Re: [PATCH] btrfs-progs: Improve the parse_size() error message.

[Qu Wenruo <quwenruo@cn.fujitsu.com>]

-------- Original Message --------
Subject: Re: [PATCH] btrfs-progs: Improve the parse_size() error message.
From: Mike Fleetwood <mike.fleetwood@googlemail.com>
To: Qu Wenruo <quwenruo@cn.fujitsu.com>
Date: 2014年05月29日 05:07
> On 20 May 2014 08:51, Qu Wenruo <quwenruo@cn.fujitsu.com> wrote:
>> When using parse_size(), even non-numeric value is passed, it will only
>> give error message "ERROR: size value is empty", which is quite
>> confusing for end users.
>>
>> This patch will introduce more meaningful error message for the
>> following new cases
>> 1) Invalid size string (non-numeric string)
>> 2) Minus size value (like "-1K")
>>
>> Also this patch will take full use of endptr returned by strtoll() to
>> reduce unneeded loop.
>>
>> Reported-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
>> Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
>> ---
>>   utils.c | 53 +++++++++++++++++++++++++++++++++--------------------
>>   1 file changed, 33 insertions(+), 20 deletions(-)
>>
>> diff --git a/utils.c b/utils.c
>> index 392c5cf..1cbe102 100644
>> --- a/utils.c
>> +++ b/utils.c
>> @@ -1612,18 +1612,20 @@ scan_again:
>>
>>   u64 parse_size(char *s)
>>   {
>> -       int i;
>>          char c;
>>          u64 mult = 1;
>> -
>> -       for (i = 0; s && s[i] && isdigit(s[i]); i++) ;
>> -       if (!i) {
>> -               fprintf(stderr, "ERROR: size value is empty\n");
>> -               exit(50);
>> -       }
>> -
>> -       if (s[i]) {
>> -               c = tolower(s[i]);
>> +       long long int ret = 0;
>> +       char *endptr;
>> +
>> +       if (!s)
>> +               goto empty;
>> +       ret = strtoll(s, &endptr, 10);
>> +       if (endptr == s)
>> +               goto invalid;
>> +       if (endptr[0] && endptr[1])
>> +               goto suffix;
>> +       if (endptr[0]) {
>> +               c = tolower(endptr[0]);
>>                  switch (c) {
>>                  case 'e':
>>                          mult *= 1024;
>> @@ -1646,18 +1648,29 @@ u64 parse_size(char *s)
>>                  case 'b':
>>                          break;
>>                  default:
>> -                       fprintf(stderr, "ERROR: Unknown size descriptor "
>> -                               "'%c'\n", c);
>> -                       exit(1);
>> +                       goto descriptor;
>>                  }
>>          }
>> -       if (s[i] && s[i+1]) {
>> -               fprintf(stderr, "ERROR: Illegal suffix contains "
>> -                       "character '%c' in wrong position\n",
>> -                       s[i+1]);
>> -               exit(51);
>> -       }
>> -       return strtoull(s, NULL, 10) * mult;
>> +       ret *= mult;
>> +       if (ret <= 0)
>> +               goto minus;
>> +       return (u64) ret;
>> +empty:
>> +       fprintf(stderr, "ERROR: Size value is empty\n");
>> +       exit(50);
>> +suffix:
>> +       fprintf(stderr, "ERROR: Illegal suffix contains character '%c' in wrong position\n",
>> +               endptr[1]);
>> +       exit(51);
>> +descriptor:
>> +       fprintf(stderr, "ERROR: Unknown size descriptor '%c'\n", c);
>> +       exit(52);
>> +invalid:
>> +       fprintf(stderr, "ERROR: Size value '%s' is invalid\n", s);
>> +       exit(53);
>> +minus:
>> +       fprintf(stderr, "ERROR: Size value '%s' is less equal than 0\n", s);
>> +       exit(54);
>>   }
>>
>>   int open_file_or_dir3(const char *fname, DIR **dirstream, int open_flags)
>> --
>> 1.9.2
>>
> IMHO use of this "if condition goto print error exit" pattern makes
> the code harder to read.  Use of gotos is used when a function creates
> state which needs tearing down in reverse on error before returning.
> I think the errors should be printed at the point of detection.  Like
> this:
>
> +       if (!s) {
> +               fprintf(stderr, "ERROR: Size value is empty\n");
> +               exit(1);
> +       }
> +       ret = strtoll(s, &endptr, 10);
> +       if (endptr == s) {
> +               fprintf(stderr, "ERROR: Size value '%s' is invalid\n", s);
> +               exit(1);
> +       }
>
> etc.
>
> Thanks,
> Mike
Yes, that's true. I will change it to the original style.

Thanks,
Qu