对Zlib单元进行再封装

对Zlib单元进行再封装

低版本DELPHI，如D7，ZLIB.pas单元封装的很简陋，因此有必要再封装，以增加使用的便利性。

高版本DELPHI，zlib.pas本身提供的接口已经相当完善。

Zlib.pas是DELPHI自带的压缩单元，下面对对Zlib单元进行再封装，增加两个压缩函数，一个压缩流，一个压缩字符串：

分别在D7和XE10.3.1下面，测试通过。

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unit Unit1;   interface   uses   ZLib, Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls,   Forms, Dialogs;   type   TForm1 = class(TForm)   private     { Private declarations }   public     { Public declarations }   end;   var   Form1: TForm1; // 两个过程都有Compress参数,这个参数用来决定进行压缩操作还是解压操作: True--压缩; false--解压. procedure Zip(Input, Output: TStream; Compress: Boolean); overload;   function Zip(Input: string; Compress: Boolean): string; overload;   implementation   {$R *.dfm}   procedure Zip(Input, Output: TStream; Compress: Boolean); const   MAXBUFSIZE = 1024 * 16; //16 KB var   CS: TCompressionStream;   DS: TDecompressionStream;   Buf: array[0..MAXBUFSIZE - 1] of Byte;   BufSize: Integer; begin   if Assigned(Input) and Assigned(Output) then   begin     if Compress then     // 压缩     begin       CS := TCompressionStream.Create(ZLib.clDefault, Output);       try         CS.CopyFrom(Input, 0); //从开始处复制       finally         CS.Free;       end;     end     else     begin        // 解压       DS := TDecompressionStream.Create(Input);       try         BufSize := DS.Read(Buf, MAXBUFSIZE);         while BufSize > 0 do         begin           Output.Write(Buf, BufSize);           BufSize := DS.Read(Buf, MAXBUFSIZE);         end;       finally         DS.Free;       end;     end;   end; end;   function Zip(Input: string; Compress: Boolean): string; var   InputStream, OutputStream: TStringStream; begin   if Input = '' then     Exit;   InputStream := TStringStream.Create(Input);   try     OutputStream := TStringStream.Create('');     try       Zip(InputStream, OutputStream, Compress);       Result := OutputStream.DataString;     finally       OutputStream.Free;     end;   finally     InputStream.Free;   end; end;   end.