Subject: [PATCH] Add strbuf_printf() to do formatted printing to a strbuf.

From: Kristian Høgsberg <[email-masked]>
Date: Tue, 31 Jul 2007 15:54:23 -0400

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

Signed-off-by: Kristian Høgsberg <[email-masked]>
---

Ok, this gets uglier as we try to work around different versions of
vsnprintf.  On windows, vsnprintf returns -1 if the output doesn't fit in
the given buffer.  What we do is to keep doubling the buffer size until it
fits.  Not sure this is the best idea.

The old hardcoded limitation of just 2048 bytes wasn't too bad, considering
that it's just the limit for one strbuf_printf invocation, not the total
size of the strbuf contents.

I dunno...
Kristian

 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