// chessengine.cpp
#include "common.h"
// global variables used in this module only
static wchar_t chessenginemodule_path[MAX_PATH];
static wchar_t chessenginemodule_pathname[MAX_PATH];
static wchar_t chessengineinitfile_pathname[MAX_PATH];
static PROCESS_INFORMATION PlayerEngine_pi;
static HANDLE hChessEngineStdinRd;
static HANDLE hChessEngineStdinWr;
static HANDLE hChessEngineStdoutRd;
static HANDLE hChessEngineStdoutWr;
static int current_obstinacy;
static bool is_hint_pending;
// prototypes of local functions
static void PlayerEngine_Recv (player_t *player);
static void PlayerEngine_Send (player_t *player);
static wchar_t *Move_BuildString (boardmove_t *move);
bool PlayerEngine_Init (player_t *player)
{
// this function starts a chess engine as a child process. This process's stdin and
// stdout are redirected to the handles we give it, so that we may read/write to it.
wchar_t widechar_buffer[256];
SYSTEM_INFO sysinfo;
SECURITY_ATTRIBUTES saAttr;
STARTUPINFO si;
FILE *fp;
// reset stuff first
hChessEngineStdinRd = NULL;
hChessEngineStdinWr = NULL;
hChessEngineStdoutRd = NULL;
hChessEngineStdoutWr = NULL;
player->wants_hint = false;
// load the selected engine parameters
Config_LoadEngine (options.engine.program);
// build the chess engine module path and pathname
swprintf_s (chessenginemodule_path, WCHAR_SIZEOF (chessenginemodule_path), L"%s/engines/%s", app_path, options.engine.program);
swprintf_s (chessenginemodule_pathname, WCHAR_SIZEOF (chessenginemodule_pathname), L"%s/engines/%s/%s", app_path, options.engine.program, options.engine.program_options.cmdline);
// prepare the pipes' security attributes
saAttr.nLength = sizeof (SECURITY_ATTRIBUTES);
saAttr.bInheritHandle = true; // set the bInheritHandle flag so pipe handles are inherited
saAttr.lpSecurityDescriptor = NULL;
// create a pipe for the child process's stdout
CreatePipe (&hChessEngineStdoutRd, &hChessEngineStdoutWr, &saAttr, 0);
SetHandleInformation (hChessEngineStdoutRd, HANDLE_FLAG_INHERIT, 0); // ensure the read handle to the pipe for STDOUT is not inherited
// create a pipe for the child process's stdin
CreatePipe (&hChessEngineStdinRd, &hChessEngineStdinWr, &saAttr, 0);
SetHandleInformation (hChessEngineStdinWr, HANDLE_FLAG_INHERIT, 0); // ensure the write handle to the pipe for STDIN is not inherited.
// spawn the chess engine process with redirected input and output
memset (&si, 0, sizeof (si));
si.cb = sizeof (STARTUPINFOA);
si.dwFlags = STARTF_USESTDHANDLES;
si.hStdInput = hChessEngineStdinRd;
si.hStdOutput = hChessEngineStdoutWr;
si.hStdError = hChessEngineStdoutWr;
if (!CreateProcess (chessenginemodule_pathname, // module pathname
options.engine.program_options.cmdline, // command line
NULL, NULL,
true, // handles are inherited
CREATE_NO_WINDOW | DETACHED_PROCESS | CREATE_NEW_PROCESS_GROUP,
NULL,
chessenginemodule_path, // process path
&si, // STARTUPINFO pointer
&PlayerEngine_pi)) // receives PROCESS_INFORMATION
{
messagebox.hWndParent = hMainWnd;
wcscpy_s (messagebox.title, WCHAR_SIZEOF (messagebox.title), LOCALIZE (L"ImportantMessage"));
wcscpy_s (messagebox.text, WCHAR_SIZEOF (messagebox.text), LOCALIZE (L"Error_ChessEngineInitializationFailed"));
messagebox.flags = MB_ICONWARNING | MB_OK;
DialogBox_Message (&messagebox); // display a modeless error message box
PlayerEngine_Shutdown (player); // on error, shutdown the engine
return (false);
}
// eventually initialize the debug log file
Debug_Init (L"Chess engine output.txt");
// build the init file full qualified path name and try to open it
swprintf_s (chessengineinitfile_pathname, WCHAR_SIZEOF (chessengineinitfile_pathname), L"%s/engines/%s/init.txt", app_path, options.engine.program);
_wfopen_s (&fp, chessengineinitfile_pathname, L"r");
// could the init file be opened ?
