Retrieves the #GFileInfo constructed from the GZIP header data
of compressed data processed by compressor, or null if decompressor's
#GZlibDecompressor:format property is not gio.types.ZlibCompressorFormat.Gzip,
or the header data was not fully processed yet, or it not present in the
data stream at all.
Retrieves the #GFileInfo constructed from the GZIP header data of compressed data processed by compressor, or null if decompressor's #GZlibDecompressor:format property is not gio.types.ZlibCompressorFormat.Gzip, or the header data was not fully processed yet, or it not present in the data stream at all.