------------------------------------------------------------------  ZLib for Ada thick binding.                               ----                                                            ----  Copyright (C) 2002-2004 Dmitriy Anisimkov                 ----                                                            ----  Open source license information is in the zlib.ads file.  ----------------------------------------------------------------------  $Id: buffer_demo.adb,v 1.3 2004/09/06 06:55:35 vagul Exp $--  This demo program provided by Dr Steve Sangwine <sjs@essex.ac.uk>----  Demonstration of a problem with Zlib-Ada (already fixed) when a buffer--  of exactly the correct size is used for decompressed data, and the last--  few bytes passed in to Zlib are checksum bytes.--  This program compresses a string of text, and then decompresses the--  compressed text into a buffer of the same size as the original text.with Ada.Streams; use Ada.Streams;with Ada.Text_IO;with ZLib; use ZLib;procedure Buffer_Demo is   EOL  : Character renames ASCII.LF;   Text : constant String     := "Four score and seven years ago our fathers brought forth," & EOL &        "upon this continent, a new nation, conceived in liberty," & EOL &        "and dedicated to the proposition that `all men are created equal'.";   Source : Stream_Element_Array (1 .. Text'Length);   for Source'Address use Text'Address;begin   Ada.Text_IO.Put (Text);   Ada.Text_IO.New_Line;   Ada.Text_IO.Put_Line     ("Uncompressed size : " & Positive'Image (Text'Length) & " bytes");   declare      Compressed_Data : Stream_Element_Array (1 .. Text'Length);      L               : Stream_Element_Offset;   begin      Compress : declare         Compressor : Filter_Type;         I : Stream_Element_Offset;      begin         Deflate_Init (Compressor);         --  Compress the whole of T at once.         Translate (Compressor, Source, I, Compressed_Data, L, Finish);         pragma Assert (I = Source'Last);         Close (Compressor);         Ada.Text_IO.Put_Line           ("Compressed size :   "            & Stream_Element_Offset'Image (L) & " bytes");      end Compress;      --  Now we decompress the data, passing short blocks of data to Zlib      --  (because this demonstrates the problem - the last block passed will      --  contain checksum information and there will be no output, only a      --  check inside Zlib that the checksum is correct).      Decompress : declare         Decompressor : Filter_Type;         Uncompressed_Data : Stream_Element_Array (1 .. Text'Length);         Block_Size : constant := 4;         --  This makes sure that the last block contains         --  only Adler checksum data.         P : Stream_Element_Offset := Compressed_Data'First - 1;         O : Stream_Element_Offset;      begin         Inflate_Init (Decompressor);         loop            Translate              (Decompressor,               Compressed_Data                 (P + 1 .. Stream_Element_Offset'Min (P + Block_Size, L)),               P,               Uncompressed_Data                 (Total_Out (Decompressor) + 1 .. Uncompressed_Data'Last),               O,               No_Flush);               Ada.Text_IO.Put_Line                 ("Total in : " & Count'Image (Total_In (Decompressor)) &                  ", out : " & Count'Image (Total_Out (Decompressor)));               exit when P = L;         end loop;         Ada.Text_IO.New_Line;         Ada.Text_IO.Put_Line           ("Decompressed text matches original text : "             & Boolean'Image (Uncompressed_Data = Source));      end Decompress;   end;end Buffer_Demo;