Added entity queries by tag, tests for queries and tests for tagging.

action.bash

@@ -133,6 +133,9 @@ case $1 in
     "b" | "build-dependencies")
         build_dependencies
         ;;
+    "t" | "test")
+        ./build_tests.bash
+        ;;
     "h" | "help")
         echo "Known Actions:"
         echo "[ d | dbg | debug ]:        Build in the debug profile; build with debug symbols."

build_tests.bash

@@ -4,6 +4,7 @@ cd $(dirname "$(pwd)/$0")
 REPOSITORY_FOLDER=$(pwd)
 
 MAIN_OBJECTS_FOLDER="$REPOSITORY_FOLDER/.build/objects/"
+CC_OPTIONS="-g3 -Wall -Wextra -Wpedantic"
 DEFAULT_INCLUDE_PATHS="
 -I .build/depends/libRR/Core/core/exports/
 -I .build/depends/libRR/Core/platform/exports/
@@ -55,7 +56,7 @@ function compile_single_test() {
 
     get_include_path_configuration $TEST_PATH
     get_linkage_path_configuration $TEST_PATH
-    gcc -g3 -o $TEST_PATH/$TEST_NAME.elf $TEST_PATH/*.c $LINKAGE_PATHS $INCLUDE_STATEMENTS
+    gcc $CC_OPTIONS -o $TEST_PATH/$TEST_NAME.elf $TEST_PATH/*.c $LINKAGE_PATHS $INCLUDE_STATEMENTS
 }
 
 function compile_all_tests_of_module() {

core/build-config/tests.txt

@@ -1,3 +1,5 @@
 tests/internal/basic-tag-registry-usage
 tests/internal/entity-lookup
+tests/interface/entity-queries
 tests/interface/entity-creation
+tests/interface/entity-tagging-api

core/exports/maintree/maintree.h

@@ -6,14 +6,15 @@
 #include <librr/types.h>
 #include <librr/linear_algebra.h>
 
-typedef void *          MtEntity;
+typedef void           MtEntity;
 
 /// @brief: An MtTask is a piece of functionality with an own state/context which will be executed on the same thread or set of threads.
-typedef void *          MtTask;
-typedef void *          MtState;
+typedef void           MtTask;
+typedef void           MtState;
 
-typedef void (*MtEffectorFn) (MtEntity entity, void *userdata, usz_t invocation_id);
-typedef void (*MtTaskMainFn) (MtTask task, void *userdata);
+typedef void (*MtEffectorFn) (MtEntity *entity, void *userdata, usz_t invocation_id);
+typedef void (*MtTaskMainFn) (MtTask *task, void *userdata);
+typedef bool_t (*MtQueryMatcherFn) (MtEntity *entity, void *userdata);
 
 typedef struct
 {
@@ -27,18 +28,18 @@ typedef struct
 
 
 
-MtState mt_initialize(char *app_name);
-void mt_cleanup(MtState state);
-void mt_start(MtState state);
+MtState * mt_initialize(char *app_name);
+void mt_cleanup(MtState *state);
+void mt_start(MtState *state);
 
-MtEntity mt_summon(MtState state);
-void mt_drop(MtEntity entity);
+MtEntity * mt_summon(MtState *state);
+void mt_drop(MtEntity *entity);
 
-void mt_add_create_effector(MtState state, char *effector_name, MtEffectorFn function, void *userdata);
-void mt_add_delete_effector(MtState state, char *effector_name, MtEffectorFn function, void *userdata);
-void mt_add_entity_effector(MtState state, char *effector_name, usz_t ticks_delta, MtEffectorFn function, void *userdata);
-void mt_add_tick_effector(MtState state, char *effector_name, usz_t ticks_delta, MtEffectorFn function, void *userdata);
-void mt_remove_effector(MtState state, const char *effector_name);
+void mt_add_create_effector(MtState *state, char *effector_name, MtEffectorFn function, void *userdata);
+void mt_add_delete_effector(MtState *state, char *effector_name, MtEffectorFn function, void *userdata);
+void mt_add_entity_effector(MtState *state, char *effector_name, usz_t ticks_delta, MtEffectorFn function, void *userdata);
+void mt_add_tick_effector(MtState *state, char *effector_name, usz_t ticks_delta, MtEffectorFn function, void *userdata);
+void mt_remove_effector(MtState *state, const char *effector_name);
 
