On Aug 5, 2012, at 11:19 PM, Mike Frysinger wrote:
> so %n is telling us how many *bytes* were read, not the number of elements
> consumed.
Yes, but the *return value* is the "the number of input *items* assigned" (man
sscanf); that's why I check that it's equal to 2 indicating that parsing didn't
fail before reaching %n:
> if (sscanf(eq, "%lu%n", lu, &dummy) == 2)
> sscanf("0a", "%lu%n", lu, &dummy);
> - return value = 1
and 1!=2
Perhaps a clearer alternative would be:
if (sscanf(eq, "%lu%c", lu, &dummy) == 1)
If there is junk left over the %c will match and it will return 2, and 2!=1.
For the record I am not a huge fan of the libc parsing/printing functions.
It's been at least five years since I last used them in code I wrote myself.
If you have a better way to check that the input was fully consumed, that's
fine with me.
> however, i'd point out that this only catches errors where the user supplied
> a
> hex value that contains non-numbers.
Yes, and that's the only situation where the user -- such as me -- is thinking
to themselves "well, I gave it something with letters in it, and it didn't
complain, so it can't possibly be parsing it as decimal or octal!"
Seriously, this is the reason why I never bothered trying a "0x" or "16'h"
prefix.
> maybe as part of the cable output, we can echo back "forcing VID=0x1234" so
> that they can immediately tell "oh, my number is being interpreted as a
> decimal when i really want hex, so i need to add the 0x prefix".
That would be fine too.
- e
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