[erlang-questions] Proper replacement for io_lib:format due to low speed

[Chandru]

Hi Max,

Is something like this not good enough in terms of speed?

iso8601({{Y,Mo,D}, {H,Mn,S}}) ->
    list_to_binary([integer_to_list(Y), $-,
                    two_digit_str(Mo),  $-,
                    two_digit_str(D),   $T,
                    two_digit_str(H),   $:,
                    two_digit_str(Mn),  $:,
                    two_digit_str(S),   $Z]).

two_digit_str(X) when X < 10 ->
    [$0 | integer_to_list(X)];
two_digit_str(X) ->
    integer_to_list(X).


cheers,
Chandru


On 22 March 2015 at 09:01, Max Lapshin <max.lapshin@REDACTED> wrote:

> Hi.
>
> I've met again performance problem with io_lib:format.
>
> iso8601({{Y,Mo,D}, {H,Mn,S}}) ->
>   FmtStr = "~4.10.0B-~2.10.0B-~2.10.0BT~2.10.0B:~2.10.0B:~2.10.0BZ",
>   IsoStr = io_lib:format(FmtStr, [Y, Mo, D, H, Mn, S]),
>   list_to_binary(IsoStr).
>
>
> Such code is a 0,01% of business logic of one small part of flussonic, but
> it takes about 95% of time to make 10% of text output.
>
>
> I've solved this problem via https://github.com/maxlapshin/io_libc  but
> I'm not sure that it is
> a best way to do.  Maybe this is better solved in pure erlang?
>
>
> Perhaps I'm not alone with this problem and somebody has some better idea
> than just exposing fprinf via nif?
>
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>
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