 /// @brief Adds a tick effector which only acts upon entitys with certain tags.
 /// @param state The state in which the tick effector should reside.
@@ -46,29 +47,32 @@ void mt_remove_effector(MtState state, const char *effector_name);
 /// @param ticks_delta The wanted number of ticks between two invocations of the effector.
 /// @param function The function to call for an entity if it contains all necessary tags.
 /// @param tag_names A nullpointer-terminated list of tag-ids that must be present in an entity for that entity to be effected.
-void mt_add_tagged_tick_effector(MtState state, char *effector_name, usz_t ticks_delta, MtEffectorFn function, char **tag_names);
+void mt_add_tagged_tick_effector(MtState *state, char *effector_name, usz_t ticks_delta, MtEffectorFn function, char **tag_names);
 
-void mt_tag_i64(MtEntity entity, char *name, i64_t integer);
-void mt_tag_f64(MtEntity entity, char *name, f64_t real);
-void mt_tag_str(MtEntity entity, char *name, char *string);
-void mt_tag_ptr(MtEntity entity, char *name, void *pointer);
-void mt_tag_vec2(MtEntity entity, char *name, rr_vec2f_s vector);
-void mt_tag_vec3(MtEntity entity, char *name, rr_vec3f_s vector);
-void mt_tag_vec4(MtEntity entity, char *name, rr_vec4f_s vector);
+usz_t mt_query(MtState *state, const char **tags, MtEntity **entities, usz_t count);
+usz_t mt_match_query(MtState *state, const char **tags, MtEntity **entities, usz_t count, MtQueryMatcherFn matcher, void *userdata);
 
-void mt_untag(MtEntity entity, char *name);
+void mt_tag_i64(MtEntity *entity, char *name, i64_t integer);
+void mt_tag_f64(MtEntity *entity, char *name, f64_t real);
+void mt_tag_str(MtEntity *entity, char *name, char *string);
+void mt_tag_ptr(MtEntity *entity, char *name, void *pointer);
+void mt_tag_vec2(MtEntity *entity, char *name, rr_vec2f_s vector);
+void mt_tag_vec3(MtEntity *entity, char *name, rr_vec3f_s vector);
+void mt_tag_vec4(MtEntity *entity, char *name, rr_vec4f_s vector);
 
-i64_t mt_get_i64_tag(MtEntity entity, char *name);
-f64_t mt_get_f64_tag(MtEntity entity, char *name);
-char * mt_get_str_tag(MtEntity entity, char *name);
-void * mt_get_ptr_tag(MtEntity entity, char *name);
-rr_vec2f_s mt_get_vec2_tag(MtEntity entity, char *name);
-rr_vec3f_s mt_get_vec3_tag(MtEntity entity, char *name);
-rr_vec4f_s mt_get_vec4_tag(MtEntity entity, char *name);
+void mt_untag(MtEntity *entity, char *name);
 
-MtTask mt_create_task(MtState state, MtTaskCreationInfo creation_info);
-void mt_delete_task(MtTask task);
+i64_t mt_get_i64_tag(MtEntity *entity, char *name);
+f64_t mt_get_f64_tag(MtEntity *entity, char *name);
+char * mt_get_str_tag(MtEntity *entity, char *name);
+void * mt_get_ptr_tag(MtEntity *entity, char *name);
+rr_vec2f_s mt_get_vec2_tag(MtEntity *entity, char *name);
+rr_vec3f_s mt_get_vec3_tag(MtEntity *entity, char *name);
+rr_vec4f_s mt_get_vec4_tag(MtEntity *entity, char *name);
 
