sfeed.c: fix time parsing regression with non-standard date format

The commit that introduced the regression was:

commit 33c50db302957bca2a850ac8d0b960d05ee0520e
Author: Hiltjo Posthuma <hiltjo@codemadness.org>
Date:   Mon Oct 12 18:55:35 2020 +0200

    simplify time parsing

Noticed on a RSS feed with the following date:

	<pubDate>2021-02-03 05:13:03</pubDate>

This format is non-standard, but sfeed should support this.
A standard format would be (for Atom): 2021-02-03T05:13:03Z

Partially revert it.

1 files changed, 11 insertions, 13 deletions

diff --git a/sfeed.c b/sfeed.c
index bd3afbc..79768f3 100644
--- a/sfeed.c
+++ b/sfeed.c
@@ -559,10 +559,7 @@ parsetime(const char *s, time_t *tp)
 	    isdigit((unsigned char)s[2]) &&
 	    isdigit((unsigned char)s[3])) {
 		/* formats "%Y-%m-%d %H:%M:%S", "%Y-%m-%dT%H:%M:%S" or "%Y%m%d%H%M%S" */
-		va[0] = ((s[0] - '0') * 1000) + ((s[1] - '0') * 100) +
-		         ((s[2] - '0') * 10) + (s[3] - '0');
-		vi = 1;
-		s += 4;
+		vi = 0;
 	} else {
 		/* format: "[%a, ]%d %b %Y %H:%M:%S" */
 		/* parse "[%a, ]%d %b %Y " part, then use time parsing as above */
@@ -608,16 +605,17 @@ parsetime(const char *s, time_t *tp)
 	}
 
 	/* parse time parts (and possibly remaining date parts) */
-	for (; *s && vi < 6; ) {
-		if (isdigit((unsigned char)s[0]) && isdigit((unsigned char)s[1])) {
-			va[vi++] = ((s[0] - '0') * 10) + (s[1] - '0');
-			s += 2;
-		} else if (vi > 2 && (*s == '-' || *s == '+' || *s == '.' ||
-		           isspace((unsigned char)*s))) {
-			break;
-		} else {
-			s++;
+	for (; *s && vi < 6; vi++) {
+		for (i = 0, v = 0; i < ((vi == 0) ? 4 : 2) &&
+		                   isdigit((unsigned char)*s); s++, i++) {
+			v = (v * 10) + (*s - '0');
 		}
+		va[vi] = v;
+
+		if ((vi < 2 && *s == '-') ||
+		    (vi == 2 && (*s == 'T' || isspace((unsigned char)*s))) ||
+		    (vi > 2 && *s == ':'))
+			s++;
 	}
 
 	/* skip milliseconds in for example: "%Y-%m-%dT%H:%M:%S.000Z" */