c# - Does CopyTo store the whole thing in memory? -

i have following code snippet, designed add files .zip file, while @ same time calculating sha1 checksum.

however, it's running out of memory on large files.

which part of causing whole file in memory? surely should streamed?

using (ziparchive archive = zipfile.open(buildfile, ziparchivemode.update)) {     foreach (var filename in namelist)     {         ziparchiveentry entry = archive.createentry(source.filename);         using (stream zipdata = entry.open())         using (sha1managed shaforfile = new sha1managed())         using (stream sourcefilestream = file.openread(filename))         using (stream sourcedata = new cryptostream(sourcefilestream, shaforfile, cryptostreammode.read))         {             sourcedata.copyto(zipdata);             print filename + ':' + shaforfile.hash;         }     } } 

(copied comment - answers question)

the problem ziparchivemode.update, can require significant alterations file on disk. can ever directly stream disk when use ziparchivemode.create