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Diffstat (limited to 'source4/lib/zlib/contrib/ada/buffer_demo.adb')
| -rw-r--r-- | source4/lib/zlib/contrib/ada/buffer_demo.adb | 106 |
1 files changed, 106 insertions, 0 deletions
diff --git a/source4/lib/zlib/contrib/ada/buffer_demo.adb b/source4/lib/zlib/contrib/ada/buffer_demo.adb new file mode 100644 index 0000000000..46b8638107 --- /dev/null +++ b/source4/lib/zlib/contrib/ada/buffer_demo.adb @@ -0,0 +1,106 @@ +---------------------------------------------------------------- +-- 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; |