zlib.adb

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            Win_Bits := Win_Bits + 32;
         when Default => null;
      end case;

      Filter.Strm        := new Z_Stream;
      Filter.Compression := False;
      Filter.Stream_End  := False;
      Filter.Header      := Header;

      if Thin.Inflate_Init
         (To_Thin_Access (Filter.Strm), Win_Bits) /= Thin.Z_OK
      then
         Raise_Error (Filter.Strm.all);
      end if;
   end Inflate_Init;

   -------------
   -- Is_Open --
   -------------

   function Is_Open (Filter : in Filter_Type) return Boolean is
   begin
      return Filter.Strm /= null;
   end Is_Open;

   -----------------
   -- Raise_Error --
   -----------------

   procedure Raise_Error (Message : in String) is
   begin
      Ada.Exceptions.Raise_Exception (ZLib_Error'Identity, Message);
   end Raise_Error;

   procedure Raise_Error (Stream : in Z_Stream) is
   begin
      Raise_Error (Last_Error_Message (Stream));
   end Raise_Error;

   ----------
   -- Read --
   ----------

   procedure Read
     (Filter : in out Filter_Type;
      Item   :    out Ada.Streams.Stream_Element_Array;
      Last   :    out Ada.Streams.Stream_Element_Offset;
      Flush  : in     Flush_Mode := No_Flush)
   is
      In_Last    : Stream_Element_Offset;
      Item_First : Ada.Streams.Stream_Element_Offset := Item'First;
      V_Flush    : Flush_Mode := Flush;

   begin
      pragma Assert (Rest_First in Buffer'First .. Buffer'Last + 1);
      pragma Assert (Rest_Last in Buffer'First - 1 .. Buffer'Last);

      loop
         if Rest_Last = Buffer'First - 1 then
            V_Flush := Finish;

         elsif Rest_First > Rest_Last then
            Read (Buffer, Rest_Last);
            Rest_First := Buffer'First;

            if Rest_Last < Buffer'First then
               V_Flush := Finish;
            end if;
         end if;

         Translate
           (Filter   => Filter,
            In_Data  => Buffer (Rest_First .. Rest_Last),
            In_Last  => In_Last,
            Out_Data => Item (Item_First .. Item'Last),
            Out_Last => Last,
            Flush    => V_Flush);

         Rest_First := In_Last + 1;

         exit when Stream_End (Filter)
           or else Last = Item'Last
           or else (Last >= Item'First and then Allow_Read_Some);

         Item_First := Last + 1;
      end loop;
   end Read;

   ----------------
   -- Stream_End --
   ----------------

   function Stream_End (Filter : in Filter_Type) return Boolean is
   begin
      if Filter.Header = GZip and Filter.Compression then
         return Filter.Stream_End
            and then Filter.Offset = Footer_Array'Last + 1;
      else
         return Filter.Stream_End;
      end if;
   end Stream_End;

   --------------
   -- Total_In --
   --------------

   function Total_In (Filter : in Filter_Type) return Count is
   begin
      return Count (Thin.Total_In (To_Thin_Access (Filter.Strm).all));
   end Total_In;

   ---------------
   -- Total_Out --
   ---------------

   function Total_Out (Filter : in Filter_Type) return Count is
   begin
      return Count (Thin.Total_Out (To_Thin_Access (Filter.Strm).all));
   end Total_Out;

   ---------------
   -- Translate --
   ---------------

   procedure Translate
     (Filter    : in out Filter_Type;
      In_Data   : in     Ada.Streams.Stream_Element_Array;
      In_Last   :    out Ada.Streams.Stream_Element_Offset;
      Out_Data  :    out Ada.Streams.Stream_Element_Array;
      Out_Last  :    out Ada.Streams.Stream_Element_Offset;
      Flush     : in     Flush_Mode) is
   begin
      if Filter.Header = GZip and then Filter.Compression then
         Translate_GZip
           (Filter   => Filter,
            In_Data  => In_Data,
            In_Last  => In_Last,
            Out_Data => Out_Data,
            Out_Last => Out_Last,
            Flush    => Flush);
      else
         Translate_Auto
           (Filter   => Filter,
            In_Data  => In_Data,
            In_Last  => In_Last,
            Out_Data => Out_Data,
            Out_Last => Out_Last,
            Flush    => Flush);
      end if;
   end Translate;

   --------------------
   -- Translate_Auto --
   --------------------

   procedure Translate_Auto
     (Filter    : in out Filter_Type;
      In_Data   : in     Ada.Streams.Stream_Element_Array;
      In_Last   :    out Ada.Streams.Stream_Element_Offset;
      Out_Data  :    out Ada.Streams.Stream_Element_Array;
      Out_Last  :    out Ada.Streams.Stream_Element_Offset;
      Flush     : in     Flush_Mode)
   is
      use type Thin.Int;
      Code : Thin.Int;

   begin
      if not Is_Open (Filter) then
         raise Status_Error;
      end if;

      if Out_Data'Length = 0 and then In_Data'Length = 0 then
         raise Constraint_Error;
      end if;

      Set_Out (Filter.Strm.all, Out_Data'Address, Out_Data'Length);
      Set_In  (Filter.Strm.all, In_Data'Address, In_Data'Length);