-void mt_task_remove_effector(MtTask task, const char *effector_name);
+MtTask mt_create_task(MtState *state, MtTaskCreationInfo creation_info);
+void mt_delete_task(MtTask *task);
+
+void mt_task_remove_effector(MtTask *task, const char *effector_name);
 
 #endif // MAINTREE_H

core/inc-c/entity.h

@@ -89,6 +89,7 @@ void mt_tag_vec2(MtEntity *entity, char *name, rr_vec2f_s vector);
 void mt_tag_vec3(MtEntity *entity, char *name, rr_vec3f_s vector);
 void mt_tag_vec4(MtEntity *entity, char *name, rr_vec4f_s vector);
 
+bool_t mt_has_tag(MtEntity *entity, const char *name);
 void mt_untag(MtEntity *entity, char *name);
 
 i64_t mt_get_i64_tag(MtEntity *entity, char *name);

core/inc-c/state.h

@@ -9,6 +9,7 @@
 #include <librr/alloc/generic.h>
 
 typedef struct MtState          MtState;
+typedef bool_t (*MtQueryMatcherFn) (MtEntity *entity, void *userdata);
 
 struct MtState
 {
@@ -25,4 +26,7 @@ void mt_start(MtState *state);
 MtEntity * mt_summon(MtState *state);
 void mt_drop(MtEntity *entity);
 
+usz_t mt_query(MtState *state, const char **tags, MtEntity **entities, usz_t count);
+usz_t mt_match_query(MtState *state, const char **tags, MtEntity **entities, usz_t count, MtQueryMatcherFn matcher, void *userdata);
+
 #endif // MT_STATE_H

core/inc-c/tag_registry.h

@@ -30,6 +30,11 @@ struct MtTagEntry
 {
     u32_t                       identifier;
     char                       *label;
+
+    usz_t                       entities_capacity;
+    usz_t                       num_entities;
+    /// @brief An array ofhe identifiers of all entities which have a tag of this type.
+    u32_t                      *entity_identifiers;
 };
 
 struct MtTagCollection
@@ -37,7 +42,7 @@ struct MtTagCollection
     u32_t                       capacity;
     u32_t                       usage;
 
-    /// @brief An array of indices for the tag-registry's 'entries'-array.
+    /// @brief An array of indices into the tag-registry's 'entries'-array.
     u32_t                      *tag_indices;
 };
 
@@ -46,5 +51,9 @@ void mt_delete_tag_registry(MtTagRegistry registry);
 
 u32_t mt_get_tag_id(MtTagRegistry *registry, const char *tag_label);
 const char * mt_get_tag_label(MtTagRegistry *registry, u32_t tag_identifier);
+MtTagEntry * mt_get_tag_entry(MtTagRegistry *registry, const char *tag_label);
+
+void mt_add_entity_to_tag_lookup_list(MtTagRegistry *registry, const char *tag_label, u32_t entity_identifier);
+void mt_remove_entity_from_tag_lookup_list(MtTagRegistry *registry, const char *tag_label, u32_t entity_identifier);
 
 #endif // MT_TAG_REGISTRY_H

core/src-c/entity_registry.c

@@ -89,6 +89,7 @@ void mt_delete_entity_data(MtEntity *entity)
 {
     if(entity->tags != NULL)
         free(entity->tags);
+    entity->tags = NULL;
 }
 
 

core/src-c/entity_tagging.c

@@ -20,6 +20,8 @@ i16_t mt_get_entity_tag_slot_index(MtEntity *entity, const char *name)
 
 MtTag * mt_get_entity_tag_slot(MtEntity *entity, char *name)
 {
+    MtState *state = entity->parent_state;
+
     i16_t tag_slot_index = mt_get_entity_tag_slot_index(entity, name);
     if(tag_slot_index >= 0)
         return &entity->tags[tag_slot_index];
@@ -34,51 +36,87 @@ MtTag * mt_get_entity_tag_slot(MtEntity *entity, char *name)
 
         entity->tags = realloc(entity->tags, sizeof(struct MtTag) * entity->tags_capacity);
     }
+    entity->tags[entity->num_tags].identifier = mt_get_tag_id(&state->tag_registry, name);
     return &entity->tags[entity->num_tags++];
 }
 
