Make the program unaware in compile time of the node types

Using "constructor" attribute

Makefile

@@ -12,7 +12,7 @@ CPPFLAGS += $(shell pkg-config --cflags $(DEPS))
 LDLIBS += $(shell pkg-config --libs $(DEPS))
 INTERP ?=
 MAIN = main
-OBJS = main.o events.o processing.o graph.o config.o hash_table.o nodes/getchar.o nodes/print.o nodes/evdev.o
+OBJS = main.o events.o processing.o graph.o config.o hash_table.o module_registry.o nodes/getchar.o nodes/print.o nodes/evdev.o
 
 all: $(MAIN)
 

defs.h

@@ -15,6 +15,8 @@
 #define IMPLICIT_CAST(dsttype, srctype, ptr) (((union { typeof(srctype) *src; typeof(dsttype) *dst; }){.src = ptr}).dst)
 #define T_ALLOC(count, T) ((T*)calloc(count, sizeof(T)))
 
+#define MODULE_CONSTRUCTOR(name) __attribute__((constructor)) static void name(void)
+
 #define DEBUG_PRINT_VALUE(x, fmt) fprintf(stderr, #x " = " fmt "\n", x); fflush(stderr)
 
 #endif /* end of include guard: DEFS_H_ */

main.c

@@ -1,14 +1,6 @@
 #include "processing.h"
 #include "hash_table.h"
-#include "nodes/print.h"
-#include "nodes/getchar.h"
-#include "nodes/evdev.h"
-
-GraphNodeSpecification *node_specifications[] = {
-	&nodespec_getchar,
-	&nodespec_print,
-	&nodespec_evdev,
-};
+#include "module_registry.h"
 
 int
 main(int argc, char ** argv)
@@ -42,13 +34,7 @@ main(int argc, char ** argv)
 			fprintf(stderr, "No node type for node %ld \"%s\"\n", i, loaded_config.nodes.items[i].name);
 			exit(1);
 		}
-		GraphNodeSpecification *spec = NULL;
-		for (size_t j = 0; j < lengthof(node_specifications); ++j) {
-			if (strcmp(type_name, node_specifications[j]->name) == 0) {
-				spec = node_specifications[j];
-				break;
-			}
-		}
+		GraphNodeSpecification *spec = lookup_graph_node_specification(type_name);
 		if (!spec) {
 			fprintf(stderr, "Unknown node type \"%s\" for node %ld \"%s\"\n", type_name, i, loaded_config.nodes.items[i].name);
 			exit(1);
@@ -103,5 +89,6 @@ main(int argc, char ** argv)
 
 	io_subscription_list_deinit(&state.wait_output);
 	io_subscription_list_deinit(&state.wait_input);
+	destroy_graph_node_specification_registry();
 	return 0;
 }

module_registry.c

@@ -0,0 +1,43 @@
+#include "module_registry.h"
+#include "hash_table.h"
+
+static TYPED_HASH_TABLE(GraphNodeSpecification*) registry;
+static bool initialized = false;
+
+static void
+ensure_initialized()
+{
+	if (!initialized) {
+		hash_table_init(&registry, NULL);
+		initialized = true;
+	}
+}
+
+void
+register_graph_node_specification(GraphNodeSpecification * spec)
+{
+	ensure_initialized();
+	if (!spec->name) {
+		return;
+	}
+	hash_table_insert(&registry, hash_table_key_from_cstr(spec->name), &spec);
+}
+
+GraphNodeSpecification *
+lookup_graph_node_specification(const char * name)
+{
+	ensure_initialized();
+	HashTableIndex idx = hash_table_find(&registry, hash_table_key_from_cstr(name));
+	if (idx < 0) {
+		return NULL;
+	}
+	return registry.value_array[idx];
+}
+
+void
+destroy_graph_node_specification_registry()
+{
+	ensure_initialized();
+	hash_table_deinit(&registry);
+	initialized = false;
+}

module_registry.h

@@ -0,0 +1,10 @@
+#ifndef MODULE_REGISTRY_H_
+#define MODULE_REGISTRY_H_
+
+#include "graph.h"
+
+void register_graph_node_specification(GraphNodeSpecification * spec);
+GraphNodeSpecification * lookup_graph_node_specification(const char * name);
+void destroy_graph_node_specification_registry();
+
+#endif /* end of include guard: MODULE_REGISTRY_H_ */

nodes/evdev.c

@@ -7,6 +7,7 @@
 #include <stdio.h>
 #include "evdev.h"
 #include "../processing.h"
+#include "../module_registry.h"
 
 typedef struct {
 	GraphNode as_GraphNode;
@@ -139,3 +140,8 @@ GraphNodeSpecification nodespec_evdev = (GraphNodeSpecification) {
 	.register_io = &register_io,
 	.name = "evdev",
 };
+
+MODULE_CONSTRUCTOR(init)
+{
+	register_graph_node_specification(&nodespec_evdev);
+}

nodes/getchar.c

@@ -2,6 +2,7 @@
 #include <unistd.h>
 #include "getchar.h"
 #include "../processing.h"
+#include "../module_registry.h"
 
 typedef struct {
 	GraphNode as_GraphNode;
@@ -98,3 +99,8 @@ GraphNodeSpecification nodespec_getchar = (GraphNodeSpecification) {
 	.register_io = &register_io,
 	.name = "getchar",
 };
+
+MODULE_CONSTRUCTOR(init)
+{
+	register_graph_node_specification(&nodespec_getchar);
+}

nodes/print.c

@@ -1,5 +1,6 @@
 #include <stdio.h>
 #include "print.h"
+#include "../module_registry.h"
 
 static bool
 handle_event(EventPositionBase * self, EventNode * event)
@@ -59,3 +60,8 @@ GraphNodeSpecification nodespec_print = (GraphNodeSpecification) {
 	.register_io = NULL,
 	.name = "print",
 };
+
+MODULE_CONSTRUCTOR(init)
+{
+	register_graph_node_specification(&nodespec_print);
+}