New support for memory IOS

[Jose E. Marchesi]

Hi people!

So I just committed support for IOS that are backed by memory buffers,
instead of files.  These IO spaces are intended to be used in a similar
way buffers are used in text editors.

At the command level, a new dot-command .mem has been added.  It is very
similar to the existing .file dot-command, and creates a new memory IOS
like this:


(poke) .file foo.o
The current file is now `foo.o'.
(poke) .mem foo
The current IOS is now `*foo*'.
(poke) .info ios
  Id    Mode    Position        Name
* #1            0x00000000#b    *foo*
  #0    rw      0x00000000#b    foo.o

Note how:

- Asterisks are automatically added to the name of the memory IOS.  This
  is to distinguish memory IOS from file IOS.  (Yeah this means we can't
  edit files with names having a leading and trailing asterisks, but we
  are gonna have to live with that.)

- The .info files command has been renamed to .info ios, for obvious
  reasons.  The column Filename is now called Name.

- The memory IOS has no mode.  We may want to change that in the future,
  so the user can set memory IOS in read-only mode to avoid overwriting
  the information they contain...

At the Poke programming level, memory IOS can be created using the
`open' built-in, function.  This time, it is up to the user to add the
asterisks, or a file will be opened instead:

defvar file = open ("foo");
defvar buffer = open ("*foo*");

The memory IOS are self-growing, i.e. they grow as needed to hold what
is written to them.

As for use cases for memory IOS, consider for example you want to mess
with a compressed ELF section: you would uncompress the section in a
memory IOS and then operate on the data there.

Salud!