3 files changed, 13 insertions, 4 deletions

diff --git a/buffer.c b/buffer.c
index ca63265..a3403fd 100644
--- a/buffer.c
+++ b/buffer.c
@@ -29,6 +29,13 @@ bool buffer_reserve(Buffer *buf, size_t size) {
 	return true;
 }
 
+bool buffer_grow(Buffer *buf, size_t len) {
+	size_t size;
+	if (!addu(buf->len, len, &size))
+		return false;
+	return buffer_reserve(buf, size);
+}
+
 bool buffer_terminate(Buffer *buf) {
 	return !buf->data || buf->len == 0 || buf->data[buf->len-1] == '\0' ||
 	        buffer_append(buf, "\0", 1);
@@ -72,7 +79,7 @@ bool buffer_insert(Buffer *buf, size_t pos, const void *data, size_t len) {
 		return false;
 	if (len == 0)
 		return true;
-	if (!buffer_reserve(buf, buf->len + len))
+	if (!buffer_grow(buf, len))
 		return false;
 	size_t move = buf->len - pos;
 	if (move > 0)
@@ -115,7 +122,7 @@ static bool buffer_vappendf(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_reserve(buf, buf->len+len+1)) {
+	if (len == -1 || !buffer_grow(buf, len+1)) {
 		va_end(ap_save);
 		return false;
 	}
diff --git a/buffer.h b/buffer.h
index 759217a..1730b05 100644
--- a/buffer.h
+++ b/buffer.h
@@ -20,6 +20,8 @@ void buffer_release(Buffer*);
 void buffer_clear(Buffer*);
 /* reserve space to store at least size bytes in this buffer.*/
 bool buffer_reserve(Buffer*, size_t size);
+/* reserve space for at least `len` more bytes in this buffer */
+bool buffer_grow(Buffer*, size_t len);
 /* if buffer is not empty, make sure it is NUL terminated */
 bool buffer_terminate(Buffer*);
 /* replace buffer content with given data, growing the buffer if needed */
diff --git a/register.c b/register.c
index 2e630b0..69409c1 100644
--- a/register.c
+++ b/register.c
@@ -61,7 +61,7 @@ bool register_put_range(Vis *vis, Register *reg, Text *txt, Filerange *range) {
 	case REGISTER_NORMAL:
 	{
 		size_t len = text_range_size(range);
-		if (!buffer_reserve(&reg->buf, len+1))
+		if (len == SIZE_MAX || !buffer_reserve(&reg->buf, len+1))
 			return false;
 		reg->buf.len = text_bytes_get(txt, range->start, len, reg->buf.data);
 		return buffer_append(&reg->buf, "\0", 1);
@@ -91,7 +91,7 @@ bool register_append_range(Register *reg, Text *txt, Filerange *range) {
 	case REGISTER_NORMAL:
 	{
 		size_t len = text_range_size(range);
-		if (!buffer_reserve(&reg->buf, reg->buf.len + len + 1))
+		if (!buffer_grow(&reg->buf, len+1))
 			return false;
 		if (reg->buf.len > 0 && reg->buf.data[reg->buf.len-1] == '\0')
 			reg->buf.len--;