> On 03/27/2018 07:17 PM, Peter Xu wrote: >> On Tue, Mar 27, 2018 at 03:42:32AM +0800, Xiao Guangrong wrote: >> >> [...] >> >>>> It'll be understandable to me if the problem is that the compress() >>>> API does not allow the input buffer to be changed during the whole >>>> period of the call. If that is a must, this patch for sure helps. >>> >>> Yes, that is exactly what i want to say. :) >> >> So I think now I know what this patch is for. :) And yeah, it makes >> sense. >> >> Though another question would be: if the buffer is updated during >> compress() and compress() returned error, would that pollute the whole >> z_stream or it only fails the compress() call? >> > > I guess deflateReset() can recover everything, i.e, keep z_stream as > it is init'ed by deflate_init(). > >> (Same question applies to decompress().) >> >> If it's only a compress() error and it won't pollute z_stream (or say, >> it can be recovered after a deflateReset() and then we can continue to >> call deflate() without problem), then we'll actually have two >> alternatives to solve this "buffer update" issue: >> >> 1. Use the approach of current patch: we copy the page every time, so >> deflate() never fails because update never happens. But it's slow >> since we copy the pages every time. >> >> 2. Use the old approach, and when compress() fail, we just ignore that >> page (since now we know that error _must_ be caused by page update, >> then we are 100% sure that we'll send that page again so it'll be >> perfectly fine). >> > > No, we can't make the assumption that "error _must_ be caused by page > update". > No document/ABI about compress/decompress promised it. :) So, as I metioned before, can we just distingush the decompress/compress errors from errors caused by page update by the return code of inflate/deflate? According to the zlib manual, there seems to be several error codes for different cases, #define Z_ERRNO (-1) #define Z_STREAM_ERROR (-2) #define Z_DATA_ERROR (-3) #define Z_MEM_ERROR (-4) #define Z_BUF_ERROR (-5) #define Z_VERSION_ERROR (-6) Did you check the return code when silent failure(not caused by page update) happened before? :)
Jiang Regards
