strncmp issue

[Channa]

Hi,
Thanks for the fix.
I used your code and tested it works fine.
But i have one doubt in the code below you have added
:
 -        cmpcs r2, #1
 +       beq     2f
 +       cmp     r2, #1
:

Instead of the branch instruction above replace the instruction
'cmpcs' with 'cmp'
since we are comparing unsigned value in 'r2' with a constant.

So the code looks as below

:
-  cmpcs r2, #1
+ cmp   r2, #1
:

I have tested the above fix it works good for me.

Please let me know your views.

Thanks & Regards,
Channa


2009/4/30 Mark Tinguely <tinguely at casselton.net>:
>
>>  Yes.  We should get the following results:
>>
>>       strncmp("a", "b", 0);     0
>>       strncmp("a", "b", *);     < 0
>>
>>  where * is any other number :)
>>
>>  Warner
>
> ENTRY(strncmp)
> /* if (len == 0) return 0 */
>        cmp     r2, #0
>        moveq   r0, #0
>        RETeq
>
> /* ip == last src address to compare */
>        add     ip, r0, r2
> 1:
>        ldrb    r2, [r0], #1
>        ldrb    r3, [r1], #1
>        cmp     ip, r0
> -       cmpcs   r2, #1
> +       beq     2f
> +       cmp     r2, #1
>        cmpcs   r2, r3
>        beq     1b
> +2:
>        sub     r0, r2, r3
>        RET
>
> also ip < r0 if r2 = (unsigned int) -1 using 32 bit math. so original
> loop will terminate and compare the first characters. For example
> strncmp("ab", "aa", -1) will result is 0.
>
> I sent Olivier a couple patches, both wrong. Again, sorry for all the noise.
>
> The above code, though, should work in all cases.
>
>        strncmp("b", "a", 0)  result is 0
>        strncmp("abcdef", "abcdef", n)  result is 0
>        strncmp("abcde", "abcdef", n)   0 if 0 <= n < 6  neg if n < 0 or n > 5
>        strncmp("abcdef", "abcde", n)   0 if 0 <= n < 6  pos if n < 0 or n > 5
>
>
> The "beq" will break out of the loop if we give a count <= the string
> length the first arguement.
>
> The next cmp looks for the NULL byte, and the last cmp checks the characters
> in the strings.
>
> --Mark.
>