------------------------------------------------------------------------------ -- -- -- GNAT COMPILER COMPONENTS -- -- -- -- G N A T . D Y N A M I C _ T A B L E S -- -- -- -- S p e c -- -- -- -- Copyright (C) 2000-2017, AdaCore -- -- -- -- GNAT is free software; you can redistribute it and/or modify it under -- -- terms of the GNU General Public License as published by the Free Soft- -- -- ware Foundation; either version 3, or (at your option) any later ver- -- -- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- -- or FITNESS FOR A PARTICULAR PURPOSE. -- -- -- -- As a special exception under Section 7 of GPL version 3, you are granted -- -- additional permissions described in the GCC Runtime Library Exception, -- -- version 3.1, as published by the Free Software Foundation. -- -- -- -- You should have received a copy of the GNU General Public License and -- -- a copy of the GCC Runtime Library Exception along with this program; -- -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- -- . -- -- -- -- GNAT was originally developed by the GNAT team at New York University. -- -- Extensive contributions were provided by Ada Core Technologies Inc. -- -- -- ------------------------------------------------------------------------------ -- Resizable one dimensional array support -- This package provides an implementation of dynamically resizable one -- dimensional arrays. The idea is to mimic the normal Ada semantics for -- arrays as closely as possible with the one additional capability of -- dynamically modifying the value of the Last attribute. -- This package provides a facility similar to that of Ada.Containers.Vectors. -- Note that these three interfaces should remain synchronized to keep as much -- coherency as possible among these related units: -- -- GNAT.Dynamic_Tables -- GNAT.Table -- Table (the compiler unit) pragma Compiler_Unit_Warning; with Ada.Unchecked_Conversion; generic type Table_Component_Type is private; type Table_Index_Type is range <>; Table_Low_Bound : Table_Index_Type := Table_Index_Type'First; Table_Initial : Positive := 8; Table_Increment : Natural := 100; Release_Threshold : Natural := 0; -- size in bytes package GNAT.Dynamic_Tables is -- Table_Component_Type and Table_Index_Type specify the type of the array, -- Table_Low_Bound is the lower bound. The effect is roughly to declare: -- Table : array (Table_Low_Bound .. <>) of Table_Component_Type; -- The lower bound of Table_Index_Type is ignored. -- Table_Component_Type must not be a type with controlled parts. -- The Table_Initial value controls the allocation of the table when it is -- first allocated. -- The Table_Increment value controls the amount of increase, if the table -- has to be increased in size. The value given is a percentage value (e.g. -- 100 = increase table size by 100%, i.e. double it). -- The Last and Set_Last subprograms provide control over the current -- logical allocation. They are quite efficient, so they can be used -- freely (expensive reallocation occurs only at major granularity -- chunks controlled by the allocation parameters). -- Note: we do not make the table components aliased, since this would -- restrict the use of table for discriminated types. If it is necessary -- to take the access of a table element, use Unrestricted_Access. -- WARNING: On HPPA, the virtual addressing approach used in this unit is -- incompatible with the indexing instructions on the HPPA. So when using -- this unit, compile your application with -mdisable-indexing. -- WARNING: If the table is reallocated, then the address of all its -- components will change. So do not capture the address of an element -- and then use the address later after the table may be reallocated. One -- tricky case of this is passing an element of the table to a subprogram -- by reference where the table gets reallocated during the execution of -- the subprogram. The best rule to follow is never to pass a table element -- as a parameter except for the case of IN mode parameters with scalar -- values. pragma Assert (Table_Low_Bound /= Table_Index_Type'Base'First); subtype Valid_Table_Index_Type is Table_Index_Type'Base range Table_Low_Bound .. Table_Index_Type'Base'Last; subtype Table_Last_Type is Table_Index_Type'Base range Table_Low_Bound - 1 .. Table_Index_Type'Base'Last; -- Table_Component_Type must not be a type with controlled parts. -- The Table_Initial value controls the allocation of the table when it is -- first allocated. -- The Table_Increment value controls the amount of increase, if the table -- has to be increased in size. The value given is a percentage value (e.g. -- 100 = increase table size by 100%, i.e. double it). -- The Last and Set_Last subprograms provide control over the current -- logical allocation. They are quite efficient, so they can be used -- freely (expensive reallocation occurs only at major granularity -- chunks controlled by the allocation parameters). -- Note: we do not make the table components aliased, since this would -- restrict the use of table for discriminated types. If it is necessary -- to take the access of a table element, use Unrestricted_Access. type Table_Type is array (Valid_Table_Index_Type range <>) of Table_Component_Type; subtype Big_Table_Type is Table_Type (Table_Low_Bound .. Valid_Table_Index_Type'Last); -- We work with pointers to a bogus array type that is constrained with -- the maximum possible range bound. This means that the pointer is a thin -- pointer, which is more efficient. Since subscript checks in any case -- must be on the logical, rather than physical bounds, safety is not -- compromised by this approach. -- To get subscript checking, rename a slice of the Table, like this: -- Table : Table_Type renames T.Table (First .. Last (T)); -- and then refer to components of Table. type Table_Ptr is access all Big_Table_Type; for Table_Ptr'Storage_Size use 0; -- The table