diff --git a/src/buffers.c b/src/buffers.c
index e71f852..7becb48 100644
--- a/src/buffers.c
+++ b/src/buffers.c
@@ -388,6 +388,34 @@
 }
 
 
+/* This function realigns input data in a possibly wrapping buffer so that it
+ * becomes contiguous and starts at the beginning of the buffer area. The
+ * function may only be used when the buffer's output is empty.
+ */
+void buffer_slow_realign(struct buffer *buf)
+{
+	/* two possible cases :
+	 *   - the buffer is in one contiguous block, we move it in-place
+	 *   - the buffer is in two blocks, we move it via the swap_buffer
+	 */
+	if (buf->i) {
+		int block1 = buf->i;
+		int block2 = 0;
+		if (buf->p + buf->i > buf->data + buf->size) {
+			/* non-contiguous block */
+			block1 = buf->data + buf->size - buf->p;
+			block2 = buf->p + buf->i - (buf->data + buf->size);
+		}
+		if (block2)
+			memcpy(swap_buffer, buf->data, block2);
+		memmove(buf->data, buf->p, block1);
+		if (block2)
+			memcpy(buf->data + block1, swap_buffer, block2);
+	}
+
+	buf->p = buf->data;
+}
+
 /* Realigns a possibly non-contiguous buffer by bouncing bytes from source to
  * destination. It does not use any intermediate buffer and does the move in
  * place, though it will be slower than a simple memmove() on contiguous data,