[PATCH v2 01/10] strbuf: add xstrfmt helper

From: Jeff King <peff@peff.net>
Date: Jun 19, 2014, 21:18 UTC
Message-ID: <20140619211812.GA28474@sigill.intra.peff.net>
In-Reply-To: <20140619211659.GA32412@sigill.intra.peff.net>

You can use a strbuf to build up a string from parts, and then detach it. In the general case, you might use multiple strbuf_add* functions to do the building. However, in many cases, a single strbuf_addf is sufficient, and we end up with:

  struct strbuf buf = STRBUF_INIT;
  ...
  strbuf_addf(&buf, fmt, some, args);
  str = strbuf_detach(&buf, NULL);

We can make this much more readable (and avoid introducing an extra variable, which can clutter the code) by introducing a convenience function:

  str = xstrfmt(fmt, some, args);

Signed-off-by: Jeff King <peff@peff.net>
---
 strbuf.c | 19 +++++++++++++++++++
 strbuf.h |  9 +++++++++
 2 files changed, 28 insertions(+)

diff --git a/strbuf.c b/strbuf.c
index ac62982..12c7865 100644
--- a/strbuf.c
+++ b/strbuf.c
@@ -600,3 +600,22 @@ char *xstrdup_tolower(const char *string)
 	result[i] = '\0';
 	return result;
 }
+
+char *xstrvfmt(const char *fmt, va_list ap)
+{
+	struct strbuf buf = STRBUF_INIT;
+	strbuf_vaddf(&buf, fmt, ap);
+	return strbuf_detach(&buf, NULL);
+}
+
+char *xstrfmt(const char *fmt, ...)
+{
+	va_list ap;
+	char *ret;
+
+	va_start(ap, fmt);
+	ret = xstrvfmt(fmt, ap);
+	va_end(ap);
+
+	return ret;
+}
diff --git a/strbuf.h b/strbuf.h
index e9ad03e..a594c24 100644
--- a/strbuf.h
+++ b/strbuf.h
@@ -187,4 +187,13 @@ extern int fprintf_ln(FILE *fp, const char *fmt, ...);
 
 char *xstrdup_tolower(const char *);
 
+/*
+ * Create a newly allocated string using printf format. You can do this easily
+ * with a strbuf, but this provides a shortcut to save a few lines.
+ */
+__attribute__((format (printf, 1, 0)))
+char *xstrvfmt(const char *fmt, va_list ap);
+__attribute__((format (printf, 1, 2)))
+char *xstrfmt(const char *fmt, ...);
+
 #endif /* STRBUF_H */

-- 
2.0.0.566.gfe3e6b2