Re: CRC in Ada?

[dewar@merv.cs.nyu.edu (Robert Dewar)]

Bob Duff said

<<Agreed, but that's what inlining is for.  All I was saying is that there
should be a standard package that does efficient I/O, with buffering,
and of course you want to inline a call that just bumps a pointer and
grabs a character out of a buffer (except in the rare case where the
buffer is exhausted).  Unfortunately, Text_IO has an awful lot of
nearly-useless cruft in it.  But why can't Stream_IO fit the bill here?>>

  It can, but be careful. If you write String'Input, then not only do you
  get the overhead of going character by character, unless a lot of
  special optimization is at work, but you also get the general inefficiency
  of dealing with unconstrained variable length objects, which usually
  involves at least one extra copy. The character by character reads come
  from the fact that this is the semantics of String'Input. yes, it could
  indeed be optimized (in the normal case, where a user level attribute is
  not supplied for type character), but you cannot count on that.

  More likely to be efficient is using Read and Write directly on
  buffers of stream elements.

  Indeed it is perfectly easy, and probably safest to do your own
  buffering in many cases (the same advice applies to C, it may be
  efficient to do indidvidual getchar's, but it may also be a disaster
  from an efficiency point of view.