is actually represented as a pointer to allow reallocation type Table_Private is private; -- Table private data that is not exported in Instance -- Private use only: subtype Empty_Table_Array_Type is Table_Type (Table_Low_Bound .. Table_Low_Bound - 1); type Empty_Table_Array_Ptr is access all Empty_Table_Array_Type; Empty_Table_Array : aliased Empty_Table_Array_Type; function Empty_Table_Array_Ptr_To_Table_Ptr is new Ada.Unchecked_Conversion (Empty_Table_Array_Ptr, Table_Ptr); Empty_Table_Ptr : constant Table_Ptr := Empty_Table_Array_Ptr_To_Table_Ptr (Empty_Table_Array'Access); -- End private use only. The above are used to initialize Table to point to -- an empty array. type Instance is record Table : Table_Ptr := Empty_Table_Ptr; -- The table itself. The lower bound is the value of First. Logically -- the upper bound is the current value of Last (although the actual -- size of the allocated table may be larger than this). The program may -- only access and modify Table entries in the range First .. Last. -- -- It's a good idea to access this via a renaming of a slice, in order -- to ensure bounds checking, as in: -- -- Tab : Table_Type renames X.Table (First .. X.Last); -- -- Note: The Table component must come first. See declarations of -- SCO_Unit_Table and SCO_Table in scos.h. Locked : Boolean := False; -- Table reallocation is permitted only if this is False. A client may -- set Locked to True, in which case any operation that might expand or -- shrink the table will cause an assertion failure. While a table is -- locked, its address in memory remains fixed and unchanging. P : Table_Private; end record; function Is_Empty (T : Instance) return Boolean; pragma Inline (Is_Empty); procedure Init (T : in out Instance); -- Reinitializes the table to empty. There is no need to call this before -- using a table; tables default to empty. procedure Free (T : in out Instance) renames Init; function First return Table_Index_Type; pragma Inline (First); -- Export First as synonym for Table_Low_Bound (parallel with use of Last) function Last (T : Instance) return Table_Last_Type; pragma Inline (Last); -- Returns the current value of the last used entry in the table, which can -- then be used as a subscript for Table. procedure Release (T : in out Instance); -- Storage is allocated in chunks according to the values given in the -- Table_Initial and Table_Increment parameters. If Release_Threshold is -- 0 or the length of the table does not exceed this threshold then a call -- to Release releases all storage that is allocated, but is not logically -- part of the current array value; otherwise the call to Release leaves -- the current array value plus 0.1% of the current table length free -- elements located at the end of the table. This parameter facilitates -- reopening large tables and adding a few elements without allocating a -- chunk of memory. In both cases current array values are not affected by -- this call. procedure Set_Last (T : in out Instance; New_Val : Table_Last_Type); pragma Inline (Set_Last); -- This procedure sets Last to the indicated value. If necessary the table -- is reallocated to accommodate the new value (i.e. on return the -- allocated table has an upper bound of at least Last). If Set_Last -- reduces the size of the table, then logically entries are removed from -- the table. If Set_Last increases the size of the table, then new entries -- are logically added to the table. procedure Increment_Last (T : in out Instance); pragma Inline (Increment_Last); -- Adds 1 to Last (same as Set_Last (Last + 1)) procedure Decrement_Last (T : in out Instance); pragma Inline (Decrement_Last); -- Subtracts 1 from Last (same as Set_Last (Last - 1)) procedure Append (T : in out Instance; New_Val : Table_Component_Type); pragma Inline (Append); -- Appends New_Val onto the end of the table -- Equivalent to: -- Increment_Last (T); -- T.Table (T.Last) := New_Val; procedure Append_All (T : in out Instance; New_Vals : Table_Type); -- Appends all components of New_Vals procedure Set_Item (T : in out Instance; Index : Valid_Table_Index_Type; Item : Table_Component_Type); pragma Inline (Set_Item); -- Put Item in the table at position Index. If Index points to an existing -- item (i.e. it is in the range First .. Last (T)), the item is replaced. -- Otherwise (i.e. Index > Last (T)), the table is expanded, and Last is -- set to Index. procedure Move (From, To : in out Instance); -- Moves from From to To, and sets From to empty procedure Allocate (T : in out Instance; Num : Integer := 1); pragma Inline (Allocate); -- Adds Num to Last generic with procedure Action (Index : Valid_Table_Index_Type; Item : Table_Component_Type; Quit : in out Boolean) is <>; procedure For_Each (Table : Instance); -- Calls procedure Action for each component of the table, or until one of -- these calls set Quit to True. generic with function Lt (Comp1, Comp2 : Table_Component_Type) return Boolean; procedure Sort_Table (Table : in out Instance); -- This procedure sorts the components of the table into ascending order -- making calls to Lt to do required comparisons, and using assignments -- to move components around. The Lt function returns True if Comp1 is -- less than Comp2 (in the sense of the desired sort), and False if Comp1 -- is greater than Comp2. For equal objects it does not matter if True or -- False is returned (it is slightly more efficient to return False). The -- sort is not stable (the order of equal items in the table is not -- preserved). private type Table_Private is record Last_Allocated : Table_Last_Type := Table_Low_Bound - 1; -- Subscript of the maximum entry in the currently allocated table. -- Initial value ensures that we initially allocate the table. Last : Table_Last_Type := Table_Low_Bound - 1; -- Current value of Last function -- Invariant: Last <= Last_Allocated end record; end GNAT.Dynamic_Tables;