extract file into memory using 7z.dll

[estux]

Hi,

I am trying to modify the CArchiveExtractCallback class from the Client7z to get files extracted into memory.

I suppose that the relevant part of code is:

_outFileStreamSpec = new COutFileStream;
CMyComPtr<ISequentialOutStream> outStreamLoc(_outFileStreamSpec);
if (!_outFileStreamSpec->Open(fullProcessedPath, CREATE_ALWAYS))
{
  PrintString((UString)L"can not open output file " + fullProcessedPath);
  return E_ABORT;
}
_outFileStream = outStreamLoc;
*outStream = outStreamLoc.Detach();

I think that I should use COutMemStream instead of COutFileStream, but I have no idea about what is the right way to use it. Is there any code sample?

The idea is extract a single file (f.e: file at index 3), and after the extraction is finished get the raw data from CArchiveExtractCallback.

Thanks

[Igor Pavlov]

If unpackSize is known, you can use CBufPtrSeqOutStream:

CBufPtrSeqOutStream *outStreamSpec = new CBufPtrSeqOutStream;
CMyComPtr<ISequentialOutStream> outStream(outStreamSpec);
outStreamSpec->Init(data, unpackSize);

If unpackSize is unknown (gzip, bzip2), you can use CDynBufSeqOutStream.

[estux]

Thank you so much Igor, now it is working fine.

[undefauth]

I'm trying to do the same thing, I was just wondering, where exactly is this "data" that is used with Init()?

Thanks.

[Igor Pavlov]

You must allocate buffer for uncompressed data.
The "data" is a pointer to that buffer.

[undefauth]

I realized thats what I must do, don't know what I was thinking. Thanks so much for the reply.

[ak24]

I'm too trying to extract the file to buffer...but how the decompressed data is filled in the buffer before/after calling outStreamSpec->Init(data, unpackSize);

[ak24]

Thanks.
With CoutFileStream there was no call back from 7z.dll when call to extract was made from Client7z.
Simply change the name of COutFileStream to CBufPtrSeqOutStream to get the stream . COutFileStream is a class declared in FileStreams.h. When CArchiveExtractCallback::GetStream is call backed from 7z.dll GetStream returns In/Out param as ISequentialOutStream** which should point to concrete implementation of CBufPtrSeqOutStream. Implement ISequentialOutStream::Write(. . . ) as per your need.

STDMETHODIMP CBufPtrSeqOutStream::Write(const void data, UInt32 size, UInt32 processedSize)
{
UInt32 realProcessedSize;
bool result = File.WritePart(data, size, realProcessedSize); //Don't call this if

// data is not required to be written on disk. but make sure realProcessedSize is correct

// otherwise it would be recursive loop
Byte buffer = new Byte[size];
memcpy(buffer, data, size); //copy data to buffer
ProcessedSize += realProcessedSize;
if (processedSize)
processedSize = realProcessedSize;
return ConvertBoolToHRESULT(result);
}