Reading a zero-terminated string

[Enrico Colombini <erix@...>]

I have to read 0-terminated 8-bit strings from a file (actually, a 
'binary' file under Windows).

I tried f:read('*l') and it worked fine... but then I noticed that its 
behavior with \0 is undocumented, so I had a look at liolib.c, saw that 
it uses fgets... and realized that fgets's behavior with \0 seems to be 
undocumented too.

So I basically see three choices:

1) use the undocumented behavior of f:read/fgets.
2) scan char-by-char to find the \0, use f:seek to move back to the 
starting point and read the string with f:read(n).
3) read a byte at a time into a table and then use table.concat.

I think 2 and 3 are both inefficient in different ways (though I guess 3 
is probably much worse), but 1 is risky being undocumented.
Using a fixed-size buffer block could possibly be more efficient but 
looks like overkill.

Did I miss a simpler and/or cleaner (pure-Lua) way to read a 
0-terminated string into a Lua string?

  Enrico