1------------------------------------------------------------------------------ 2-- -- 3-- GNAT RUNTIME COMPONENTS -- 4-- -- 5-- G N A T . T A B L E -- 6-- -- 7-- S p e c -- 8-- -- 9-- Copyright (C) 1998-2003 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, 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-- -- 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.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 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.Table is 59pragma 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 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. 105 106 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 163 -- table is reallocated to accommodate the new value (i.e. on return 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); 171 -- Adds 1 to Last (same as Set_Last (Last + 1) 172 173 procedure Decrement_Last; 174 pragma Inline (Decrement_Last); 175 -- Subtracts 1 from Last (same as Set_Last (Last - 1) 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 201end GNAT.Table; 202