Improved Lua backend with intervals

3 files changed, 318 insertions, 26 deletions

diff --git a/backends/lua.c b/backends/lua.c
index ae2d460..08d8d3c 100644
--- a/backends/lua.c
+++ b/backends/lua.c
@@ -1,10 +1,18 @@
 #include <string.h>
+#include <sys/timerfd.h>
+#include <unistd.h>
+#include <errno.h>
 #include "lua.h"
 
 #define BACKEND_NAME "lua"
 #define LUA_REGISTRY_KEY "_midimonster_lua_instance"
 
-//TODO instance identification for callvacks
+static size_t timers = 0;
+static lua_timer* timer = NULL;
+static struct itimerspec timer_config = {
+	0
+};
+static int timer_fd = -1;
 
 int init(){
 	backend lua = {
@@ -24,31 +32,83 @@ int init(){
 		fprintf(stderr, "Failed to register lua backend\n");
 		return 1;
 	}
+
+	//create the timer to expire intervals
+	timer_fd = timerfd_create(CLOCK_MONOTONIC, TFD_NONBLOCK);
+	if(timer_fd < 0){
+		fprintf(stderr, "Failed to create timer for Lua backend\n");
+		return 1;
+	}
+	return 0;
+}
+
+static int lua_update_timerfd(){
+	uint64_t interval = 0, gcd, residual;
+	size_t n = 0;
+
+	//find the minimum for the lower interval bounds
+	for(n = 0; n < timers; n++){
+		if(timer[n].interval && (!interval || timer[n].interval < interval)){
+			interval = timer[n].interval;
+		}
+	}
+
+	//stop the timer
+	if(!interval){
+		memset(&timer_config, 0, sizeof(struct itimerspec));
+	}
+	//calculate gcd of all timers
+	else{
+		for(n = 0; n < timers; n++){
+			if(timer[n].interval){
+				//calculate gcd of current interval and this timers interval
+				gcd = timer[n].interval;
+				while(gcd){
+					residual = interval % gcd;
+					interval = gcd;
+					gcd = residual;
+				}
+				//since we round everything, 10 is the lowest interval we get
+				if(interval == 10){
+					break;
+				}
+			}
+		}
+
+		timer_config.it_interval.tv_sec = interval / 1000;
+		timer_config.it_interval.tv_nsec = (interval % 1000) * 1e6;
+		timer_config.it_value.tv_nsec = 1;
+	}
+
+	//configure the new interval
+	timerfd_settime(timer_fd, 0, &timer_config, NULL);
 	return 0;
 }
 
 static int lua_callback_output(lua_State* interpreter){
-	int arguments = lua_gettop(interpreter);
-	size_t n;
+	size_t n = 0;
 	channel_value val;
 	const char* channel_name = NULL;
 	channel* channel = NULL;
 	instance* inst = NULL;
 	lua_instance_data* data = NULL;
 
-	if(arguments != 2){
-		fprintf(stderr, "Lua output function called with %d arguments, expected 2\n", arguments);
+	if(lua_gettop(interpreter) != 2){
+		fprintf(stderr, "Lua output function called with %d arguments, expected 2 (string, number)\n", lua_gettop(interpreter));
 		return 0;
 	}
 
-	channel_name = lua_tostring(interpreter, 1);
-	val.normalised = clamp(lua_tonumber(interpreter, 2), 1.0, 0.0);
-
+	//get instance pointer from registry
 	lua_pushstring(interpreter, LUA_REGISTRY_KEY);
 	lua_gettable(interpreter, LUA_REGISTRYINDEX);
-	inst = (instance *) lua_touserdata(interpreter, -1);
+	inst = (instance*) lua_touserdata(interpreter, -1);
 	data = (lua_instance_data*) inst->impl;
 
+	//fetch function parameters
+	channel_name = lua_tostring(interpreter, 1);
+	val.normalised = clamp(luaL_checknumber(interpreter, 2), 1.0, 0.0);
+
+	//find correct channel & output value
 	for(n = 0; n < data->channels; n++){
 		if(!strcmp(channel_name, data->channel_name[n])){
 			channel = mm_channel(inst, n, 0);
@@ -56,6 +116,7 @@ static int lua_callback_output(lua_State* interpreter){
 				return 0;
 			}
 			mm_channel_event(channel, val);
+			data->output[n] = val.normalised;
 			return 0;
 		}
 	}
@@ -64,6 +125,122 @@ static int lua_callback_output(lua_State* interpreter){
 	return 0;
 }
 