 void mt_tag_i64(MtEntity *entity, char *name, i64_t integer)
 {
+    MtState *state = entity->parent_state;
     MtTag *tag = mt_get_entity_tag_slot(entity, name);
+
+    mt_add_entity_to_tag_lookup_list(&state->tag_registry, name, entity->identifier);
     tag->data.integer = integer;
 }
 
 void mt_tag_f64(MtEntity *entity, char *name, f64_t real)
 {
+    MtState *state = entity->parent_state;
     MtTag *tag = mt_get_entity_tag_slot(entity, name);
+
+    mt_add_entity_to_tag_lookup_list(&state->tag_registry, name, entity->identifier);
     tag->data.real = real;
 }
 
 void mt_tag_str(MtEntity *entity, char *name, char *string)
 {
+    MtState *state = entity->parent_state;
     MtTag *tag = mt_get_entity_tag_slot(entity, name);
+
+    mt_add_entity_to_tag_lookup_list(&state->tag_registry, name, entity->identifier);
     tag->data.string = string;
 }
 
 void mt_tag_ptr(MtEntity *entity, char *name, void *pointer)
 {
+    MtState *state = entity->parent_state;
     MtTag *tag = mt_get_entity_tag_slot(entity, name);
+
+    mt_add_entity_to_tag_lookup_list(&state->tag_registry, name, entity->identifier);
     tag->data.pointer = pointer;
 }
 
 void mt_tag_vec2(MtEntity *entity, char *name, rr_vec2f_s vector)
 {
+    MtState *state = entity->parent_state;
     MtTag *tag = mt_get_entity_tag_slot(entity, name);
+
+    mt_add_entity_to_tag_lookup_list(&state->tag_registry, name, entity->identifier);
     tag->data.vec2f = vector;
 }
 
 void mt_tag_vec3(MtEntity *entity, char *name, rr_vec3f_s vector)
 {
+    MtState *state = entity->parent_state;
     MtTag *tag = mt_get_entity_tag_slot(entity, name);
+
+    mt_add_entity_to_tag_lookup_list(&state->tag_registry, name, entity->identifier);
     tag->data.vec3f = vector;
 }
 void mt_tag_vec4(MtEntity *entity, char *name, rr_vec4f_s vector)
 {
+    MtState *state = entity->parent_state;
     MtTag *tag = mt_get_entity_tag_slot(entity, name);
+
+    mt_add_entity_to_tag_lookup_list(&state->tag_registry, name, entity->identifier);
     tag->data.vec4f = vector;
 }
 
+bool_t mt_has_tag(MtEntity *entity, const char *name)
+{
+    MtState *state = entity->parent_state;
+    usz_t tag_id = mt_get_tag_id(&state->tag_registry, name);
 
+    usz_t tag_index = 0;
+    while(tag_index < entity->num_tags)
+    {
+        if(entity->tags[tag_index].identifier == tag_id)
+            return TRUE;
+
+        ++tag_index;
+    }
+    return FALSE;
+}
 
