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

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

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