流的压缩和解压_Delphi教程

(*//
标题:流的压缩和解压
说明:适用文件压缩、图象压缩等;调用ZLib单元的方法实现
设计:Zswang
支持:wjhu111@21cn.com
日期:2004-03-24
//*)

(*//============================================================================
设计思路:
创建TCompressionStream、TDecompressionStream实例进行压缩和解压
============================================================================//*)

uses ZLib;

const cBufferSize = $4096;

function StreamCompression(mInputStream: TStream; mOutputStream: TStream): Integer;
var
  I: Integer;
  vBuffer: array[0..cBufferSize]of Char;
begin
  Result := -1;
  if not (Assigned(mInputStream) and Assigned(mOutputStream)) then Exit;
  with TCompressionStream.Create(clMax, mOutputStream) do try
    for I := 1 to mInputStream.Size div cBufferSize do begin
      mInputStream.Read(vBuffer, cBufferSize);
      Write(vBuffer, cBufferSize);
    end;
    I := mInputStream.Size mod cBufferSize;
    if I > 0 then begin
      mInputStream.Read(vBuffer, I);
      Write(vBuffer, I);
    end;
  finally
    Free;
  end;
end; { StreamCompression }

function StreamDecompression(mInputStream: TStream; mOutputStream: TStream): Integer;
var
  vBuffer: array[0..cBufferSize]of Char;
  I: Integer;
begin
  Result := -1;
  if not (Assigned(mInputStream) and Assigned(mOutputStream)) then Exit;
  with TDecompressionStream.Create(mInputStream) do try
    repeat
      I := Read(vBuffer, cBufferSize);
      mOutputStream.Write(vBuffer, I);
    until I = 0;
    Result := mOutputStream.Size;
  finally
    Free;
  end;
end; { StreamDecompression }

//Example
procedure TForm1.Button1Click(Sender: TObject);
var
  vInputStream: TFileStream;
  vOutputStream: TFileStream;
begin
  vInputStream := TFileStream.Create('c:\temp\temp.exe', fmOpenRead);
  vOutputStream := TFileStream.Create('c:\temp\temp.exe.z', fmCreate);
  try
    StreamCompression(vInputStream, vOutputStream);
  finally
    vInputStream.Free;
    vOutputStream.Free;
  end;
end;

procedure TForm1.Button2Click(Sender: TObject);
var
  vInputStream: TFileStream;
  vOutputStream: TFileStream;
begin
  vInputStream := TFileStream.Create('c:\temp\temp.exe.z', fmOpenRead);
  vOutputStream := TFileStream.Create('c:\temp\temp~.exe', fmCreate);
  try
    StreamDecompression(vInputStream, vOutputStream);
  finally
    vInputStream.Free;
    vOutputStream.Free;
  end;
end;