> In that case the number of bytes to write is a function of the number > of processed bytes. The filter can count how many bytes it processed > after the last reset, in a local way. > > Consider: > > > -> filter1 -> aesv2 -> filter2 -> > > > Both filter1 and filter2 may be implementing quite different filtering > algorithms. How would aesv2 benefit with the knowledge of the number > of bytes already written by filter2, for example?
Sorry, I think I don't explain enough well. I mean that due to some filters, _we_ could require know the output size. Consider we create a new memory writing stream. It is possible stream doesn't fill the buffer. Then, how I know how many bytes it wrote? I hope it is clear now :-) To know how many bytes a filter wrote in a memory backend you can use the 'pdf_stm_tell' function, that will tell you the current read/write position.
