1388773 - add an nsIFixedLengthInputStream

Status: NEW

(Core :: XPCOM, enhancement, P3)

Description

[Ben Kelly [:bkelly, not reviewing]]

We have a number of places that try to use nsIInputStream::Available() to determine the total length of the stream.  These are very fragile because they have to ensure that the stream is fully available before its called.  For anything like a pipe you will end up getting a partial size instead.

We could, however, provide a better mechanism by exposing an explicit interface for "fixed length streams with a known total size".  Something like:

interface nsIFixedLengthInputStream
{
  // True when all the data is known.  For file streams it will always
  // be true.  For streams like storage streams it may be false and become
  // true.
  readonly attribute bool complete;
  
  unsigned long long totalSize();

  // Maybe add a callback mechanism to be notified when the stream
  // is "complete".
};