On Wed, Mar 28, 2018 at 12:08:19PM +0800, jiang.biao2@xxxxxxxxxx wrote: > > > > On Tue, Mar 27, 2018 at 10:35:29PM +0800, Xiao Guangrong wrote: > > > >> > > No, we can't make the assumption that "error _must_ be caused by page update". > >> > > No document/ABI about compress/decompress promised it. :) > > > > Indeed, I found no good documents about below errors that jiang.biao > > pointed out. > Hi, Peter > The description about the errors comes from here, > http://www.zlib.net/manual.html > And about the error codes returned by inflate(), they are described as， > ** inflate() returns > Z_OK if some progress has been made (more input processed or more output produced), > Z_STREAM_END if the end of the compressed data has been reached and all uncompressed output has been produced, > Z_NEED_DICT if a preset dictionary is needed at this point, > Z_DATA_ERROR if the input data was corrupted (input stream not conforming to the zlib format or incorrect check value, in which case strm->msg points to a string with a more specific error), > Z_STREAM_ERROR if the stream structure was inconsistent (for example next_in or next_out was Z_NULL, or the state was inadvertently written over by the application), > Z_MEM_ERROR if there was not enough memory, > Z_BUF_ERROR if no progress was possible or if there was not enough room in the output buffer when Z_FINISH is used. ... > ** Ah yes. My bad to be so uncareful. :) > According to the above description, the error caused by page update looks > more like tend to return Z_DATA_ERROR, but I do not have env to verify that. :) > As I understand it, the real compress/decompress error cases other than that > caused by page update should be rare, maybe the error code is enough to > distinguish those if we can verify the the error codes returned by page update > and other silent failures by test. If so, we can cut the cost of memcpy. > If not, I agree with Guangrong's idea too. I never read the zlib code and all my > information comes from the manual, so if anything inaccurate, pls ignore my > option. :) So I suppose all of us know that alternative now, we just need a solid way to confirm the uncertainty. I'll leave this to Guangrong. Thanks, -- Peter Xu
