1 files changed, 20 insertions, 4 deletions
diff --git a/src/lib/_vec.rs b/src/lib/_vec.rs
index 509737d519c..5f1d2baaeb4 100644
--- a/src/lib/_vec.rs
+++ b/src/lib/_vec.rs
@@ -3,13 +3,25 @@ import op = util.operator;
 
 native "rust" mod rustrt {
   type vbuf;
+
   fn vec_buf[T](vec[T] v, uint offset) -> vbuf;
+
   fn vec_len[T](vec[T] v) -> uint;
-  /* The T in vec_alloc[T, U] is the type of the vec to allocate.  The
+  /**
+   * Sometimes we modify the vec internal data via vec_buf and need to update
+   * the vec's fill length accordingly.
+   */
+  fn vec_len_set[T](vec[T] v, uint n);
+
+  /**
+   * The T in vec_alloc[T, U] is the type of the vec to allocate.  The
    * U is the type of an element in the vec.  So to allocate a vec[U] we
-   * want to invoke this as vec_alloc[vec[U], U]. */
+   * want to invoke this as vec_alloc[vec[U], U].
+   */
   fn vec_alloc[T, U](uint n_elts) -> vec[U];
+
   fn refcount[T](vec[T] v) -> uint;
+
   fn vec_print_debug_info[T](vec[T] v);
 }
 
@@ -46,12 +58,16 @@ fn init_elt[T](&T t, uint n_elts) -> vec[T] {
   ret v;
 }
 
+fn buf[T](vec[T] v) -> vbuf {
+  ret rustrt.vec_buf[T](v, 0u);
+}
+
 fn len[T](vec[T] v) -> uint {
   ret rustrt.vec_len[T](v);
 }
 
-fn buf[T](vec[T] v) -> vbuf {
-  ret rustrt.vec_buf[T](v, 0u);
+fn len_set[T](vec[T] v, uint n) {
+  rustrt.vec_len_set[T](v, n);
 }
 
 fn buf_off[T](vec[T] v, uint offset) -> vbuf {