340 lines
11 KiB
Ada
340 lines
11 KiB
Ada
------------------------------------------------------------------------------
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-- --
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-- GNAT COMPILER COMPONENTS --
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-- --
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-- S Y S T E M . E X C E P T I O N _ 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) 1996-2014, 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. --
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-- --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
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-- additional permissions described in the GCC Runtime Library Exception, --
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-- version 3.1, as published by the Free Software Foundation. --
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-- --
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-- You should have received a copy of the GNU General Public License and --
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-- a copy of the GCC Runtime Library Exception along with this program; --
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-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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-- <http://www.gnu.org/licenses/>. --
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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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pragma Compiler_Unit_Warning;
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with System.Soft_Links; use System.Soft_Links;
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package body System.Exception_Table is
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use System.Standard_Library;
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type Hash_Val is mod 2 ** 8;
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subtype Hash_Idx is Hash_Val range 1 .. 37;
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HTable : array (Hash_Idx) of aliased Exception_Data_Ptr;
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-- Actual hash table containing all registered exceptions
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--
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-- The table is very small and the hash function weak, as looking up
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-- registered exceptions is rare and minimizing space and time overhead
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-- of registration is more important. In addition, it is expected that the
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-- exceptions that need to be looked up are registered dynamically, and
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-- therefore will be at the begin of the hash chains.
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--
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-- The table differs from System.HTable.Static_HTable in that the final
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-- element of each chain is not marked by null, but by a pointer to self.
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-- This way it is possible to defend against the same entry being inserted
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-- twice, without having to do a lookup which is relatively expensive for
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-- programs with large number
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--
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-- All non-local subprograms use the global Task_Lock to protect against
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-- concurrent use of the exception table. This is needed as local
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-- exceptions may be declared concurrently with those declared at the
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-- library level.
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-- Local Subprograms
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generic
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with procedure Process (T : Exception_Data_Ptr; More : out Boolean);
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procedure Iterate;
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-- Iterate over all
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function Lookup (Name : String) return Exception_Data_Ptr;
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-- Find and return the Exception_Data of the exception with the given Name
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-- (which must be in all uppercase), or null if none was registered.
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procedure Register (Item : Exception_Data_Ptr);
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-- Register an exception with the given Exception_Data in the table.
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function Has_Name (Item : Exception_Data_Ptr; Name : String) return Boolean;
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-- Return True iff Item.Full_Name and Name are equal. Both names are
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-- assumed to be in all uppercase and end with ASCII.NUL.
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function Hash (S : String) return Hash_Idx;
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-- Return the index in the hash table for S, which is assumed to be all
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-- uppercase and end with ASCII.NUL.
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--------------
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-- Has_Name --
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--------------
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function Has_Name (Item : Exception_Data_Ptr; Name : String) return Boolean
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is
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S : constant Big_String_Ptr := To_Ptr (Item.Full_Name);
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J : Integer := S'First;
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begin
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for K in Name'Range loop
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-- Note that as both items are terminated with ASCII.NUL, the
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-- comparison below must fail for strings of different lengths.
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if S (J) /= Name (K) then
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return False;
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end if;
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J := J + 1;
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end loop;
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return True;
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end Has_Name;
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------------
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-- Lookup --
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------------
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function Lookup (Name : String) return Exception_Data_Ptr is
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Prev : Exception_Data_Ptr;
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Curr : Exception_Data_Ptr;
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begin
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Curr := HTable (Hash (Name));
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Prev := null;
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while Curr /= Prev loop
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if Has_Name (Curr, Name) then
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return Curr;
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end if;
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Prev := Curr;
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Curr := Curr.HTable_Ptr;
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end loop;
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return null;
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end Lookup;
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----------
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-- Hash --
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----------
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function Hash (S : String) return Hash_Idx is
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Hash : Hash_Val := 0;
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begin
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for J in S'Range loop
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exit when S (J) = ASCII.NUL;
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Hash := Hash xor Character'Pos (S (J));
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end loop;
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return Hash_Idx'First + Hash mod (Hash_Idx'Last - Hash_Idx'First + 1);
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end Hash;
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-------------
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-- Iterate --
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-------------
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procedure Iterate is
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More : Boolean;
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Prev, Curr : Exception_Data_Ptr;
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begin
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Outer : for Idx in HTable'Range loop
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Prev := null;
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Curr := HTable (Idx);
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while Curr /= Prev loop
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Process (Curr, More);
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exit Outer when not More;
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Prev := Curr;
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Curr := Curr.HTable_Ptr;
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end loop;
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end loop Outer;
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end Iterate;
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--------------
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-- Register --
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--------------
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procedure Register (Item : Exception_Data_Ptr) is
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begin
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if Item.HTable_Ptr = null then
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Prepend_To_Chain : declare
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Chain : Exception_Data_Ptr
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renames HTable (Hash (To_Ptr (Item.Full_Name).all));
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begin
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if Chain = null then
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Item.HTable_Ptr := Item;
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else
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Item.HTable_Ptr := Chain;
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end if;
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Chain := Item;
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end Prepend_To_Chain;
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end if;
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end Register;
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-------------------------------
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-- Get_Registered_Exceptions --
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-------------------------------
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procedure Get_Registered_Exceptions
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(List : out Exception_Data_Array;
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Last : out Integer)
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is
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procedure Get_One (Item : Exception_Data_Ptr; More : out Boolean);
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-- Add Item to List (List'First .. Last) by first incrementing Last
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-- and storing Item in List (Last). Last should be in List'First - 1
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-- and List'Last.