if (fp != NULL)
{
Debug_Log (L"===Found initialization file, parsing...===\n");
// SMP HACK -- assume our engine is CECP compatible and set the max CPUs to use to core max - 1
// (the computer will look like hung if all CPU is taken)
GetSystemInfo (&sysinfo); // get the number of cores and build the corresponding engine initialization order
Player_SendBuffer_Add (player, 1000, L"mt %d\n", max (1, sysinfo.dwNumberOfProcessors - 1));
// read line per line
while (fgetws (widechar_buffer, WCHAR_SIZEOF (widechar_buffer), fp) != NULL)
{
if ((widechar_buffer[0] == L'#') || (widechar_buffer[0] == L'\n'))
continue; // skip comments and empty lines
// new command line found, append it to the send buffer
Player_SendBuffer_Add (player, 1000, widechar_buffer);
}
fclose (fp); // finished, close the file
}
// everything's okay, set engine name as the player's name
wcscpy_s (player->name, WCHAR_SIZEOF (player->name), options.engine.program_options.name);
return (true); // finished
}
void PlayerEngine_Shutdown (player_t *player)
{
// this function terminates the chess engine process and releases all handles attached to it
unsigned long exit_code;
unsigned long handle_flags;
int attempt_index;
// send the engine a quit command
Player_SendBuffer_Add (player, 1000, options.engine.program_options.command_quit);
Player_SendBuffer_Add (player, 1000, L"\n"); // since the format string was read from the options, don't forget to end it with a carriage return
PlayerEngine_Send (player);
// close the pipe handles
if (hChessEngineStdinRd)
CloseHandle (hChessEngineStdinRd);
hChessEngineStdinRd = NULL;
if (hChessEngineStdinWr)
CloseHandle (hChessEngineStdinWr);
hChessEngineStdinWr = NULL;
if (hChessEngineStdoutRd)
CloseHandle (hChessEngineStdoutRd);
hChessEngineStdoutRd = NULL;
if (hChessEngineStdoutWr)
CloseHandle (hChessEngineStdoutWr);
hChessEngineStdoutWr = NULL;
// check 10 times if the engine process has ended cleanly
for (attempt_index = 0; attempt_index < 10; attempt_index++)
{
if (GetExitCodeProcess (PlayerEngine_pi.hProcess, &exit_code) && (exit_code != STILL_ACTIVE))
break; // break as soon as we've told the process exited cleanly
Sleep (100); // else wait one tenth second
}
// has the engine NOT closen by itself yet ?
if ((attempt_index == 10) && GetExitCodeProcess (PlayerEngine_pi.hProcess, &exit_code) && (exit_code == STILL_ACTIVE))
{
Debug_Log (L"===Engine not closen, terminating process manually===\n");
// terminate the chess engine process using our smart technique ^^
if (!SafeTerminateProcess (PlayerEngine_pi.hProcess, 0))
TerminateProcess (PlayerEngine_pi.hProcess, 0); // if process doesn't want to shutdown, kill it
}
else
Debug_Log (L"===Engine closed cleanly===\n");
if (PlayerEngine_pi.hProcess)
CloseHandle (PlayerEngine_pi.hProcess);
PlayerEngine_pi.hProcess = NULL;
if (GetHandleInformation (PlayerEngine_pi.hThread, &handle_flags))
CloseHandle (PlayerEngine_pi.hThread);
PlayerEngine_pi.hThread = NULL;
// and finally reset the process information structure
memset (&PlayerEngine_pi, 0, sizeof (PlayerEngine_pi));
return; // finished
}
bool PlayerEngine_Think (player_t *player)
{
// this function reads and writes any necessary data from and to the chess engine. Returns TRUE if scene needs to be updated.
wchar_t line_buffer[256];
wchar_t *line_pointer;
wchar_t *move_string;
int char_index;
int length;
boardmove_t move;
player_t *current_player;
player_t *opposite_player;
bool do_update;
// don't update the scene until told otherwise
do_update = false;
// get current and opposite players
current_player = Player_GetCurrent ();
opposite_player = Player_GetOpposite ();
// read from pipe (non-blocking)
PlayerEngine_Recv (player);
////////////////
// START PARSING
// read line per line...
