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-- Efficient expandable one dimensional array.
-- Copyright (C) 2015 - 2016 Tristan Gingold
--
-- This program is free software: you can redistribute it and/or modify
-- it under the terms of the GNU General Public License as published by
-- the Free Software Foundation, either version 2 of the License, or
-- (at your option) any later version.
--
-- This program is distributed in the hope that it will be useful,
-- but WITHOUT ANY WARRANTY; without even the implied warranty of
-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-- GNU General Public License for more details.
--
-- You should have received a copy of the GNU General Public License
-- along with this program. If not, see <gnu.org/licenses>.
with Interfaces.C; use Interfaces.C;
with System;
package body Dyn_Tables is
-- Size of an element in storage units (bytes).
El_Size : constant size_t :=
size_t (Table_Type'Component_Size / System.Storage_Unit);
-- Expand the table by doubling its size. The table must have been
-- initialized. Memory space for the extra elements are allocated but the
-- length of the table is not increased.
procedure Reserve (T : in out Instance; Num : Unsigned)
is
-- For efficiency, directly call realloc.
function Crealloc (Ptr : Table_Thin_Ptr; Size : size_t)
return Table_Thin_Ptr;
pragma Import (C, Crealloc, "realloc");
New_Len : Unsigned;
New_Last : Unsigned;
begin
pragma Assert (T.Priv.Length /= 0);
pragma Assert (T.Table /= null);
-- Expand the bound.
New_Last := T.Priv.Last_Pos + Num;
if New_Last < T.Priv.Last_Pos then
raise Constraint_Error;
end if;
-- Check if need to reallocate.
if New_Last < T.Priv.Length then
return;
end if;
-- Double the length.
loop
New_Len := T.Priv.Length * 2;
-- Check overflow.
if New_Len < T.Priv.Length then
raise Constraint_Error;
end if;
T.Priv.Length := New_Len;
exit when New_Len > New_Last;
end loop;
-- Realloc and check result.
if size_t (T.Priv.Length) > size_t'Last / El_Size then
raise Constraint_Error;
end if;
T.Table := Crealloc (T.Table, size_t (T.Priv.Length) * El_Size);
if T.Table = null then
raise Storage_Error;
end if;
end Reserve;
-- Expand the table (allocate and increase the length).
procedure Expand (T : in out Instance; Num : Unsigned) is
begin
Reserve (T, Num);
T.Priv.Last_Pos := T.Priv.Last_Pos + Num;
end Expand;
procedure Reserve (T : in out Instance; Num : Natural) is
begin
Reserve (T, Unsigned (Num));
end Reserve;
procedure Allocate (T : in out Instance; Num : Natural := 1) is
begin
Expand (T, Unsigned (Num));
end Allocate;
procedure Increment_Last (T : in out Instance) is
begin
-- Increase by 1.
Expand (T, 1);
end Increment_Last;
procedure Decrement_Last (T : in out Instance) is
begin
T.Priv.Last_Pos := T.Priv.Last_Pos - 1;
end Decrement_Last;
procedure Set_Last (T : in out Instance; Index : Table_Index_Type)
is
New_Last : constant Unsigned :=
(Table_Index_Type'Pos (Index)
- Table_Index_Type'Pos (Table_Low_Bound) + 1);
begin
if New_Last < T.Priv.Last_Pos then
-- Decrease length.
T.Priv.Last_Pos := New_Last;
else
-- Increase length.
Expand (T, New_Last - T.Priv.Last_Pos);
end if;
end Set_Last;
procedure Init (T : in out Instance; Table_Initial : Positive)
is
-- Direct interface to malloc.
function Cmalloc (Size : size_t) return Table_Thin_Ptr;
pragma Import (C, Cmalloc, "malloc");
begin
if T.Table = null then
-- Allocate memory if not already allocated.
T.Priv.Length := Unsigned (Table_Initial);
T.Table := Cmalloc (size_t (T.Priv.Length) * El_Size);
end if;
-- Table is initially empty.
T.Priv.Last_Pos := 0;
end Init;
function Last (T : Instance) return Table_Index_Type is
begin
return Table_Index_Type'Val
(Table_Index_Type'Pos (Table_Low_Bound)
+ Unsigned'Pos (T.Priv.Last_Pos) - 1);
end Last;
function Next (T : Instance) return Table_Index_Type is
begin
return Table_Index_Type'Val
(Table_Index_Type'Pos (Table_Low_Bound) + T.Priv.Last_Pos);
end Next;
procedure Free (T : in out Instance) is
-- Direct interface to free.
procedure Cfree (Ptr : Table_Thin_Ptr);
pragma Import (C, Cfree, "free");
begin
Cfree (T.Table);
T := (Table => null,
Priv => (Length => 0,
Last_Pos => 0));
end Free;
procedure Append (T : in out Instance; Val : Table_Component_Type) is
begin
Increment_Last (T);
T.Table (Last (T)) := Val;
end Append;
end Dyn_Tables;
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