I've got a minor issue with decompressing using the ZLib unit in Delphi
unit uZCompression;
interface
uses
uCompression;
type
TZZipCompression = class(TInterfacedObject, ICompression)
public
function DoCompression(aContent: TArray<Byte>): TArray<Byte>;
function DoDecompression(aContent: TArray<Byte>): TArray<Byte>;
function GetWindowsBits: Integer; virtual;
end;
TZGZipCompression = class(TZZipCompression)
function GetWindowsBits: Integer; override;
end;
implementation
uses
System.ZLib, System.Classes, uMxKxUtils;
{ TZCompression }
function TZZipCompression.DoCompression(aContent: TArray<Byte>): TArray<Byte>;
var
LContentStream, LOutputStream: TMemoryStream;
LCompressedStream: TZCompressionStream;
begin
LContentStream := ByteArrayToStream(aContent);
LOutputStream := TMemoryStream.Create;
LCompressedStream := TZCompressionStream.Create(LOutputStream, zcDefault, GetWindowsBits);
LCompressedStream.CopyFrom(LContentStream, LContentStream.Size);
LCompressedStream.Free;
Result := StreamToByteArray(LOutputStream);
LOutputStream.Free;
LContentStream.Free;
end;
function TZZipCompression.DoDecompression(aContent: TArray<Byte>): TArray<Byte>;
var
LContentStream, LOutputStream: TMemoryStream;
LDecompressedStream: TZDecompressionStream;
begin
LContentStream := ByteArrayToStream(aContent);
LOutputStream := TMemoryStream.Create;
LDecompressedStream := TZDecompressionStream.Create(LContentStream);
LOutputStream.CopyFrom(LDecompressedStream, LDecompressedStream.Size);
LDecompressedStream.Free;
Result := StreamToByteArray(LOutputStream);
LOutputStream.Free;
LContentStream.Free;
end;
function TZZipCompression.GetWindowsBits: Integer;
begin
Result := 15;
end;
{ TZGZipCompression }
function TZGZipCompression.GetWindowsBits: Integer;
begin
Result := inherited;
Result := Result + 16;
end;
end.
This is my unit which is driven by an interface (which you don't need to know about), and data is passed in and out through a TArray variables.
I've coded it to be able to do 2 types of compression, standard zip and gzip which is determined by the windowsbits passed in to the functions.
Here are a couple of other functions being used to convert the TArray to TMemoryStream
function ByteArrayToStream(aContent: TArray<Byte>): TMemoryStream;
begin
Result := TMemoryStream.Create;
Result.Write(aContent, length(aContent)*SizeOf(aContent[0]));
Result.Position := 0;
end;
function StreamToByteArray(aStream: TMemoryStream): TArray<Byte>;
var
LStreamPos: Int64;
begin
if Assigned(aStream) then
begin
LStreamPos := aStream.Position;
aStream.Position := 0;
SetLength(Result, aStream.Size);
aStream.Read(Result, aStream.Size);
aStream.Position := LStreamPos;
end
else
SetLength(Result, 0);
end;
Now I can compress and decompress to .zip using the TZZipCompression class perfectly fine (it doesn't open up as a zip file, but it does decompress back to the original file which I can open and edit).
I can also compress to .gz using the TZGZipCompression class fine as well (interestingly I can open this gzip file perfectly well).
My issue however is that it won't decompress back from the .gz file and throws and error as soon as it hits
LOutputStream.CopyFrom(LDecompressedStream, LDecompressedStream.Size)
Funnily enough the Help file example has it as below
LOutputStream.CopyFrom(LDecompressedStream, 0)
But this doesn't work either.
Can anyone spot the issue?