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-------------------------------------------------------------------------------
--- --
--- GNAT RUNTIME COMPONENTS --
--- --
--- G N A T . T A B L E --
--- --
--- S p e c --
--- --
--- $Revision: 1.2 $
--- --
--- Copyright (C) 1998-2001 Ada Core Technologies, 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 2, 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 COPYING. If not, write --
--- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
--- MA 02111-1307, USA. --
--- --
--- As a special exception, if other files instantiate generics from this --
--- unit, or you link this unit with other files to produce an executable, --
--- this unit does not by itself cause the resulting executable to be --
--- covered by the GNU General Public License. This exception does not --
--- however invalidate any other reasons why the executable file might be --
--- covered by the GNU Public License. --
--- --
--- GNAT is maintained by Ada Core Technologies Inc (http://www.gnat.com). --
--- --
-------------------------------------------------------------------------------
-
--- Resizable one dimensional array support
-
--- This package provides an implementation of dynamically resizable one
--- dimensional arrays. The idea is to mimic the normal Ada semantics for
--- arrays as closely as possible with the one additional capability of
--- dynamically modifying the value of the Last attribute.
-
--- This package provides a facility similar to that of GNAT.Dynamic_Tables,
--- except that this package declares a single instance of the table type,
--- while an instantiation of GNAT.Dynamic_Tables creates a type that can be
--- used to define dynamic instances of the table.
-
--- Note that this interface should remain synchronized with those in
--- GNAT.Dynamic_Tables and the GNAT compiler source unit Table to keep
--- as much coherency as possible between these three related units.
-
-generic
- type Table_Component_Type is private;
- type Table_Index_Type is range <>;
-
- Table_Low_Bound : Table_Index_Type;
- Table_Initial : Positive;
- Table_Increment : Natural;
-
-package GNAT.Table is
-pragma Elaborate_Body (Table);
-
- -- Table_Component_Type and Table_Index_Type specify the type of the
- -- array, Table_Low_Bound is the lower bound. Index_type must be an
- -- integer type. The effect is roughly to declare:
-
- -- Table : array (Table_Index_Type range Table_Low_Bound .. <>)
- -- of Table_Component_Type;
-
- -- Note: since the upper bound can be one less than the lower
- -- bound for an empty array, the table index type must be able
- -- to cover this range, e.g. if the lower bound is 1, then the
- -- Table_Index_Type should be Natural rather than Positive.
-
- -- Table_Component_Type may be any Ada type, except that controlled
- -- types are not supported. Note however that default initialization
- -- will NOT occur for array components.
-
- -- The Table_Initial values controls the allocation of the table when
- -- it is first allocated, either by default, or by an explicit Init call.
-
- -- The Table_Increment value controls the amount of increase, if the
- -- table has to be increased in size. The value given is a percentage
- -- value (e.g. 100 = increase table size by 100%, i.e. double it).
-
- -- The Last and Set_Last subprograms provide control over the current
- -- logical allocation. They are quite efficient, so they can be used
- -- freely (expensive reallocation occurs only at major granularity
- -- chunks controlled by the allocation parameters).
-
- -- Note: we do not make the table components aliased, since this would
- -- restrict the use of table for discriminated types. If it is necessary
- -- to take the access of a table element, use Unrestricted_Access.
-
- type Table_Type is
- array (Table_Index_Type range <>) of Table_Component_Type;
-
- subtype Big_Table_Type is
- Table_Type (Table_Low_Bound .. Table_Index_Type'Last);
- -- We work with pointers to a bogus array type that is constrained
- -- with the maximum possible range bound. This means that the pointer
- -- is a thin pointer, which is more efficient. Since subscript checks
- -- in any case must be on the logical, rather than physical bounds,
- -- safety is not compromised by this approach.
-
- type Table_Ptr is access all Big_Table_Type;
- -- The table is actually represented as a pointer to allow reallocation
-
- Table : aliased Table_Ptr := null;
- -- The table itself. The lower bound is the value of Low_Bound.
- -- Logically the upper bound is the current value of Last (although
- -- the actual size of the allocated table may be larger than this).
- -- The program may only access and modify Table entries in the range
- -- First .. Last.
-
- Locked : Boolean := False;
- -- Table expansion is permitted only if this switch is set to False. A
- -- client may set Locked to True, in which case any attempt to expand
- -- the table will cause an assertion failure. Note that while a table
- -- is locked, its address in memory remains fixed and unchanging.
-
- procedure Init;
- -- This procedure allocates a new table of size Initial (freeing any
- -- previously allocated larger table). It is not necessary to call
- -- Init when a table is first instantiated (since the instantiation does
- -- the same initialization steps). However, it is harmless to do so, and
- -- Init is convenient in reestablishing a table for new use.
-
- function Last return Table_Index_Type;
- pragma Inline (Last);
- -- Returns the current value of the last used entry in the table, which
- -- can then be used as a subscript for Table. Note that the only way to
- -- modify Last is to call the Set_Last procedure. Last must always be
- -- used to determine the logically last entry.
-
- procedure Release;
- -- Storage is allocated in chunks according to the values given in the
- -- Initial and Increment parameters. A call to Release releases all
- -- storage that is allocated, but is not logically part of the current
- -- array value. Current array values are not affected by this call.
-
- procedure Free;
- -- Free all allocated memory for the table. A call to init is required
- -- before any use of this table after calling Free.
-
- First : constant Table_Index_Type := Table_Low_Bound;
- -- Export First as synonym for Low_Bound (parallel with use of Last)
-
- procedure Set_Last (New_Val : Table_Index_Type);
- pragma Inline (Set_Last);
- -- This procedure sets Last to the indicated value. If necessary the
- -- table is reallocated to accommodate the new value (i.e. on return
- -- the allocated table has an upper bound of at least Last). If Set_Last
- -- reduces the size of the table, then logically entries are removed
- -- from the table. If Set_Last increases the size of the table, then
- -- new entries are logically added to the table.
-
- procedure Increment_Last;
- pragma Inline (Increment_Last);
- -- Adds 1 to Last (same as Set_Last (Last + 1).
-
- procedure Decrement_Last;
- pragma Inline (Decrement_Last);
- -- Subtracts 1 from Last (same as Set_Last (Last - 1).
-
- procedure Append (New_Val : Table_Component_Type);
- pragma Inline (Append);
- -- Equivalent to:
- -- x.Increment_Last;
- -- x.Table (x.Last) := New_Val;
- -- i.e. the table size is increased by one, and the given new item
- -- stored in the newly created table element.
-
- procedure Set_Item
- (Index : Table_Index_Type;
- Item : Table_Component_Type);
- pragma Inline (Set_Item);
- -- Put Item in the table at position Index. The table is expanded if the
- -- current table length is less than Index and in that case Last is set to
- -- Index. Item will replace any value already present in the table at this
- -- position.
-
- function Allocate (Num : Integer := 1) return Table_Index_Type;
- pragma Inline (Allocate);
- -- Adds Num to Last, and returns the old value of Last + 1. Note that
- -- this function has the possible side effect of reallocating the table.
- -- This means that a reference X.Table (X.Allocate) is incorrect, since
- -- the call to X.Allocate may modify the results of calling X.Table.
-
-end GNAT.Table;
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