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1 706 jeremybenn
------------------------------------------------------------------------------
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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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--                                 S p e c                                  --
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--                                                                          --
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--          Copyright (C) 1992-2009, 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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--  This package provides an implementation of dynamically resizable one
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--  dimensional arrays. The idea is to mimic the normal Ada semantics for
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--  arrays as closely as possible with the one additional capability of
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--  dynamically modifying the value of the Last attribute.
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--  Note that this interface should remain synchronized with those in
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--  GNAT.Table and GNAT.Dynamic_Tables to keep coherency between these
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--  three related units.
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with Types; use Types;
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package Table is
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   pragma Elaborate_Body;
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   generic
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      type Table_Component_Type is private;
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      type Table_Index_Type     is range <>;
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      Table_Low_Bound  : Table_Index_Type;
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      Table_Initial    : Pos;
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      Table_Increment  : Nat;
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      Table_Name       : String;
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   package Table is
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      --  Table_Component_Type and Table_Index_Type specify the type of the
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      --  array, Table_Low_Bound is the lower bound. Index_type must be an
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      --  integer type. The effect is roughly to declare:
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      --    Table : array (Table_Index_Type range Table_Low_Bound .. <>)
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      --                       of Table_Component_Type;
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      --    Note: since the upper bound can be one less than the lower
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      --    bound for an empty array, the table index type must be able
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      --    to cover this range, e.g. if the lower bound is 1, then the
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      --    Table_Index_Type should be Natural rather than Positive.
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      --  Table_Component_Type may be any Ada type, except that controlled
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      --  types are not supported. Note however that default initialization
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      --  will NOT occur for array components.
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      --  The Table_Initial values controls the allocation of the table when
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      --  it is first allocated, either by default, or by an explicit Init
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      --  call. The value used is Opt.Table_Factor * Table_Initial.
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      --  The Table_Increment value controls the amount of increase, if the
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      --  table has to be increased in size. The value given is a percentage
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      --  value (e.g. 100 = increase table size by 100%, i.e. double it).
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      --  The Table_Name parameter is simply use in debug output messages it
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      --  has no other usage, and is not referenced in non-debugging mode.
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      --  The Last and Set_Last subprograms provide control over the current
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      --  logical allocation. They are quite efficient, so they can be used
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      --  freely (expensive reallocation occurs only at major granularity
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      --  chunks controlled by the allocation parameters).
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      --  Note: We do not make the table components aliased, since this would
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      --  restrict the use of table for discriminated types. If it is necessary
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      --  to take the access of a table element, use Unrestricted_Access.
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      --  WARNING: On HPPA, the virtual addressing approach used in this unit
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      --  is incompatible with the indexing instructions on the HPPA. So when
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      --  using this unit, compile your application with -mdisable-indexing.
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      --  WARNING: If the table is reallocated, then the address of all its
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      --  components will change. So do not capture the address of an element
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      --  and then use the address later after the table may be reallocated.
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      --  One tricky case of this is passing an element of the table to a
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      --  subprogram by reference where the table gets reallocated during
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      --  the execution of the subprogram. The best rule to follow is never
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      --  to pass a table element as a parameter except for the case of IN
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      --  mode parameters with scalar values.
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      type Table_Type is
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        array (Table_Index_Type range <>) of Table_Component_Type;
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      subtype Big_Table_Type is
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        Table_Type (Table_Low_Bound .. Table_Index_Type'Last);
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      --  We work with pointers to a bogus array type that is constrained
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      --  with the maximum possible range bound. This means that the pointer
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      --  is a thin pointer, which is more efficient. Since subscript checks
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      --  in any case must be on the logical, rather than physical bounds,
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      --  safety is not compromised by this approach.
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      type Table_Ptr is access all Big_Table_Type;
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      for Table_Ptr'Storage_Size use 0;
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      --  The table is actually represented as a pointer to allow reallocation
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      Table : aliased Table_Ptr := null;
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      --  The table itself. The lower bound is the value of Low_Bound.
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      --  Logically the upper bound is the current value of Last (although
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      --  the actual size of the allocated table may be larger than this).
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      --  The program may only access and modify Table entries in the range
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      --  First .. Last.
