Implement Lua backend

1 files changed, 202 insertions, 0 deletions

diff --git a/backends/lua.c b/backends/lua.c
new file mode 100644
index 0000000..ae2d460
--- /dev/null
+++ b/backends/lua.c
@@ -0,0 +1,202 @@
+#include <string.h>
+#include "lua.h"
+
+#define BACKEND_NAME "lua"
+#define LUA_REGISTRY_KEY "_midimonster_lua_instance"
+
+//TODO instance identification for callvacks
+
+int init(){
+	backend lua = {
+		.name = BACKEND_NAME,
+		.conf = lua_configure,
+		.create = lua_instance,
+		.conf_instance = lua_configure_instance,
+		.channel = lua_channel,
+		.handle = lua_set,
+		.process = lua_handle,
+		.start = lua_start,
+		.shutdown = lua_shutdown
+	};
+
+	//register backend
+	if(mm_backend_register(lua)){
+		fprintf(stderr, "Failed to register lua backend\n");
+		return 1;
+	}
+	return 0;
+}
+
+static int lua_callback_output(lua_State* interpreter){
+	int arguments = lua_gettop(interpreter);
+	size_t n;
+	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);
+		return 0;
+	}
+
+	channel_name = lua_tostring(interpreter, 1);
+	val.normalised = clamp(lua_tonumber(interpreter, 2), 1.0, 0.0);
+
+	lua_pushstring(interpreter, LUA_REGISTRY_KEY);
+	lua_gettable(interpreter, LUA_REGISTRYINDEX);
+	inst = (instance *) lua_touserdata(interpreter, -1);
+	data = (lua_instance_data*) inst->impl;
+
+	for(n = 0; n < data->channels; n++){
+		if(!strcmp(channel_name, data->channel_name[n])){
+			channel = mm_channel(inst, n, 0);
+			if(!channel){
+				return 0;
+			}
+			mm_channel_event(channel, val);
+			return 0;
+		}
+	}
+
+	fprintf(stderr, "Tried to set unknown channel %s.%s\n", inst->name, channel_name);
+	return 0;
+}
+
+static int lua_configure(char* option, char* value){
+	fprintf(stderr, "The lua backend does not take any global configuration\n");
+	return 1;
+}
+
+static int lua_configure_instance(instance* inst, char* option, char* value){
+	lua_instance_data* data = (lua_instance_data*) inst->impl;
+
+	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));
+			return 1;
+		}
+		return 0;
+	}
+
+	fprintf(stderr, "Unknown configuration parameter %s for lua backend\n", option);
+	return 1;
+}
+
+static instance* lua_instance(){
+	instance* inst = mm_instance();
+	if(!inst){
+		return NULL;
+	}
+
+	lua_instance_data* data = calloc(1, sizeof(lua_instance_data));
+	if(!data){
+		fprintf(stderr, "Failed to allocate memory\n");
+		return NULL;
+	}
+
+	//load the interpreter
+	data->interpreter = luaL_newstate();
+	if(!data->interpreter){
+		fprintf(stderr, "Failed to initialize LUA\n");
+		free(data);
+		return NULL;
+	}
+	luaL_openlibs(data->interpreter);
+
+	//register lua api functions
+	lua_register(data->interpreter, "output", lua_callback_output);
+
+	//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);   
+
+	inst->impl = data;
+	return inst;
+}
+
+static channel* lua_channel(instance* inst, char* spec){
+	size_t u;
+	lua_instance_data* data = (lua_instance_data*) inst->impl;
+
+	//find matching channel
+	for(u = 0; u < data->channels; u++){
+		if(!strcmp(spec, data->channel_name[u])){
+			break;
+		}
+	}
+
+	//allocate new channel
+	if(u == data->channels){
+		data->channel_name = realloc(data->channel_name, (u + 1) * sizeof(char*));
+		if(!data->channel_name){
+			fprintf(stderr, "Failed to allocate memory\n");
+			return NULL;
+		}
+
+		data->channel_name[u] = strdup(spec);
+		if(!data->channel_name[u]){
+			fprintf(stderr, "Failed to allocate memory\n");
+			return NULL;
+		}
+		data->channels++;
+	}
+
+	return mm_channel(inst, u, 1);
+}
+
+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;
+
+	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);
+		}
+	}
+	return 0;
+}
+
+static int lua_handle(size_t num, managed_fd* fds){
+	//TODO call timer callbacks
+	return 0;
+}
+
+static int lua_start(){
+	//TODO start timers / register fds
+	return 0;
+}
+
+static int lua_shutdown(){
+	size_t n, u, p;
+	instance** inst = NULL;
+	lua_instance_data* data = NULL;
+
+	if(mm_backend_instances(BACKEND_NAME, &n, &inst)){
+		fprintf(stderr, "Failed to fetch instance list\n");
+		return 1;
+	}
+
+	for(u = 0; u < n; u++){
+		data = (lua_instance_data*) inst[u]->impl;
+		//stop the interpreter
+		lua_close(data->interpreter);
+		//cleanup channel data
+		for(p = 0; p < data->channels; p++){
+			free(data->channel_name[p]);
+		}
+		free(data->channel_name);
+		free(inst[u]->impl);
+	}
+
+	free(inst);
+
+	fprintf(stderr, "Lua backend shut down\n");
+	return 0;
+}