ZLib压缩

uses ZLib;
{ Compress a stream }
procedure CompressStream(inpStream, outStream: TStream);
var
InpBuf, OutBuf: Pointer;
InpBytes, OutBytes: Integer;
begin
InpBuf := nil;
OutBuf := nil;
try
GetMem(InpBuf, inpStream.Size);
inpStream.Position := 0;
InpBytes := inpStream.Read(InpBuf^, inpStream.Size);
CompressBuf(InpBuf, InpBytes, OutBuf, OutBytes);
outStream.Write(OutBuf^, OutBytes);
finally
if InpBuf <> nil then FreeMem(InpBuf);
if OutBuf <> nil then FreeMem(OutBuf);
end;
end;
　
{ Decompress a stream }
procedure DecompressStream(inpStream, outStream: TStream);
var
InpBuf, OutBuf: Pointer;
OutBytes, sz: Integer;
begin
InpBuf := nil;
OutBuf := nil;
sz := inpStream.Size - inpStream.Position;
if sz > 0 then
try
GetMem(InpBuf, sz);
inpStream.Read(InpBuf^, sz);
DecompressBuf(InpBuf, sz, 0, OutBuf, OutBytes);
outStream.Write(OutBuf^, OutBytes);
finally
if InpBuf <> nil then FreeMem(InpBuf);
if OutBuf <> nil then FreeMem(OutBuf);
end;
outStream.Position := 0;
end;
　
{
Example:
Compress the contents of RichEdit1 and
calculate the compression rate.
Then save the stream to a file (ms2.dat)
Beispiel:
Komprimiert den Inhalt von RichEdit1 und
berechnet die Kompressionsrate.
Dann wird der Stream in eine Datei (ms2.dat) gespeichert.
}
procedure TForm1.Button1Click(Sender: TObject);
var
ms1, ms2: TMemoryStream;
begin
ms1 := TMemoryStream.Create;
try
ms2 := TMemoryStream.Create;
try
RichEdit1.Lines.SaveToStream(ms1);
CompressStream(ms1, ms2);
ShowMessage(Format('Stream Compression Rate: %d %%',
[round(100 / ms1.Size * ms2.Size)]));
ms2.SaveToFile('C:.dat');
finally
ms1.Free;
end;
finally
ms2.Free;
end;
end;
{
Loads the stream from a file (ms2.dat)
and decompresses it.
Then loads the Stream to RichEdit1.
L?dt den komprimierten Stream von einer Datei (ms2.dat)
und dekomprimiert ihn.
Dann wird der Stream wieder in RichEdit1 geladen.
}
procedure TForm1.Button2Click(Sender: TObject);
var
ms1, ms2: TMemoryStream;
begin
ms1 := TMemoryStream.Create;
try
ms2 := TMemoryStream.Create;
try
ms1.LoadFromFile('C:.dat');
DecompressStream(ms1, ms2);
RichEdit1.Lines.LoadFromStream(ms2);
finally
ms1.Free;
end;
finally
ms2.Free;
end;
end;
**********************************
procedure Compress(var CompressedStream: TMemoryStream);
var
SourceStream: TCompressionStream;
DestStream: TMemoryStream;
Count: Integer;
Begin
Count := CompressedStream.Size;
DestStream := TMemoryStream.Create;
SourceStream:=TCompressionStream.Create(clMax, DestStream);
Try
CompressedStream.SaveToStream(SourceStream);
SourceStream.Free;
CompressedStream.Clear;
CompressedStream.WriteBuffer(Count, SizeOf(Count));
CompressedStream.CopyFrom(DestStream, 0);
finally
DestStream.Free;
end;
end;
procedure UnCompress(const CompressedStream: TMemoryStream);
var
SourceStream: TDecompressionStream;
DestStream: TMemoryStream;
Buffer: PChar;
Count: integer;
Begin
CompressedStream.Seek(0,soFromBeginning);
CompressedStream.ReadBuffer(Count, SizeOf(Count));
GetMem(Buffer, Count);
DestStream := TMemoryStream.Create;
SourceStream := TDecompressionStream.Create(CompressedStream);
Try
SourceStream.ReadBuffer(Buffer^, Count);
DestStream.WriteBuffer(Buffer^, Count);
DestStream.Position := 0;//复位流指针
CompressedStream.LoadFromStream(DestStream);
finally
FreeMem(Buffer);
DestStream.Free;
end;
end;