Make arena allocator align depending on size #3

include/gp/allocator/arena.hpp

@@ -3,27 +3,27 @@
 #include "gp/buffer.hpp"
 #include <type_traits>
 #include <gp/algorithm/tmp_manip.hpp>
+#include "gp/math/integer_math.hpp"
+#include "gp/algorithm/min_max.hpp"
 
-
-
-namespace gp{
-	template<typename page_allocator = int, size_t align = 1>
-	class arena{
+namespace gp {
+	template<typename page_allocator = int>
+	class arena {
 		page_allocator allocator;
 		gp::buffer<char> data;
-		size_t last;
+		size_t next;
 		size_t count;
 	public: 
 		arena()
-		:last(0)
-		,count(0)
-		,data(gp::buffer<char>(nullptr,nullptr))
+		: next(0)
+		, count(0)
+		, data(gp::buffer<char>(nullptr,nullptr))
 		{}
 
 		arena(size_t sz)
-		:last(0)
-		,count(0)
-		,data(nullptr,nullptr)
+		: next(0)
+		, count(0)
+		, data(nullptr,nullptr)
 		{
 			if constexpr (gp::has_allocator_interface<page_allocator>::value)
 			{
@@ -39,28 +39,22 @@ namespace gp{
 		}
 
 		arena(char* pos,size_t sz)
-		:last(0)
-		,count(0)
-		,data(pos,pos+sz)
-		{
-		}
+		: next(0)
+		, count(0)
+		, data(pos,pos+sz)
+		{}
 
 		void* allocate(size_t sz)
 		{
-			[[maybe_unused]]
-			size_t mod = 0;
-
-			if constexpr (align != 1)
-			{
-				mod = align - ((intptr_t)data.begin())%align;
-			}
+			size_t align = gp::min((1 << gp::math::log2(sz)), 16);
+			size_t padding = align - (reinterpret_cast<uintptr_t>(data.begin().data + next)) % align;
 
-			auto ret=data.begin()+last+mod;
+			auto ret=data.begin()+padding+next;
 			if(data.contains(ret))
 			{
 				count++;
-				last+=sz+mod;
-				return o">&*(ret);
+				next+=padding+sz;
+				return n">ret.data;
 			}
 			else
 			{
@@ -83,7 +77,7 @@ namespace gp{
 					{
 						i=0;
 					}
-					last=0;
+					next=0;
 				}
 				return true;
 			}
@@ -98,4 +92,4 @@ namespace gp{
 			}
 		}
 	};
-}
+}