gcc/ada/g-dyntab.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                   G N A T . D Y N A M I C _ T A B L E S                  --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --            Copyright (C) 2000-2005 Ada Core Technologies, Inc.           --
  10 --                                                                          --
  11 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  14 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  19 -- to  the  Free Software Foundation,  51  Franklin  Street,  Fifth  Floor, --
  20 -- Boston, MA 02110-1301, USA.                                              --
  21 --                                                                          --
  22 -- As a special exception,  if other files  instantiate  generics from this --
  23 -- unit, or you link  this unit with other files  to produce an executable, --
  24 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  25 -- covered  by the  GNU  General  Public  License.  This exception does not --
  26 -- however invalidate  any other reasons why  the executable file  might be --
  27 -- covered by the  GNU Public License.                                      --
  28 --                                                                          --
  29 -- GNAT was originally developed  by the GNAT team at  New York University. --
  30 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  31 --                                                                          --
  32 ------------------------------------------------------------------------------
  33
  34 --  Resizable one dimensional array support
  35
  36 --  This package provides an implementation of dynamically resizable one
  37 --  dimensional arrays. The idea is to mimic the normal Ada semantics for
  38 --  arrays as closely as possible with the one additional capability of
  39 --  dynamically modifying the value of the Last attribute.
  40
  41 --  This package provides a facility similar to that of GNAT.Table, except
  42 --  that this package declares a type that can be used to define dynamic
  43 --  instances of the table, while an instantiation of GNAT.Table creates a
  44 --  single instance of the table type.
  45
  46 --  Note that this interface should remain synchronized with those in
  47 --  GNAT.Table and the GNAT compiler source unit Table to keep as much
  48 --  coherency as possible between these three related units.
  49
  50 generic
  51    type Table_Component_Type is private;
  52    type Table_Index_Type     is range <>;
  53
  54    Table_Low_Bound : Table_Index_Type;
  55    Table_Initial   : Positive;
  56    Table_Increment : Natural;
  57
  58 package GNAT.Dynamic_Tables is
  59
  60    --  Table_Component_Type and Table_Index_Type specify the type of the
  61    --  array, Table_Low_Bound is the lower bound. Index_type must be an
  62    --  integer type. The effect is roughly to declare:
  63
  64    --    Table : array (Table_Low_Bound .. <>) of Table_Component_Type;
  65
  66    --    Note: since the upper bound can be one less than the lower
  67    --    bound for an empty array, the table index type must be able
  68    --    to cover this range, e.g. if the lower bound is 1, then the
  69    --    Table_Index_Type should be Natural rather than Positive.
  70
  71    --  Table_Component_Type may be any Ada type, except that controlled
  72    --  types are not supported. Note however that default initialization
  73    --  will NOT occur for array components.
  74
  75    --  The Table_Initial values controls the allocation of the table when
  76    --  it is first allocated, either by default, or by an explicit Init
  77    --  call.
  78
  79    --  The Table_Increment value controls the amount of increase, if the
  80    --  table has to be increased in size. The value given is a percentage
  81    --  value (e.g. 100 = increase table size by 100%, i.e. double it).
  82
  83    --  The Last and Set_Last subprograms provide control over the current
  84    --  logical allocation. They are quite efficient, so they can be used
  85    --  freely (expensive reallocation occurs only at major granularity
  86    --  chunks controlled by the allocation parameters).
  87
  88    --  Note: we do not make the table components aliased, since this would
  89    --  restrict the use of table for discriminated types. If it is necessary
  90    --  to take the access of a table element, use Unrestricted_Access.
  91
  92    type Table_Type is
  93      array (Table_Index_Type range <>) of Table_Component_Type;
  94
  95    subtype Big_Table_Type is
  96      Table_Type (Table_Low_Bound .. Table_Index_Type'Last);
  97    --  We work with pointers to a bogus array type that is constrained
  98    --  with the maximum possible range bound. This means that the pointer
  99    --  is a thin pointer, which is more efficient. Since subscript checks
 100    --  in any case must be on the logical, rather than physical bounds,
 101    --  safety is not compromised by this approach.
 102
 103    type Table_Ptr is access all Big_Table_Type;
 104    --  The table is actually represented as a pointer to allow
 105    --  reallocation.
 106
 107    type Table_Private is private;
 108    --  table private data that is not exported in Instance.
 109
 110    type Instance is record
 111       Table : aliased Table_Ptr := null;
 112    --  The table itself. The lower bound is the value of Low_Bound.
 113    --  Logically the upper bound is the current value of Last (although
 114    --  the actual size of the allocated table may be larger than this).