line_pointer = player->recvbuffer; // start at the first character
while ((line_pointer = ReadACompleteLine (line_buffer, WCHAR_SIZEOF (line_buffer), line_pointer)) != NULL)
{
// is it an empty line or engine noise ?
if ((line_buffer[0] == 0) || iswspace (line_buffer[0]))
continue; // skip empty lines and engine noise
// is engine allowed to resign ? if so, check if it's a game results
if (options.engine.obstinacy_level >= 0)
{
// is it a game result AND are we still in play ?
if ((wcsstr (line_buffer, L"1-0") != NULL) && (the_board.game_state == STATE_PLAYING))
{
// have we NOT been obstinate enough ?
if (current_obstinacy < options.engine.obstinacy_level)
current_obstinacy++; // if so, discard this resign and go on
else
{
Debug_Log (L"===Engine tells us that black resigns: white wins!===\n");
// if opponent player is human, play the victory sound, else, play defeat sound
Audio_PlaySound (opposite_player->type == PLAYER_HUMAN ? SOUNDTYPE_VICTORY : SOUNDTYPE_DEFEAT);
// display the game over dialog box
the_board.game_state = STATE_WHITEWIN_RESIGNORFORFEIT;
DialogBox_EndGame ();
do_update = true; // remember to update the 3D scene
}
continue; // we processed that line
}
else if ((wcsstr (line_buffer, L"0-1") != NULL) && (the_board.game_state == STATE_PLAYING))
{
// have we NOT been obstinate enough ?
if (current_obstinacy < options.engine.obstinacy_level)
current_obstinacy++; // if so, discard this resign and go on
else
{
Debug_Log (L"===Engine tells us that white resigns: black wins!===\n");
// if opponent player is human, play the victory sound, else, play defeat sound
Audio_PlaySound (opposite_player->type == PLAYER_HUMAN ? SOUNDTYPE_VICTORY : SOUNDTYPE_DEFEAT);
// display the game over dialog box
the_board.game_state = STATE_BLACKWIN_RESIGNORFORFEIT;
DialogBox_EndGame ();
do_update = true; // remember to update the 3D scene
}
continue; // we processed that line
}
}
// has the game ended already ?
if (the_board.game_state > STATE_PLAYING)
continue; // ignore all that the engine tells us. Game is over already.
// else is it a normal move ?
else if ((move_string = wcsstr (line_buffer, options.engine.program_options.replystring_move)) != NULL)
move_string += wcslen (options.engine.program_options.replystring_move); // go to the parsable data
// else it's any other sort of line
else
continue; // skip lines that don't contain any valid move data
// now we are sure it's either a hint or a move (or some pondering)
length = wcslen (move_string);
if ((length < 2) || (length > 9))
continue; // if string is too long to be a move, skip it
// there must be valid move data on that line.
// evaluate the engine move string
memcpy (move.slots, the_board.moves[the_board.move_count - 1].slots, sizeof (move.slots));
wcscpy_s (move.pgntext, WCHAR_SIZEOF (move.pgntext), move_string);
if (!Move_SetupFromSAN (&the_board.moves[the_board.move_count - 1], &move, Board_ColorToMove (&the_board)))
{
Debug_Log (L"===Skipping line (invalid move syntax)===\n%s", move_string);
continue; // so now, if there are NOT two digits AND it's not a kind of castle, it can't be a move so skip that line
}
// is it NOT a hint, are blunders allowed, should we do one now AND can we do one now ?
if (!is_hint_pending && (options.engine.blunder_chances > 0) && (rand () % 100 < options.engine.blunder_chances)
&& Move_FindRandomMove (&the_board.moves[the_board.move_count - 1], player->color, &move))
{
Player_SendBuffer_Add (player, 1000, options.engine.program_options.command_force, Move_BuildString (&move)); // send the blunderous move to the engine
Player_SendBuffer_Add (player, 1000, L"\n"); // since the format string was read from the options, don't forget to end it with a carriage return
if (wcscmp (options.engine.program, L"Crafty") == 0)
Player_SendBuffer_Add (player, 1000, L"disp\n");
Debug_Log (L"===Discarding engine move, forcing a blunderous move (%s) instead===\n", Move_BuildString (&move)); // blunder
}
// mark the engine's selected and hovered squares
Board_SetSelectedAndHovered (&the_board, move.source[0], move.source[1], move.target[0], move.target[1]);
// was it NOT a hint ?
