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1 | ------------------------------------------------------------------------------ |
2 | -- -- | |
3 | -- GNAT RUNTIME COMPONENTS -- | |
4 | -- -- | |
5 | -- G N A T . T A B L E -- | |
6 | -- -- | |
7 | -- S p e c -- | |
8 | -- -- | |
fbf5a39b | 9 | -- Copyright (C) 1998-2003 Ada Core Technologies, Inc. -- |
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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, 59 Temple Place - Suite 330, Boston, -- | |
20 | -- MA 02111-1307, 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 | -- -- | |
fbf5a39b AC |
29 | -- GNAT was originally developed by the GNAT team at New York University. -- |
30 | -- Extensive contributions were provided by Ada Core Technologies Inc. -- | |
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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.Dynamic_Tables, | |
42 | -- except that this package declares a single instance of the table type, | |
43 | -- while an instantiation of GNAT.Dynamic_Tables creates a type that can be | |
44 | -- used to define dynamic instances of the table. | |
45 | ||
46 | -- Note that this interface should remain synchronized with those in | |
47 | -- GNAT.Dynamic_Tables and the GNAT compiler source unit Table to keep | |
48 | -- as much 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.Table is | |
59 | pragma Elaborate_Body (Table); | |
60 | ||
61 | -- Table_Component_Type and Table_Index_Type specify the type of the | |
62 | -- array, Table_Low_Bound is the lower bound. Index_type must be an | |
63 | -- integer type. The effect is roughly to declare: | |
64 | ||
65 | -- Table : array (Table_Index_Type range Table_Low_Bound .. <>) | |
66 | -- of Table_Component_Type; | |
67 | ||
68 | -- Note: since the upper bound can be one less than the lower | |
69 | -- bound for an empty array, the table index type must be able | |
70 | -- to cover this range, e.g. if the lower bound is 1, then the | |
71 | -- Table_Index_Type should be Natural rather than Positive. | |
72 | ||
73 | -- Table_Component_Type may be any Ada type, except that controlled | |
74 | -- types are not supported. Note however that default initialization | |
75 | -- will NOT occur for array components. | |
76 | ||
77 | -- The Table_Initial values controls the allocation of the table when | |
78 | -- it is first allocated, either by default, or by an explicit Init call. | |
79 | ||
80 | -- The Table_Increment value controls the amount of increase, if the | |
81 | -- table has to be increased in size. The value given is a percentage | |
82 | -- value (e.g. 100 = increase table size by 100%, i.e. double it). | |
83 | ||
84 | -- The Last and Set_Last subprograms provide control over the current | |
85 | -- logical allocation. They are quite efficient, so they can be used | |
86 | -- freely (expensive reallocation occurs only at major granularity | |
87 | -- chunks controlled by the allocation parameters). | |
88 | ||
89 | -- Note: we do not make the table components aliased, since this would | |
90 | -- restrict the use of table for discriminated types. If it is necessary | |
91 | -- to take the access of a table element, use Unrestricted_Access. | |
92 | ||
fbf5a39b AC |
93 | -- WARNING: On HPPA, the virtual addressing approach used in this unit |
94 | -- is incompatible with the indexing instructions on the HPPA. So when | |
95 | -- using this unit, compile your application with -mdisable-indexing. | |
96 | ||
97 | -- WARNING: If the table is reallocated, then the address of all its | |
98 | -- components will change. So do not capture the address of an element | |
99 | -- and then use the address later after the table may be reallocated. | |
100 | -- One tricky case of this is passing an element of the table to a | |
101 | -- subprogram by reference where the table gets reallocated during | |
102 | -- the execution of the subprogram. The best rule to follow is never | |
103 | -- to pass a table element as a parameter except for the case of IN | |
104 | -- mode parameters with scalar values. | |
105 | ||
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106 | type Table_Type is |
107 | array (Table_Index_Type range <>) of Table_Component_Type; | |
108 | ||
109 | subtype Big_Table_Type is | |
110 | Table_Type (Table_Low_Bound .. Table_Index_Type'Last); | |
111 | -- We work with pointers to a bogus array type that is constrained | |
112 | -- with the maximum possible range bound. This means that the pointer | |
113 | -- is a thin pointer, which is more efficient. Since subscript checks | |
114 | -- in any case must be on the logical, rather than physical bounds, | |
115 | -- safety is not compromised by this approach. | |
