Re: Data Overlays

[gvls1!lonjers@louie.udel.edu (Jim Lonjers)]

In article <25um9l$rfk@seine.cs.umd.edu> alex@cs.umd.edu (Alex Blakemore) write
s:
>unfortunately, if the entire object cannot be read, "the number of
>POSIX characters actually transferred is unspecified and there is no
>way for the POSIX application to know this number".  this is fine if
>you wish to read and write Ada objects whose size is known in advance,
>but is a real impediment if you wish to read in a blocks of
>characters, and dont know the total size in advance (i.e. to
>repeatedly fill a buffer, and the last time the number read may be
>less than the size of the buffer).

Yes, you have really identified a failing here:  the generic operations
should have allowed for transfer of multiple objects of a type, with an
indicator of how many of those objects are actually transferred.  This
would bridge the gap between the "one-at-a-time" generic model and the
essentially untyped transfer provided by the "buffer" model.  Good idea for
future standards.

>I think the Ada POSIX binding is really fine and a big improvement
>over the C version in most respects.  for most applications, text_io
>would be fine.  I sure wish there was one 8 bit character that all the
>packages agreed upon.
>
>instead for those of using ASIS, we have
>  POSIX.POSIX_Character
>  Standard.Character
>  ASIS.ASIS_Character

Obviously, ASIS goofed, they could have picked POSIX.POSIX_Character :-)

>and all are very likely physically identical, sheesh.

Yea, when we invented POSIX.POSIX_Character, we felt the same way.  I
believe most of this problem goes away in 9X.