if (!is_hint_pending)
{
the_scene.gui.central_text.disappear_time = current_time + 1.0f; // fade the "thinking" phrase out now (FIXME: ugly)
the_scene.gui.want_spinwheel = false; // stop spinning wheel
Board_AppendMove (&the_board, the_board.selected_position[0], the_board.selected_position[1], the_board.hovered_position[0], the_board.hovered_position[1], move.promotion_type, NULL);
the_board.has_playerchanged = true; // do the movement and switch players
// forget the hovered and selected positions
Board_SetSelectedAndHovered (&the_board, -1, -1, -1, -1);
animation_endtime = current_time + ANIMATION_DURATION; // wait for animation time seconds
sound_playtime = current_time + ANIMATION_DURATION - 0.1f; // play sound near the end of animation
}
// else it was a hint
else
{
the_scene.gui.central_text.disappear_time = current_time + 0.1f; // fade the "thinking" phrase out now quickly (FIXME: ugly)
the_scene.gui.want_spinwheel = false; // stop spinning wheel
highlight_endtime = current_time + 2.0f; // just highlight this part for a little more than one second
is_hint_pending = false; // remember no hint is pending any longer
// we must now restore the board to its last state. Just set up the board again from its current Forsyth-Edwards notation
Debug_Log (L"===Hint received, rebuilding board and telling engine to backup 1 move===\n");
Debug_Log (L"===setting up board using FEN string===\n");
// instruct it about its allowed search depth BEFORE each table set (this ensures engine will be "ready" to handle the command)
// then get the current game state in FEN format and feed it to the engine
Player_SendBuffer_Add (player, 1000, options.engine.program_options.command_sd, options.engine.depth);
Player_SendBuffer_Add (player, 1000, L"\n"); // since the format string was read from the options, don't forget to end it with a carriage return
Player_SendBuffer_Add (player, 1000, options.engine.program_options.command_setboard, the_board.moves[the_board.move_count - 1].fen_string);
Player_SendBuffer_Add (player, 1000, L"\n"); // since the format string was read from the options, don't forget to end it with a carriage return
if (wcscmp (options.engine.program, L"Crafty") == 0)
Player_SendBuffer_Add (player, 1000, L"disp\n");
}
do_update = true; // remember to update the 3D scene
}
// now clean the input buffer of all the lines we parsed
line_pointer = wcsrchr (player->recvbuffer, L'\n'); // reach the last carriage return
if (line_pointer != NULL)
{
line_pointer++; // skip the carriage return
length = wcslen (line_pointer); // get the remaining string length
for (char_index = 0; char_index < length; char_index++)
player->recvbuffer[char_index] = line_pointer[char_index]; // and recopy the remaining string at the beginning of the buffer
player->recvbuffer[char_index] = 0; // finish the string ourselves
}
// END PARSING
//////////////
/////////////////////////////////
// START NOTIFICATIONS PROCESSING
// have we been notified that the board was just set up ?
if (the_board.was_setup)
{
Debug_Log (L"===Got board setup notification from interface===\n");
// send a new game command to the chess engine
Player_SendBuffer_Add (player, 1000, options.engine.program_options.command_new);
Player_SendBuffer_Add (player, 1000, L"\n"); // since the format string was read from the options, don't forget to end it with a carriage return
// just set up the board from its Forsyth-Edwards notation
Debug_Log (L"===setting up board using FEN string===\n");
// instruct it about its allowed search depth BEFORE each table set (this ensures engine will be "ready" to handle the command)
// then get the current game state in FEN format and feed it to the engine
Player_SendBuffer_Add (player, 1000, options.engine.program_options.command_sd, options.engine.depth);
Player_SendBuffer_Add (player, 1000, L"\n"); // since the format string was read from the options, don't forget to end it with a carriage return
Player_SendBuffer_Add (player, 1000, options.engine.program_options.command_setboard, the_board.moves[the_board.move_count - 1].fen_string);
Player_SendBuffer_Add (player, 1000, L"\n"); // since the format string was read from the options, don't forget to end it with a carriage return
current_obstinacy = 0; // reset current obstinacy
is_hint_pending = false; // no hint was requested so far
if (wcscmp (options.engine.program, L"Crafty") == 0)
Player_SendBuffer_Add (player, 1000, L"disp\n");
}
// have we been notified that players are swapping colors ? (N.B. when this happens in human vs. computer mode, it's always that the human player is *GIVING* his turn)
if (the_board.want_playerswap)
{
Debug_Log (L"===Got player SWAP notification from interface===\n");
Player_SendBuffer_Add (player, 1000, options.engine.program_options.command_go); // tell engine it's now the current player
Player_SendBuffer_Add (player, 1000, L"\n"); // since the format string was read from the options, don't forget to end it with a carriage return
}
// have we been notified that the current player just changed ?
