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131 | -- SPDX-License-Identifier: Apache-2.0
--
-- Copyright (c) 2018 onox <denkpadje@gmail.com>
--
-- Licensed under the Apache License, Version 2.0 (the "License");
-- you may not use this file except in compliance with the License.
-- You may obtain a copy of the License at
--
-- http://www.apache.org/licenses/LICENSE-2.0
--
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" BASIS,
-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-- See the License for the specific language governing permissions and
-- limitations under the License.
with Ada.Containers.Indefinite_Holders;
with Orka.Rendering.Buffers.Mapped.Persistent;
with Orka.Types;
generic
type Partition_Index_Type is mod <>;
package Orka.Instances is
pragma Preelaborate;
type Manager is tagged limited private;
function Create_Manager (Capacity, Parts : Positive) return Manager;
-- Return a manager that manages a persistent mapped buffer with
-- Capacity * Parts transforms.
type Cursor is private;
function Add_Instance (Object : in out Manager) return Cursor
with Pre => Object.Length < Object.Capacity,
Post => Object.Length'Old + 1 = Object.Length;
procedure Remove_Instance (Object : in out Manager; Instance : Cursor)
with Pre => Object.Length > 0,
Post => Object.Length'Old - 1 = Object.Length;
procedure Set_Transform
(Object : in out Manager;
Value : Orka.Types.Singles.Matrix4;
Instance : Cursor;
Part : Natural)
with Pre => Part < Object.Parts;
function Transforms (Object : Manager) return Rendering.Buffers.Bindable_Buffer'Class;
function Parts (Object : Manager) return Positive;
-- Return number of parts of each instance
function Length (Object : Manager) return Natural;
-- Return current number of instances
function Capacity (Object : Manager) return Positive;
-- Return maximum number of instances
procedure Complete_Frame (Object : in out Manager);
private
package PMB renames Rendering.Buffers.Mapped.Persistent;
type Cursor is new Positive;
subtype Instance is Positive;
subtype Index is Positive;
type Instance_Array is array (Index range <>) of Instance;
type Indices_Array is array (Instance range <>) of Index;
type Instances_Type (Capacity : Positive) is record
Instances : Instance_Array (1 .. Capacity);
Indices : Indices_Array (1 .. Capacity);
end record;
-- Instances is an array containing a contiguous number of instance
-- ID's that have been added, followed by a contiguous number of ID's
-- that have been removed. This array is used to quickly determine a
-- free ID that can be returned by the function Add_Instance.
--
-- Indices is an array that is used to look up the position of an
-- instance ID in Instances in O(1) time. Iterating over Instances
-- would be an O(n) operation.
--
-- For example:
--
-- Instances:
--
-- 1 3 4 | 2 5
-- ----- ---
-- added removed
--
-- Indices:
--
-- 1 4 2 3 5
--
-- To add an instance, the '|' is moved to the right and the ID next
-- to it (2 in the example above) is returned.
--
-- To remove an instance, we look up the index of the instance and
-- then swap its ID with the instance at the end of the array of
-- added instances. Finally, we move the '|' to the left.
--
-- The indices of the two swapped instances are updated in Indices.
--
-- For example, given the above array, removing instance 1 results in:
--
-- 4 3 | 1 2 5
-- --- -----
-- added removed
package Instances_Holder is new Ada.Containers.Indefinite_Holders
(Element_Type => Instances_Type);
type Manager is tagged limited record
Added : Natural := 0;
-- Represents the '|' barrier between the added and removed instances
Capacity, Parts : Positive;
Instances : Instances_Holder.Holder;
Transforms : PMB.Persistent_Mapped_Buffer
(Kind => Orka.Types.Single_Matrix_Type,
Mode => Rendering.Buffers.Mapped.Write);
end record;
end Orka.Instances;
|