 void mt_untag(MtEntity *entity, char *name)
 {

core/src-c/queries.c

@@ -0,0 +1,107 @@
+#include <state.h>
+#include <entity.h>
+
+usz_t mt_find_tag_with_least_entries(MtState *state, const char **tags)
+{
+    u32_t least_entries_count = 0xffffffff;
+    usz_t least_entries_index = 0;
+
+    usz_t tag_index = 0;
+    while(tags[tag_index] != NULL)
+    {
+        MtTagEntry *tag_entry = mt_get_tag_entry(&state->tag_registry, tags[tag_index]);
+        if(tag_entry->num_entities > least_entries_count)
+        {
+            least_entries_count = tag_entry->num_entities;
+            least_entries_index = tag_index;
+        }
+        ++tag_index;
+    }
+    return least_entries_index;
+}
+
+usz_t mt_count_entities_with_matching_tags(MtState *state, const char **tags)
+{
+    usz_t num_matching_entities = 0;
+
+    const char *least_used_tag = tags[mt_find_tag_with_least_entries(state, tags)];
+    MtTagEntry *tag_entry = mt_get_tag_entry(&state->tag_registry, least_used_tag);
+    usz_t entity_index = 0;
+    while(entity_index < tag_entry->num_entities)
+    {
+        MtEntity *entity = mt_get_entity(state, tag_entry->entity_identifiers[entity_index]);
+        bool_t matching = TRUE;
+        usz_t wanted_tag_index = 0;
+        while(tags[wanted_tag_index] != NULL)
+        {
+            if(!mt_has_tag(entity, tags[wanted_tag_index]))
+            {
+                matching = FALSE;
+                break;
+            }
+            ++wanted_tag_index;
+        }
+        if(matching)
+            ++num_matching_entities;
+        
+        ++entity_index;
+    }
+    return num_matching_entities;
+}
+
+usz_t mt_query(MtState *state, const char **tags, MtEntity **entities, usz_t count)
+{
+    if(count == 0)
+        return mt_count_entities_with_matching_tags(state, tags);;
+    
+    usz_t num_written_entities = 0;
+    const char *least_used_tag = tags[mt_find_tag_with_least_entries(state, tags)];
+    MtTagEntry *tag_entry = mt_get_tag_entry(&state->tag_registry, least_used_tag);
+    usz_t entity_index = 0;
+    while((entity_index < tag_entry->num_entities) && (num_written_entities < count))
+    {
+        MtEntity *entity = mt_get_entity(state, tag_entry->entity_identifiers[entity_index]);
+        bool_t matching = TRUE;
+        usz_t wanted_tag_index = 0;
+        while(tags[wanted_tag_index] != NULL)
+        {
+            if(!mt_has_tag(entity, tags[wanted_tag_index]))
+            {
+                matching = FALSE;
+                break;
+            }
+            ++wanted_tag_index;
+        }
+        if(matching)
+        {
+            entities[num_written_entities] = entity;
+            ++num_written_entities;
+        }
+        ++entity_index;
+    }
+    return num_written_entities;
+}
+
+usz_t mt_match_query(MtState *state, const char **tags, MtEntity **entities, usz_t count, MtQueryMatcherFn matcher, void *userdata)
+{
+    usz_t num_matching_entities = mt_query(state, tags, entities, 0);
+    if(count == 0)
+        return num_matching_entities;
+    
+    // TODO: If 'num_matching_entities" is too big, this must be allocated on the heap!
+    MtEntity *generally_matching_entities[num_matching_entities];
+    mt_query(state, tags, &generally_matching_entities[0], num_matching_entities);
+    
+    usz_t written_entities = 0;
+    usz_t entity_index = 0;
+    while((entity_index < num_matching_entities) && (written_entities < count))
+    {
+        if(matcher(generally_matching_entities[entity_index], userdata))
+        {
+            entities[written_entities] = generally_matching_entities[entity_index];
+            ++written_entities;
+        }
+        ++entity_index;
+    }
+    return written_entities;
+}

core/src-c/state.c

@@ -5,6 +5,10 @@
 
 MtState * mt_initialize(char *app_name)
 {
+    if(app_name == NULL)
+    {
+        app_name = "Unnamed Application";
+    }
     usz_t len_app_name = rr_measure_string(app_name);
     MtState *state = malloc(sizeof(struct MtState));
 

core/src-c/tag_registry.c

@@ -3,6 +3,8 @@
 #include <librr/memory.h>
 #include <stdlib.h>
 
+#define MT_INITIAL_ENTITIES_CAPACITY_PER_TAG 32
+
 MtTagRegistry mt_create_tag_registry(void *parent_state)
 {
     MtTagRegistry registry;
@@ -82,9 +84,30 @@ u32_t mt_tag_label_to_hash(const char *tag_label, usz_t range)
 