if (the_board.has_playerchanged)
{
Debug_Log (L"===Got player change notification from interface===\n");
// is the current player our color ? (meaning is it engine's turn to play) ?
if (Board_ColorToMove (&the_board) == player->color)
{
// is it NOT a board setup AND has at least one move been played (meaning it was just the other's turn before) ?
if (!the_board.was_setup && (the_board.move_count > 1))
{
Debug_Log (L"===Player just played, sending the chosen move to engine===\n");
if (wcscmp (options.engine.program, L"Crafty") == 0)
Player_SendBuffer_Add (player, 1000, L"disp\n");
// instruct it about its allowed search depth BEFORE each move (this ensures engine will be "ready" to handle the command)
// then build the move string, and send the move string to the engine
Player_SendBuffer_Add (player, 1000, options.engine.program_options.command_sd, options.engine.depth);
Player_SendBuffer_Add (player, 1000, L"\n"); // since the format string was read from the options, don't forget to end it with a carriage return
Player_SendBuffer_Add (player, 1000, options.engine.program_options.command_move, Move_BuildString (&the_board.moves[the_board.move_count - 1]));
Player_SendBuffer_Add (player, 1000, L"\n"); // end the send buffer with a carriage return
}
// else game has not started yet, but it's our turn
else
{
Player_SendBuffer_Add (player, 1000, options.engine.program_options.command_go); // so let's start the game
Player_SendBuffer_Add (player, 1000, L"\n"); // since the format string was read from the options, don't forget to end it with a carriage return
}
}
}
// END NOTIFICATIONS PROCESSING
///////////////////////////////
// is it NOT our turn ?
if (current_player != player)
{
// does our opponent want a hint ?
if (current_player->wants_hint)
{
current_player->wants_hint = false; // don't ask twice
Debug_Log (L"===Hint requested, asking engine for it===\n");
Player_SendBuffer_Add (player, 1000, options.engine.program_options.command_go); // tell the computer to analyze this position
Player_SendBuffer_Add (player, 1000, L"\n"); // since the format string was read from the options, don't forget to end it with a carriage return
is_hint_pending = true; // remember a hint is pending
// FIXME: move to scene.cpp
Scene_SetText (&the_scene.gui.central_text, 50.0f, 40.0f, -1, ALIGN_CENTER, ALIGN_CENTER, ALIGN_CENTER, centermsg_fontindex, RGBA_TO_RGBACOLOR (255, 255, 255, 191),
999999.0f, true, LOCALIZE (L"Thinking")); // display the "thinking" phrase in the middle of the screen
the_scene.gui.want_spinwheel = true; // start spinning wheel
do_update = true; // remember to update the 3D scene
}
// does our opponent want to cancel a move ?
if (current_player->wants_cancel)
{
current_player->wants_cancel = false; // don't ask twice (remember now before we switch players)
Debug_Log (L"===Move cancellation requested, rebuilding board and telling engine to backup 2 moves===\n");
// rewind game 2 moves back
the_board.moves = (boardmove_t *) SAFE_realloc (the_board.moves, the_board.move_count, max (1, the_board.move_count - 2), sizeof (boardmove_t), false);
the_board.move_count = max (1, the_board.move_count - 2); // figure out how many moves we have now
the_board.viewed_move = the_board.move_count - 1; // take us back to the last move
// just set up the board from its Forsyth-Edwards notation
Debug_Log (L"===setting up board using FEN string===\n");
// instruct it about its allowed search depth BEFORE each table set (this ensures engine will be "ready" to handle the command)
// then get the current game state in FEN format and feed it to the engine
Player_SendBuffer_Add (player, 1000, options.engine.program_options.command_sd, options.engine.depth);
Player_SendBuffer_Add (player, 1000, L"\n"); // since the format string was read from the options, don't forget to end it with a carriage return
Player_SendBuffer_Add (player, 1000, options.engine.program_options.command_setboard, the_board.moves[the_board.move_count - 1].fen_string);
Player_SendBuffer_Add (player, 1000, L"\n"); // since the format string was read from the options, don't forget to end it with a carriage return
if (wcscmp (options.engine.program, L"Crafty") == 0)
Player_SendBuffer_Add (player, 1000, L"disp\n");
do_update = true; // remember to update the 3D scene
}
}
// write to pipe (when we're allowed to)
if (!player->sendbuffer_locked && (animation_endtime + 1.0f < current_time))
PlayerEngine_Send (player);
return (do_update); // finished, return whether we should update the scene or not
}
static void PlayerEngine_Recv (player_t *player)
{
// helper function to read data from the pipe communicating with the game engine process
unsigned long amount_to_read;
unsigned long read_count;
int byte_index;
int rewrite_index;
int length;
unsigned int initial_pos;
// get reception buffer's initial end position
initial_pos = wcslen (player->recvbuffer);
// as long as the pipe reports us there is data to read...
