------------------------------------------------------------------------------
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--                         GNAT COMPILER COMPONENTS                         --
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------------------------------------------------------------------------------

with System; use System;

package body GNAT.Dynamic_Tables is

   Min : constant Integer := Integer (Table_Low_Bound);
   --  Subscript of the minimum entry in the currently allocated table

   type size_t is new Integer;

   -----------------------
   -- Local Subprograms --
   -----------------------

   procedure Reallocate (T : in out Instance);
   --  Reallocate the existing table according to the current value stored
   --  in Max. Works correctly to do an initial allocation if the table
   --  is currently null.

   --------------
   -- Allocate --
   --------------

   procedure Allocate
     (T   : in out Instance;
      Num : Integer := 1)
   is
   begin
      T.P.Last_Val := T.P.Last_Val + Num;

      if T.P.Last_Val > T.P.Max then
         Reallocate (T);
      end if;
   end Allocate;

   ------------
   -- Append --
   ------------

   procedure Append (T : in out Instance; New_Val : Table_Component_Type) is
   begin
      Increment_Last (T);
      T.Table (Table_Index_Type (T.P.Last_Val)) := New_Val;
   end Append;

   --------------------
   -- Decrement_Last --
   --------------------

   procedure Decrement_Last (T : in out Instance) is
   begin
      T.P.Last_Val := T.P.Last_Val - 1;
   end Decrement_Last;

   ----------
   -- Free --
   ----------

   procedure Free (T : in out Instance) is
      procedure free (T : Table_Ptr);
      pragma Import (C, free);

   begin
      free (T.Table);
      T.Table := null;
      T.P.Length := 0;
   end Free;

   --------------------
   -- Increment_Last --
   --------------------

   procedure Increment_Last (T : in out Instance) is
   begin
      T.P.Last_Val := T.P.Last_Val + 1;

      if T.P.Last_Val > T.P.Max then
         Reallocate (T);
      end if;
   end Increment_Last;

   ----------
   -- Init --
   ----------

   procedure Init (T : in out Instance) is
      Old_Length : constant Integer := T.P.Length;

   begin
      T.P.Last_Val := Min - 1;
      T.P.Max      := Min + Table_Initial - 1;
      T.P.Length   := T.P.Max - Min + 1;

      --  If table is same size as before (happens when table is never
      --  expanded which is a common case), then simply reuse it. Note
      --  that this also means that an explicit Init call right after
      --  the implicit one in the package body is harmless.

      if Old_Length = T.P.Length then
         return;

      --  Otherwise we can use Reallocate to get a table of the right size.
      --  Note that Reallocate works fine to allocate a table of the right
      --  initial size when it is first allocated.

      else
         Reallocate (T);
      end if;
   end Init;

   ----------
   -- Last --
   ----------

   function Last (T : in Instance) return Table_Index_Type is
   begin
      return Table_Index_Type (T.P.Last_Val);
   end Last;

   ----------------
   -- Reallocate --
   ----------------

   procedure Reallocate (T : in out Instance) is

      function realloc
        (memblock : Table_Ptr;
         size     : size_t)
         return     Table_Ptr;
      pragma Import (C, realloc);

      function malloc
        (size     : size_t)
         return     Table_Ptr;
      pragma Import (C, malloc);

      New_Size : size_t;

   begin
      if T.P.Max < T.P.Last_Val then
         while T.P.Max < T.P.Last_Val loop
            T.P.Length := T.P.Length * (100 + Table_Increment) / 100;
            T.P.Max := Min + T.P.Length - 1;
         end loop;
      end if;

      New_Size :=
        size_t ((T.P.Max - Min + 1) *
                (Table_Type'Component_Size / Storage_Unit));

      if T.Table = null then
         T.Table := malloc (New_Size);

      elsif New_Size > 0 then
         T.Table :=
           realloc
             (memblock => T.Table,
              size     => New_Size);
      end if;

      if T.P.Length /= 0 and then T.Table = null then
         raise Storage_Error;
      end if;

   end Reallocate;

   -------------
   -- Release --
   -------------

   procedure Release (T : in out Instance) is
   begin
      T.P.Length := T.P.Last_Val - Integer (Table_Low_Bound) + 1;
      T.P.Max    := T.P.Last_Val;
      Reallocate (T);
   end Release;

   --------------
   -- Set_Item --
   --------------

   procedure Set_Item
     (T     : in out Instance;
      Index : Table_Index_Type;
      Item  : Table_Component_Type)
   is
   begin
      if Integer (Index) > T.P.Max then
         Set_Last (T, Index);
      end if;

      T.Table (Index) := Item;
   end Set_Item;

   --------------
   -- Set_Last --
   --------------

   procedure Set_Last (T : in out Instance; New_Val : Table_Index_Type) is
   begin
      if Integer (New_Val) < T.P.Last_Val then
         T.P.Last_Val := Integer (New_Val);

      else
         T.P.Last_Val := Integer (New_Val);

         if T.P.Last_Val > T.P.Max then
            Reallocate (T);
         end if;
      end if;
   end Set_Last;

end GNAT.Dynamic_Tables;