 MtTagEntry * mt_create_tag_hash_entry(MtTagRegistry *registry, const char *tag_label)
 {
+    // Create a new entry in the flat array of entries
+
+    usz_t entry_index = registry->num_entries;
+    MtTagEntry *entry =  &registry->entries[entry_index];
+    ++registry->num_entries;
+
+    usz_t len_tag_label = rr_measure_string(tag_label);
+
+    // TODO: There MUST be an arena allocator for this!
+    entry->label = malloc(len_tag_label + 1);
+    rr_memcopy(entry->label, tag_label, len_tag_label+1);
+    entry->entities_capacity = MT_INITIAL_ENTITIES_CAPACITY_PER_TAG;
+    entry->entity_identifiers = calloc(sizeof(u32_t), entry->entities_capacity);
+    entry->num_entities = 0;
+    entry->identifier = registry->next_identifier;
+    ++registry->next_identifier;
+
+    // Create an entry in the lookup structure
+
     u32_t collection_index = mt_tag_label_to_hash(tag_label, registry->num_collections);
     MtTagCollection *collection = &registry->collections[collection_index];
 
+    // Resize the collection to be larger if needed
+
     if(collection->usage >= collection->capacity)
     {
         collection->capacity *= 2;
@@ -94,23 +117,14 @@ MtTagEntry * mt_create_tag_hash_entry(MtTagRegistry *registry, const char *tag_l
         collection->tag_indices = realloc(collection->tag_indices, sizeof(u32_t) * collection->capacity);
         rr_memset(&collection->tag_indices[collection->usage], collection->capacity - collection->usage, 0x00);
     }
-    MtTagEntry *entry =  &registry->entries[collection->tag_indices[collection->usage]];
-    ++registry->num_entries;
+
+    collection->tag_indices[collection->usage] = entry_index;
     ++collection->usage;
 
-    usz_t len_tag_label = rr_measure_string(tag_label);
-
-    // TODO: There must be an arena allocator for this!
-    entry->label = malloc(len_tag_label + 1);
-    rr_memcopy(entry->label, tag_label, len_tag_label+1);
-
-    entry->identifier = registry->next_identifier;
-    ++registry->next_identifier;
-
     return entry;
 }
 
-u32_t mt_get_tag_id(MtTagRegistry *registry, const char *tag_label)
+MtTagEntry * mt_get_tag_entry(MtTagRegistry *registry, const char *tag_label)
 {
     u32_t collection_index = mt_tag_label_to_hash(tag_label, registry->num_collections);
     MtTagCollection collection = registry->collections[collection_index];
@@ -119,12 +133,16 @@ u32_t mt_get_tag_id(MtTagRegistry *registry, const char *tag_label)
     {
         MtTagEntry *entry = &registry->entries[collection.tag_indices[entry_index]];
         if(rr_strings_equal(entry->label, tag_label))
-            return entry->identifier;
+            return entry;
 
         ++entry_index;
     }
-    MtTagEntry *entry = mt_create_tag_hash_entry(registry, tag_label);
-    return entry->identifier;
+    return mt_create_tag_hash_entry(registry, tag_label);
+}
+
+u32_t mt_get_tag_id(MtTagRegistry *registry, const char *tag_label)
+{
+    return mt_get_tag_entry(registry, tag_label)->identifier;
 }
 
