[PATCH 3/9] Add strbuf_printf() to do formatted printing to a strbuf.

["Kristian Høgsberg" <krh@redhat.com>]

Also, expose strbuf_add() and strbuf_add_char() to add raw data to the buffer.

Signed-off-by: Kristian Høgsberg <krh@redhat.com>
---
 strbuf.c |   69 +++++++++++++++++++++++++++++++++++++++++++++++++++++++------
 strbuf.h |    3 ++
 2 files changed, 65 insertions(+), 7 deletions(-)

diff --git a/strbuf.c b/strbuf.c
index e33d06b..2805c11 100644
--- a/strbuf.c
+++ b/strbuf.c
@@ -11,16 +11,26 @@ static void strbuf_begin(struct strbuf *sb) {
 	strbuf_init(sb);
 }
 
-static void inline strbuf_add(struct strbuf *sb, int ch) {
-	if (sb->alloc <= sb->len) {
-		sb->alloc = sb->alloc * 3 / 2 + 16;
-		sb->buf = xrealloc(sb->buf, sb->alloc);
-	}
+static void inline strbuf_grow(struct strbuf *sb, size_t extra)
+{
+	ALLOC_GROW(sb->buf, sb->len + extra, sb->alloc);
+}
+
+void strbuf_add(struct strbuf *sb, const char *data, size_t len)
+{
+	strbuf_grow(sb, len);
+	memcpy(sb->buf + sb->len, data, len);
+	sb->len += len;
+}
+
+void strbuf_add_char(struct strbuf *sb, int ch)
+{
+	strbuf_grow(sb, 1);
 	sb->buf[sb->len++] = ch;
 }
 
 static void strbuf_end(struct strbuf *sb) {
-	strbuf_add(sb, 0);
+	strbuf_add_char(sb, 0);
 }
 
 void read_line(struct strbuf *sb, FILE *fp, int term) {
@@ -33,9 +43,54 @@ void read_line(struct strbuf *sb, FILE *fp, int term) {
 	while ((ch = fgetc(fp)) != EOF) {
 		if (ch == term)
 			break;
-		strbuf_add(sb, ch);
+		strbuf_add_char(sb, ch);
 	}
 	if (ch == EOF && sb->len == 0)
 		sb->eof = 1;
 	strbuf_end(sb);
 }
+
+void strbuf_printf(struct strbuf *sb, const char *fmt, ...)
+{
+	char buffer[2048];
+	va_list args;
+	int len, size = 2 * sizeof buffer;
+
+	va_start(args, fmt);
+	len = vsnprintf(buffer, sizeof(buffer), fmt, args);
+	va_end(args);
+
+	if (len > sizeof(buffer)) {
+		/*
+		 * Didn't fit in the buffer, but this vsnprintf at
+		 * least gives us the required length back.  Grow the
+		 * buffer acccordingly and try again.
+		 */
+		strbuf_grow(sb, len);
+		va_start(args, fmt);
+		len = vsnprintf(sb->buf + sb->len,
+				sb->alloc - sb->len, fmt, args);
+		va_end(args);
+	} else if (len >= 0) {
+		/*
+		 * The initial vsnprintf fit in the temp buffer, just
+		 * copy it to the strbuf.
+		 */
+		strbuf_add(sb, buffer, len);
+	} else {
+		/*
+		 * This vnsprintf sucks and just returns -1 when the
+		 * buffer is too small.  Keep doubling the size until
+		 * it fits.
+		 */
+		while (len < 0) {
+			strbuf_grow(sb, size);
+			va_start(args, fmt);
+			len = vsnprintf(sb->buf + sb->len,
+					sb->alloc - sb->len, fmt, args);
+			va_end(args);
+			size *= 2;
+		}
+	}
+}
+
diff --git a/strbuf.h b/strbuf.h
index 74cc012..1e5d09e 100644
--- a/strbuf.h
+++ b/strbuf.h
@@ -9,5 +9,8 @@ struct strbuf {
 
 extern void strbuf_init(struct strbuf *);
 extern void read_line(struct strbuf *, FILE *, int);
+extern void strbuf_add(struct strbuf *sb, const char *data, size_t len);
+extern void strbuf_add_char(struct strbuf *sb, int ch);
+extern void strbuf_printf(struct strbuf *sb, const char *fmt, ...);
 
 #endif /* STRBUF_H */
-- 
1.5.2.GIT