Re: [bug-gawk] How to print an unsigned char?

[arnold]

Awk and gawk are the wrong language to use for binary I/O.

If you insist on doing stuff like that, first use the -b option, so
that each byte in a string is treated as a character on it own.
Next, you can use the lshift, rshift, or, xor, and "and" functions to
do bit manipulations if you really want to.

But I really think that trying to use gawk for serious bit manipulation
and binary I/O is forcing a square peg into a round hole, and won't work
well.

Arnold

Wolfgang Laun <address@hidden> wrote:

> Having the system calls read and write as functions is only one part of the
> cake. You'd need to have a data type that can play the role of the char[]
> used as data buffer in these calls *with a well-defined, portable memory
> representation. *As an example: how to compose something with the size of
> 10 memory units (bytes) consisting of the lowermost 1/2/3/4 bytes of
> a/b/c/d, densely packed?
>
> (I have browsed the gawk user manual's sections that sound relevant. Sorry
> if I missed this being already available.)
> Wolfgang
>
>
> On Mon, 25 Feb 2019 at 00:07, Andrew J. Schorr <
> address@hidden> wrote:
>
> > On Sun, Feb 24, 2019 at 02:40:54PM -0600, Peng Yu wrote:
> > > On 2/24/19, Eli Zaretskii <address@hidden> wrote:
> > > > [Please use Reply All, please don't take this off-list.]
> > > >
> > > >> From: Peng Yu <address@hidden>
> > > >> Date: Sun, 24 Feb 2019 12:11:45 -0600
> > > >>
> > > >> > Yes, don't use %c.
> > > >> How?
> > > >
> > > > It depends on what you want to accomplish.  Can you describe your
> > > > goal(s) in this matter?
> > >
> > > As the title says "How to print an unsigned char?"
> >
> > This can be done using the extension API. The get_file hook provides
> > access to
> > the file descriptor via the returned awk_input_buf_t or awk_output_buf_t.
> > The
> > select extension uses this in the "input_fd" and "output_fd" functions. So
> > it
> > should be fairly simple to create an extension that provides access to the
> > read
> > & write system calls for a gawk "file". We will eventually need this if
> > anybody
> > wants to implement a socket library.
> >
> > So it's simple: write a new gawk extension implementing read and write, and
> > then you can use those functions to do binary I/O. Or just use Python
> > where the
> > file objects can be accessed through the high-level print function or the
> > low-level read and write methods.
> >
> > Regards,
> > Andy
> >
> >