[syslog-ng] [PATCH] basicfuncs: Implement a few numeric template functions.

[Balazs Scheidler]

Hi Gergely,

Thanks for the patch, I see an immediate use-case for this.

I applied the patch to the 3.4 tree, and at the same time, I've changed
it slightly.

On Tue, 2011-05-03 at 22:19 +0200, Gergely Nagy wrote:
> Implement addition, substraction, multiplication, division and modulus
> template functions: $(+ N M), $(- N M), $(* N M), $(/ N M) and $(% N
> M), respectively.
> 
> All of them take two numeric arguments, and log an error,

instead of logging an error, always, insert a "NaN" into the output
stream, which stands for Not-a-Number, commonly used to represent
non-numbers in underflows. I know it's not that intuitive, but in
production environments, generating loads of error messages such as
these in the fast path (even more, since you can several invocation of
these functions per message), would do no good.

So, I've changed errors to debug (so if someone is running it with
debugging enabled still get the messages), and in all error paths I've
used NaN instead of the empty string.

Also, tests didn't cover negative numbers, now I've added to cover them
too.

Also, while I was at it, I've changed all g_string_append_printf() calls
to format_int32_padded(), which is much faster.

g_string_append_printf() is double slow, because:

  1) it uses printf, but to measure the length of the string, it runs
printf without storing its results, and then
  2) allocates a buffer to format this result, and then
  3) moves the temp buffer to the end of the gstring
  4) frees the buffer.

So it is not even double, but quadraple slow. :)

>  if they
> receive less or more, or in case the number cannot be fully parsed as
> a number.
> 
> Signed-off-by: Gergely Nagy <algernon at balabit.hu>

This is the commit message, please let me know if you disagree with my
changes.

commit 89b5006f1fc015f1049ec3713638074434beba65
Author: Balazs Scheidler <bazsi at balabit.hu>
Date:   Tue May 3 23:01:09 2011 +0200

    basicfuncs: Implement a few numeric template functions
    
    Implement addition, substraction, multiplication, division and modulus
    template functions: $(+ N M), $(- N M), $(* N M), $(/ N M) and $(% N
    M), respectively.
    
    All of them take two numeric arguments, and result in "NaN"
    (aka Not-a-Number) in case parameters cannot be parsed, or if a
    division by zero would occur.
    
    Signed-off-by: Gergely Nagy <algernon at balabit.hu>
    Signed-off-by: Balazs Scheidler <bazsi at balabit.hu>



-- 
Bazsi