1------------------------------------------------------------------------------ 2-- -- 3-- GNAT COMPILER COMPONENTS -- 4-- -- 5-- T A B L E -- 6-- -- 7-- S p e c -- 8-- -- 9-- Copyright (C) 1992-2009, Free Software Foundation, 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 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-- This package provides an implementation of dynamically resizable one 33-- dimensional arrays. The idea is to mimic the normal Ada semantics for 34-- arrays as closely as possible with the one additional capability of 35-- dynamically modifying the value of the Last attribute. 36 37-- Note that this interface should remain synchronized with those in 38-- GNAT.Table and GNAT.Dynamic_Tables to keep coherency between these 39-- three related units. 40 41with Types; use Types; 42 43package Table is 44 pragma Elaborate_Body; 45 46 generic 47 type Table_Component_Type is private; 48 type Table_Index_Type is range <>; 49 50 Table_Low_Bound : Table_Index_Type; 51 Table_Initial : Pos; 52 Table_Increment : Nat; 53 Table_Name : String; 54 55 package Table is 56 57 -- Table_Component_Type and Table_Index_Type specify the type of the 58 -- array, Table_Low_Bound is the lower bound. Index_type must be an 59 -- integer type. The effect is roughly to declare: 60 61 -- Table : array (Table_Index_Type range Table_Low_Bound .. <>) 62 -- of Table_Component_Type; 63 64 -- Note: since the upper bound can be one less than the lower 65 -- bound for an empty array, the table index type must be able 66 -- to cover this range, e.g. if the lower bound is 1, then the 67 -- Table_Index_Type should be Natural rather than Positive. 68 69 -- Table_Component_Type may be any Ada type, except that controlled 70 -- types are not supported. Note however that default initialization 71 -- will NOT occur for array components. 72 73 -- The Table_Initial values controls the allocation of the table when 74 -- it is first allocated, either by default, or by an explicit Init 75 -- call. The value used is Opt.Table_Factor * Table_Initial. 76 77 -- The Table_Increment value controls the amount of increase, if the 78 -- table has to be increased in size. The value given is a percentage 79 -- value (e.g. 100 = increase table size by 100%, i.e. double it). 80 81 -- The Table_Name parameter is simply use in debug output messages it 82 -- has no other usage, and is not referenced in non-debugging mode. 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 for Table_Ptr'Storage_Size use 0; 119 -- The table is actually represented as a pointer to allow reallocation 120 121 Table : aliased Table_Ptr := null; 122 -- The table itself. The lower bound is the value of Low_Bound. 123 -- Logically the upper bound is the current value of Last (although 124 -- the actual size of the allocated table may be larger than this). 125 -- The program may only access and modify Table entries in the range 126 -- First .. Last. 127 128 Locked : Boolean := False; 129 -- Table expansion is permitted only if this switch is set to False. A 130 -- client may set Locked to True, in which case any attempt to expand 131 -- the table will cause an assertion failure. Note that while a table 132 -- is locked, its address in memory remains fixed and unchanging. This 133 -- feature is used to control table expansion during Gigi processing. 134 -- Gigi assumes that tables other than the Uint and Ureal tables do 135 -- not move during processing, which means that they cannot be expanded. 136 -- The Locked flag is used to enforce this restriction. 137 138 procedure Init; 139 -- This procedure allocates a new table of size Initial (freeing any 140 -- previously allocated larger table). It is not necessary to call 141 -- Init when a table is first instantiated (since the instantiation does 142 -- the same initialization steps). However, it is harmless to do so, and 143 -- Init is convenient in reestablishing a table for new use. 144 145 function Last return Table_Index_Type; 146 pragma Inline (Last); 147 -- Returns the current value of the last used entry in the table, which 148 -- can then be used as a subscript for Table. Note that the only way to 149 -- modify Last is to call the Set_Last procedure. Last must always be 150 -- used to determine the logically last entry. 151 152 procedure Release; 153 -- Storage is allocated in chunks according to the values given in the 154 -- Initial and Increment parameters. A call to Release releases all 155 -- storage that is allocated, but is not logically part of the current 156 -- array value. Current array values are not affected by this call. 157 158 procedure Free; 159 -- Free all allocated memory for the table. A call to init is required 160 -- before any use of this table after calling Free. 161 162 First : constant Table_Index_Type := Table_Low_Bound; 163 -- Export First as synonym for Low_Bound (parallel with use of Last) 164 165 procedure Set_Last (New_Val : Table_Index_Type); 166 pragma Inline (Set_Last); 167 -- This procedure sets Last to the indicated value. If necessary the 168 -- table is reallocated to accommodate the new value (i.e. on return 169 -- the allocated table has an upper bound of at least Last). If Set_Last 170 -- reduces the size of the table, then logically entries are removed 171 -- from the table. If Set_Last increases the size of the table, then 172 -- new entries are logically added to the table. 173 174 procedure Increment_Last; 175 pragma Inline (Increment_Last); 176 -- Adds 1 to Last (same as Set_Last (Last + 1) 177 178 procedure Decrement_Last; 179 pragma Inline (Decrement_Last); 180 -- Subtracts 1 from Last (same as Set_Last (Last - 1) 181 182 procedure Append (New_Val : Table_Component_Type); 183 pragma Inline (Append); 184 -- Equivalent to: 185 -- x.Increment_Last; 186 -- x.Table (x.Last) := New_Val; 187 -- i.e. the table size is increased by one, and the given new item 188 -- stored in the newly created table element. 189 190 procedure Append_All (New_Vals : Table_Type); 191 -- Appends all components of New_Vals 192 193 procedure Set_Item 194 (Index : Table_Index_Type; 195 Item : Table_Component_Type); 196 pragma Inline (Set_Item); 197 -- Put Item in the table at position Index. The table is expanded if 198 -- current table length is less than Index and in that case Last is set 199 -- to Index. Item will replace any value already present in the table 200 -- at this position. 201 202 type Saved_Table is private; 203 -- Type used for Save/Restore subprograms 204 205 function Save return Saved_Table; 206 -- Resets table to empty, but saves old contents of table in returned 207 -- value, for possible later restoration by a call to Restore. 208 209 procedure Restore (T : Saved_Table); 210 -- Given a Saved_Table value returned by a prior call to Save, restores 211 -- the table to the state it was in at the time of the Save call. 212 213 procedure Tree_Write; 214 -- Writes out contents of table using Tree_IO 215 216 procedure Tree_Read; 217 -- Initializes table by reading contents previously written 218 -- with the Tree_Write call (also using Tree_IO) 219 220 private 221 222 Last_Val : Int; 223 -- Current value of Last. Note that we declare this in the private part 224 -- because we don't want the client to modify Last except through one of 225 -- the official interfaces (since a modification to Last may require a 226 -- reallocation of the table). 227 228 Max : Int; 229 -- Subscript of the maximum entry in the currently allocated table 230 231 type Saved_Table is record 232 Last_Val : Int; 233 Max : Int; 234 Table : Table_Ptr; 235 end record; 236 237 end Table; 238end Table; 239