Changes in udhcp

[Denys Vlasenko]

On Thursday 29 November 2007 06:37, Ralf Friedl wrote:
> Hi
>
> I have two remarks to the recent changes to udhcp.
>
> networking/udhcp/script.c contains "static int mton()" to count the bits
> of a network mask. This could use the ffs() function:
>        The ffs() function returns the position of the first (least
> significant) bit set in the word i.  The least significant bit is
> position 1 and the most significant position is 32.
>
> So mton could be written as
>   return 32 - (ffs (ntohl(mask)) - 1);

I'm afraid you need to add some code to handle mask==0.

Existing code compiles to 6 instructions (11 bytes):

        xorl    %edx, %edx      # i
        jmp     .L55    #
.L56:   incl    %edx    # i
        sall    %eax    # mask
.L55:   testl   %eax, %eax      # mask
        jne     .L56    #,

Seems good enough to me.
--
vda