------------------------------------------------------------------------------
-- --
-- GNAT COMPILER COMPONENTS --
-- --
-- T A B L E --
-- --
-- B o d y --
-- --
-- Copyright (C) 1992-2023, 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. See the GNU General Public License --
-- for more details. You should have received a copy of the GNU General --
-- Public License distributed with GNAT; see file COPYING3. If not, go to --
-- http://www.gnu.org/licenses for a complete copy of the license. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
with Debug; use Debug;
with Opt; use Opt;
with Output; use Output;
with System; use System;
with System.Memory; use System.Memory;
with Ada.Unchecked_Conversion;
pragma Elaborate_All (Output);
package body Table is
package body Table is
Min : constant Int := Int (Table_Low_Bound);
-- Subscript of the minimum entry in the currently allocated table
Length : Int := 0;
-- Number of entries in currently allocated table. The value of zero
-- ensures that we initially allocate the table.
-----------------------
-- Local Subprograms --
-----------------------
procedure Reallocate;
-- Reallocate the existing table according to the current value stored
-- in Max. Works correctly to do an initial allocation if the table
-- is currently null.
pragma Warnings (Off);
-- Turn off warnings. The following unchecked conversions are only used
-- internally in this package, and cannot never result in any instances
-- of improperly aliased pointers for the client of the package.
function To_Address is new Ada.Unchecked_Conversion (Table_Ptr, Address);
function To_Pointer is new Ada.Unchecked_Conversion (Address, Table_Ptr);
pragma Warnings (On);
------------
-- Append --
------------
procedure Append (New_Val : Table_Component_Type) is
begin
pragma Assert (not Locked);
Set_Item (Table_Index_Type (Last_Val + 1), New_Val);
end Append;
----------------
-- Append_All --
----------------
procedure Append_All (New_Vals : Table_Type) is
begin
for J in New_Vals'Range loop
Append (New_Vals (J));
end loop;
end Append_All;
--------------------
-- Decrement_Last --
--------------------
procedure Decrement_Last is
begin
Last_Val := Last_Val - 1;
end Decrement_Last;
----------
-- Free --
----------
procedure Free is
begin
Free (To_Address (Table));
Table := null;
Length := 0;
end Free;
--------------------
-- Increment_Last --
--------------------
procedure Increment_Last is
begin
pragma Assert (not Locked);
Last_Val := Last_Val + 1;
if Last_Val > Max then
Reallocate;
end if;
end Increment_Last;
----------
-- Init --
----------
procedure Init is
Old_Length : constant Int := Length;
begin
Locked := False;
Last_Val := Min - 1;
Max := Min + (Table_Initial * Table_Factor) - 1;
Length := Max - Min + 1;
-- If table is same size as before (happens when table is never
-- expanded which is a common case), then simply reuse it. Note
-- that this also means that an explicit Init call right after
-- the implicit one in the package body is harmless.
if Old_Length = Length then
return;
-- Otherwise we can use Reallocate to get a table of the right size.
-- Note that Reallocate works fine to allocate a table of the right
-- initial size when it is first allocated.
else
Reallocate;
end if;
end Init;
----------
-- Last --
----------
function Last return Table_Index_Type is
begin
return Table_Index_Type (Last_Val);
end Last;
----------------
-- Reallocate --
----------------
procedure Reallocate is
New_Size : Memory.size_t;
New_Length : Long_Long_Integer;
begin
if Max < Last_Val then
pragma Assert (not Locked);
-- Make sure that we have at least the initial allocation. This
-- is needed in cases where a zero length table is written out.
Length := Int'Max (Length, Table_Initial);
-- Now increment table length until it is sufficiently large. Use
-- the increment value or 10, which ever is larger (the reason
-- for the use of 10 here is to ensure that the table does really
-- increase in size (which would not be the case for a table of
-- length 10 increased by 3% for instance). Do the intermediate
-- calculation in Long_Long_Integer to avoid overflow.
while Max < Last_Val loop
New_Length :=
Long_Long_Integer (Length) *
(100 + Long_Long_Integer (Table_Increment)) / 100;
Length := Int'Max (Int (New_Length), Length + 10);
Max := Min + Length - 1;
end loop;
if Debug_Flag_D then
Write_Str ("--> Allocating new ");
Write_Str (Table_Name);
Write_Str (" table, size = ");
Write_Int (Max - Min + 1);
Write_Eol;
end if;
end if;
-- Do the intermediate calculation in size_t to avoid signed overflow
New_Size :=
Memory.size_t (Max - Min + 1) *
(Table_Type'Component_Size / Storage_Unit);
if Table = null then
Table := To_Pointer (Alloc (New_Size));
elsif New_Size > 0 then
Table :=
To_Pointer (Realloc (Ptr => To_Address (Table),
Size => New_Size));
end if;
if Length /= 0 and then Table = null then
Set_Standard_Error;
Write_Str ("available memory exhausted");
Write_Eol;
Set_Standard_Output;
raise Unrecoverable_Error;
end if;
end Reallocate;
-------------
-- Release --
-------------
procedure Release is
Extra_Length : Int;
Size : Memory.size_t;
begin
Length := Last_Val - Int (Table_Low_Bound) + 1;
Size := Memory.size_t (Length) *
(Table_Type'Component_Size / Storage_Unit);
-- If the size of the table exceeds the release threshold then leave
-- space to store as many extra elements as 0.1% of the table length.