+static int lua_callback_interval(lua_State* interpreter){
+	size_t n = 0;
+	instance* inst = NULL;
+	lua_instance_data* data = NULL;
+	uint64_t interval = 0;
+	int reference = LUA_NOREF;
+
+	if(lua_gettop(interpreter) != 2){
+		fprintf(stderr, "Lua output function called with %d arguments, expected 2 (string, number)\n", lua_gettop(interpreter));
+		return 0;
+	}
+
+	//get instance pointer from registry
+	lua_pushstring(interpreter, LUA_REGISTRY_KEY);
+	lua_gettable(interpreter, LUA_REGISTRYINDEX);
+	inst = (instance*) lua_touserdata(interpreter, -1);
+	data = (lua_instance_data*) inst->impl;
+
+	//fetch and round the interval
+	interval = luaL_checkinteger(interpreter, 2);
+	if(interval % 10 < 5){
+		interval -= interval % 10;
+	}
+	else{
+		interval += (10 - (interval % 10));
+	}
+
+	//push the function again
+	lua_pushvalue(interpreter, 1);
+	if(lua_gettable(interpreter, LUA_REGISTRYINDEX) == LUA_TNUMBER){
+		//already interval'd
+		reference = luaL_checkinteger(interpreter, 4);
+	}
+	else if(interval){
+		//get a reference to the function
+		lua_pushvalue(interpreter, 1);
+		reference = luaL_ref(interpreter, LUA_REGISTRYINDEX);
+
+		//the function indexes the reference
+		lua_pushvalue(interpreter, 1);
+		lua_pushinteger(interpreter, reference);
+		lua_settable(interpreter, LUA_REGISTRYINDEX);
+	}
+
+	//find matching timer
+	for(n = 0; n < timers; n++){
+		if(timer[n].reference == reference && timer[n].interpreter == interpreter){
+			break;
+		}
+	}
+
+	if(n < timers){
+		//set new interval
+		timer[n].interval = interval;
+		timer[n].delta = 0;
+	}
+	else if(interval){
+		//append new timer
+		timer = realloc(timer, (timers + 1) * sizeof(lua_timer));
+		if(!timer){
+			fprintf(stderr, "Failed to allocate memory\n");
+			timers = 0;
+			return 0;
+		}
+		timer[timers].interval = interval;
+		timer[timers].delta = 0;
+		timer[timers].interpreter = interpreter;
+		timer[timers].reference = reference;
+		timers++;
+	}
+
+	//recalculate timerspec
+	lua_update_timerfd();
+	return 0;
+}
+
+static int lua_callback_value(lua_State* interpreter, uint8_t input){
+	size_t n = 0;
+	instance* inst = NULL;
+	lua_instance_data* data = NULL;
+	const char* channel_name = NULL;
+
+	if(lua_gettop(interpreter) != 1){
+		fprintf(stderr, "Lua get_value function called with %d arguments, expected 1 (string)\n", lua_gettop(interpreter));
+		return 0;
+	}
+
+	//get instance pointer from registry
+	lua_pushstring(interpreter, LUA_REGISTRY_KEY);
+	lua_gettable(interpreter, LUA_REGISTRYINDEX);
+	inst = (instance*) lua_touserdata(interpreter, -1);
+	data = (lua_instance_data*) inst->impl;
+
+	//fetch argument
+	channel_name = lua_tostring(interpreter, 1);
+
+	//find correct channel & return value
+	for(n = 0; n < data->channels; n++){
+		if(!strcmp(channel_name, data->channel_name[n])){
+			lua_pushnumber(data->interpreter, (input) ? data->input[n] : data->output[n]);
+			return 1;
+		}
+	}
+
+	fprintf(stderr, "Tried to get unknown channel %s.%s\n", inst->name, channel_name);
+	return 0;
+}
+
+static int lua_callback_input_value(lua_State* interpreter){
+	return lua_callback_value(interpreter, 1);
+}
+
+static int lua_callback_output_value(lua_State* interpreter){
+	return lua_callback_value(interpreter, 0);
+}
+
 static int lua_configure(char* option, char* value){
 	fprintf(stderr, "The lua backend does not take any global configuration\n");
 	return 1;
@@ -72,6 +249,7 @@ static int lua_configure(char* option, char* value){
 static int lua_configure_instance(instance* inst, char* option, char* value){
 	lua_instance_data* data = (lua_instance_data*) inst->impl;
 
+	//load a lua file into the interpreter
 	if(!strcmp(option, "script")){
 		if(luaL_dofile(data->interpreter, value)){
 			fprintf(stderr, "Failed to load lua source file %s for instance %s: %s\n", value, inst->name, lua_tostring(data->interpreter, -1));
@@ -105,13 +283,16 @@ static instance* lua_instance(){
 	}
 	luaL_openlibs(data->interpreter);
 
-	//register lua api functions
+	//register lua interface functions
 	lua_register(data->interpreter, "output", lua_callback_output);
+	lua_register(data->interpreter, "interval", lua_callback_interval);
+	lua_register(data->interpreter, "input_value", lua_callback_input_value);
+	lua_register(data->interpreter, "output_value", lua_callback_output_value);
 
