------------------------------------------------------------------------------ -- -- -- GNAT RUN-TIME COMPONENTS -- -- -- -- S Y S T E M . P O O L _ S I Z E -- -- -- -- B o d y -- -- -- -- Copyright (C) 1992-2018, Free Software Foundation, Inc. -- -- -- -- GNAT is free software; you can redistribute it and/or modify it under -- -- terms of the GNU General Public License as published by the Free Soft- -- -- ware Foundation; either version 3, or (at your option) any later ver- -- -- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- -- or FITNESS FOR A PARTICULAR PURPOSE. -- -- -- -- As a special exception under Section 7 of GPL version 3, you are granted -- -- additional permissions described in the GCC Runtime Library Exception, -- -- version 3.1, as published by the Free Software Foundation. -- -- -- -- You should have received a copy of the GNU General Public License and -- -- a copy of the GCC Runtime Library Exception along with this program; -- -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- -- . -- -- -- -- GNAT was originally developed by the GNAT team at New York University. -- -- Extensive contributions were provided by Ada Core Technologies Inc. -- -- -- ------------------------------------------------------------------------------ with System.Soft_Links; with Ada.Unchecked_Conversion; package body System.Pool_Size is package SSE renames System.Storage_Elements; use type SSE.Storage_Offset; -- Even though these storage pools are typically only used by a single -- task, if multiple tasks are declared at the same or a more nested scope -- as the storage pool, there still may be concurrent access. The current -- implementation of Stack_Bounded_Pool always uses a global lock for -- protecting access. This should eventually be replaced by an atomic -- linked list implementation for efficiency reasons. package SSL renames System.Soft_Links; type Storage_Count_Access is access SSE.Storage_Count; function To_Storage_Count_Access is new Ada.Unchecked_Conversion (Address, Storage_Count_Access); SC_Size : constant := SSE.Storage_Count'Object_Size / System.Storage_Unit; package Variable_Size_Management is -- Embedded pool that manages allocation of variable-size data -- This pool is used as soon as the Elmt_Size of the pool object is 0 -- Allocation is done on the first chunk long enough for the request. -- Deallocation just puts the freed chunk at the beginning of the list. procedure Initialize (Pool : in out Stack_Bounded_Pool); procedure Allocate (Pool : in out Stack_Bounded_Pool; Address : out System.Address; Storage_Size : SSE.Storage_Count; Alignment : SSE.Storage_Count); procedure Deallocate (Pool : in out Stack_Bounded_Pool; Address : System.Address; Storage_Size : SSE.Storage_Count; Alignment : SSE.Storage_Count); end Variable_Size_Management; package Vsize renames Variable_Size_Management; -------------- -- Allocate -- -------------- procedure Allocate (Pool : in out Stack_Bounded_Pool; Address : out System.Address; Storage_Size : SSE.Storage_Count; Alignment : SSE.Storage_Count) is begin SSL.Lock_Task.all; if Pool.Elmt_Size = 0 then Vsize.Allocate (Pool, Address, Storage_Size, Alignment); elsif Pool.First_Free /= 0 then Address := Pool.The_Pool (Pool.First_Free)'Address; Pool.First_Free := To_Storage_Count_Access (Address).all; elsif Pool.First_Empty <= (Pool.Pool_Size - Pool.Aligned_Elmt_Size + 1) then Address := Pool.The_Pool (Pool.First_Empty)'Address; Pool.First_Empty := Pool.First_Empty + Pool.Aligned_Elmt_Size; else raise Storage_Error; end if; SSL.Unlock_Task.all; exception when others => SSL.Unlock_Task.all; raise; end Allocate; ---------------- -- Deallocate -- ---------------- procedure Deallocate (Pool : in out Stack_Bounded_Pool; Address : System.Address; Storage_Size : SSE.Storage_Count; Alignment : SSE.Storage_Count) is begin SSL.Lock_Task.all; if Pool.Elmt_Size = 0 then Vsize.Deallocate (Pool, Address, Storage_Size, Alignment); else To_Storage_Count_Access (Address).all := Pool.First_Free; Pool.First_Free := Address - Pool.The_Pool'Address + 1; end if; SSL.Unlock_Task.all; exception when others => SSL.Unlock_Task.all; raise; end Deallocate; ---------------- -- Initialize -- ---------------- procedure Initialize (Pool : in out Stack_Bounded_Pool) is -- Define the appropriate alignment for allocations. This is the -- maximum of the requested alignment, and the alignment required -- for Storage_Count values. The latter test is to ensure that we -- can properly reference the linked list pointers for free lists. Align : constant SSE.Storage_Count := SSE.Storage_Count'Max (SSE.Storage_Count'Alignment, Pool.Alignment); begin if Pool.Elmt_Size = 0 then Vsize.Initialize (Pool); else Pool.First_Free := 0; Pool.First_Empty := 1; -- Compute the size to allocate given the size of the element and -- the possible alignment requirement as defined above. Pool.Aligned_Elmt_Size := SSE.Storage_Count'Max (SC_Size, ((Pool.Elmt_Size + Align - 1) / Align) * Align); end if; end Initialize; ------------------ -- Storage_Size -- ------------------ function Storage_Size (Pool : Stack_Bounded_Pool) return SSE.Storage_Count