Add: less overly complicated becs2.h

becs2.h

@@ -0,0 +1,175 @@
+#ifndef BECS_H
+#define BECS_H
+
+#include <stdint.h>
+#include <stddef.h>
+
+#define MAX_ENTITIES 100
+#define NUM_COMPONENTS 2
+
+#ifdef MAX_ENTITIES
+#ifdef NUM_COMPONENTS
+#ifdef BECS_IMPLEMENTATION
+
+#define BECS_NULL_INDEX MAX_ENTITIES + 1
+
+struct Entity {
+    uint64_t componentBitMask;
+};
+
+struct BECS_Properties {
+    uint32_t componentSizes[NUM_COMPONENTS];
+};
+
+struct BECS_ComponentArray {
+    uint32_t lastEntityAdded;
+    size_t unitSize;
+    uint32_t sparseArray[MAX_ENTITIES];
+    void *denseArray;
+    uint32_t denseArraylength;
+};
+
+struct BECS_ECS {
+    Entity entities[MAX_ENTITIES];
+    BECS_Properties props;
+    BECS_ComponentArray componentArrays[NUM_COMPONENTS];
+};
+
+size_t BECS_GetMinMemorySize(BECS_Properties props)
+{
+    size_t totalSize = 0;
+    totalSize += sizeof(BECS_ECS);
+    totalSize += sizeof(BECS_ComponentArray) * NUM_COMPONENTS;
+
+    for (uint32_t i = 0; i < NUM_COMPONENTS; i++)
+    {
+        totalSize += props.componentSizes[i] * MAX_ENTITIES;
+    }
+
+    return totalSize;
+}
+
+void BECS_InitComponentArray(BECS_ECS *ecs, size_t size, uint32_t componentIndex)
+{
+    ecs->componentArrays[componentIndex] = {};
+    ecs->componentArrays[componentIndex].lastEntityAdded = BECS_NULL_INDEX;
+    ecs->componentArrays[componentIndex].unitSize = size;
+    ecs->componentArrays[componentIndex].denseArraylength= 0;
+    ecs->componentArrays[componentIndex].denseArray = NULL;
+}
+
+BECS_ECS *BECS_Init
+(void *memory, size_t size, BECS_Properties props)
+{
+    BECS_ECS *ecs = (BECS_ECS *)memory;
+    *ecs = {};
+    ecs->props = props;
+
+    for (uint32_t i = 0; i < NUM_COMPONENTS; i++)
+    {
+        ecs->componentArrays[i] = {};
+        ecs->componentArrays[i].lastEntityAdded = BECS_NULL_INDEX;
+        ecs->componentArrays[i].unitSize = props.componentSizes[i];
+        ecs->componentArrays[i].denseArraylength = 0;
+        for (uint32_t j = 0; i < MAX_ENTITIES; i++)
+        {
+            ecs->componentArrays[i].sparseArray[j] = BECS_NULL_INDEX;
+        }
+    }
+
+    uintptr_t startOfComponentArrays = (uintptr_t)(ecs + 1);
+    for (uint32_t i = 0; i < NUM_COMPONENTS; i++)
+    {
+        startOfComponentArrays += props.componentSizes[i] * MAX_ENTITIES;
+        ecs->componentArrays[i].denseArray = (void *)startOfComponentArrays;
+    }
+    return ecs;
+}
+
+void *BECS_AddComponent(BECS_ECS *ecs, uint32_t entityID, uint32_t componentIndex)
+{
+    if (entityID > MAX_ENTITIES)
+    {
+        return NULL;
+    }
+
+    uint64_t componentBitMask = 0 | (1 << (componentIndex + 1));
+    if (ecs->entities[entityID].componentBitMask & componentBitMask)
+    {
+        return NULL;
+    }
+
+    ecs->entities[entityID].componentBitMask |= componentBitMask;
+    BECS_ComponentArray *componentArray = &ecs->componentArrays[componentIndex];
+    componentArray->sparseArray[entityID] = componentArray->denseArraylength;
+    size_t componentSize = ecs->props.componentSizes[componentIndex];
+    uint32_t componentOffset = componentSize * componentArray->sparseArray[entityID];
+    void *component = (void *)((uintptr_t)componentArray->denseArray + componentOffset);
+
+    componentArray->denseArraylength++;
+    componentArray->lastEntityAdded = entityID;
+
+    return component;
+}
+
+int32_t BECS_RemoveComponent(BECS_ECS *ecs, uint32_t entityID, uint32_t componentIndex)
+{
+    if (entityID > MAX_ENTITIES)
+    {
+        return 1;
+    }
+
+    uint64_t componentBitMask = 0 | (1 << (componentIndex + 1));
+    if (!(ecs->entities[entityID].componentBitMask & componentBitMask))
+    {
+        return 2;
+    }
+
+    BECS_ComponentArray * componentArray = &ecs->componentArrays[componentIndex];
+
+    if (entityID == componentArray->lastEntityAdded)
+    {
+        componentArray->sparseArray[entityID] = BECS_NULL_INDEX;
+        componentArray->denseArraylength--;
+        for (uint32_t i = 0; i < MAX_ENTITIES; i++)
+        {
+            if (componentArray->sparseArray[i] == componentArray->denseArraylength - 1)
+            {
+                componentArray->lastEntityAdded = componentArray->sparseArray[i];
+                break;
+            }
+        }
+        return 0;
+    }
+
+    uint32_t lastEntityAdded = componentArray->sparseArray[componentArray->lastEntityAdded];
+    uint32_t deletedCompIndex = componentArray->sparseArray[entityID];
+
+    return 0;
+}
+
+void *BECS_GetComponent(BECS_ECS *ecs, uint32_t entityID, uint32_t componentIndex)
+{
+    void *component = NULL;
+    if (componentIndex > NUM_COMPONENTS)
+        return component;
+
+    BECS_ComponentArray *componentArray = &ecs->componentArrays[componentIndex];
+
+    uint32_t componentDenseIndex = componentArray->sparseArray[entityID];
+
+    if (componentDenseIndex == BECS_NULL_INDEX)
+    {
+        return component;
+    } else {
+        component = componentArray->denseArray;
+    }
+
+    return component;
+}
+
+#endif
+#endif
+#endif
+
+#endif