 	//store instance pointer to the lua state
 	lua_pushstring(data->interpreter, LUA_REGISTRY_KEY);
 	lua_pushlightuserdata(data->interpreter, (void *) inst);
-	lua_settable(data->interpreter, LUA_REGISTRYINDEX);   
+	lua_settable(data->interpreter, LUA_REGISTRYINDEX);
 
 	inst->impl = data;
 	return inst;
@@ -131,11 +312,16 @@ static channel* lua_channel(instance* inst, char* spec){
 	//allocate new channel
 	if(u == data->channels){
 		data->channel_name = realloc(data->channel_name, (u + 1) * sizeof(char*));
-		if(!data->channel_name){
+		data->reference = realloc(data->reference, (u + 1) * sizeof(int));
+		data->input = realloc(data->input, (u + 1) * sizeof(double));
+		data->output = realloc(data->output, (u + 1) * sizeof(double));
+		if(!data->channel_name || !data->reference || !data->input || !data->output){
 			fprintf(stderr, "Failed to allocate memory\n");
 			return NULL;
 		}
 
+		data->reference[u] = LUA_NOREF;
+		data->input[u] = data->output[u] = 0.0;
 		data->channel_name[u] = strdup(spec);
 		if(!data->channel_name[u]){
 			fprintf(stderr, "Failed to allocate memory\n");
@@ -151,25 +337,91 @@ static int lua_set(instance* inst, size_t num, channel** c, channel_value* v){
 	size_t n = 0;
 	lua_instance_data* data = (lua_instance_data*) inst->impl;
 
+	//handle all incoming events
 	for(n = 0; n < num; n++){
-		//call lua channel handlers
-		lua_getglobal(data->interpreter, data->channel_name[c[n]->ident]);
-		lua_pushnumber(data->interpreter, v[n].normalised);
-		if(lua_pcall(data->interpreter, 1, 0, 0) != LUA_OK){
-			fprintf(stderr, "Failed to call handler for %s.%s: %s\n", inst->name, data->channel_name[c[n]->ident], lua_tostring(data->interpreter, -1));
-			lua_pop(data->interpreter, 1);
+		data->input[c[n]->ident] = v[n].normalised;
+		//call lua channel handlers if present
+		if(data->reference[n] != LUA_NOREF){
+			lua_rawgeti(data->interpreter, LUA_REGISTRYINDEX, data->reference[c[n]->ident]);
+			lua_pushnumber(data->interpreter, v[n].normalised);
+			if(lua_pcall(data->interpreter, 1, 0, 0) != LUA_OK){
+				fprintf(stderr, "Failed to call handler for %s.%s: %s\n", inst->name, data->channel_name[c[n]->ident], lua_tostring(data->interpreter, -1));
+				lua_pop(data->interpreter, 1);
+			}
 		}
 	}
 	return 0;
 }
 
 static int lua_handle(size_t num, managed_fd* fds){
-	//TODO call timer callbacks
+	uint8_t read_buffer[100];
+	uint64_t delta = timer_config.it_interval.tv_sec * 1000 + timer_config.it_interval.tv_nsec / 1e6;
+	size_t n;
+
+	if(!num){
+		return 0;
+	}
+
+	//read the timer iteration to acknowledge the fd
+	if(read(timer_fd, read_buffer, sizeof(read_buffer)) < 0){
+		fprintf(stderr, "Failed to read from Lua timer: %s\n", strerror(errno));
+		return 1;
+	}
+
+	//add delta to all active timers
+	for(n = 0; n < timers; n++){
+		if(timer[n].interval){
+			timer[n].delta += delta;
+			//call lua function if timer expired
+			if(timer[n].delta >= timer[n].interval){
+				timer[n].delta %= timer[n].interval;
+				lua_rawgeti(timer[n].interpreter, LUA_REGISTRYINDEX, timer[n].reference);
+				lua_pcall(timer[n].interpreter, 0, 0, 0);
+			}
+		}
+	}
 	return 0;
 }
 