      Code := Flate (Filter.Compression).Step
        (To_Thin_Access (Filter.Strm),
         Thin.Int (Flush));

      if Code = Thin.Z_STREAM_END then
         Filter.Stream_End := True;
      else
         Check_Error (Filter.Strm.all, Code);
      end if;

      In_Last  := In_Data'Last
         - Stream_Element_Offset (Avail_In (Filter.Strm.all));
      Out_Last := Out_Data'Last
         - Stream_Element_Offset (Avail_Out (Filter.Strm.all));
   end Translate_Auto;

   --------------------
   -- Translate_GZip --
   --------------------

   procedure Translate_GZip
     (Filter    : in out Filter_Type;
      In_Data   : in     Ada.Streams.Stream_Element_Array;
      In_Last   :    out Ada.Streams.Stream_Element_Offset;
      Out_Data  :    out Ada.Streams.Stream_Element_Array;
      Out_Last  :    out Ada.Streams.Stream_Element_Offset;
      Flush     : in     Flush_Mode)
   is
      Out_First : Stream_Element_Offset;

      procedure Add_Data (Data : in Stream_Element_Array);
      --  Add data to stream from the Filter.Offset till necessary,
      --  used for add gzip headr/footer.

      procedure Put_32
        (Item : in out Stream_Element_Array;
         Data : in     Unsigned_32);
      pragma Inline (Put_32);

      --------------
      -- Add_Data --
      --------------

      procedure Add_Data (Data : in Stream_Element_Array) is
         Data_First : Stream_Element_Offset renames Filter.Offset;
         Data_Last  : Stream_Element_Offset;
         Data_Len   : Stream_Element_Offset; --  -1
         Out_Len    : Stream_Element_Offset; --  -1
      begin
         Out_First := Out_Last + 1;

         if Data_First > Data'Last then
            return;
         end if;

         Data_Len  := Data'Last     - Data_First;
         Out_Len   := Out_Data'Last - Out_First;

         if Data_Len <= Out_Len then
            Out_Last  := Out_First  + Data_Len;
            Data_Last := Data'Last;
         else
            Out_Last  := Out_Data'Last;
            Data_Last := Data_First + Out_Len;
         end if;

         Out_Data (Out_First .. Out_Last) := Data (Data_First .. Data_Last);

         Data_First := Data_Last + 1;
         Out_First  := Out_Last + 1;
      end Add_Data;

      ------------
      -- Put_32 --
      ------------

      procedure Put_32
        (Item : in out Stream_Element_Array;
         Data : in     Unsigned_32)
      is
         D : Unsigned_32 := Data;
      begin
         for J in Item'First .. Item'First + 3 loop
            Item (J) := Stream_Element (D and 16#FF#);
            D := Shift_Right (D, 8);
         end loop;
      end Put_32;

   begin
      Out_Last := Out_Data'First - 1;

      if not Filter.Stream_End then
         Add_Data (Simple_GZip_Header);

         Translate_Auto
           (Filter   => Filter,
            In_Data  => In_Data,
            In_Last  => In_Last,
            Out_Data => Out_Data (Out_First .. Out_Data'Last),
            Out_Last => Out_Last,
            Flush    => Flush);

         CRC32 (Filter.CRC, In_Data (In_Data'First .. In_Last));
      end if;

      if Filter.Stream_End and then Out_Last <= Out_Data'Last then
         --  This detection method would work only when
         --  Simple_GZip_Header'Last > Footer_Array'Last

         if Filter.Offset = Simple_GZip_Header'Last + 1 then
            Filter.Offset := Footer_Array'First;
         end if;

         declare
            Footer : Footer_Array;
         begin
            Put_32 (Footer, Filter.CRC);
            Put_32 (Footer (Footer'First + 4 .. Footer'Last),
                    Unsigned_32 (Total_In (Filter)));
            Add_Data (Footer);
         end;
      end if;
   end Translate_GZip;

   -------------
   -- Version --
   -------------

   function Version return String is
   begin
      return Interfaces.C.Strings.Value (Thin.zlibVersion);
   end Version;

   -----------
   -- Write --
   -----------

   procedure Write
     (Filter : in out Filter_Type;
      Item   : in     Ada.Streams.Stream_Element_Array;
      Flush  : in     Flush_Mode := No_Flush)
   is
      Buffer   : Stream_Element_Array (1 .. Buffer_Size);
      In_Last  : Stream_Element_Offset;
      Out_Last : Stream_Element_Offset;
      In_First : Stream_Element_Offset := Item'First;
   begin
      if Item'Length = 0 and Flush = No_Flush then
         return;
      end if;

      loop
         Translate
           (Filter   => Filter,
            In_Data  => Item (In_First .. Item'Last),
            In_Last  => In_Last,
            Out_Data => Buffer,
            Out_Last => Out_Last,
            Flush    => Flush);

         if Out_Last >= Buffer'First then
            Write (Buffer (1 .. Out_Last));
         end if;

         exit when In_Last = Item'Last or Stream_End (Filter);

         In_First := In_Last + 1;
      end loop;
   end Write;

end ZLib;