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[PATCH v2] strbuf: let strbuf_addftime handle %z and %Z itself

From
René Scharfe <l.s.r@web.de>
Date
Jun 15, 2017, 08:46 UTC
Message-ID
<d578d104-79c6-6c07-db4d-3e4ccb0c0dd9@web.de>
In-Reply-To
<a8b789e6-d0cd-6d96-1bfb-ccc5bc174013@web.de>

There is no portable way to pass timezone information to strftime. Add parameters for timezone offset and name to strbuf_addftime and let it handle the timezone-related format specifiers %z and %Z internally.

Callers can opt out for %Z by passing NULL as timezone name. %z is always handled internally -- this helps on Windows, where strftime would expand it to a timezone name (same as %Z), in violation of POSIX. Modifiers are not handled, e.g. %Ez is still passed to strftime.

Use an empty string as timezone name in show_date (the only current caller) for now because we only have the timezone offset in non-local mode. POSIX allows %Z to resolve to an empty string in case of missing information.

Helped-by: Ulrich Mueller <ulm@gentoo.org>
Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Rene Scharfe <l.s.r@web.de>
---
Changes from v1:
- Always handle %z internally.
- Move tests from t6006 to t0006, as that's a more appropriate place.
- Changed tests to only use %%, %z and %Z to avoid incompatibilities.
- Tested on mingw (applies there with patch and some fuzz).
 date.c          |  2 +-
 strbuf.c        | 41 +++++++++++++++++++++++++++++++++++++----
 strbuf.h        | 11 ++++++++---
 t/t0006-date.sh |  6 ++++++
 4 files changed, 52 insertions(+), 8 deletions(-)
diff --git a/date.c b/date.c
index 63fa99685e..5580577334 100644
--- a/date.c
+++ b/date.c
@@ -246,7 +246,7 @@ const char *show_date(timestamp_t time, int tz, const struct date_mode *mode)
 			month_names[tm->tm_mon], tm->tm_year + 1900,
 			tm->tm_hour, tm->tm_min, tm->tm_sec, tz);
 	else if (mode->type == DATE_STRFTIME)
-		strbuf_addftime(&timebuf, mode->strftime_fmt, tm);
+		strbuf_addftime(&timebuf, mode->strftime_fmt, tm, tz, "");
 	else
 		strbuf_addf(&timebuf, "%.3s %.3s %d %02d:%02d:%02d %d%c%+05d",
 				weekday_names[tm->tm_wday],
diff --git a/strbuf.c b/strbuf.c
index 00457940cf..be3b9e37b1 100644
--- a/strbuf.c
+++ b/strbuf.c
@@ -785,14 +785,48 @@ char *xstrfmt(const char *fmt, ...)
 	return ret;
 }
 
-void strbuf_addftime(struct strbuf *sb, const char *fmt, const struct tm *tm)
+void strbuf_addftime(struct strbuf *sb, const char *fmt, const struct tm *tm,
+		     int tz_offset, const char *tz_name)
 {
+	struct strbuf munged_fmt = STRBUF_INIT;
 	size_t hint = 128;
 	size_t len;
 
 	if (!*fmt)
 		return;
 
+	/*
+	 * There is no portable way to pass timezone information to
+	 * strftime, so we handle %z and %Z here.
+	 */
+	for (;;) {
+		const char *percent = strchrnul(fmt, '%');
+		strbuf_add(&munged_fmt, fmt, percent - fmt);
+		if (!*percent)
+			break;
+		fmt = percent + 1;
+		switch (*fmt) {
+		case '%':
+			strbuf_addstr(&munged_fmt, "%%");
+			fmt++;
+			break;
+		case 'z':
+			strbuf_addf(&munged_fmt, "%+05d", tz_offset);
+			fmt++;
+			break;
+		case 'Z':
+			if (tz_name) {
+				strbuf_addstr(&munged_fmt, tz_name);
+				fmt++;
+				break;
+			}
+			/* FALLTHROUGH */
+		default:
+			strbuf_addch(&munged_fmt, '%');
+		}
+	}
+	fmt = munged_fmt.buf;
+
 	strbuf_grow(sb, hint);
 	len = strftime(sb->buf + sb->len, sb->alloc - sb->len, fmt, tm);
 
@@ -804,17 +838,16 @@ void strbuf_addftime(struct strbuf *sb, const char *fmt, const struct tm *tm)
 		 * output contains at least one character, and then drop the extra
 		 * character before returning.
 		 */
-		struct strbuf munged_fmt = STRBUF_INIT;
-		strbuf_addf(&munged_fmt, "%s ", fmt);
+		strbuf_addch(&munged_fmt, ' ');
 		while (!len) {
 			hint *= 2;
 			strbuf_grow(sb, hint);
 			len = strftime(sb->buf + sb->len, sb->alloc - sb->len,
 				       munged_fmt.buf, tm);
 		}
-		strbuf_release(&munged_fmt);
 		len--; /* drop munged space */
 	}
+	strbuf_release(&munged_fmt);
 	strbuf_setlen(sb, sb->len + len);
 }
 
diff --git a/strbuf.h b/strbuf.h
index 80047b1bb7..39d5836abd 100644
--- a/strbuf.h
+++ b/strbuf.h
@@ -339,9 +339,14 @@ __attribute__((format (printf,2,0)))
 extern void strbuf_vaddf(struct strbuf *sb, const char *fmt, va_list ap);
 