is begin return Pool.Pool_Size; end Storage_Size; ------------------------------ -- Variable_Size_Management -- ------------------------------ package body Variable_Size_Management is Minimum_Size : constant := 2 * SC_Size; procedure Set_Size (Pool : Stack_Bounded_Pool; Chunk, Size : SSE.Storage_Count); -- Update the field 'size' of a chunk of available storage procedure Set_Next (Pool : Stack_Bounded_Pool; Chunk, Next : SSE.Storage_Count); -- Update the field 'next' of a chunk of available storage function Size (Pool : Stack_Bounded_Pool; Chunk : SSE.Storage_Count) return SSE.Storage_Count; -- Fetch the field 'size' of a chunk of available storage function Next (Pool : Stack_Bounded_Pool; Chunk : SSE.Storage_Count) return SSE.Storage_Count; -- Fetch the field 'next' of a chunk of available storage function Chunk_Of (Pool : Stack_Bounded_Pool; Addr : System.Address) return SSE.Storage_Count; -- Give the chunk number in the pool from its Address -------------- -- Allocate -- -------------- procedure Allocate (Pool : in out Stack_Bounded_Pool; Address : out System.Address; Storage_Size : SSE.Storage_Count; Alignment : SSE.Storage_Count) is Chunk : SSE.Storage_Count; New_Chunk : SSE.Storage_Count; Prev_Chunk : SSE.Storage_Count; Our_Align : constant SSE.Storage_Count := SSE.Storage_Count'Max (SSE.Storage_Count'Alignment, Alignment); Align_Size : constant SSE.Storage_Count := SSE.Storage_Count'Max ( Minimum_Size, ((Storage_Size + Our_Align - 1) / Our_Align) * Our_Align); begin -- Look for the first big enough chunk Prev_Chunk := Pool.First_Free; Chunk := Next (Pool, Prev_Chunk); while Chunk /= 0 and then Size (Pool, Chunk) < Align_Size loop Prev_Chunk := Chunk; Chunk := Next (Pool, Chunk); end loop; -- Raise storage_error if no big enough chunk available if Chunk = 0 then raise Storage_Error; end if; -- When the chunk is bigger than what is needed, take appropriate -- amount and build a new shrinked chunk with the remainder. if Size (Pool, Chunk) - Align_Size > Minimum_Size then New_Chunk := Chunk + Align_Size; Set_Size (Pool, New_Chunk, Size (Pool, Chunk) - Align_Size); Set_Next (Pool, New_Chunk, Next (Pool, Chunk)); Set_Next (Pool, Prev_Chunk, New_Chunk); -- If the chunk is the right size, just delete it from the chain else Set_Next (Pool, Prev_Chunk, Next (Pool, Chunk)); end if; Address := Pool.The_Pool (Chunk)'Address; end Allocate; -------------- -- Chunk_Of -- -------------- function Chunk_Of (Pool : Stack_Bounded_Pool; Addr : System.Address) return SSE.Storage_Count is begin return 1 + abs (Addr - Pool.The_Pool (1)'Address); end Chunk_Of; ---------------- -- Deallocate -- ---------------- procedure Deallocate (Pool : in out Stack_Bounded_Pool; Address : System.Address; Storage_Size : SSE.Storage_Count; Alignment : SSE.Storage_Count) is pragma Warnings (Off, Pool); Align_Size : constant SSE.Storage_Count := ((Storage_Size + Alignment - 1) / Alignment) * Alignment; Chunk : constant SSE.Storage_Count := Chunk_Of (Pool, Address); begin -- Attach the freed chunk to the chain Set_Size (Pool, Chunk, SSE.Storage_Count'Max (Align_Size, Minimum_Size)); Set_Next (Pool, Chunk, Next (Pool, Pool.First_Free)); Set_Next (Pool, Pool.First_Free, Chunk); end Deallocate; ---------------- -- Initialize -- ---------------- procedure Initialize (Pool : in out Stack_Bounded_Pool) is begin Pool.First_Free := 1; if Pool.Pool_Size > Minimum_Size then Set_Next (Pool, Pool.First_Free, Pool.First_Free + Minimum_Size); Set_Size (Pool, Pool.First_Free, 0); Set_Size (Pool, Pool.First_Free + Minimum_Size, Pool.Pool_Size - Minimum_Size); Set_Next (Pool, Pool.First_Free + Minimum_Size, 0); end if; end Initialize; ---------- -- Next -- ---------- function Next (Pool : Stack_Bounded_Pool; Chunk : SSE.Storage_Count) return SSE.Storage_Count is begin pragma Warnings (Off); -- Kill alignment warnings, we are careful to make sure -- that the alignment is correct. return To_Storage_Count_Access (Pool.The_Pool (Chunk + SC_Size)'Address).all; pragma Warnings (On); end Next; -------------- -- Set_Next -- -------------- procedure Set_Next (Pool : Stack_Bounded_Pool; Chunk, Next : SSE.Storage_Count) is begin pragma Warnings (Off); -- Kill alignment warnings, we are careful to make sure -- that the alignment is correct. To_Storage_Count_Access (Pool.The_Pool (Chunk + SC_Size)'Address).all := Next; pragma Warnings (On); end Set_Next; -------------- -- Set_Size -- -------------- procedure Set_Size (Pool : Stack_Bounded_Pool; Chunk, Size : SSE.Storage_Count) is begin pragma Warnings (Off); -- Kill alignment warnings, we are careful to make sure -- that the alignment is correct. To_Storage_Count_Access (Pool.The_Pool (Chunk)'Address).all := Size; pragma Warnings (On); end Set_Size; ---------- -- Size -- ---------- function Size (Pool : Stack_Bounded_Pool; Chunk : SSE.Storage_Count) return SSE.Storage_Count is begin pragma Warnings (Off); -- Kill alignment warnings, we are careful to make sure -- that the alignment is correct. return To_Storage_Count_Access (Pool.The_Pool (Chunk)'Address).all; pragma Warnings (On); end Size; end Variable_Size_Management; end System.Pool_Size;