86 lines
2.7 KiB
C
86 lines
2.7 KiB
C
#include <basics.h>
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#include <stdio.h>
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typedef struct {
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double x;
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double y;
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} Position, Velocity;
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int main(int argc, char *argv[]) {
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ecs_world_t *ecs = ecs_init_w_args(argc, argv);
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ECS_COMPONENT(ecs, Position);
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ECS_COMPONENT(ecs, Velocity);
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// Create a query for Position, Velocity. Queries are the fastest way to
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// iterate entities as they cache results.
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ecs_query_t *q = ecs_query(ecs, {
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.filter.terms = {
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{ .id = ecs_id(Position) },
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{ .id = ecs_id(Velocity), .inout = EcsIn}
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}
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});
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// Create a few test entities for a Position, Velocity query
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ecs_entity_t e1 = ecs_new_entity(ecs, "e1");
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ecs_set(ecs, e1, Position, {10, 20});
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ecs_set(ecs, e1, Velocity, {1, 2});
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ecs_entity_t e2 = ecs_new_entity(ecs, "e2");
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ecs_set(ecs, e2, Position, {10, 20});
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ecs_set(ecs, e2, Velocity, {3, 4});
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// This entity will not match as it does not have Position, Velocity
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ecs_entity_t e3 = ecs_new_entity(ecs, "e3");
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ecs_set(ecs, e3, Position, {10, 20});
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// Iterate entities matching the query
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ecs_iter_t it = ecs_query_iter(ecs, q);
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// Outer loop, iterates archetypes
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while (ecs_query_next(&it)) {
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Position *p = ecs_field(&it, Position, 1);
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const Velocity *v = ecs_field(&it, Velocity, 2);
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// Inner loop, iterates entities in archetype
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for (int i = 0; i < it.count; i ++) {
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p[i].x += v[i].x;
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p[i].y += v[i].y;
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printf("%s: {%f, %f}\n", ecs_get_name(ecs, it.entities[i]),
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p[i].x, p[i].y);
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}
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}
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// Filters are uncached queries. They are a bit slower to iterate but faster
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// to create & have lower overhead as they don't have to maintain a cache.
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ecs_filter_t *f = ecs_filter(ecs, {
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.terms = {
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{ .id = ecs_id(Position) },
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{ .id = ecs_id(Velocity), .inout = EcsIn}
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}
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});
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// Filter iteration looks the same as query iteration
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it = ecs_filter_iter(ecs, f);
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while (ecs_filter_next(&it)) {
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Position *p = ecs_field(&it, Position, 1);
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const Velocity *v = ecs_field(&it, Velocity, 2);
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for (int i = 0; i < it.count; i ++) {
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p[i].x += v[i].x;
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p[i].y += v[i].y;
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printf("%s: {%f, %f}\n", ecs_get_name(ecs, it.entities[i]),
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p[i].x, p[i].y);
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}
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}
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// Cleanup filter. Filters can allocate memory if the number of terms
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// exceeds their internal buffer, or when terms have names. In this case the
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// filter didn't allocate, so while fini isn't strictly necessary here, it's
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// still good practice to add it.
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ecs_filter_fini(f);
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return ecs_fini(ecs);
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}
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