)(bool enabled);

struct retro_audio_callback
{
 retro_audio_callback_t callback;
 retro_audio_set_state_callback_t set_state;
};

/* Notifies a libretro core of time spent since last invocation
 * of retro_run() in microseconds.
 *
 * It will be called right before retro_run() every frame.
 * The frontend can tamper with timing to support cases like
 * fast-forward, slow-motion and framestepping.
 *
 * In those scenarios the reference frame time value will be used. */
typedef int64_t retro_usec_t;
typedef void (RETRO_CALLCONV *retro_frame_time_callback_t)(retro_usec_t usec);
struct retro_frame_time_callback
{
 retro_frame_time_callback_t callback;
 /* Represents the time of one frame. It is computed as
 * 1000000 / fps, but the implementation will resolve the
 * rounding to ensure that framestepping, etc is exact. */
 retro_usec_t reference;
};

/* Pass this to retro_video_refresh_t if rendering to hardware.
 * Passing NULL to retro_video_refresh_t is still a frame dupe as normal.
 * */
#define RETRO_HW_FRAME_BUFFER_VALID ((void*)-1)

/* Invalidates the current HW context.
 * Any GL state is lost, and must not be deinitialized explicitly.
 * If explicit deinitialization is desired by the libretro core,
 * it should implement context_destroy callback.
 * If called, all GPU resources must be reinitialized.
 * Usually called when frontend reinits video driver.
 * Also called first time video driver is initialized,
 * allowing libretro core to initialize resources.
 */
typedef void (RETRO_CALLCONV *retro_hw_context_reset_t)(void);

/* Gets current framebuffer which is to be rendered to.
 * Could change every frame potentially.
 */
typedef uintptr_t (RETRO_CALLCONV *retro_hw_get_current_framebuffer_t)(void);

/* Get a symbol from HW context. */
typedef retro_proc_address_t (RETRO_CALLCONV *retro_hw_get_proc_address_t)(const char *sym);

enum retro_hw_context_type
{
 RETRO_HW_CONTEXT_NONE = 0,
 /* OpenGL 2.x. Driver can choose to use latest compatibility context. */
 RETRO_HW_CONTEXT_OPENGL = 1,
 /* OpenGL ES 2.0. */
 RETRO_HW_CONTEXT_OPENGLES2 = 2,
 /* Modern desktop core GL context. Use version_major/
 * version_minor fields to set GL version. */
 RETRO_HW_CONTEXT_OPENGL_CORE = 3,
 /* OpenGL ES 3.0 */
 RETRO_HW_CONTEXT_OPENGLES3 = 4,
 /* OpenGL ES 3.1+. Set version_major/version_minor. For GLES2 and GLES3,
 * use the corresponding enums directly. */
 RETRO_HW_CONTEXT_OPENGLES_VERSION = 5,

 /* Vulkan, see RETRO_ENVIRONMENT_GET_HW_RENDER_INTERFACE. */
 RETRO_HW_CONTEXT_VULKAN = 6,

 /* Direct3D, set version_major to select the type of interface
 * returned by RETRO_ENVIRONMENT_GET_HW_RENDER_INTERFACE */
 RETRO_HW_CONTEXT_DIRECT3D = 7,

 RETRO_HW_CONTEXT_DUMMY = INT_MAX
};

struct retro_hw_render_callback
{
 /* Which API to use. Set by libretro core. */
 enum retro_hw_context_type context_type;

 /* Called when a context has been created or when it has been reset.
 * An OpenGL context is only valid after context_reset() has been called.
 *
 * When context_reset is called, OpenGL resources in the libretro
 * implementation are guaranteed to be invalid.
 *
 * It is possible that context_reset is called multiple times during an
 * application lifecycle.
 * If context_reset is called without any notification (context_destroy),
 * the OpenGL context was lost and resources should just be recreated
 * without any attempt to "free" old resources.
 */
 retro_hw_context_reset_t context_reset;

 /* Set by frontend.
 * TODO: This is rather obsolete. The frontend should not
 * be providing preallocated framebuffers. */
 retro_hw_get_current_framebuffer_t get_current_framebuffer;

 /* Set by frontend.
 * Can return all relevant functions, including glClear on Windows. */
 retro_hw_get_proc_address_t get_proc_address;

 /* Set if render buffers should have depth component attached.
 * TODO: Obsolete. */
 bool depth;

 /* Set if stencil buffers should be attached.
 * TODO: Obsolete. */
 bool stencil;

