compress.~dpr

具有数据压缩和解压缩功能的地动态库。 采用Delphi内置的压缩库实现。压缩效率略低于zip。

library Compress;

{ Important note about DLL memory management: ShareMem must be the
  first unit in your library's USES clause AND your project's (select
  Project-View Source) USES clause if your DLL exports any procedures or
  functions that pass strings as parameters or function results. This
  applies to all strings passed to and from your DLL--even those that
  are nested in records and classes. ShareMem is the interface unit to
  the BORLNDMM.DLL shared memory manager, which must be deployed along
  with your DLL. To avoid using BORLNDMM.DLL, pass string information
  using PChar or ShortString parameters. }


uses
  SysUtils, ZLib,
  Classes;


function InitZLib: Integer;
begin
  Result := 1;
end;

function CompressBuffer(InS: PChar; IL: Integer;
    OutS: PChar; out OL: Integer): Integer; stdcall; export;
var
  Compressor: TCompressionStream; // 用于压缩
  OutStream: TMemoryStream;
begin
  OutStream := nil;
  try
    Result := 0;
    OutStream := TMemoryStream.Create;
    Compressor := TCompressionStream.Create(clDefault, OutStream);
    Compressor.Write(InS^, IL);
    Compressor.Free;
    OutStream.Seek(0, soFromBeginning);
    OL := OutStream.Read(OutS^, OutStream.Size);
    Result := 1;
  finally
    OutStream.Free;
  end;
end;


function DecompressBuffer(InS: PChar; IL: Integer;
    OutS: PChar; out OL: Integer): Integer; stdcall; export;
var
  Decompressor: TDecompressionStream; // 用于解压缩
  InStream: TMemoryStream;
begin
  Decompressor := nil;
  InStream := nil;
  try
    Result := 0;
    InStream := TMemoryStream.Create;
    InStream.Write(InS^, IL);
    InStream.Seek(0, soFromBeginning);
    Decompressor := TDecompressionStream.Create(InStream);
    OL := Decompressor.Read(OutS^, 100000);
    Result := 1;
  finally
    Decompressor.Free;
    InStream.Free;
  end;
end;

{$R *.res}

exports
  CompressBuffer,
  DecompressBuffer;

begin
  InitZLib;
end.