Stdlib: SingleSizeObjectPool implementation (#2360)

* implement working single size object pool
---------

Co-authored-by: Christoffer Lerno <christoffer@aegik.com>

lib/std/core/mem_allocator.c3

@@ -65,7 +65,7 @@ alias MemoryAllocFn = fn char[]?(usz);
 
 
 
-fn usz alignment_for_allocation(usz alignment) @inline @private
+fn usz alignment_for_allocation(usz alignment) @inline
 {
 	return alignment < mem::DEFAULT_MEM_ALIGNMENT ? mem::DEFAULT_MEM_ALIGNMENT : alignment;
 }

lib/std/core/mem_mempool.c3

@@ -0,0 +1,234 @@
+module std::core::mem::mempool;
+import std::core::mem, std::core::mem::allocator, std::math;
+
+const INITIAL_CAPACITY = 0;
+
+struct FixedBlockPoolNode
+{
+	void* buffer;
+	FixedBlockPoolNode *next;
+	usz capacity;
+}
+
+struct FixedBlockPoolEntry
+{
+	void *previous;
+}
+
+<*
+ Fixed blocks pool pre-allocating blocks backed by an Allocator which are then reserved for the user,
+ blocks deallocated by the user are later re-used by future blocks allocations
+
+ `grow_capacity` can be changed in order to affect how many blocks will be allocated by next pool allocation,
+ it has to be greater than 0
+ `allocated` number of allocated blocks
+ `used` number of used blocks by the user
+*>
+struct FixedBlockPool
+{
+	Allocator allocator;
+	FixedBlockPoolNode head;
+	FixedBlockPoolNode *tail;
+	void *next_free;
+	void *freelist;
+	usz block_size;
+	usz grow_capacity;
+	usz allocated;
+	usz page_size;
+	usz alignment;
+	usz used;
+	bool initialized;
+}
+
+<*
+ Initialize an block pool
+
+ @param [in] allocator : "The allocator to use"
+ @param block_size : "The block size to use"
+ @param capacity : "The amount of blocks to be pre-allocated"
+ @param alignment : "The alignment of the buffer"
+ @require !alignment || math::is_power_of_2(alignment)
+ @require !self.initialized : "The block pool must not be initialized"
+ @require block_size > 0 : "Block size must be non zero"
+ @require calculate_actual_capacity(capacity, block_size) * block_size >= block_size
+    : "Total memory would overflow"
+*>
+macro FixedBlockPool* FixedBlockPool.init(&self, Allocator allocator, usz block_size, usz capacity = INITIAL_CAPACITY, usz alignment = 0)
+{
+	self.allocator = allocator;
+	self.tail = &self.head;
+	self.head.next = null;
+	self.block_size = math::max(block_size, FixedBlockPoolEntry.sizeof);
+	capacity = calculate_actual_capacity(capacity, self.block_size);
+	self.alignment = allocator::alignment_for_allocation(alignment);
+	self.page_size = capacity * self.block_size;
+    assert(self.page_size >= self.block_size, "Total memory would overflow %d %d", block_size, capacity);
+	self.head.buffer = self.allocate_page();
+	self.head.capacity = capacity;
+	self.next_free = self.head.buffer;
+	self.freelist = null;
+	self.grow_capacity = capacity;
+	self.initialized = true;
+	self.allocated = capacity;
+	self.used = 0;
+	return self;
+}
+
+<*
+ Initialize an block pool
+
+ @param [in] allocator : "The allocator to use"
+ @param $Type : "The type used for setting the block size"
+ @param capacity : "The amount of blocks to be pre-allocated"
+ @require !self.initialized : "The block pool must not be initialized"
+*>
+macro FixedBlockPool* FixedBlockPool.init_for_type(&self, Allocator allocator, $Type, usz capacity = INITIAL_CAPACITY)
+{
+	return self.init(allocator, $Type.sizeof, capacity, $Type.alignof);
+}
+
+<*
+ Initialize an block pool using Temporary allocator
+
+ @param $Type : "The type used for setting the block size"
+ @param capacity : "The amount of blocks to be pre-allocated"
+ @require !self.initialized : "The block pool must not be initialized"
+*>