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      Locked : Boolean := False;
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      --  Table expansion is permitted only if this switch is set to False. A
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      --  client may set Locked to True, in which case any attempt to expand
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      --  the table will cause an assertion failure. Note that while a table
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      --  is locked, its address in memory remains fixed and unchanging. This
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      --  feature is used to control table expansion during Gigi processing.
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      --  Gigi assumes that tables other than the Uint and Ureal tables do
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      --  not move during processing, which means that they cannot be expanded.
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      --  The Locked flag is used to enforce this restriction.
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      procedure Init;
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      --  This procedure allocates a new table of size Initial (freeing any
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      --  previously allocated larger table). It is not necessary to call
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      --  Init when a table is first instantiated (since the instantiation does
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      --  the same initialization steps). However, it is harmless to do so, and
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      --  Init is convenient in reestablishing a table for new use.
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      function Last return Table_Index_Type;
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      pragma Inline (Last);
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      --  Returns the current value of the last used entry in the table, which
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      --  can then be used as a subscript for Table. Note that the only way to
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      --  modify Last is to call the Set_Last procedure. Last must always be
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      --  used to determine the logically last entry.
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      procedure Release;
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      --  Storage is allocated in chunks according to the values given in the
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      --  Initial and Increment parameters. A call to Release releases all
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      --  storage that is allocated, but is not logically part of the current
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      --  array value. Current array values are not affected by this call.
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      procedure Free;
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      --  Free all allocated memory for the table. A call to init is required
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      --  before any use of this table after calling Free.
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      First : constant Table_Index_Type := Table_Low_Bound;
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      --  Export First as synonym for Low_Bound (parallel with use of Last)
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      procedure Set_Last (New_Val : Table_Index_Type);
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      pragma Inline (Set_Last);
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      --  This procedure sets Last to the indicated value. If necessary the
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      --  table is reallocated to accommodate the new value (i.e. on return
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      --  the allocated table has an upper bound of at least Last). If Set_Last
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      --  reduces the size of the table, then logically entries are removed
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      --  from the table. If Set_Last increases the size of the table, then
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      --  new entries are logically added to the table.
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      procedure Increment_Last;
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      pragma Inline (Increment_Last);
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      --  Adds 1 to Last (same as Set_Last (Last + 1)
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      procedure Decrement_Last;
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      pragma Inline (Decrement_Last);
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      --  Subtracts 1 from Last (same as Set_Last (Last - 1)
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      procedure Append (New_Val : Table_Component_Type);
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      pragma Inline (Append);
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      --  Equivalent to:
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      --    x.Increment_Last;
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      --    x.Table (x.Last) := New_Val;
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      --  i.e. the table size is increased by one, and the given new item
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      --  stored in the newly created table element.
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      procedure Append_All (New_Vals : Table_Type);
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      --  Appends all components of New_Vals
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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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      pragma Inline (Set_Item);
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      --  Put Item in the table at position Index. The table is expanded if
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      --  current table length is less than Index and in that case Last is set
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      --  to Index. Item will replace any value already present in the table
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      --  at this position.
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      type Saved_Table is private;
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      --  Type used for Save/Restore subprograms
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      function Save return Saved_Table;
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      --  Resets table to empty, but saves old contents of table in returned
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      --  value, for possible later restoration by a call to Restore.
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      procedure Restore (T : Saved_Table);
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      --  Given a Saved_Table value returned by a prior call to Save, restores
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      --  the table to the state it was in at the time of the Save call.
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      procedure Tree_Write;
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      --  Writes out contents of table using Tree_IO
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      procedure Tree_Read;
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      --  Initializes table by reading contents previously written
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      --  with the Tree_Write call (also using Tree_IO)
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   private
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      Last_Val : Int;
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      --  Current value of Last. Note that we declare this in the private part
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      --  because we don't want the client to modify Last except through one of
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      --  the official interfaces (since a modification to Last may require a
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      --  reallocation of the table).
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      Max : Int;
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      --  Subscript of the maximum entry in the currently allocated table
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      type Saved_Table is record
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         Last_Val : Int;
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         Max      : Int;
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         Table    : Table_Ptr;
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      end record;
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   end Table;
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end Table;

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