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procedure Get_All is new Iterate (Get_One);
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-- Store all registered exceptions in List, updating Last
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-------------
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-- Get_One --
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-------------
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procedure Get_One (Item : Exception_Data_Ptr; More : out Boolean) is
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begin
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if Last < List'Last then
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Last := Last + 1;
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List (Last) := Item;
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More := True;
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else
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More := False;
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end if;
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end Get_One;
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begin
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-- In this routine the invariant is that List (List'First .. Last)
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-- contains the registered exceptions retrieved so far.
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Last := List'First - 1;
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Lock_Task.all;
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Get_All;
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Unlock_Task.all;
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end Get_Registered_Exceptions;
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------------------------
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-- Internal_Exception --
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------------------------
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function Internal_Exception
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(X : String;
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Create_If_Not_Exist : Boolean := True) return Exception_Data_Ptr
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is
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-- If X was not yet registered and Create_if_Not_Exist is True,
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-- dynamically allocate and register a new exception.
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type String_Ptr is access all String;
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Dyn_Copy : String_Ptr;
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Copy : aliased String (X'First .. X'Last + 1);
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Result : Exception_Data_Ptr;
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begin
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Lock_Task.all;
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Copy (X'Range) := X;
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Copy (Copy'Last) := ASCII.NUL;
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Result := Lookup (Copy);
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-- If unknown exception, create it on the heap. This is a legitimate
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-- situation in the distributed case when an exception is defined
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-- only in a partition
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if Result = null and then Create_If_Not_Exist then
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Dyn_Copy := new String'(Copy);
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Result :=
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new Exception_Data'
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(Not_Handled_By_Others => False,
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Lang => 'A',
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Name_Length => Copy'Length,
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Full_Name => Dyn_Copy.all'Address,
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HTable_Ptr => null,
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Foreign_Data => Null_Address,
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Raise_Hook => null);
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Register (Result);
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end if;
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Unlock_Task.all;
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return Result;
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end Internal_Exception;
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------------------------
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-- Register_Exception --
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------------------------
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procedure Register_Exception (X : Exception_Data_Ptr) is
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begin
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Lock_Task.all;
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Register (X);
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Unlock_Task.all;
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end Register_Exception;
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---------------------------------
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-- Registered_Exceptions_Count --
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---------------------------------
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function Registered_Exceptions_Count return Natural is
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Count : Natural := 0;
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procedure Count_Item (Item : Exception_Data_Ptr; More : out Boolean);
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-- Update Count for given Item
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procedure Count_Item (Item : Exception_Data_Ptr; More : out Boolean) is
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pragma Unreferenced (Item);
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begin
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Count := Count + 1;
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More := Count < Natural'Last;
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end Count_Item;
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procedure Count_All is new Iterate (Count_Item);
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begin
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Lock_Task.all;
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Count_All;
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Unlock_Task.all;
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return Count;
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end Registered_Exceptions_Count;
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begin
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-- Register the standard exceptions at elaboration time
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-- We don't need to use the locking version here as the elaboration
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-- will not be concurrent and no tasks can call any subprograms of this
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-- unit before it has been elaborated.
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Register (Abort_Signal_Def'Access);
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Register (Tasking_Error_Def'Access);
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Register (Storage_Error_Def'Access);
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Register (Program_Error_Def'Access);
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Register (Numeric_Error_Def'Access);
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Register (Constraint_Error_Def'Access);
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end System.Exception_Table;
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