while (PeekNamedPipe (hChessEngineStdoutRd, NULL, 0, NULL, &amount_to_read, NULL) && (amount_to_read > 0))
{
if (!ReadFile (hChessEngineStdoutRd, player->ascii_recvbuffer, min (amount_to_read, (unsigned long) player->recvbuffer_size - 1), &read_count, NULL))
break; // read the pipe; if it fails, stop trying
// parse all received data and eradicate all carriage returns and percent signs
rewrite_index = 0;
for (byte_index = 0; byte_index < (int) read_count; byte_index++)
if ((player->ascii_recvbuffer[byte_index] != '\r') && (player->ascii_recvbuffer[byte_index] != '%'))
{
player->ascii_recvbuffer[rewrite_index] = player->ascii_recvbuffer[byte_index];
rewrite_index++;
}
player->ascii_recvbuffer[rewrite_index] = 0; // terminate the buffer ourselves
// convert to wide char and append it to recvbuffer
length = wcslen (player->recvbuffer);
ConvertToWideChar (&player->recvbuffer[length], player->recvbuffer_size - length, player->ascii_recvbuffer);
}
// write what we received (if we received anything)
if (wcslen (player->recvbuffer) > initial_pos)
Debug_Log (L"===================================RECEIVED:===================================\n%s\n", &player->recvbuffer[initial_pos]);
return; // finished
}
static void PlayerEngine_Send (player_t *player)
{
// helper function to send data through the pipe communicating with the game engine process
wchar_t widechar_buffer[256];
wchar_t *line_pointer;
char ascii_buffer[256];
unsigned long amount_written;
player->sendbuffer_locked = true; // lock the buffer
// write what we're sending (if we're sending anything)
if (player->sendbuffer[0] != 0)
Debug_Log (L"====================================SENDING:===================================\n%s\n", player->sendbuffer);
// now read line per line...
line_pointer = player->sendbuffer; // start at the first character
while ((line_pointer = wcsgets (widechar_buffer, WCHAR_SIZEOF (widechar_buffer), line_pointer)) != NULL)
{
wcscat_s (widechar_buffer, WCHAR_SIZEOF (widechar_buffer), L"\n"); // put the carriage return back
ConvertTo7BitASCII (ascii_buffer, sizeof (ascii_buffer), widechar_buffer); // convert to ASCII
WriteFile (hChessEngineStdinWr, ascii_buffer, strlen (ascii_buffer), &amount_written, NULL); // send data
}
player->sendbuffer[0] = 0; // what we had to send has been sent, reset the send buffer
player->sendbuffer_locked = false; // and unlock it
return; // finished
}
static wchar_t *Move_BuildString (boardmove_t *move)
{
// helper function to build a move string to send to the engine from a particular board move. NOT THREAD SAFE.
static wchar_t output_string[8];
// construct the four first characters
swprintf_s (output_string, WCHAR_SIZEOF (output_string), L"%c%c%c%c",
L'a' + move->source[1], L'1' + move->source[0],
L'a' + move->target[1], L'1' + move->target[0]);
// append any eventual promotion
if (move->promotion_type == PART_ROOK)
wcscat_s (output_string, WCHAR_SIZEOF (output_string), L"r");
else if (move->promotion_type == PART_KNIGHT)
wcscat_s (output_string, WCHAR_SIZEOF (output_string), L"n");
else if (move->promotion_type == PART_BISHOP)
wcscat_s (output_string, WCHAR_SIZEOF (output_string), L"b");
else if (move->promotion_type == PART_QUEEN)
wcscat_s (output_string, WCHAR_SIZEOF (output_string), L"q");
return (output_string); // finished, return the move string
}