116 | ||
117 | type Table_Ptr is access all Big_Table_Type; | |
118 | -- The table is actually represented as a pointer to allow reallocation | |
119 | ||
120 | Table : aliased Table_Ptr := null; | |
121 | -- The table itself. The lower bound is the value of Low_Bound. | |
122 | -- Logically the upper bound is the current value of Last (although | |
123 | -- the actual size of the allocated table may be larger than this). | |
124 | -- The program may only access and modify Table entries in the range | |
125 | -- First .. Last. | |
126 | ||
127 | Locked : Boolean := False; | |
128 | -- Table expansion is permitted only if this switch is set to False. A | |
129 | -- client may set Locked to True, in which case any attempt to expand | |
130 | -- the table will cause an assertion failure. Note that while a table | |
131 | -- is locked, its address in memory remains fixed and unchanging. | |
132 | ||
133 | procedure Init; | |
134 | -- This procedure allocates a new table of size Initial (freeing any | |
135 | -- previously allocated larger table). It is not necessary to call | |
136 | -- Init when a table is first instantiated (since the instantiation does | |
137 | -- the same initialization steps). However, it is harmless to do so, and | |
138 | -- Init is convenient in reestablishing a table for new use. | |
139 | ||
140 | function Last return Table_Index_Type; | |
141 | pragma Inline (Last); | |
142 | -- Returns the current value of the last used entry in the table, which | |
143 | -- can then be used as a subscript for Table. Note that the only way to | |
144 | -- modify Last is to call the Set_Last procedure. Last must always be | |
145 | -- used to determine the logically last entry. | |
146 | ||
147 | procedure Release; | |
148 | -- Storage is allocated in chunks according to the values given in the | |
149 | -- Initial and Increment parameters. A call to Release releases all | |
150 | -- storage that is allocated, but is not logically part of the current | |
151 | -- array value. Current array values are not affected by this call. | |
152 | ||
153 | procedure Free; | |
154 | -- Free all allocated memory for the table. A call to init is required | |
155 | -- before any use of this table after calling Free. | |
156 | ||
157 | First : constant Table_Index_Type := Table_Low_Bound; | |
158 | -- Export First as synonym for Low_Bound (parallel with use of Last) | |
159 | ||
160 | procedure Set_Last (New_Val : Table_Index_Type); | |
161 | pragma Inline (Set_Last); | |
162 | -- This procedure sets Last to the indicated value. If necessary the | |
638e383e | 163 | -- table is reallocated to accommodate the new value (i.e. on return |
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164 | -- the allocated table has an upper bound of at least Last). If Set_Last |
165 | -- reduces the size of the table, then logically entries are removed | |
166 | -- from the table. If Set_Last increases the size of the table, then | |
167 | -- new entries are logically added to the table. | |
168 | ||
169 | procedure Increment_Last; | |
170 | pragma Inline (Increment_Last); | |
fbf5a39b | 171 | -- Adds 1 to Last (same as Set_Last (Last + 1) |
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172 | |
173 | procedure Decrement_Last; | |
174 | pragma Inline (Decrement_Last); | |
fbf5a39b | 175 | -- Subtracts 1 from Last (same as Set_Last (Last - 1) |
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176 | |
177 | procedure Append (New_Val : Table_Component_Type); | |
178 | pragma Inline (Append); | |
179 | -- Equivalent to: | |
180 | -- x.Increment_Last; | |
181 | -- x.Table (x.Last) := New_Val; | |
182 | -- i.e. the table size is increased by one, and the given new item | |
183 | -- stored in the newly created table element. | |
184 | ||
185 | procedure Set_Item | |
186 | (Index : Table_Index_Type; | |
187 | Item : Table_Component_Type); | |
188 | pragma Inline (Set_Item); | |
189 | -- Put Item in the table at position Index. The table is expanded if the | |
190 | -- current table length is less than Index and in that case Last is set to | |
191 | -- Index. Item will replace any value already present in the table at this | |
192 | -- position. | |
193 | ||
194 | function Allocate (Num : Integer := 1) return Table_Index_Type; | |
195 | pragma Inline (Allocate); | |
196 | -- Adds Num to Last, and returns the old value of Last + 1. Note that | |
197 | -- this function has the possible side effect of reallocating the table. | |
198 | -- This means that a reference X.Table (X.Allocate) is incorrect, since | |
199 | -- the call to X.Allocate may modify the results of calling X.Table. | |
200 | ||
201 | end GNAT.Table; |