 const char * mt_get_tag_label(MtTagRegistry *registry, u32_t tag_identifier)
@@ -140,3 +158,47 @@ const char * mt_get_tag_label(MtTagRegistry *registry, u32_t tag_identifier)
     }
     return NULL;
 }
+
+u32_t mt_get_or_create_entity_id_slot_in_tag_entry(MtTagEntry *entry, u32_t entity_identifier)
+{
+    // Option 1: Find the entity identifier (if it was already registered)
+
+    usz_t index = 0;
+    while(index < entry->num_entities)
+    {
+        if(entry->entity_identifiers[index] == entity_identifier)
+            return index;
+
+        ++index;
+    }
+
+    // Option 2: Get a slot for the entity identifier and write the ID.
+
+    // Resize the entity_identifiers array if needed
+
+    if(entry->num_entities >= entry->entities_capacity)
+    {
+        entry->entities_capacity *= 2;
+        if(entry->entities_capacity == 0)
+            entry->entities_capacity = MT_INITIAL_ENTITIES_CAPACITY_PER_TAG;
+        entry->entity_identifiers = realloc(entry->entity_identifiers, sizeof(u32_t) * entry->entities_capacity);
+    }
+    usz_t entity_identifier_index = entry->num_entities;
+    entry->entity_identifiers[entity_identifier_index] = entity_identifier;
+    ++entry->num_entities;
+    return entity_identifier_index;
+}
+
+void mt_add_entity_to_tag_lookup_list(MtTagRegistry *registry, const char *tag_label, u32_t entity_identifier)
+{
+    MtTagEntry *entry = mt_get_tag_entry(registry, tag_label);
+    mt_get_or_create_entity_id_slot_in_tag_entry(entry, entity_identifier);
+}
+
+void mt_remove_entity_from_tag_lookup_list(MtTagRegistry *registry, const char *tag_label, u32_t entity_identifier)
+{
+    MtTagEntry *entry = mt_get_tag_entry(registry, tag_label);
+    u32_t entity_index = mt_get_or_create_entity_id_slot_in_tag_entry(entry, entity_identifier);
+    entry->entity_identifiers[entity_index] = entry->entity_identifiers[entry->num_entities-1];
+    --entry->num_entities;
+}

core/tests/interface/entity-creation/main.c

@@ -1,9 +1,13 @@
 #include <maintree/maintree.h>
+#include <stdio.h>
 
-int main(int argc, char **argv)
+int main()
 {
-    MtState state = mt_initialize("Interface Test");;
-    MtEntity entity = mt_summon(state);
+    MtState *state = mt_initialize("Interface Test");;
+    MtEntity* entity = mt_summon(state);
     mt_drop(entity);
     mt_cleanup(state);
+    puts("The program reached the end; this test is considered as passed. SUCCESS!");
+    puts("Note: A memory leak check utility should be used to verify the success.");
+    return 0;
 }

core/tests/interface/entity-queries/main.c

@@ -0,0 +1,49 @@
+#include <state.h>
+#include <entity.h>
+
+#include <stdio.h>
+
+int main()
+{
+    MtState *state = mt_initialize("Interface Test");
+    MtEntity *entity_1 = mt_summon(state);
+    mt_tag_i64(entity_1, "some_tag", 3);
+    mt_tag_i64(entity_1, "another_tag", 42);
+    mt_tag_i64(entity_1, "listed_tag", 1337);
+
+    MtEntity *entity_2 = mt_summon(state);
+    mt_tag_i64(entity_2, "some_tag", 3);
+    mt_tag_i64(entity_2, "another_tag", 42);
+
+    MtEntity *entity_3 = mt_summon(state);
+    mt_tag_i64(entity_3, "some_tag", 3);
+    mt_tag_i64(entity_3, "another_tag", 42);
+    mt_tag_i64(entity_3, "listed_tag", 236512);
+
+    const char *tag_list[4] =
+    {
+        "some_tag",
+        "another_tag",
+        "listed_tag",
+        NULL
+    };
+    usz_t num_matching_entities = mt_query(state, tag_list, NULL, 0);
+    printf("Number of matching entities: %ld\n", num_matching_entities);
+
+    MtEntity *entities[8];
+    mt_query(state, tag_list, entities, 8);
+
+    printf("Entity 1: %p\nEntity 2: %p\nEntity 3: %p\n", (void *) entity_1, (void *) entity_2, (void *) entity_3);
+    usz_t entity_index = 0;
+    while(entity_index < num_matching_entities)
+    {
+        printf("Entity-Pointer: %p\n", (void *) entities[entity_index]);
+        ++entity_index;
+    }
+
+    mt_drop(entity_1);
+    mt_drop(entity_2);
+    mt_drop(entity_3);
+    mt_cleanup(state);
+    return 0;
+}

