From aa1462cc3d3b0c4c8ad6a60aaf31e0f3a424162d Mon Sep 17 00:00:00 2001 From: Jeff King Date: Thu, 25 Jun 2015 12:55:45 -0400 Subject: introduce "format" date-mode This feeds the format directly to strftime. Besides being a little more flexible, the main advantage is that your system strftime may know more about your locale's preferred format (e.g., how to spell the days of the week). Signed-off-by: Jeff King Signed-off-by: Junio C Hamano --- strbuf.c | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) (limited to 'strbuf.c') diff --git a/strbuf.c b/strbuf.c index 0d4f4e54e..a7ba02813 100644 --- a/strbuf.c +++ b/strbuf.c @@ -709,3 +709,32 @@ char *xstrfmt(const char *fmt, ...) return ret; } + +void strbuf_addftime(struct strbuf *sb, const char *fmt, const struct tm *tm) +{ + size_t len; + + /* + * strftime reports "0" if it could not fit the result in the buffer. + * Unfortunately, it also reports "0" if the requested time string + * takes 0 bytes. So if we were to probe and grow, we have to choose + * some arbitrary cap beyond which we guess that the format probably + * just results in a 0-length output. Since we have to choose some + * reasonable cap anyway, and since it is not that big, we may + * as well just grow to their in the first place. + */ + strbuf_grow(sb, 128); + len = strftime(sb->buf + sb->len, sb->alloc - sb->len, fmt, tm); + + if (!len) { + /* + * Either we failed, or the format actually produces a 0-length + * output. There's not much we can do, so we leave it blank. + * However, the output array is left in an undefined state, so + * we must re-assert our NUL terminator. + */ + sb->buf[sb->len] = '\0'; + } else { + sb->len += len; + } +} -- cgit v1.2.1 From e4f031e34b08e3217c10942e682920a6939308a0 Mon Sep 17 00:00:00 2001 From: Jeff King Date: Tue, 30 Jun 2015 09:26:53 -0400 Subject: strbuf: make strbuf_addftime more robust The return value of strftime is poorly designed; when it returns 0, the caller cannot tell if the buffer was not large enough, or if the output was actually 0 bytes. In the original implementation of strbuf_addftime, we simply punted and guessed that our 128-byte hint would be large enough. We can do better, though, if we're willing to treat strftime like less of a black box. We can munge the incoming format to make sure that it never produces 0-length output, and then "fix" the resulting output. That lets us reliably grow the buffer based on strftime's return value. Clever-idea-by: Eric Sunshine Signed-off-by: Jeff King Signed-off-by: Junio C Hamano --- strbuf.c | 38 +++++++++++++++++++++----------------- 1 file changed, 21 insertions(+), 17 deletions(-) (limited to 'strbuf.c') diff --git a/strbuf.c b/strbuf.c index a7ba02813..e5e737009 100644 --- a/strbuf.c +++ b/strbuf.c @@ -712,29 +712,33 @@ char *xstrfmt(const char *fmt, ...) void strbuf_addftime(struct strbuf *sb, const char *fmt, const struct tm *tm) { + size_t hint = 128; size_t len; - /* - * strftime reports "0" if it could not fit the result in the buffer. - * Unfortunately, it also reports "0" if the requested time string - * takes 0 bytes. So if we were to probe and grow, we have to choose - * some arbitrary cap beyond which we guess that the format probably - * just results in a 0-length output. Since we have to choose some - * reasonable cap anyway, and since it is not that big, we may - * as well just grow to their in the first place. - */ - strbuf_grow(sb, 128); + if (!*fmt) + return; + + strbuf_grow(sb, hint); len = strftime(sb->buf + sb->len, sb->alloc - sb->len, fmt, tm); if (!len) { /* - * Either we failed, or the format actually produces a 0-length - * output. There's not much we can do, so we leave it blank. - * However, the output array is left in an undefined state, so - * we must re-assert our NUL terminator. + * strftime reports "0" if it could not fit the result in the buffer. + * Unfortunately, it also reports "0" if the requested time string + * takes 0 bytes. So our strategy is to munge the format so that the + * output contains at least one character, and then drop the extra + * character before returning. */ - sb->buf[sb->len] = '\0'; - } else { - sb->len += len; + struct strbuf munged_fmt = STRBUF_INIT; + strbuf_addf(&munged_fmt, "%s ", 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_setlen(sb, sb->len + len); } -- cgit v1.2.1