ensure all plugins properly use BF, move shared logic to shared library

1 files changed, 32 insertions, 0 deletions

diff --git a/src/block/bg_bf.c b/src/block/bg_bf.c
index 9c4dc9060..1a17ec84e 100644
--- a/src/block/bg_bf.c
+++ b/src/block/bg_bf.c
@@ -232,4 +232,36 @@ GNUNET_BLOCK_GROUP_bf_test_and_set (struct GNUNET_BLOCK_Group *bg,
 }
 
 
+/**
+ * How many bytes should a bloomfilter be if we have already seen
+ * entry_count responses?  Sized so that do not have to
+ * re-size the filter too often (to keep it cheap).
+ *
+ * Since other peers will also add entries but not resize the filter,
+ * we should generally pick a slightly larger size than what the
+ * strict math would suggest.
+ *
+ * @param entry_count expected number of entries in the Bloom filter
+ * @param k number of bits set per entry
+ * @return must be a power of two and smaller or equal to 2^15.
+ */
+size_t
+GNUNET_BLOCK_GROUP_compute_bloomfilter_size (unsigned int entry_count,
+                                             unsigned int k)
+{
+  size_t size;
+  unsigned int ideal = (entry_count * k) / 4;
+  uint16_t max = 1 << 15;
+
+  if (entry_count > max)
+    return max;
+  size = 8;
+  while ((size < max) && (size < ideal))
+    size *= 2;
+  if (size > max)
+    return max;
+  return size;
+}
+
+
 /* end of bg_bf.c */