| ------------------------------------------------------------------------------ |
| -- -- |
| -- 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) 2000-2021, 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 -- |
| -- <http://www.gnu.org/licenses/>. -- |
| -- -- |
| -- 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; |
