This is a simple Lua library for packing and unpacking binary data.

To try this Lua library, edit Makefile to reflect your installation of Lua.
Then run make. This will build lpack.so and run a simple test. If everything
is ok, install lpack.so and pack.lua in some official place. You may want to
edit pack.lua to change the default value of SOPATH (you can also set the
environment variable LUA_SOPATH at run time).

Here is a brief explanation of the files in this package:
  lpack.c        pack library
  pack.lua       support code
  test.lua       test code

The library adds two functions to the string library: pack and unpack.

pack is called as follows: pack(F,x1,x2,...), where F is a string describing
how the values x1, x2, ... are to be interpreted and formatted. Each letter
in the format string F consumes one of the given values. Only values of type
number or string are accepted. pack returns a (binary) string containing the
values packed as described in F. The letter codes understood by pack are listed
in lpack.c (they are inspired by Perl's codes but are not the same). Numbers
following letter codes in F indicate repetitions.

unpack is called as follows: unpack(s,F,[init]), where s is a (binary) string
containing data packed as if by pack, F is a format string describing what is
to be read from s, and the optional init marks where in s to begin reading the
values. unpack returns one value per letter in F until F or s is exhausted
(the letters codes are the same as for pack, except that numbers following `A'
are interpreted as the number of characters to read into the string, not as
repetitions).

The first value returned by unpack is the next unread position in s, which can
be used as the init position in a subsequent call to unpack. This allows you to
unpack values in a loop or in several steps. If the position returned by unpack
is beyond the end of s, then s has been exhausted; any calls to unpack starting
beyond the end of s will always return nil values.

This code is hereby placed in the public domain.
Please send comments, suggestions, and bug reports to lhf@tecgraf.puc-rio.br .
