Common update:

-added multiple new function to allocate template and add entity
-updated README.md (complete initial version)
-empty components now don't take memory
-fixedd small bug with TestRunner
-added many new tests (HashMap, Vector, EntityMeta, ...)
-added default hashing function to HashMap
-fixed critical bug with adding entities
-fixed small bug with adding entity with remplacement components
-added asserts into code to better bug detection
-small performance improvement for events
-added ComponentRef structure which contain data pointer and componentID
-remove EntityID from Event structure
-now events are handled before removing entiteis
-fixed GDC compilation
-fixed rendering of rotated sprites
-added weapons as separate entities to space ship and others
-added Tower enemy to SpaceInvaders demo
-added Boss to SpaceInvaders demo (boss has four tower attached to it)
-Boss towers shoot multiple bullets upon death
-fixed critical bug with demos switching
-fixed critical bug related to adding/removing entities form inside onAdd/onRemove entity callback
-added animation support
-added particles sypport and particles for firing and explostions, and more
-multithreaded rendering now has same rendering order as singlethreaded
-application automaticallu detect host CPU threads count
-added upgrades to SPaceInvaders demo
-fixed texture memory freeing
-improved documentation
-improved multithreaded performance
-improve shader code
-fixed registration issue
-some additional performance improvements
-added depth and colors to rendering parameters
-jobs now has names corresponding to their systems
-change execute() -> willExecute()
-added EntityMeta structure to speedup getting fetching components form entity
-improved multithreading rendering
-added possibility tio change number of threads runtime
-added bullets collision detection in SpaceInvaders demo
-some CI changes
-added VBO batch rendering (current default, no render mode switch yet)
-fixed camera positioning calculation
-fixed buffer issue with WebGL
-added viewport scalling (at least 300 pixels height). Pixels are scalled if screen is bigger.
-center demos gameplay area
-added fullpage html template for Emscripten build
-added many new sprites to atlas
-fixed critical bug with CPU usage in multithreaded mode
-snake render tile coresponding to body part
-snake is destroyed after collision and emit some particles
-added some functionality to vectors
-fixed documentation issue in Manager.d
-more minor code changes and cleanup

source/bubel/ecs/block_allocator.d

@@ -0,0 +1,99 @@
+/************************************************************************************************************************
+It's internal code.
+
+Module contain memory allocator.
+
+Copyright: Copyright © 2018-2019, Dawid Masiukiewicz, Michał Masiukiewicz
+License: BSD 3-clause, see LICENSE file in project root folder.
+*/
+module bubel.ecs.block_allocator;
+
+import bubel.ecs.manager;
+import bubel.ecs.std;
+
+/************************************************************************************************************************
+Allocator allocate large blocks and return smaller blocks. When there is no more blocks then next large block is allocated.
+By default freeing memory only returns it to allocator. To free large memory chunks freeMemory function is used.
+freeMemory function return to system memory even if chunk blocks wasn't freed.
+*/
+struct BlockAllocator
+{
+    /************************************************************************************************************************
+    Get new block. Allocator automatically allocate next memory chunk if needed.
+    */
+    void* getBlock() nothrow @nogc
+    {
+        if (next_block is null)
+            allocBlock();
+        void* ret = next_block;
+        next_block = *cast(void**) next_block;
+        return ret;
+    }
+
+    /************************************************************************************************************************
+    Return block to allocator for further use.
+    */
+    void freeBlock(void* block) nothrow @nogc
+    {
+        *cast(void**) block = next_block;
+        next_block = block;
+    }
+
+    /************************************************************************************************************************
+    Free whole used memory. This function return to system all memory chunks even if not every black was freed.
+    */
+    void freeMemory() nothrow @nogc
+    {
+        while (pointers)
+        {
+            foreach (i; 0 .. pointers.numberof)
+            {
+                Mallocator.alignDispose(pointers.blocks[i]);
+            }
+            BlockPointers* next_pointers = pointers.next_pointers;
+            Mallocator.dispose(pointers);
+            pointers = next_pointers;
+        }
+    }
+
+private:
+
+    void allocBlock() nothrow @nogc
+    {
+        next_block = cast(void*) Mallocator.alignAlloc(block_size * blocks_in_allocation,
+                block_size);
+        if (next_block is null)
+            assert(0);
+
+        if (pointers is null)
+            pointers = Mallocator.make!BlockPointers;
+        if (pointers.numberof >= 32)
+        {
+            BlockPointers* new_pointers = Mallocator.make!BlockPointers;
+            new_pointers.next_pointers = pointers;
+            pointers = new_pointers;
+        }
+        pointers.blocks[pointers.numberof++] = next_block;
+
+        foreach (i; 0 .. blocks_in_allocation - 1)
+        {
+            void** pointer = cast(void**)(next_block + i * block_size);
+            *pointer = next_block + (i + 1) * block_size;
+        }
+        void** pointer = cast(void**)(next_block + (blocks_in_allocation - 1) * block_size);
+        *pointer = null;
+    }
+
+    struct BlockPointers
+    {
+        void*[32] blocks;
+        uint numberof = 0;
+        BlockPointers* next_pointers = null;
+    }
+
+    uint block_size;
+    uint blocks_in_allocation;
+
+    void* next_block = null;
+    BlockPointers* pointers = null;
+}