396 lines
13 KiB
Ada
396 lines
13 KiB
Ada
------------------------------------------------------------------------------
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-- --
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-- GNAT COMPILER COMPONENTS --
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-- --
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-- T A B L E --
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-- --
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-- B o d y --
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-- --
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-- Copyright (C) 1992-2020, Free Software Foundation, Inc. --
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-- --
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-- GNAT is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 3, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
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-- for more details. You should have received a copy of the GNU General --
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-- Public License distributed with GNAT; see file COPYING3. If not, go to --
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-- http://www.gnu.org/licenses for a complete copy of the license. --
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-- --
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-- GNAT was originally developed by the GNAT team at New York University. --
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-- Extensive contributions were provided by Ada Core Technologies Inc. --
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-- --
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------------------------------------------------------------------------------
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with Debug; use Debug;
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with Opt; use Opt;
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with Output; use Output;
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with System; use System;
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with System.Memory; use System.Memory;
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with Unchecked_Conversion;
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pragma Elaborate_All (Output);
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package body Table is
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package body Table is
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Min : constant Int := Int (Table_Low_Bound);
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-- Subscript of the minimum entry in the currently allocated table
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Length : Int := 0;
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-- Number of entries in currently allocated table. The value of zero
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-- ensures that we initially allocate the table.
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-----------------------
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-- Local Subprograms --
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-----------------------
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procedure Reallocate;
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-- Reallocate the existing table according to the current value stored
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-- in Max. Works correctly to do an initial allocation if the table
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-- is currently null.
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pragma Warnings (Off);
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-- Turn off warnings. The following unchecked conversions are only used
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-- internally in this package, and cannot never result in any instances
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-- of improperly aliased pointers for the client of the package.
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function To_Address is new Unchecked_Conversion (Table_Ptr, Address);
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function To_Pointer is new Unchecked_Conversion (Address, Table_Ptr);
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pragma Warnings (On);
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------------
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-- Append --
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------------
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procedure Append (New_Val : Table_Component_Type) is
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begin
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pragma Assert (not Locked);
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Set_Item (Table_Index_Type (Last_Val + 1), New_Val);
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end Append;
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----------------
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-- Append_All --
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----------------
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procedure Append_All (New_Vals : Table_Type) is
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begin
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for J in New_Vals'Range loop
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Append (New_Vals (J));
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end loop;
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end Append_All;
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--------------------
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-- Decrement_Last --
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--------------------
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procedure Decrement_Last is
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begin
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Last_Val := Last_Val - 1;
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end Decrement_Last;
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----------
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-- Free --
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----------
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procedure Free is
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begin
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Free (To_Address (Table));
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Table := null;
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Length := 0;
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end Free;
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--------------------
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-- Increment_Last --
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--------------------
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procedure Increment_Last is
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begin
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pragma Assert (not Locked);
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Last_Val := Last_Val + 1;
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if Last_Val > Max then
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Reallocate;
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end if;
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end Increment_Last;
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----------
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-- Init --
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----------
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procedure Init is
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Old_Length : constant Int := Length;
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begin
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Locked := False;
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Last_Val := Min - 1;
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Max := Min + (Table_Initial * Table_Factor) - 1;
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Length := Max - Min + 1;
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-- If table is same size as before (happens when table is never
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-- expanded which is a common case), then simply reuse it. Note
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-- that this also means that an explicit Init call right after
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-- the implicit one in the package body is harmless.
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if Old_Length = Length then
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return;
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-- Otherwise we can use Reallocate to get a table of the right size.
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-- Note that Reallocate works fine to allocate a table of the right
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-- initial size when it is first allocated.
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else
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Reallocate;
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end if;
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end Init;
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----------
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-- Last --
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----------
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function Last return Table_Index_Type is
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begin
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return Table_Index_Type (Last_Val);
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end Last;
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----------------
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-- Reallocate --
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----------------
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procedure Reallocate is
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New_Size : Memory.size_t;
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New_Length : Long_Long_Integer;
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begin
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if Max < Last_Val then
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pragma Assert (not Locked);
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-- Make sure that we have at least the initial allocation. This
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-- is needed in cases where a zero length table is written out.
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Length := Int'Max (Length, Table_Initial);
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-- Now increment table length until it is sufficiently large. Use
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-- the increment value or 10, which ever is larger (the reason
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-- for the use of 10 here is to ensure that the table does really
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-- increase in size (which would not be the case for a table of
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-- length 10 increased by 3% for instance). Do the intermediate
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-- calculation in Long_Long_Integer to avoid overflow.
