Implement stream isolation

This is the meat of proposal 171: we change circuit_is_acceptable()
to require that the connection is compatible with every connection
that has been linked to the circuit; we update circuit_is_better to
prefer attaching streams to circuits in the way that decreases the
circuits' usefulness the least; and we update link_apconn_to_circ()
to do the appropriate bookkeeping.

1 files changed, 26 insertions, 0 deletions

diff --git a/src/common/util.c b/src/common/util.c
index b95ee3a612..bf0bbe0603 100644
--- a/src/common/util.c
+++ b/src/common/util.c
@@ -412,6 +412,32 @@ round_uint64_to_next_multiple_of(uint64_t number, uint64_t divisor)
   return number;
 }
 
+/** Return the number of bits set in <b>v</b>. */
+int
+n_bits_set_u8(uint8_t v)
+{
+  static const int nybble_table[] = {
+    0, /* 0000 */
+    1, /* 0001 */
+    1, /* 0010 */
+    2, /* 0011 */
+    1, /* 0100 */
+    2, /* 0101 */
+    2, /* 0110 */
+    3, /* 0111 */
+    1, /* 1000 */
+    2, /* 1001 */
+    2, /* 1010 */
+    3, /* 1011 */
+    2, /* 1100 */
+    3, /* 1101 */
+    3, /* 1110 */
+    4, /* 1111 */
+  };
+
+  return nybble_table[v & 15] + nybble_table[v>>4];
+}
+
 /* =====
  * String manipulation
  * ===== */