 /* If depth and stencil are true, a packed 24/8 buffer will be added.
 * Only attaching stencil is invalid and will be ignored. */

 /* Use conventional bottom-left origin convention. If false,
 * standard libretro top-left origin semantics are used.
 * TODO: Move to GL specific interface. */
 bool bottom_left_origin;

 /* Major version number for core GL context or GLES 3.1+. */
 unsigned version_major;

 /* Minor version number for core GL context or GLES 3.1+. */
 unsigned version_minor;

 /* If this is true, the frontend will go very far to avoid
 * resetting context in scenarios like toggling fullscreen, etc.
 * TODO: Obsolete? Maybe frontend should just always assume this ...
 */
 bool cache_context;

 /* The reset callback might still be called in extreme situations
 * such as if the context is lost beyond recovery.
 *
 * For optimal stability, set this to false, and allow context to be
 * reset at any time.
 */

 /* A callback to be called before the context is destroyed in a
 * controlled way by the frontend. */
 retro_hw_context_reset_t context_destroy;

 /* OpenGL resources can be deinitialized cleanly at this step.
 * context_destroy can be set to NULL, in which resources will
 * just be destroyed without any notification.
 *
 * Even when context_destroy is non-NULL, it is possible that
 * context_reset is called without any destroy notification.
 * This happens if context is lost by external factors (such as
 * notified by GL_ARB_robustness).
 *
 * In this case, the context is assumed to be already dead,
 * and the libretro implementation must not try to free any OpenGL
 * resources in the subsequent context_reset.
 */

 /* Creates a debug context. */
 bool debug_context;
};

/* Callback type passed in RETRO_ENVIRONMENT_SET_KEYBOARD_CALLBACK.
 * Called by the frontend in response to keyboard events.
 * down is set if the key is being pressed, or false if it is being released.
 * keycode is the RETROK value of the char.
 * character is the text character of the pressed key. (UTF-32).
 * key_modifiers is a set of RETROKMOD values or'ed together.
 *
 * The pressed/keycode state can be indepedent of the character.
 * It is also possible that multiple characters are generated from a
 * single keypress.
 * Keycode events should be treated separately from character events.
 * However, when possible, the frontend should try to synchronize these.
 * If only a character is posted, keycode should be RETROK_UNKNOWN.
 *
 * Similarily if only a keycode event is generated with no corresponding
 * character, character should be 0.
 */
typedef void (RETRO_CALLCONV *retro_keyboard_event_t)(bool down, unsigned keycode,
 uint32_t character, uint16_t key_modifiers);

struct retro_keyboard_callback
{
 retro_keyboard_event_t callback;
};

/* Callbacks for RETRO_ENVIRONMENT_SET_DISK_CONTROL_INTERFACE.
 * Should be set for implementations which can swap out multiple disk
 * images in runtime.
 *
 * If the implementation can do this automatically, it should strive to do so.
 * However, there are cases where the user must manually do so.
 *
 * Overview: To swap a disk image, eject the disk image with
 * set_eject_state(true).
 * Set the disk index with set_image_index(index). Insert the disk again
 * with set_eject_state(false).
 */

/* If ejected is true, "ejects" the virtual disk tray.
 * When ejected, the disk image index can be set.
 */
typedef bool (RETRO_CALLCONV *retro_set_eject_state_t)(bool ejected);

/* Gets current eject state. The initial state is 'not ejected'. */
typedef bool (RETRO_CALLCONV *retro_get_eject_state_t)(void);

/* Gets current disk index. First disk is index 0.
 * If return value is >= get_num_images(), no disk is currently inserted.
 */
typedef unsigned (RETRO_CALLCONV *retro_get_image_index_t)(void);

/* Sets image index. Can only be called when disk is ejected.
 * The implementation supports setting "no disk" by using an
 * index >= get_num_images().
 */
typedef bool (RETRO_CALLCONV *retro_set_image_index_t)(unsigned index);

/* Gets total number of images which are available to use. */
typedef unsigned (RETRO_CALLCONV *retro_get_num_images_t)(void);

struct retro_game_info;

/* Replaces the disk image associated with index.
 * Arguments to pass in info have same requirements as retro_load_game().
 * Virtual disk tray must be ejected when calling this.
 *
 * Replacing a disk image with info = NULL will remove the disk image
 * from the internal list.
 * As a result, calls to get_image_index() can change.
 *
 * E.g. replace_image_index(1, NULL), and previous get_image_index()
 * returned 4 before.
 * Index 1 will be removed, and the new index is 3.
 */
typedef bool (RETRO_CALLCONV *retro_replace_image_index_t)(unsigned index,
 const struct retro_game_info *info);

