2 files changed, 12 insertions, 7 deletions

diff --git a/src/lib/buf/buffers.c b/src/lib/buf/buffers.c
index a5031a47a6..e9d5f7f031 100644
--- a/src/lib/buf/buffers.c
+++ b/src/lib/buf/buffers.c
@@ -14,7 +14,7 @@
  *
  * All socket-backed and TLS-based connection_t objects have a pair of
  * buffers: one for incoming data, and one for outcoming data.  These are fed
- * and drained from functions in connection.c, trigged by events that are
+ * and drained from functions in connection.c, triggered by events that are
  * monitored in main.c.
  *
  * This module only handles the buffer implementation itself. To use a buffer
@@ -685,19 +685,22 @@ buf_move_to_buf(buf_t *buf_out, buf_t *buf_in, size_t *buf_flushlen)
 }
 
 /** Moves all data from <b>buf_in</b> to <b>buf_out</b>, without copying.
+ * Return the number of bytes that were moved.
  */
-void
+size_t
 buf_move_all(buf_t *buf_out, buf_t *buf_in)
 {
   tor_assert(buf_out);
   if (!buf_in)
-    return;
+    return 0;
   if (buf_datalen(buf_in) == 0)
-    return;
+    return 0;
   if (BUG(buf_out->datalen > BUF_MAX_LEN || buf_in->datalen > BUF_MAX_LEN))
-    return;
+    return 0;
   if (BUG(buf_out->datalen > BUF_MAX_LEN - buf_in->datalen))
-    return;
+    return 0;
+
+  size_t n_bytes_moved = buf_in->datalen;
 
   if (buf_out->head == NULL) {
     buf_out->head = buf_in->head;
@@ -710,6 +713,8 @@ buf_move_all(buf_t *buf_out, buf_t *buf_in)
   buf_out->datalen += buf_in->datalen;
   buf_in->head = buf_in->tail = NULL;
   buf_in->datalen = 0;
+
+  return n_bytes_moved;
 }
 
 /** Internal structure: represents a position in a buffer. */
diff --git a/src/lib/buf/buffers.h b/src/lib/buf/buffers.h
index d8a77feb72..1361a02eba 100644
--- a/src/lib/buf/buffers.h
+++ b/src/lib/buf/buffers.h
@@ -46,7 +46,7 @@ void buf_add_printf(buf_t *buf, const char *format, ...)
 void buf_add_vprintf(buf_t *buf, const char *format, va_list args)
   CHECK_PRINTF(2, 0);
 int buf_move_to_buf(buf_t *buf_out, buf_t *buf_in, size_t *buf_flushlen);
-void buf_move_all(buf_t *buf_out, buf_t *buf_in);
+size_t buf_move_all(buf_t *buf_out, buf_t *buf_in);
 void buf_peek(const buf_t *buf, char *string, size_t string_len);
 void buf_drain(buf_t *buf, size_t n);
 int buf_get_bytes(buf_t *buf, char *string, size_t string_len);