Re: bitstreams

[Tucker Taft <stt@averstar.com>]

mark_lundquist@my-deja.com wrote:
> 
> In article <3A622CE5.89C9378E@worldnet.att.net>,
>   srini <r.srinivasan@worldnet.att.net> wrote:
> >
> > I do not know much about mp3 etc but I have developed a bit stream
> > package which allows you to perform reads in terms of bits. I use
> these
> > in my own compression/decompression test software. The spec is
> attached.
> 
> > ----------------------------------------------------------------------
> > package Bits_Io is
> >
> >    type File_Type is limited private;
> >    type File_Mode is (In_File, Out_File, Append_File);
> >
> >    type Vector_type is array (natural range <>) of boolean ;
> >    pragma pack( Vector_Type ) ;
> .
> .
> .
> 
> Beware, though... this is implementation-dependent. If the compiler
> doesn't represent a packed array of boolean as a bit vector, it doesn't
> work.

Any Ada 95 compiler that has passed the chapter 13 ACATS (aka ACVCs) 
supports packed bit vectors, so not-to-worry (cf. generic Length_Check
used by many chapter 13 "cd*.*" tests).
 
Ada 95 requires support for packed bit vectors as part of
conforming to the Systems Programming Annex, and about the
only compilers that don't support the Systems Programming Annex
these days are those that generate Java byte codes (and even those
can support packed bit vectors without too much pain, though 
supporting arbitrary unchecked conversion is generally not possible).

> ...
> Mark Lundquist

-- 
-Tucker Taft   stt@avercom.net   http://www.averstar.com/~stt/
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