 /**
- * Add the time specified by `tm`, as formatted by `strftime`.
- */
-extern void strbuf_addftime(struct strbuf *sb, const char *fmt, const struct tm *tm);
+ * Add the time specified by `tm`, as formatted by `strftime`.  `tz_offset`
+ * and `tz_name` are used to expand %z and %Z internally, unless `tz_name`
+ * is NULL.  `tz_offset` is in decimal hhmm format, e.g. -600 means six
+ * hours west of Greenwich.
+ */
+extern void strbuf_addftime(struct strbuf *sb, const char *fmt,
+			    const struct tm *tm, int tz_offset,
+			    const char *tz_name);
 
 /**
  * Read a given size of data from a FILE* pointer to the buffer.
diff --git a/t/t0006-date.sh b/t/t0006-date.sh
index 42d4ea61ef..71082008f0 100755
--- a/t/t0006-date.sh
+++ b/t/t0006-date.sh
@@ -51,6 +51,12 @@ check_show iso-local "$TIME" '2016-06-15 14:13:20 +0000'
 check_show raw-local "$TIME" '1466000000 +0000'
 check_show unix-local "$TIME" '1466000000'
 
+check_show 'format:%z' "$TIME" '+0200'
+check_show 'format-local:%z' "$TIME" '+0000'
+check_show 'format:%Z' "$TIME" ''
+check_show 'format:%%z' "$TIME" '%z'
+check_show 'format-local:%%z' "$TIME" '%z'
+
 # arbitrary time absurdly far in the future
 FUTURE="5758122296 -0400"
 check_show iso       "$FUTURE" "2152-06-19 18:24:56 -0400" TIME_IS_64BIT,TIME_T_IS_64BIT

-- 
2.13.0
Previous: Jeff KingNext: Ulrich Mueller
Message 35 of 44 in “git-2.13.0: log --date=format:%z not working”
  1. Ulrich MuellerMay 26, 2017
  2. Ævar Arnfjörð BjarmasonMay 27, 2017
  3. Jeff KingMay 27, 2017
  4. Ævar Arnfjörð BjarmasonMay 28, 2017
  5. Junio C HamanoMay 29, 2017
  6. René ScharfeMay 28, 2017
  7. Junio C HamanoJun 2, 2017
  8. Jeff KingJun 2, 2017
  9. René ScharfeJun 2, 2017
  10. Jeff KingJun 2, 2017
  11. Ulrich MuellerJun 2, 2017
  12. Jeff KingJun 2, 2017
  13. Ulrich MuellerJun 2, 2017
  14. Jeff KingJun 2, 2017
  15. strbuf: let strbuf_addftime handle %z and %Z itselfRené Scharfe, Jun 3, 2017
  16. Ulrich MuellerJun 3, 2017
  17. René ScharfeJun 3, 2017
  18. Jeff KingJun 7, 2017
  19. date: use localtime() for "-local" time formatsJeff King, Jun 7, 2017
  20. René ScharfeJun 11, 2017
  21. Junio C HamanoJun 12, 2017
  22. Ævar Arnfjörð BjarmasonJun 12, 2017
  23. Ulrich MuellerJun 12, 2017
  24. Ævar Arnfjörð BjarmasonJun 12, 2017
  25. Junio C HamanoJun 12, 2017
  26. Jeff KingJun 12, 2017
  27. Ævar Arnfjörð BjarmasonJun 12, 2017
  28. Jeff KingJun 12, 2017
  29. Linus TorvaldsJun 13, 2017
  30. René ScharfeJun 12, 2017
  31. Ævar Arnfjörð BjarmasonJun 13, 2017
  32. Ulrich MuellerJun 13, 2017
  33. René ScharfeJun 12, 2017
  34. Jeff KingJun 12, 2017
  35. strbuf: let strbuf_addftime handle %z and %Z itselfRené Scharfe, Jun 15, 2017
  36. Ulrich MuellerJun 15, 2017
  37. René ScharfeJun 15, 2017
  38. strbuf: let strbuf_addftime handle %z and %Z itselfRené Scharfe, Jun 15, 2017
  39. Jeff KingJun 15, 2017
  40. 1/2 t0006: check --date=format zone offsetsJeff King, Jun 15, 2017
  41. 2/2 date: use localtime() for "-local" time formatsJeff King, Jun 15, 2017
  42. René ScharfeJun 15, 2017
  43. Junio C HamanoJun 15, 2017
  44. Jeff KingJun 16, 2017

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