From 28bbaeac8058653a4a46ae439c37d251a550f4f9 Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@tavianator.com>
Date: Thu, 23 May 2019 17:03:17 -0400
Subject: dstring: Add a printf()-style creation API

---
 dstring.c | 28 ++++++++++++++++++++++++++++
 dstring.h | 14 ++++++++++++++
 2 files changed, 42 insertions(+)

diff --git a/dstring.c b/dstring.c
index 35ea5b2..d7ce456 100644
--- a/dstring.c
+++ b/dstring.c
@@ -15,6 +15,9 @@
  ****************************************************************************/
 
 #include "dstring.h"
+#include <assert.h>
+#include <stdarg.h>
+#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ -117,6 +120,31 @@ int dstrapp(char **str, char c) {
 	return dstrcat_impl(str, &c, 1);
 }
 
+char *dstrprintf(const char *format, ...) {
+	va_list args;
+
+	va_start(args, format);
+	int len = vsnprintf(NULL, 0, format, args);
+	va_end(args);
+
+	assert(len > 0);
+
+	char *str = dstralloc(len);
+	if (!str) {
+		return NULL;
+	}
+
+	va_start(args, format);
+	len = vsnprintf(str, len + 1, format, args);
+	va_end(args);
+
+	struct dstring *header = dstrheader(str);
+	assert(len == header->capacity);
+	header->length = len;
+
+	return str;
+}
+
 void dstrfree(char *dstr) {
 	if (dstr) {
 		free(dstrheader(dstr));
diff --git a/dstring.h b/dstring.h
index 0374447..22476b9 100644
--- a/dstring.h
+++ b/dstring.h
@@ -21,6 +21,7 @@
 #ifndef BFS_DSTRING_H
 #define BFS_DSTRING_H
 
+#include "util.h"
 #include <stddef.h>
 
 /**
@@ -105,6 +106,19 @@ int dstrncat(char **dest, const char *src, size_t n);
  */
 int dstrapp(char **str, char c);
 
+/**
+ * Create a dynamic string from a format string.
+ *
+ * @param format
+ *         The format string to fill in.
+ * @param ...
+ *         Any arguments for the format string.
+ * @return
+ *         The created string, or NULL on failure.
+ */
+BFS_FORMATTER(1, 2)
+char *dstrprintf(const char *format, ...);
+
 /**
  * Free a dynamic string.
  *
-- 
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