date: use strbufs in date-formatting functions

Many of the date functions write into fixed-size buffers.
This is a minor pain, as we have to take special
precautions, and frequently end up copying the result into a
strbuf or heap-allocated buffer anyway (for which we
sometimes use strcpy!).

Let's instead teach parse_date, datestamp, etc to write to a
strbuf. The obvious downside is that we might need to
perform a heap allocation where we otherwise would not need
to. However, it turns out that the only two new allocations
required are:

  1. In test-date.c, where we don't care about efficiency.

  2. In determine_author_info, which is not performance
     critical (and where the use of a strbuf will help later
     refactoring).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 7 insertions, 6 deletions

diff --git a/date.c b/date.c
index 782de95d90..2c33468dfb 100644
--- a/date.c
+++ b/date.c
@@ -605,7 +605,7 @@ static int match_tz(const char *date, int *offp)
 	return end - date;
 }
 
-static int date_string(unsigned long date, int offset, char *buf, int len)
+static void date_string(unsigned long date, int offset, struct strbuf *buf)
 {
 	int sign = '+';
 
@@ -613,7 +613,7 @@ static int date_string(unsigned long date, int offset, char *buf, int len)
 		offset = -offset;
 		sign = '-';
 	}
-	return snprintf(buf, len, "%lu %c%02d%02d", date, sign, offset / 60, offset % 60);
+	strbuf_addf(buf, "%lu %c%02d%02d", date, sign, offset / 60, offset % 60);
 }
 
 /*
@@ -735,13 +735,14 @@ int parse_expiry_date(const char *date, unsigned long *timestamp)
 	return errors;
 }
 
-int parse_date(const char *date, char *result, int maxlen)
+int parse_date(const char *date, struct strbuf *result)
 {
 	unsigned long timestamp;
 	int offset;
 	if (parse_date_basic(date, &timestamp, &offset))
 		return -1;
-	return date_string(timestamp, offset, result, maxlen);
+	date_string(timestamp, offset, result);
+	return 0;
 }
 
 enum date_mode parse_date_format(const char *format)
@@ -766,7 +767,7 @@ enum date_mode parse_date_format(const char *format)
 		die("unknown date format %s", format);
 }
 
-void datestamp(char *buf, int bufsize)
+void datestamp(struct strbuf *out)
 {
 	time_t now;
 	int offset;
@@ -776,7 +777,7 @@ void datestamp(char *buf, int bufsize)
 	offset = tm_to_time_t(localtime(&now)) - now;
 	offset /= 60;
 
-	date_string(now, offset, buf, bufsize);
+	date_string(now, offset, out);
 }
 
 /*