with Ada.Unchecked_Deallocation;
with System.Address_To_Access_Conversions;


package body Preference_Arrays is


    type Ranking is range 1 .. 255;

    type Preference_Array is array (Positive range <>, Positive range <>) of Ranking;
    pragma Pack (Preference_Array);




    --  these following functions would be a lot smaller and neater
    --  if the FFI could make use of fat pointers




    function Create_Preference_Array
           (Number_Of_Ballots, Size_Of_Ballot : in Interfaces.C.int)
        return System.Address
    is
        subtype Constrained is Preference_Array
               (1 .. Positive (Number_Of_Ballots),
                1 .. Positive (Size_Of_Ballot));

        package Convert is new System.Address_To_Access_Conversions
               (Object => Constrained);

        Pref_Array : Convert.Object_Pointer;
    begin
        Pref_Array := new Preference_Array
               (1 .. Positive (Number_Of_Ballots),
                1 .. Positive (Size_Of_Ballot));
        return Convert.To_Address (Pref_Array);
    end Create_Preference_Array;




    procedure Free_Preference_Array
           (Number_Of_Ballots, Size_Of_Ballot : in Interfaces.C.int;
            Pref_Array_Address                : in System.Address)
    is
        subtype Constrained is Preference_Array
               (1 .. Positive (Number_Of_Ballots),
                1 .. Positive (Size_Of_Ballot));

        package Convert is new System.Address_To_Access_Conversions
               (Object => Constrained);
        procedure Free_Pref_Array is new Ada.Unchecked_Deallocation
               (Object => Constrained, Name => Convert.Object_Pointer);

        Pref_Array : Convert.Object_Pointer;
    begin
        Pref_Array := Convert.To_Pointer (Pref_Array_Address);
        Free_Pref_Array (Pref_Array);
    end Free_Preference_Array;




    procedure Poke_Preference_Array
           (Number_Of_Ballots, Size_Of_Ballot : in Interfaces.C.int;
            Pref_Array_Address                : in System.Address;
            Ballot_Index, Box_Number, Rank    : in Interfaces.C.int)
    is
        subtype Constrained is Preference_Array
               (1 .. Positive (Number_Of_Ballots),
                1 .. Positive (Size_Of_Ballot));

        package Convert is new System.Address_To_Access_Conversions
               (Object => Constrained);

        Pref_Array : Convert.Object_Pointer;
    begin
        Pref_Array := Convert.To_Pointer (Pref_Array_Address);
        Pref_Array (Positive (Ballot_Index), Positive (Box_Number)) := Ranking (Rank);
    end Poke_Preference_Array;




    function Peek_Preference_Array
           (Number_Of_Ballots, Size_Of_Ballot : in Interfaces.C.int;
            Pref_Array_Address                : in System.Address;
            Ballot_Index, Box_Number, Rank    : in Interfaces.C.int)
        return Interfaces.C.int
    is
        subtype Constrained is Preference_Array
               (1 .. Positive (Number_Of_Ballots),
                1 .. Positive (Size_Of_Ballot));

        package Convert is new System.Address_To_Access_Conversions
               (Object => Constrained);

        Pref_Array : Convert.Object_Pointer;
    begin
        Pref_Array := Convert.To_Pointer (Pref_Array_Address);
        if Pref_Array (Positive (Ballot_Index), Positive (Box_Number)) = Ranking (Rank) then
            return 1;
        else
            return 0;
        end if;
    end Peek_Preference_Array;


end Preference_Arrays;