nsIInputStream
unsigned long readsegments(in nswritesegmentfun awriter, in voidptr aclosure, in unsigned long acount); native code only!
... unsigned long readsegments( in nswritesegmentfun awriter, in voidptr aclosure, in unsigned long acount ); parameters awriter the "consumer" of the data to be read.
...see nswritesegmentfun for more details on this function.