Shared Memory Specs

For programmers out there--this is how I've done the shared memory and external input.

The memory is shared in the file mappings: "fceu.GameMemBlock" (128k), "fceu.RAM" (2k), "fceu.BotInput" (4k), "fceu.XBuf" (the graphics buffer) (256*256+8), "fceu.ROM" (varies), "fceu.VROM" (varies). Probably the RAM and the BotInput are the only things you'll need to open.

You will want to use OpenFileMapping to get the data. This is a Windows NT kernel function, and so should be available under this name (or a very similar name) in whatever programming language you are using. Example in C/C++:

#include "windows.h"

int main(int argc, char* argv[])
{
	HANDLE mapBotInput;
	unsigned int * BotInput;

	//Get the shared memory
	mapBotInput = OpenFileMapping(FILE_MAP_ALL_ACCESS, false, "fceu.BotInput");
	if(!mapBotInput)
	{
		//Error
	}
	
	//Get a pointer to it
	BotInput = (unsigned int *) MapViewOfFile(mapBotInput, FILE_MAP_WRITE, 0, 0, 0);
	if(!BotInput)
	{
		//Error
	}

	//Now BotInput[] is available for reading/writing.
	
	//Cleanup
	UnmapViewOfFile(mapBotInput);
	CloseHandle(mapBotInput);
	BotInput = NULL;
}

The external input is read from fceu.BotInput. This is an array of 1024 uint32s. I'll use BotInput[x] to refer to the x-th value (0-based). A value of '0' in BotInput[0] means it's safe to write to BotInput. BotInput[1] through [1023] store the input in chronological order. The input format is: high word = 1 means load state (low word ignored currently), high word = 0 means 1 frame of input, where the 4th byte is controller 1 and the 3rd is controller 2. After writing the input, write the length of the input (i.e. the highest x such that BotInput[x] contains data) in BotInput[0]. (This is a good place to let your program idle, so windows will give the CPU to FCEU!) Then FCEU will run the input, writing '0' to BotInput[0] when it's done. Code is probably more explanatory:

	if(BotInput[0])
	{
		BotPointer++;
		switch(BotInput[BotPointer] >> 16)
		{
		case 0:
			joy[0] = BotInput[BotPointer] & 255;
			joy[1] = BotInput[BotPointer] >> 8;
			joy[2] = joy[3] = 0;
			FCEUI_FrameAdvance();
			break;
		case 1:
			FCEUI_LoadState(0);
			break;
		default:
			break;
		}

		if(BotPointer >= BotInput[0] || BotPointer >= 1023)
		{
			BotInput[0] = 0;
			BotPointer = 0;
		}
	}

#define JOY_A   	1
#define JOY_B   	2
#define JOY_SELECT      4
#define JOY_START       8
#define JOY_UP  	0x10
#define JOY_DOWN        0x20
#define JOY_LEFT        0x40
#define JOY_RIGHT       0x80

If you're confused by "high word" and "low word" or whatver, note that LoadState is just a value of 65536, player 1 A is 1, player 1 right is 128, player 2 A is 256, player 2 right is 32768.

I recommend always loading the save state when you start your bot, so you know where you're starting from!

Example bot code:

	BotInput[1] = 65536; //Load state
	BotInput[2] = 1;     //First frame = player 1 A
	BotInput[3] = 2;     //Second frame = player 1 B
	BotInput[4] = 3;     //Third frame = player 1 AB

	BotInput[0] = 4;     //Tell FCEU to read 4 values from BotInput
	
	while(BotInput[0] != 0) //Wait for FCEU to write 0 to BotInput[0]
	{
		Sleep(1);       //It's a good idea to idle while you wait.
	}

	//Now you can write to BotInput again.