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) 2000-2013, AdaCore                     --
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 3,  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.                                     --
17--                                                                          --
18-- As a special exception under Section 7 of GPL version 3, you are granted --
19-- additional permissions described in the GCC Runtime Library Exception,   --
20-- version 3.1, as published by the Free Software Foundation.               --
21--                                                                          --
22-- You should have received a copy of the GNU General Public License and    --
23-- a copy of the GCC Runtime Library Exception along with this program;     --
24-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
25-- <http://www.gnu.org/licenses/>.                                          --
26--                                                                          --
27-- GNAT was originally developed  by the GNAT team at  New York University. --
28-- Extensive contributions were provided by Ada Core Technologies Inc.      --
29--                                                                          --
30------------------------------------------------------------------------------
31
32--  Resizable one dimensional array support
33
34--  This package provides an implementation of dynamically resizable one
35--  dimensional arrays. The idea is to mimic the normal Ada semantics for
36--  arrays as closely as possible with the one additional capability of
37--  dynamically modifying the value of the Last attribute.
38
39--  This package provides a facility similar to that of GNAT.Table, except
40--  that this package declares a type that can be used to define dynamic
41--  instances of the table, while an instantiation of GNAT.Table creates a
42--  single instance of the table type.
43
44--  Note that this interface should remain synchronized with those in
45--  GNAT.Table and the GNAT compiler source unit Table to keep as much
46--  coherency as possible between these three related units.
47
48pragma Compiler_Unit_Warning;
49
50generic
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
58package 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   subtype Big_Table_Type is
95     Table_Type (Table_Low_Bound .. Table_Index_Type'Last);
96   --  We work with pointers to a bogus array type that is constrained with
97   --  the maximum possible range bound. This means that the pointer is a thin
98   --  pointer, which is more efficient. Since subscript checks in any case
99   --  must be on the logical, rather than physical bounds, safety is not
100   --  compromised by this approach. These types should not be used by the
101   --  client.
102
103   type Table_Ptr is access all Big_Table_Type;
104   for Table_Ptr'Storage_Size use 0;
105   --  The table is actually represented as a pointer to allow reallocation.
106   --  This type should not be used by the client.
107
108   type Table_Private is private;
109   --  Table private data that is not exported in Instance
110
111   type Instance is record
112      Table : aliased Table_Ptr := null;
113   --  The table itself. The lower bound is the value of Low_Bound.
114   --  Logically the upper bound is the current value of Last (although
115   --  the actual size of the allocated table may be larger than this).
116   --  The program may only access and modify Table entries in the
117   --  range First .. Last.
118
119      P : Table_Private;
120   end record;
121
122   procedure Init (T : in out Instance);
123   --  This procedure allocates a new table of size Initial (freeing any
124   --  previously allocated larger table). Init must be called before using
125   --  the table. Init is convenient in reestablishing a table for new use.
126
127   function Last (T : Instance) return Table_Index_Type;
128   pragma Inline (Last);
129   --  Returns the current value of the last used entry in the table,
130   --  which can then be used as a subscript for Table. Note that the
131   --  only way to modify Last is to call the Set_Last procedure. Last
132   --  must always be used to determine the logically last entry.
133
134   procedure Release (T : in out Instance);
135   --  Storage is allocated in chunks according to the values given in the
136   --  Initial and Increment parameters. A call to Release releases all
137   --  storage that is allocated, but is not logically part of the current
138   --  array value. Current array values are not affected by this call.
139
140   procedure Free (T : in out Instance);
141   --  Free all allocated memory for the table. A call to init is required
142   --  before any use of this table after calling Free.
143
144   First : constant Table_Index_Type := Table_Low_Bound;
145   --  Export First as synonym for Low_Bound (parallel with use of Last)
146
147   procedure Set_Last (T : in out Instance; New_Val : Table_Index_Type);
148   pragma Inline (Set_Last);
149   --  This procedure sets Last to the indicated value. If necessary the
150   --  table is reallocated to accommodate the new value (i.e. on return
151   --  the allocated table has an upper bound of at least Last). If
152   --  Set_Last reduces the size of the table, then logically entries are
153   --  removed from the table. If Set_Last increases the size of the
154   --  table, then new entries are logically added to the table.
155
156   procedure Increment_Last (T : in out Instance);
157   pragma Inline (Increment_Last);
158   --  Adds 1 to Last (same as Set_Last (Last + 1)
159
160   procedure Decrement_Last (T : in out Instance);
161   pragma Inline (Decrement_Last);
162   --  Subtracts 1 from Last (same as Set_Last (Last - 1)
163
164   procedure Append (T : in out Instance; New_Val : Table_Component_Type);
165   pragma Inline (Append);
166   --  Equivalent to:
167   --    Increment_Last (T);
168   --    T.Table (T.Last) := New_Val;
169   --  i.e. the table size is increased by one, and the given new item
170   --  stored in the newly created table element.
171
172   procedure Append_All (T : in out Instance; New_Vals : Table_Type);
173   --  Appends all components of New_Vals
174
175   procedure Set_Item
176     (T     : in out Instance;
177      Index : Table_Index_Type;
178      Item  : Table_Component_Type);
179   pragma Inline (Set_Item);
180   --  Put Item in the table at position Index. The table is expanded if
181   --  current table length is less than Index and in that case Last is set to
182   --  Index. Item will replace any value already present in the table at this
183   --  position.
184
185   procedure Allocate (T : in out Instance; Num : Integer := 1);
186   pragma Inline (Allocate);
187   --  Adds Num to Last
188
189   generic
190     with procedure Action
191       (Index : Table_Index_Type;
192        Item  : Table_Component_Type;
193        Quit  : in out Boolean) is <>;
194   procedure For_Each (Table : Instance);
195   --  Calls procedure Action for each component of the table Table, or until
196   --  one of these calls set Quit to True.
197
198   generic
199     with function Lt (Comp1, Comp2 : Table_Component_Type) return Boolean;
200   procedure Sort_Table (Table : in out Instance);
201   --  This procedure sorts the components of table Table into ascending
202   --  order making calls to Lt to do required comparisons, and using
203   --  assignments to move components around. The Lt function returns True
204   --  if Comp1 is less than Comp2 (in the sense of the desired sort), and
205   --  False if Comp1 is greater than Comp2. For equal objects it does not
206   --  matter if True or False is returned (it is slightly more efficient
207   --  to return False). The sort is not stable (the order of equal items
208   --  in the table is not preserved).
209
210private
211   type Table_Private is record
212      Max : Integer;
213      --  Subscript of the maximum entry in the currently allocated table
214
215      Length : Integer := 0;
216      --  Number of entries in currently allocated table. The value of zero
217      --  ensures that we initially allocate the table.
218
219      Last_Val : Integer;
220      --  Current value of Last
221   end record;
222
223end GNAT.Dynamic_Tables;
224