 static int lua_start(){
-	//TODO start timers / register fds
+	size_t n, u, p;
+	instance** inst = NULL;
+	lua_instance_data* data = NULL;
+
+	//fetch all defined instances
+	if(mm_backend_instances(BACKEND_NAME, &n, &inst)){
+		fprintf(stderr, "Failed to fetch instance list\n");
+		return 1;
+	}
+
+	//resolve channels to their handler functions
+	for(u = 0; u < n; u++){
+		data = (lua_instance_data*) inst[u]->impl;
+		for(p = 0; p < data->channels; p++){
+			//exclude reserved names
+			if(strcmp(data->channel_name[p], "output")
+					&& strcmp(data->channel_name[p], "input_value")
+					&& strcmp(data->channel_name[p], "output_value")
+					&& strcmp(data->channel_name[p], "interval")){
+				lua_getglobal(data->interpreter, data->channel_name[p]);
+				data->reference[p] = luaL_ref(data->interpreter, LUA_REGISTRYINDEX);
+				if(data->reference[p] == LUA_REFNIL){
+					data->reference[p] = LUA_NOREF;
+				}
+			}
+		}
+	}
+
+	free(inst);
+	if(!n){
+		return 0;
+	}
+
+	//register the timer with the core
+	fprintf(stderr, "Lua backend registering 1 descriptor to core\n");
+	if(mm_manage_fd(timer_fd, BACKEND_NAME, 1, NULL)){
+		return 1;
+	}
 	return 0;
 }
 
@@ -178,6 +430,7 @@ static int lua_shutdown(){
 	instance** inst = NULL;
 	lua_instance_data* data = NULL;
 
+	//fetch all instances
 	if(mm_backend_instances(BACKEND_NAME, &n, &inst)){
 		fprintf(stderr, "Failed to fetch instance list\n");
 		return 1;
@@ -192,10 +445,19 @@ static int lua_shutdown(){
 			free(data->channel_name[p]);
 		}
 		free(data->channel_name);
+		free(data->reference);
+		free(data->input);
+		free(data->output);
 		free(inst[u]->impl);
 	}
 
 	free(inst);
+	//free module-global data
+	free(timer);
+	timer = NULL;
+	timers = 0;
+	close(timer_fd);
+	timer_fd = -1;
 
 	fprintf(stderr, "Lua backend shut down\n");
 	return 0;
diff --git a/backends/lua.h b/backends/lua.h
index 27e1afd..ccffef7 100644
--- a/backends/lua.h
+++ b/backends/lua.h
@@ -17,5 +17,15 @@ static int lua_shutdown();
 typedef struct /*_lua_instance_data*/ {
 	size_t channels;
 	char** channel_name;
+	int* reference;
+	double* input;
+	double* output;
 	lua_State* interpreter;
 } lua_instance_data;
+
+typedef struct /*_lua_interval_callback*/ {
+	uint64_t interval;
+	uint64_t delta;
+	lua_State* interpreter;
+	int reference;
+} lua_timer;
diff --git a/backends/lua.md b/backends/lua.md
index 91e8fe2..970e8e2 100644
--- a/backends/lua.md
+++ b/backends/lua.md
@@ -5,15 +5,32 @@ events using the Lua programming language.
 
 Every instance has it's own interpreter state which can be loaded with custom handler scripts.
 
-To process incoming channel events, the MIDIMonster calls corresponding Lua functions with
-the value (as a Lua `number` type) as parameter. To send output on a channel, the Lua environment
-provides the function `output(channel-name, value)`.
+To process incoming channel events, the MIDIMonster calls corresponding Lua functions (if they exist)
+with the value (as a Lua `number` type) as parameter.
+
+The following functions are provided within the Lua interpreter for interaction with the MIDIMonster
+
+| Function			| Usage example			| Description				|
+|-------------------------------|-------------------------------|---------------------------------------|
+| `output(string, number)`	| `output("foo", 0.75)`		| Output a value event to a channel	|
+| `interval(function, number)`	| `interval(update, 100)`	| Register a function to be called periodically. Intervals are milliseconds (rounded to the nearest 10 ms) |
+| `input_value(string)`		| `input_value("foo")`		| Get the last input value on a channel	|
+| `output_value(string)`	| `output_value("bar")		| Get the last output value on a channel |
+
 
 Example script:
 ```
 function bar(value)
 	output("foo", value / 2)
 end
+
+step = 0
+function toggle()
+	output("bar", step * 1.0)
+	step = (step + 1) % 2;
+end
+
+interval(toggle, 1000)
 ```
 
 Input values range between 0.0 and 1.0, output values are clamped to the same range.
@@ -41,9 +58,12 @@ lua1.foo > lua2.bar
 
 #### Known bugs / problems
 
-Using `output` as an input channel name to a Lua instance does not work, as the interpreter has
-`output` globally assigned to the event output function. Using `output` as an output channel name
-via `output("output", value)` works as intended.
+Using any of the interface functions (`output`, `interval`, `input\_value`, `output\_value`) as an
+input channel name to a Lua instance will not call any handler functions.
+Using these names as arguments to the output and value interface functions works as intended.
+
+Output values will not trigger corresponding input event handlers unless the channel is mapped
+back in the MIDIMonster configuration.
 
 The path to the Lua source files is relative to the current working directory. This may lead
 to problems when copying configuration between installations.