/* Adds a new valid index (get_num_images()) to the internal disk list.
 * This will increment subsequent return values from get_num_images() by 1.
 * This image index cannot be used until a disk image has been set
 * with replace_image_index. */
typedef bool (RETRO_CALLCONV *retro_add_image_index_t)(void);

struct retro_disk_control_callback
{
 retro_set_eject_state_t set_eject_state;
 retro_get_eject_state_t get_eject_state;

 retro_get_image_index_t get_image_index;
 retro_set_image_index_t set_image_index;
 retro_get_num_images_t get_num_images;

 retro_replace_image_index_t replace_image_index;
 retro_add_image_index_t add_image_index;
};

enum retro_pixel_format
{
 /* 0RGB1555, native endian.
 * 0 bit must be set to 0.
 * This pixel format is default for compatibility concerns only.
 * If a 15/16-bit pixel format is desired, consider using RGB565. */
 RETRO_PIXEL_FORMAT_0RGB1555 = 0,

 /* XRGB8888, native endian.
 * X bits are ignored. */
 RETRO_PIXEL_FORMAT_XRGB8888 = 1,

 /* RGB565, native endian.
 * This pixel format is the recommended format to use if a 15/16-bit
 * format is desired as it is the pixel format that is typically
 * available on a wide range of low-power devices.
 *
 * It is also natively supported in APIs like OpenGL ES. */
 RETRO_PIXEL_FORMAT_RGB565 = 2,

 /* Ensure sizeof() == sizeof(int). */
 RETRO_PIXEL_FORMAT_UNKNOWN = INT_MAX
};

struct retro_message
{
 const char *msg; /* Message to be displayed. */
 unsigned frames; /* Duration in frames of message. */
};

/* Describes how the libretro implementation maps a libretro input bind
 * to its internal input system through a human readable string.
 * This string can be used to better let a user configure input. */
struct retro_input_descriptor
{
 /* Associates given parameters with a description. */
 unsigned port;
 unsigned device;
 unsigned index;
 unsigned id;

 /* Human readable description for parameters.
 * The pointer must remain valid until
 * retro_unload_game() is called. */
 const char *description;
};

struct retro_system_info
{
 /* All pointers are owned by libretro implementation, and pointers must
 * remain valid until retro_deinit() is called. */

 const char *library_name; /* Descriptive name of library. Should not
 * contain any version numbers, etc. */
 const char *library_version; /* Descriptive version of core. */

 const char *valid_extensions; /* A string listing probably content
 * extensions the core will be able to
 * load, separated with pipe.
 * I.e. "bin|rom|iso".
 * Typically used for a GUI to filter
 * out extensions. */

 /* Libretro cores that need to have direct access to their content
 * files, including cores which use the path of the content files to
 * determine the paths of other files, should set need_fullpath to true.
 *
 * Cores should strive for setting need_fullpath to false,
 * as it allows the frontend to perform patching, etc.
 *
 * If need_fullpath is true and retro_load_game() is called:
 * - retro_game_info::path is guaranteed to have a valid path
 * - retro_game_info::data and retro_game_info::size are invalid
 *
 * If need_fullpath is false and retro_load_game() is called:
 * - retro_game_info::path may be NULL
 * - retro_game_info::data and retro_game_info::size are guaranteed
 * to be valid
 *
 * See also:
 * - RETRO_ENVIRONMENT_GET_SYSTEM_DIRECTORY
 * - RETRO_ENVIRONMENT_GET_SAVE_DIRECTORY
 */
 bool need_fullpath;

 /* If true, the frontend is not allowed to extract any archives before
 * loading the real content.
 * Necessary for certain libretro implementations that load games
 * from zipped archives. */
 bool block_extract;
};

struct retro_game_geometry
{
 unsigned base_width; /* Nominal video width of game. */
 unsigned base_height; /* Nominal video height of game. */
 unsigned max_width; /* Maximum possible width of game. */
 unsigned max_height; /* Maximum possible height of game. */

 float aspect_ratio; /* Nominal aspect ratio of game. If
 * aspect_ratio is <= 0.0, an aspect ratio
 * of base_width / base_height is assumed.
 * A frontend could override this setting,
 * if desired. */
};

struct retro_system_timing
{
 double fps; /* FPS of video content. */
 double sample_rate; /* Sampling rate of audio. */
};

struct retro_system_av_info
{
 struct retro_game_geometry geometry;
 struct retro_system_timing timing;
};

struct retro_variable
{
 /* Variable to query in RETRO_ENVIRONMENT_GET_VARIABLE.
 * If NULL, obtains the complete environment string if more
 * complex parsing is necessary.
 * The environment string is formatted as key-value pairs
 * delimited by semicolons as so:
 * "key1=value1;key2=value2;..."
 */
 const char *key;