core/tests/interface/entity-tagging-api/main.c

@@ -0,0 +1,26 @@
+#include <maintree/maintree.h>
+#include <stdio.h>
+
+#define TEST_INTEGER 1337
+
+int main()
+{
+    MtState *state = mt_initialize("Interface Test");
+    MtEntity* entity = mt_summon(state);
+    mt_tag_i64(entity, "test-tag", TEST_INTEGER);
+    i64_t returned_integer = mt_get_i64_tag(entity, "test-tag");
+    if(returned_integer != TEST_INTEGER)
+    {
+        puts("The integer returned from the get_i64_tag-function doesn't match the tag which was put in!");
+        printf("Input:  %d\nOutput: %ld\n", TEST_INTEGER, returned_integer);
+        mt_drop(entity);
+        mt_cleanup(state);
+        return -1;
+    }
+
+    mt_drop(entity);
+    mt_cleanup(state);
+    puts("The program reached the end; this test is considered as passed. SUCCESS!");
+    puts("Note: A memory leak check utility should be used to verify the success.");
+    return 0;
+}

core/tests/internal/basic-tag-registry-usage/main.c

@@ -2,14 +2,43 @@
 #include <librr/types.h>
 #include <stdio.h>
 
-int main(int argc, char **argv)
+int main()
 {
     MtTagRegistry tag_registry = mt_create_tag_registry(NULL);
     u32_t some_tag = mt_get_tag_id(&tag_registry, "some_tag");
+    u32_t another_tag = mt_get_tag_id(&tag_registry, "another_tag");
+    u32_t theres_more = mt_get_tag_id(&tag_registry, "there's more");
     if(some_tag != mt_get_tag_id(&tag_registry, "some_tag"))
     {
-        puts("Inconsistent returned tag identifiers.");
+        puts("Inconsistently returned tag identifier in test subject 1. ERROR!");
+        mt_delete_tag_registry(tag_registry);
+        return -1;
+    }
+    if(another_tag != mt_get_tag_id(&tag_registry, "another_tag"))
+    {
+        puts("Inconsistently returned tag identifier in test subject 2. ERROR!");
+        mt_delete_tag_registry(tag_registry);
+        return -1;
+    }
+    if(theres_more != mt_get_tag_id(&tag_registry, "there's more"))
+    {
+        puts("Inconsistently returned tag identifier in test subject 3. ERROR!");
+        mt_delete_tag_registry(tag_registry);
+        return -1;
+    }
+    if(some_tag == theres_more)
+    {
+        puts("Tags are being duplicated in test subject 4. ERROR!");
+        mt_delete_tag_registry(tag_registry);
+        return -1;
+    }
+    if(some_tag == another_tag)
+    {
+        puts("Tags are being duplicated in test subject 5. ERROR!");
+        mt_delete_tag_registry(tag_registry);
+        return -1;
     }
     mt_delete_tag_registry(tag_registry);
+    puts("The identifier which is returned for a tag name is consistent. SUCCESS!");
     return 0;
 }

core/tests/internal/entity-lookup/main.c

@@ -3,17 +3,21 @@
 
 #include <stdio.h>
 
-int main(int argc, char **argv)
+int main()
 {
-    MtState *state = mt_initialize("Interface Test");;
+    MtState *state = mt_initialize("Internal Test");
     MtEntity *entity = mt_summon(state);
     MtEntity *looked_up_entity = mt_get_entity(state, entity->identifier);
 
     if(entity != looked_up_entity)
-        printf("Failed looking up entity; the pointers don't match:\nOriginal:   %p\nLooked Up:  %p\n", entity, looked_up_entity);
-    else
-        puts("The entity which was looked up from the identifier does match the original. SUCCESS!");
-
+    {
+        printf("Failed looking up entity; the pointers don't match:\nOriginal:   %p\nLooked Up:  %p\nERROR!", (void *) entity, (void *) looked_up_entity);
         mt_drop(entity);
         mt_cleanup(state);
+        return -1;
+    }
+    puts("The entity which was looked up from the identifier does match the original. SUCCESS!");
+    mt_drop(entity);
+    mt_cleanup(state);
+    return 0;
 }