Re: string.pack with bit resolution

[Sean Conner <sean@...>]

It was thus said that the Great bil til once stated:
> One further offer, concerning the “n” specifier.

  [ ... snip of about 100 lines of specification ... ]

  At this point, it would be wise to actually look for an explicit module to
do the packing that you want.  One such example would be CBOR, as it's a
documented standard (RFC-7049) and there are a lot of implementations for
many languages.  It defines, I think, a nice balance between dense packing
and efficient encoding/decoding.

  Seriously, please!  Look into that [1] and stop trying to modify
string.pack()/string.unpack().  Even *IF* (and that's a big "if") the Lua
team decide to implement your ideas, they won't be in the Lua 5.4 release,
so you are looking at several *YEARS* at the minimum.

> (As I told already in my blogs before, I see no application why to support
> alignment larger than 1 Byte … and I think this alignment support bloats the
> C code quite a bit … 

  And your 100+ line wish list won't bloat the C code?

  But more seriously, not every machine in existance is x86; there ARE
architetures out there with alignment restrictions STILL in use today (I use
them at work).  And they can run Lua (which I also do at work).  So
alignment is STILL important.

> but if there are good reasons to support alignment,
> then please correct me, then no problem to re-install the option ![n]’ …
> just I really do NOT understand what you mean with the option ‘Xop’ in your
> existing format table… .)

  It's for alignment purposes.  An example, if I want to pack the following
C structure [2]:

	struct foo
	{
	  char c;
	  int  i;
	};

	with the following packing string:

		"=! c1 XI I" -- [3]

  The "XI" part says advance to the next alignment spot and not return said
padding.  

  -spc

[1]	Here's one for Lua:

		https://github.com/spc476/CBOR

	And it supports half floats, which seem to be important to you.
	Heck, here's a whole list of implementations for various languages:
	
		http://cbor.io/impls.html
	
[2]	The rules for C structures is that the order is kept, but padding
	bytes can be added.

[3]	I know!  The size of the integer is unspecified---it's an example. 
	Deal with it!