1 files changed, 15 insertions, 0 deletions
diff --git a/src/common/container.h b/src/common/container.h
index 6a795d996c..7560ad48c8 100644
--- a/src/common/container.h
+++ b/src/common/container.h
@@ -336,6 +336,21 @@ bitarray_init_zero(int n_bits)
   size_t sz = (n_bits+BITARRAY_MASK) / (1u << BITARRAY_SHIFT);
   return tor_malloc_zero(sz*sizeof(unsigned int));
 }
+static INLINE bitarray_t *
+bitarray_expand(bitarray_t *ba, int n_bits_old, int n_bits_new)
+{
+  size_t sz_old = (n_bits_old+BITARRAY_MASK) / (1u << BITARRAY_SHIFT);
+  size_t sz_new = (n_bits_new+BITARRAY_MASK) / (1u << BITARRAY_SHIFT);
+  char *ptr;
+  if (sz_new <= sz_old)
+    return ba;
+  ptr = tor_realloc(ba, sz_new);
+  memset(ptr+sz_old, 0, sz_new-sz_old); /* This does nothing to the older
+                                         * excess bytes.  But they were
+                                         * already set to 0 by
+                                         * bitarry_init_zero. */
+  return (bitarray_t*) ptr;
+}
 /** Free the bit array <b>ba</b>. */
 static INLINE void
 bitarray_free(bitarray_t *ba)