 /* Value to be obtained. If key does not exist, it is set to NULL. */
 const char *value;
};

struct retro_game_info
{
 const char *path; /* Path to game, UTF-8 encoded.
 * Sometimes used as a reference for building other paths.
 * May be NULL if game was loaded from stdin or similar,
 * but in this case some cores will be unable to load `data`.
 * So, it is preferable to fabricate something here instead
 * of passing NULL, which will help more cores to succeed.
 * retro_system_info::need_fullpath requires
 * that this path is valid. */
 const void *data; /* Memory buffer of loaded game. Will be NULL
 * if need_fullpath was set. */
 size_t size; /* Size of memory buffer. */
 const char *meta; /* String of implementation specific meta-data. */
};

#define RETRO_MEMORY_ACCESS_WRITE (1 << 0)
 /* The core will write to the buffer provided by retro_framebuffer::data. */
#define RETRO_MEMORY_ACCESS_READ (1 << 1)
 /* The core will read from retro_framebuffer::data. */
#define RETRO_MEMORY_TYPE_CACHED (1 << 0)
 /* The memory in data is cached.
 * If not cached, random writes and/or reading from the buffer is expected to be very slow. */
struct retro_framebuffer
{
 void *data; /* The framebuffer which the core can render into.
 Set by frontend in GET_CURRENT_SOFTWARE_FRAMEBUFFER.
 The initial contents of data are unspecified. */
 unsigned width; /* The framebuffer width used by the core. Set by core. */
 unsigned height; /* The framebuffer height used by the core. Set by core. */
 size_t pitch; /* The number of bytes between the beginning of a scanline,
 and beginning of the next scanline.
 Set by frontend in GET_CURRENT_SOFTWARE_FRAMEBUFFER. */
 enum retro_pixel_format format; /* The pixel format the core must use to render into data.
 This format could differ from the format used in
 SET_PIXEL_FORMAT.
 Set by frontend in GET_CURRENT_SOFTWARE_FRAMEBUFFER. */

 unsigned access_flags; /* How the core will access the memory in the framebuffer.
 RETRO_MEMORY_ACCESS_* flags.
 Set by core. */
 unsigned memory_flags; /* Flags telling core how the memory has been mapped.
 RETRO_MEMORY_TYPE_* flags.
 Set by frontend in GET_CURRENT_SOFTWARE_FRAMEBUFFER. */
};

/* Callbacks */

/* Environment callback. Gives implementations a way of performing
 * uncommon tasks. Extensible. */
typedef bool (RETRO_CALLCONV *retro_environment_t)(unsigned cmd, void *data);

/* Render a frame. Pixel format is 15-bit 0RGB1555 native endian
 * unless changed (see RETRO_ENVIRONMENT_SET_PIXEL_FORMAT).
 *
 * Width and height specify dimensions of buffer.
 * Pitch specifices length in bytes between two lines in buffer.
 *
 * For performance reasons, it is highly recommended to have a frame
 * that is packed in memory, i.e. pitch == width * byte_per_pixel.
 * Certain graphic APIs, such as OpenGL ES, do not like textures
 * that are not packed in memory.
 */
typedef void (RETRO_CALLCONV *retro_video_refresh_t)(const void *data, unsigned width,
 unsigned height, size_t pitch);

/* Renders a single audio frame. Should only be used if implementation
 * generates a single sample at a time.
 * Format is signed 16-bit native endian.
 */
typedef void (RETRO_CALLCONV *retro_audio_sample_t)(int16_t left, int16_t right);

/* Renders multiple audio frames in one go.
 *
 * One frame is defined as a sample of left and right channels, interleaved.
 * I.e. int16_t buf[4] = { l, r, l, r }; would be 2 frames.
 * Only one of the audio callbacks must ever be used.
 */
typedef size_t (RETRO_CALLCONV *retro_audio_sample_batch_t)(const int16_t *data,
 size_t frames);

/* Polls input. */
typedef void (RETRO_CALLCONV *retro_input_poll_t)(void);

