Difference between revisions of "LMD VCL - ZLib support"

Revision as of 13:30, 5 October 2008

Introduction

Since 2007 series the LMD shared Runtime provides built-in ZLib library to compress/decompress any data. This is a native pascal solution and it doesn't require any external obj or dll files.

Units

• LMDZCommonUnit.pas - Common code and types for compress/decompress routines (raw ZLib api)
• LMDZCompressUnit.pas - Unit that contain compression code (raw ZLib api)
• LMDZUncompressUnit.pas - Unit with uncompression code (raw ZLib api)
• LMDZLib.pas - TStream wrappers that provide interface to compress/decompress data directly into any TStream descendants.

LMDZLib interface

TLMDCompressionStream wrapper class that compress data directly to any TStream descendant, and has transparent interface that compatible with TStream, so you can easily add compression for exists application. Example:

<delphi> uses

 ..., LMDZLib, ...;

// code before using TLMDCompressionStream ... var

 LDataStream: TFileStream;

begin

 LDataStream := TFileStream.Create(FileName, fmCreate);
 try
   LDataStream(FSomeData, FSizeOfSomeData);
 finally
   LDataStream.Free;
 end;

end; ...

// code with TLMDCompressionStream ... var

 LDataStream: TLMDCompressionStream;
 LFileStream: TFileStream;

begin

 LFileStream := TFileStream.Create(FileName, fmCreate);
 try 
   LDataStream := TLMDCompressionStream.Create(clDefault, LFileStream); 
   try
     LDataStream.Write(FSomeData, FSizeOfSomeData);
   finally
     LDestStream.Free;
   end;
 finally
   LFileStream.Free;
 end;

end; ... </delphi>

TLMDDecompressionStream can be used as decompression layer for stream with compressed data. Example:

<delphi> uses

 ..., LMDZLib, ...;

// code before using TLMDDecompressionStream ... var

 LDataStream: TFileStream;

begin

 LDataStream := TFileStream.Create(FileName, fmOpenRead);
 try
   LDataStream.Read(FSomeData, FSizeOfSomeData);
 finally
   LDataStream.Free;
 end;

end; ...

// code with TLMDDecompressionStream ... var

 LDataStream: TLMDDecompressionStream;
 LFileStream: TFileStream;

begin

 LFileStream := TFileStream.Create(FileName, fmOpenRead);
 try 
   LDataStream := TLMDDecompressionStream.Create(LFileStream); 
   try
     LDataStream.Read(FSomeData, FSizeOfSomeData);
   finally
     LDestStream.Free;
   end;
 finally
   LFileStream.Free;
 end;

end; ... </delphi>

As you can note required changes in your code are minimal.