 115    --  The program may only access and modify Table entries in the
 116    --  range First .. Last.
 117
 118       P : Table_Private;
 119    end record;
 120
 121    procedure Init (T : in out Instance);
 122    --  This procedure allocates a new table of size Initial (freeing any
 123    --  previously allocated larger table). Init must be called before using
 124    --  the table. Init is convenient in reestablishing a table for new use.
 125
 126    function Last (T : in Instance) return Table_Index_Type;
 127    pragma Inline (Last);
 128    --  Returns the current value of the last used entry in the table,
 129    --  which can then be used as a subscript for Table. Note that the
 130    --  only way to modify Last is to call the Set_Last procedure. Last
 131    --  must always be used to determine the logically last entry.
 132
 133    procedure Release (T : in out Instance);
 134    --  Storage is allocated in chunks according to the values given in the
 135    --  Initial and Increment parameters. A call to Release releases all
 136    --  storage that is allocated, but is not logically part of the current
 137    --  array value. Current array values are not affected by this call.
 138
 139    procedure Free (T : in out Instance);
 140    --  Free all allocated memory for the table. A call to init is required
 141    --  before any use of this table after calling Free.
 142
 143    First : constant Table_Index_Type := Table_Low_Bound;
 144    --  Export First as synonym for Low_Bound (parallel with use of Last)
 145
 146    procedure Set_Last (T : in out Instance; New_Val : Table_Index_Type);
 147    pragma Inline (Set_Last);
 148    --  This procedure sets Last to the indicated value. If necessary the
 149    --  table is reallocated to accommodate the new value (i.e. on return
 150    --  the allocated table has an upper bound of at least Last). If
 151    --  Set_Last reduces the size of the table, then logically entries are
 152    --  removed from the table. If Set_Last increases the size of the
 153    --  table, then new entries are logically added to the table.
 154
 155    procedure Increment_Last (T : in out Instance);
 156    pragma Inline (Increment_Last);
 157    --  Adds 1 to Last (same as Set_Last (Last + 1)
 158
 159    procedure Decrement_Last (T : in out Instance);
 160    pragma Inline (Decrement_Last);
 161    --  Subtracts 1 from Last (same as Set_Last (Last - 1)
 162
 163    procedure Append (T : in out Instance; New_Val : Table_Component_Type);
 164    pragma Inline (Append);
 165    --  Equivalent to:
 166    --    Increment_Last (T);
 167    --    T.Table (T.Last) := New_Val;
 168    --  i.e. the table size is increased by one, and the given new item
 169    --  stored in the newly created table element.
 170
 171    procedure Set_Item
 172      (T     : in out Instance;
 173       Index : Table_Index_Type;
 174       Item  : Table_Component_Type);
 175    pragma Inline (Set_Item);
 176    --  Put Item in the table at position Index. The table is expanded if
 177    --  current table length is less than Index and in that case Last is set to
 178    --  Index. Item will replace any value already present in the table at this
 179    --  position.
 180
 181    procedure Allocate (T : in out Instance; Num : Integer := 1);
 182    pragma Inline (Allocate);
 183    --  Adds Num to Last
 184
 185    generic
 186      with procedure Action
 187        (Index : Table_Index_Type;
 188         Item  : Table_Component_Type;
 189         Quit  : in out Boolean) is <>;
 190    procedure For_Each (Table : Instance);
 191    --  Calls procedure Action for each component of the table Table, or until
 192    --  one of these calls set Quit to True.
 193
 194    generic
 195      with function Lt (Comp1, Comp2 : Table_Component_Type) return Boolean;
 196    procedure Sort_Table (Table : in out Instance);
 197    --  This procedure sorts the components of table Table into ascending
 198    --  order making calls to Lt to do required comparisons, and using
 199    --  assignments to move components around. The Lt function returns True
 200    --  if Comp1 is less than Comp2 (in the sense of the desired sort), and
 201    --  False if Comp1 is greater than Comp2. For equal objects it does not
 202    --  matter if True or False is returned (it is slightly more efficient
 203    --  to return False). The sort is not stable (the order of equal items
 204    --  in the table is not preserved).
 205
 206 private
 207    type Table_Private is record
 208       Max : Integer;
 209       --  Subscript of the maximum entry in the currently allocated table
 210
 211       Length : Integer := 0;
 212       --  Number of entries in currently allocated table. The value of zero
 213       --  ensures that we initially allocate the table.
 214
 215       Last_Val : Integer;
 216       --  Current value of Last
 217    end record;
 218
 219 end GNAT.Dynamic_Tables;