The most common use of addf() was to init a strbuf and addf() right away.
Since it is so common, it makes sense to have a function strbuf_initf()
to wrap both calls into one.

Unfortunately, C (and cpp) has no way to make this easy without code
duplication, as we need to va_init() in strbuf_addf() possibly a few
times.  So the code for addf() is copied.  Fortunately, the code is
pretty short, so not too much had to be copied as-is.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---

	On Wed, 5 Mar 2008, Johannes Schindelin wrote:

	> On Wed, 5 Mar 2008, Junio C Hamano wrote:
	> 
	> > Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:
	> > 
	> > > [... I'd submit my ] a Reviewed-by:, but I think that this 
	> > > would only be a burden on our maintainer.
	> > 
	> > I think Reviewed-by: would indeed be a very good addition to 
	> > our patch flow convention, borrowing from the kernel folks.
	> 
	> You mean you have more people to blame, then? ;-)

	Well, it was meant as a joke...

	Anyway, here is a start of a patch series that should help the 
	King Penguin...

	strbuf_initf() is something I long planned to do; Kristian just 
	pushed me over the edge.

 strbuf.c |   23 +++++++++++++++++++++++
 strbuf.h |    2 ++
 2 files changed, 25 insertions(+), 0 deletions(-)

diff --git a/strbuf.c b/strbuf.c
index 5afa8f3..067d55a 100644
--- a/strbuf.c
+++ b/strbuf.c
@@ -147,6 +147,29 @@ void strbuf_addf(struct strbuf *sb, const char *fmt, ...)
 	strbuf_setlen(sb, sb->len + len);
 }
 
+void strbuf_initf(struct strbuf *sb, const char *fmt, ...)
+{
+	int len;
+	va_list ap;
+
+	strbuf_init(sb, strlen(fmt) + 64);
+	va_start(ap, fmt);
+	len = vsnprintf(sb->buf + sb->len, sb->alloc - sb->len, fmt, ap);
+	va_end(ap);
+	if (len < 0)
+		die("your vsnprintf is broken");
+	if (len > strbuf_avail(sb)) {
+		strbuf_grow(sb, len);
+		va_start(ap, fmt);
+		len = vsnprintf(sb->buf + sb->len, sb->alloc - sb->len, fmt, ap);
+		va_end(ap);
+		if (len > strbuf_avail(sb)) {
+			die("this should not happen, your snprintf is broken");
+		}
+	}
+	strbuf_setlen(sb, sb->len + len);
+}
+
 void strbuf_expand(struct strbuf *sb, const char *format, expand_fn_t fn,
 		   void *context)
 {
diff --git a/strbuf.h b/strbuf.h
index faec229..eaf2409 100644
--- a/strbuf.h
+++ b/strbuf.h
@@ -108,6 +108,8 @@ extern void strbuf_expand(struct strbuf *sb, const char *format, expand_fn_t fn,
 
 __attribute__((format(printf,2,3)))
 extern void strbuf_addf(struct strbuf *sb, const char *fmt, ...);
+__attribute__((format(printf,2,3)))
+extern void strbuf_initf(struct strbuf *sb, const char *fmt, ...);
 
 extern size_t strbuf_fread(struct strbuf *, size_t, FILE *);
 /* XXX: if read fails, any partial read is undone */
-- 
1.5.4.3.571.g9aec3

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