+macro FixedBlockPool* FixedBlockPool.tinit_for_type(&self, $Type, usz capacity = INITIAL_CAPACITY) => self.init_for_type(tmem, $Type, capacity);
+
+<*
+ Initialize an block pool using Temporary allocator
+
+ @param block_size : "The block size to use"
+ @param capacity : "The amount of blocks to be pre-allocated"
+ @require !self.initialized : "The block pool must not be initialized"
+*>
+macro FixedBlockPool* FixedBlockPool.tinit(&self, usz block_size, usz capacity = INITIAL_CAPACITY) => self.init(tmem, block_size, capacity);
+
+<*
+ Free up the entire block pool
+
+ @require self.initialized : "The block pool must be initialized"
+*>
+fn void FixedBlockPool.free(&self)
+{
+	self.free_page(self.head.buffer);
+	FixedBlockPoolNode* iter = self.head.next;
+
+	while (iter)
+	{
+		self.free_page(iter.buffer);
+		FixedBlockPoolNode* current = iter;
+		iter = iter.next;
+		allocator::free(self.allocator, current);
+	}
+	self.initialized = false;
+	self.allocated = 0;
+	self.used = 0;
+}
+
+<*
+ Allocate an block on the block pool, re-uses previously deallocated blocks
+
+ @require self.initialized : "The block pool must be initialized"
+*>
+fn void* FixedBlockPool.alloc(&self)
+{
+	defer self.used++;
+
+	if (self.freelist)
+	{
+		FixedBlockPoolEntry* entry = self.freelist;
+		self.freelist = entry.previous;
+		mem::clear(entry, self.block_size);
+		return entry;
+	}
+
+	void* end = self.tail.buffer + (self.tail.capacity * self.block_size);
+	if (self.next_free >= end) self.new_node();
+	void* ptr = self.next_free;
+	self.next_free += self.block_size;
+
+	return ptr;
+}
+
+<*
+ Deallocate a block from the block pool
+
+ @require self.initialized : "The block pool must be initialized"
+ @require self.check_ptr(ptr) : "The pointer should be part of the pool"
+*>
+fn void FixedBlockPool.dealloc(&self, void* ptr)
+{
+	$if env::COMPILER_SAFE_MODE && !env::ADDRESS_SANITIZER:
+		if (self.block_size > FixedBlockPoolEntry.sizeof)
+		{
+			mem::set(ptr + FixedBlockPoolEntry.sizeof, 0xAA, self.block_size);
+		}
+	$else
+		// POINT FOR IMPROVEMENT, something like:
+		// asan::poison_memory_region(&ptr, self.block_size);
+	$endif
+
+	FixedBlockPoolEntry* entry = ptr;
+	entry.previous = self.freelist;
+	self.freelist = entry;
+	self.used--;
+}
+
+<*
+ @require self.initialized : "The block pool must be initialized"
+*>
+fn bool FixedBlockPool.check_ptr(&self, void *ptr) @local
+{
+	FixedBlockPoolNode* iter = &self.head;
+
+	while (iter)
+	{
+		void* end = iter.buffer + (iter.capacity * self.block_size);
+		if (ptr >= iter.buffer && ptr < end) return true;
+		iter = iter.next;
+	}
+
+	return false;
+}
+
+<*
+ @require self.grow_capacity > 0 : "How many blocks will it store"
+*>
+fn void FixedBlockPool.new_node(&self) @local
+{
+	FixedBlockPoolNode* node = allocator::new(self.allocator, FixedBlockPoolNode);
+	node.buffer = self.allocate_page();
+	node.capacity = self.grow_capacity;
+	self.tail.next = node;
+	self.tail = node;
+	self.next_free = node.buffer;
+	self.allocated += node.capacity;
+}
+
+macro void* FixedBlockPool.allocate_page(&self) @private
+{
+	return self.alignment > mem::DEFAULT_MEM_ALIGNMENT
+	       ? allocator::calloc_aligned(self.allocator, self.page_size, self.alignment)!!
+           : allocator::calloc(self.allocator, self.page_size);
+}
+macro void FixedBlockPool.free_page(&self, void* page) @private
+{
+	if (self.alignment > mem::DEFAULT_MEM_ALIGNMENT)
+	{
+		allocator::free_aligned(self.allocator, page);
+	}
+	else
+	{
+		allocator::free(self.allocator, page);
+	}
+}
+
+macro usz calculate_actual_capacity(usz capacity, usz block_size) @private
+{
+	// Assume some overhead
+	if (capacity) return capacity;
+	capacity = (mem::os_pagesize() - 128) / block_size;
+	return capacity ?: 1;
+}