/* Queries for input for player 'port'. device will be masked with
 * RETRO_DEVICE_MASK.
 *
 * Specialization of devices such as RETRO_DEVICE_JOYPAD_MULTITAP that
 * have been set with retro_set_controller_port_device()
 * will still use the higher level RETRO_DEVICE_JOYPAD to request input.
 */
typedef int16_t (RETRO_CALLCONV *retro_input_state_t)(unsigned port, unsigned device,
 unsigned index, unsigned id);

/* Sets callbacks. retro_set_environment() is guaranteed to be called
 * before retro_init().
 *
 * The rest of the set_* functions are guaranteed to have been called
 * before the first call to retro_run() is made. */
RETRO_API void retro_set_environment(retro_environment_t);
RETRO_API void retro_set_video_refresh(retro_video_refresh_t);
RETRO_API void retro_set_audio_sample(retro_audio_sample_t);
RETRO_API void retro_set_audio_sample_batch(retro_audio_sample_batch_t);
RETRO_API void retro_set_input_poll(retro_input_poll_t);
RETRO_API void retro_set_input_state(retro_input_state_t);

/* Library global initialization/deinitialization. */
RETRO_API void retro_init(void);
RETRO_API void retro_deinit(void);

/* Must return RETRO_API_VERSION. Used to validate ABI compatibility
 * when the API is revised. */
RETRO_API unsigned retro_api_version(void);

/* Gets statically known system info. Pointers provided in *info
 * must be statically allocated.
 * Can be called at any time, even before retro_init(). */
RETRO_API void retro_get_system_info(struct retro_system_info *info);

/* Gets information about system audio/video timings and geometry.
 * Can be called only after retro_load_game() has successfully completed.
 * NOTE: The implementation of this function might not initialize every
 * variable if needed.
 * E.g. geom.aspect_ratio might not be initialized if core doesn't
 * desire a particular aspect ratio. */
RETRO_API void retro_get_system_av_info(struct retro_system_av_info *info);

/* Sets device to be used for player 'port'.
 * By default, RETRO_DEVICE_JOYPAD is assumed to be plugged into all
 * available ports.
 * Setting a particular device type is not a guarantee that libretro cores
 * will only poll input based on that particular device type. It is only a
 * hint to the libretro core when a core cannot automatically detect the
 * appropriate input device type on its own. It is also relevant when a
 * core can change its behavior depending on device type.
 *
 * As part of the core's implementation of retro_set_controller_port_device,
 * the core should call RETRO_ENVIRONMENT_SET_INPUT_DESCRIPTORS to notify the
 * frontend if the descriptions for any controls have changed as a
 * result of changing the device type.
 */
RETRO_API void retro_set_controller_port_device(unsigned port, unsigned device);

/* Resets the current game. */
RETRO_API void retro_reset(void);

/* Runs the game for one video frame.
 * During retro_run(), input_poll callback must be called at least once.
 *
 * If a frame is not rendered for reasons where a game "dropped" a frame,
 * this still counts as a frame, and retro_run() should explicitly dupe
 * a frame if GET_CAN_DUPE returns true.
 * In this case, the video callback can take a NULL argument for data.
 */
RETRO_API void retro_run(void);

/* Returns the amount of data the implementation requires to serialize
 * internal state (save states).
 * Between calls to retro_load_game() and retro_unload_game(), the
 * returned size is never allowed to be larger than a previous returned
 * value, to ensure that the frontend can allocate a save state buffer once.
 */
RETRO_API size_t retro_serialize_size(void);

/* Serializes internal state. If failed, or size is lower than
 * retro_serialize_size(), it should return false, true otherwise. */
RETRO_API bool retro_serialize(void *data, size_t size);
RETRO_API bool retro_unserialize(const void *data, size_t size);

RETRO_API void retro_cheat_reset(void);
RETRO_API void retro_cheat_set(unsigned index, bool enabled, const char *code);

/* Loads a game.
 * Return true to indicate successful loading and false to indicate load failure.
 */
RETRO_API bool retro_load_game(const struct retro_game_info *game);

/* Loads a "special" kind of game. Should not be used,
 * except in extreme cases. */
RETRO_API bool retro_load_game_special(
 unsigned game_type,
 const struct retro_game_info *info, size_t num_info
);

/* Unloads the currently loaded game. Called before retro_deinit(void). */
RETRO_API void retro_unload_game(void);

/* Gets region of game. */
RETRO_API unsigned retro_get_region(void);

/* Gets region of memory. */
RETRO_API void *retro_get_memory_data(unsigned id);
RETRO_API size_t retro_get_memory_size(unsigned id);

#ifdef __cplusplus
}
#endif

#endif