buffer: implement buffer_{v,}printf functions

2 files changed, 26 insertions, 0 deletions

diff --git a/buffer.c b/buffer.c
index 410a059..b3c05d6 100644
--- a/buffer.c
+++ b/buffer.c
@@ -1,5 +1,7 @@
 #include <stdlib.h>
 #include <string.h>
+#include <stdarg.h>
+#include <stdio.h>
 
 #include "buffer.h"
 #include "util.h"
@@ -94,6 +96,27 @@ bool buffer_prepend0(Buffer *buf, const char *data) {
 	return buffer_prepend(buf, data, strlen(data) + (buf->len == 0));
 }
 
+bool buffer_printf(Buffer *buf, const char *fmt, ...) {
+	va_list ap;
+	va_start(ap, fmt);
+	bool ret = buffer_vprintf(buf, fmt, ap);
+	va_end(ap);
+	return ret;
+}
+
+bool buffer_vprintf(Buffer *buf, const char *fmt, va_list ap) {
+	va_list ap_save;
+	va_copy(ap_save, ap);
+	int len = vsnprintf(NULL, 0, fmt, ap);
+	if (len == -1 || !buffer_grow(buf, len+1))
+		return false;
+	bool ret = vsnprintf(buf->data, len+1, fmt, ap_save) == len;
+	if (ret)
+		buf->len = len+1;
+	va_end(ap_save);
+	return ret;
+}
+
 size_t buffer_length0(Buffer *buf) {
 	size_t len = buf->len;
 	if (len > 0 && buf->data[len-1] == '\0')
diff --git a/buffer.h b/buffer.h
index 6b44a53..d0ecd63 100644
--- a/buffer.h
+++ b/buffer.h
@@ -40,6 +40,9 @@ bool buffer_append0(Buffer*, const char *data);
 bool buffer_prepend(Buffer*, const void *data, size_t len);
 /* prepend NUL-terminated data */
 bool buffer_prepend0(Buffer*, const char *data);
+
+bool buffer_printf(Buffer*, const char *fmt, ...);
+bool buffer_vprintf(Buffer*, const char *fmt, va_list);
 /* return length of a buffer without trailing NUL byte */
 size_t buffer_length0(Buffer*);
 /* return length of a buffer including possible NUL byte */