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while Max < Last_Val loop
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New_Length :=
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Long_Long_Integer (Length) *
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(100 + Long_Long_Integer (Table_Increment)) / 100;
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Length := Int'Max (Int (New_Length), Length + 10);
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Max := Min + Length - 1;
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end loop;
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if Debug_Flag_D then
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Write_Str ("--> Allocating new ");
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Write_Str (Table_Name);
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Write_Str (" table, size = ");
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Write_Int (Max - Min + 1);
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Write_Eol;
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end if;
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end if;
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-- Do the intermediate calculation in size_t to avoid signed overflow
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New_Size :=
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Memory.size_t (Max - Min + 1) *
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(Table_Type'Component_Size / Storage_Unit);
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if Table = null then
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Table := To_Pointer (Alloc (New_Size));
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elsif New_Size > 0 then
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Table :=
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To_Pointer (Realloc (Ptr => To_Address (Table),
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Size => New_Size));
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end if;
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if Length /= 0 and then Table = null then
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Set_Standard_Error;
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Write_Str ("available memory exhausted");
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Write_Eol;
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Set_Standard_Output;
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raise Unrecoverable_Error;
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end if;
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end Reallocate;
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-------------
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-- Release --
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-------------
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procedure Release is
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Extra_Length : Int;
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Size : Memory.size_t;
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begin
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Length := Last_Val - Int (Table_Low_Bound) + 1;
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Size := Memory.size_t (Length) *
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(Table_Type'Component_Size / Storage_Unit);
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-- If the size of the table exceeds the release threshold then leave
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-- space to store as many extra elements as 0.1% of the table length.
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if Release_Threshold > 0
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and then Size > Memory.size_t (Release_Threshold)
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then
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Extra_Length := Length / 1000;
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Length := Length + Extra_Length;
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Max := Int (Table_Low_Bound) + Length - 1;
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if Debug_Flag_D then
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Write_Str ("--> Release_Threshold reached (length=");
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Write_Int (Int (Size));
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Write_Str ("): leaving room space for ");
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Write_Int (Extra_Length);
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Write_Str (" components");
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Write_Eol;
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end if;
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else
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Max := Last_Val;
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end if;
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Reallocate;
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end Release;
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-------------
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-- Restore --
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-------------
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procedure Restore (T : Saved_Table) is
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begin
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Free (To_Address (Table));
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Last_Val := T.Last_Val;
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Max := T.Max;
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Table := T.Table;
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Length := Max - Min + 1;
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end Restore;
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----------
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-- Save --
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----------
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function Save return Saved_Table is
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Res : Saved_Table;
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begin
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Res.Last_Val := Last_Val;
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Res.Max := Max;
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Res.Table := Table;
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Table := null;
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Length := 0;
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Init;
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return Res;
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end Save;
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--------------
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-- Set_Item --
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--------------
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procedure Set_Item
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(Index : Table_Index_Type;
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Item : Table_Component_Type)
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is
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-- If Item is a value within the current allocation, and we are going
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-- to reallocate, then we must preserve an intermediate copy here
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-- before calling Increment_Last. Otherwise, if Table_Component_Type
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-- is passed by reference, we are going to end up copying from
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-- storage that might have been deallocated from Increment_Last
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-- calling Reallocate.
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subtype Allocated_Table_T is
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Table_Type (Table'First .. Table_Index_Type (Max + 1));
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-- A constrained table subtype one element larger than the currently
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-- allocated table.
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Allocated_Table_Address : constant System.Address :=
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Table.all'Address;
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-- Used for address clause below (we can't use non-static expression
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-- Table.all'Address directly in the clause because some older
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-- versions of the compiler do not allow it).
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Allocated_Table : Allocated_Table_T;
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pragma Import (Ada, Allocated_Table);
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pragma Suppress (Range_Check, On => Allocated_Table);
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for Allocated_Table'Address use Allocated_Table_Address;
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-- Allocated_Table represents the currently allocated array, plus one
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-- element (the supplementary element is used to have a convenient
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-- way of computing the address just past the end of the current
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-- allocation). Range checks are suppressed because this unit
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-- uses direct calls to System.Memory for allocation, and this can
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-- yield misaligned storage (and we cannot rely on the bootstrap
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-- compiler supporting specifically disabling alignment checks, so we
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-- need to suppress all range checks). It is safe to suppress this
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-- check here because we know that a (possibly misaligned) object
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-- of that type does actually exist at that address.
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-- ??? We should really improve the allocation circuitry here to
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-- guarantee proper alignment.
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Need_Realloc : constant Boolean := Int (Index) > Max;
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-- True if this operation requires storage reallocation (which may
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-- involve moving table contents around).
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begin
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-- If we're going to reallocate, check whether Item references an
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-- element of the currently allocated table.
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if Need_Realloc
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and then Allocated_Table'Address <= Item'Address
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and then Item'Address <
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Allocated_Table (Table_Index_Type (Max + 1))'Address
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then
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-- If so, save a copy on the stack because Increment_Last will
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-- reallocate storage and might deallocate the current table.
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declare
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Item_Copy : constant Table_Component_Type := Item;
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begin
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Set_Last (Index);
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Table (Index) := Item_Copy;
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end;
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else
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-- Here we know that either we won't reallocate (case of Index <
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-- Max) or that Item is not in the currently allocated table.
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if Int (Index) > Last_Val then
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Set_Last (Index);
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end if;
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Table (Index) := Item;
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end if;
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end Set_Item;
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--------------
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-- Set_Last --
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--------------
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procedure Set_Last (New_Val : Table_Index_Type) is
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begin
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pragma Assert (Int (New_Val) <= Last_Val or else not Locked);
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if Int (New_Val) < Last_Val then
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Last_Val := Int (New_Val);
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else
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Last_Val := Int (New_Val);
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if Last_Val > Max then
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Reallocate;
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end if;
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end if;
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end Set_Last;
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begin
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Init;
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end Table;
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end Table;
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