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Delphi的单元文件ZLib.pas提供了使用ZLib数据压缩算法的接口，只要在我们的Delphi工程里引用该单元即可使用ZLib数据压缩功能，以下是使用ZLib对数据流进行压缩和解压的函数：
uses ZLib;
procedure CompressIt(var CompressedStream: TMemoryStream; const CompressionLevel: TCompressionLevel);
// 参数是传递的流和压缩方式
var
SourceStream: TCompressionStream;
DestStream: TMemoryStream;
Count: int64; //注意，此处修改了,原来是int
begin
//获得流的原始尺寸
Count := CompressedStream.Size;
DestStream := TMemoryStream.Create;
SourceStream := TCompressionStream.Create(CompressionLevel, DestStream);
try
//SourceStream中保存着原始的流
CompressedStream.SaveToStream(SourceStream);
//将原始流进行压缩， DestStream中保存着压缩后的流
SourceStream.Free;
CompressedStream.Clear;
//写入原始流的尺寸
CompressedStream.WriteBuffer(Count, SizeOf(Count));
//写入经过压缩的流
CompressedStream.CopyFrom(DestStream, 0);
finally
DestStream.Free;
end;
end;
procedure UnCompressIt(const CompressedStream: TMemoryStream; var UnCompressedStream: TMemoryStream);
//参数 压缩过的流，解压后的流
var
SourceStream: TDecompressionStream;
DestStream: TMemoryStream;
Buffer: PChar;
Count: int64;
begin
//从被压缩的流中读出原始的尺寸
CompressedStream.ReadBuffer(Count, SizeOf(Count));
//根据尺寸大小为将要读入的原始流分配内存块
GetMem(Buffer, Count);
DestStream := TMemoryStream.Create;
SourceStream := TDecompressionStream.Create(CompressedStream);
try
//将被压缩的流解压缩，然后存入 Buffer内存块中
SourceStream.ReadBuffer(Buffer^, Count);
//将原始流保存至 DestStream流中
DestStream.WriteBuffer(Buffer^, Count);
DestStream.Position := 0; //复位流指针
//从DestStream流中载入数据流
UnCompressedStream.LoadFromStream(DestStream);
finally
FreeMem(Buffer);
DestStream.Free;
end;
end;
//对文件进行压缩
procedure TForm1.Button1Click(Sender: TObject);
var
SM: TMemoryStream;
begin
if OpenDialog1.Execute then
begin
if SaveDialog1.Execute then
begin
SM := TMemoryStream.Create;
try
Sm.LoadFromFile(OpenDialog1.FileName);
SM.Position := 0;
Compressit(sm, clDefault);
SM.SaveToFile(SaveDialog1.FileName);
finally
SM.Free;
end;
end;
end;
end;
//对文件进行解压
procedure TForm1.Button2Click(Sender: TObject);
var
SM, DM: TMemoryStream;
begin
if OpenDialog1.Execute then
begin
if SaveDialog1.Execute then
begin
SM := TMemoryStream.Create;
DM := TMemoryStream.Create;
try
Sm.LoadFromFile(OpenDialog1.FileName);
SM.Position := 0;
UnCompressit(sm, dm);
dm.Position := 0;
dm.SaveToFile(SaveDialog1.FileName);
finally
SM.Free;
DM.Free;
end;
end;
end;
end;
以上代码在Delphi7编译环境下调试通过。
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