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Date: Wed, 19 Feb 2014 19:39:55 -0600
From: Eric Sandeen <sandeen@redhat.com>
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To: Wang Shilong <wangsl.fnst@cn.fujitsu.com>, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH v2 1/4] Btrfs-progs: new helper to parse string to u64
 for btrfs
References: <1392859852-15829-1-git-send-email-wangsl.fnst@cn.fujitsu.com> <1392859852-15829-2-git-send-email-wangsl.fnst@cn.fujitsu.com>
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On 2/19/14, 7:30 PM, Wang Shilong wrote:
> There are many places that need parse string to u64 for btrfs commands,
> in fact, we do such things *too casually*, using atoi/atol/atoll..is not
> right at all, and even we don't check whether it is a valid string.
> 
> Let's do everything more gracefully, we introduce a new helper
> arg_strtou64() which will do all the necessary checks.If we fail to
> parse string to u64, we will output message and exit directly, this is
> something like what usage() is doing. It is ok to not return erro to
> it's caller, because this function should be called when parsing arg
> (just like usage!)
> 
> Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
> ---
>  utils.c | 33 +++++++++++++++++++++++++++++++++
>  utils.h |  1 +
>  2 files changed, 34 insertions(+)
> 
> diff --git a/utils.c b/utils.c
> index 97e23d5..d570967 100644
> --- a/utils.c
> +++ b/utils.c
> @@ -1520,6 +1520,39 @@ scan_again:
>  	return 0;
>  }
>  
> +/*
> + * This function should be only used when parsing
> + * command arg, it won't return error to it's
> + * caller and rather exit directly just like usage().
> + */
> +u64 arg_strtou64(const char *str)
> +{
> +	u64 value;
> +	char *ptr_parse_end = NULL;
> +	char *ptr_str_end = (char *)str + strlen(str);
> +
> +	/*
> +	 * if we pass a negative number to strtoull,
> +	 * it will return an unexpected number to us,
> +	 * so let's do the check ourselves firstly.
> +	 */
> +	if (str[0] == '-') {
> +		fprintf(stderr, "ERROR: %s may be negative value.\n", str);

well, it _is_ a negative value right?  (vs. "may be")

So perhaps:

fprintf(stderr, "ERROR: %s: negative value is invalid.\n", str);


> +		exit(1);
> +	}
> +
> +	value = strtoull(str, &ptr_parse_end, 0);
> +	if (ptr_parse_end != ptr_str_end) {
> +		fprintf(stderr, "ERROR: %s is not valid value.\n", str);

maybe:

fprintf(stderr, "ERROR: %s is not a valid numeric value.\n", str);

Otherwise, this looks fine to me.  We'll see what the others on the thread
think.  :)

thanks,
-Eric

> +		exit(1);
> +	}
> +	if (value == ULLONG_MAX) {
> +		fprintf(stderr, "ERROR: %s is too large.\n", str);
> +		exit(1);
> +	}
> +	return value;
> +}
> +
>  u64 parse_size(char *s)
>  {
>  	int i;
> diff --git a/utils.h b/utils.h
> index 04b8c45..a201085 100644
> --- a/utils.h
> +++ b/utils.h
> @@ -71,6 +71,7 @@ int pretty_size_snprintf(u64 size, char *str, size_t str_bytes);
>  int get_mountpt(char *dev, char *mntpt, size_t size);
>  int btrfs_scan_block_devices(int run_ioctl);
>  u64 parse_size(char *s);
> +u64 arg_strtou64(const char *str);
>  int open_file_or_dir(const char *fname, DIR **dirstream);
>  void close_file_or_dir(int fd, DIR *dirstream);
>  int get_fs_info(char *path, struct btrfs_ioctl_fs_info_args *fi_args,
>