if Release_Threshold > 0
and then Size > Memory.size_t (Release_Threshold)
then
Extra_Length := Length / 1000;
Length := Length + Extra_Length;
Max := Int (Table_Low_Bound) + Length - 1;
if Debug_Flag_D then
Write_Str ("--> Release_Threshold reached (length=");
Write_Int (Int (Size));
Write_Str ("): leaving room space for ");
Write_Int (Extra_Length);
Write_Str (" components");
Write_Eol;
end if;
else
Max := Last_Val;
end if;
Reallocate;
end Release;
-------------
-- Restore --
-------------
procedure Restore (T : Saved_Table) is
begin
Free (To_Address (Table));
Last_Val := T.Last_Val;
Max := T.Max;
Table := T.Table;
Length := Max - Min + 1;
end Restore;
----------
-- Save --
----------
function Save return Saved_Table is
Res : Saved_Table;
begin
Res.Last_Val := Last_Val;
Res.Max := Max;
Res.Table := Table;
Table := null;
Length := 0;
Init;
return Res;
end Save;
--------------
-- Set_Item --
--------------
procedure Set_Item
(Index : Table_Index_Type;
Item : Table_Component_Type)
is
-- If Item is a value within the current allocation, and we are going
-- to reallocate, then we must preserve an intermediate copy here
-- before calling Increment_Last. Otherwise, if Table_Component_Type
-- is passed by reference, we are going to end up copying from
-- storage that might have been deallocated from Increment_Last
-- calling Reallocate.
subtype Allocated_Table_T is
Table_Type (Table'First .. Table_Index_Type (Max + 1));
-- A constrained table subtype one element larger than the currently
-- allocated table.
Allocated_Table_Address : constant System.Address :=
Table.all'Address;
-- Used for address clause below (we can't use non-static expression
-- Table.all'Address directly in the clause because some older
-- versions of the compiler do not allow it).
Allocated_Table : Allocated_Table_T;
pragma Import (Ada, Allocated_Table);
pragma Suppress (Range_Check, On => Allocated_Table);
for Allocated_Table'Address use Allocated_Table_Address;
-- Allocated_Table represents the currently allocated array, plus one
-- element (the supplementary element is used to have a convenient
-- way of computing the address just past the end of the current
-- allocation). Range checks are suppressed because this unit
-- uses direct calls to System.Memory for allocation, and this can
-- yield misaligned storage (and we cannot rely on the bootstrap
-- compiler supporting specifically disabling alignment checks, so we
-- need to suppress all range checks). It is safe to suppress this
-- check here because we know that a (possibly misaligned) object
-- of that type does actually exist at that address.
-- ??? We should really improve the allocation circuitry here to
-- guarantee proper alignment.
Need_Realloc : constant Boolean := Int (Index) > Max;
-- True if this operation requires storage reallocation (which may
-- involve moving table contents around).
begin
-- If we're going to reallocate, check whether Item references an
-- element of the currently allocated table.
if Need_Realloc
and then Allocated_Table'Address <= Item'Address
and then Item'Address <
Allocated_Table (Table_Index_Type (Max + 1))'Address
then
-- If so, save a copy on the stack because Increment_Last will
-- reallocate storage and might deallocate the current table.
declare
Item_Copy : constant Table_Component_Type := Item;
begin
Set_Last (Index);
Table (Index) := Item_Copy;
end;
else
-- Here we know that either we won't reallocate (case of Index <
-- Max) or that Item is not in the currently allocated table.
if Int (Index) > Last_Val then
Set_Last (Index);
end if;
Table (Index) := Item;
end if;
end Set_Item;
--------------
-- Set_Last --
--------------
procedure Set_Last (New_Val : Table_Index_Type) is
begin
pragma Assert (Int (New_Val) <= Last_Val or else not Locked);
if Int (New_Val) < Last_Val then
Last_Val := Int (New_Val);
else
Last_Val := Int (New_Val);
if Last_Val > Max then
Reallocate;
end if;
end if;
end Set_Last;
begin
Init;
end Table;
end Table;