From 3db8f726a7ac29d56182195e9a6d61eef0b0f7dd Mon Sep 17 00:00:00 2001
From: Alex Grintsvayg <git@grin.io>
Date: Thu, 15 Mar 2018 14:42:57 -0400
Subject: [PATCH] fix bitmap prefix len

---
 dht/bitmap.go        |  2 +-
 dht/bitmap_test.go   | 23 +++++++++++++++++++++++
 dht/decode_test.go   |  3 +++
 dht/dht.go           |  2 +-
 dht/routing_table.go |  4 ++--
 5 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/dht/bitmap.go b/dht/bitmap.go
index 3125d6c..90f83fa 100644
--- a/dht/bitmap.go
+++ b/dht/bitmap.go
@@ -53,7 +53,7 @@ func (b bitmap) PrefixLen() (ret int) {
 			}
 		}
 	}
-	return nodeIDLength*8 - 1
+	return numBuckets
 }
 
 func (b *bitmap) UnmarshalBencode(encoded []byte) error {
diff --git a/dht/bitmap_test.go b/dht/bitmap_test.go
index 8b237ce..16a9bec 100644
--- a/dht/bitmap_test.go
+++ b/dht/bitmap_test.go
@@ -96,3 +96,26 @@ func TestBitmapMarshalEmbedded2(t *testing.T) {
 		t.Error("encoding does not match expected")
 	}
 }
+
+func TestBitmap_PrefixLen(t *testing.T) {
+	tt := []struct {
+		str string
+		len int
+	}{
+		{len: 0, str: "F00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"},
+		{len: 0, str: "800000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"},
+		{len: 1, str: "700000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"},
+		{len: 1, str: "400000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"},
+		{len: 384, str: "000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"},
+		{len: 383, str: "000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001"},
+		{len: 382, str: "000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002"},
+		{len: 382, str: "000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000003"},
+	}
+
+	for _, test := range tt {
+		len := newBitmapFromHex(test.str).PrefixLen()
+		if len != test.len {
+			t.Errorf("got prefix len %d; expected %d for %s", len, test.len, test.str)
+		}
+	}
+}
diff --git a/dht/decode_test.go b/dht/decode_test.go
index 2ce78e7..70feab0 100644
--- a/dht/decode_test.go
+++ b/dht/decode_test.go
@@ -29,6 +29,9 @@ func TestDecode(t *testing.T) {
 			continue
 		}
 
+		t.Error("TODO")
+		continue
+
 		spew.Dump(decoded)
 	}
 }
diff --git a/dht/dht.go b/dht/dht.go
index bc57393..03de2fa 100644
--- a/dht/dht.go
+++ b/dht/dht.go
@@ -17,7 +17,7 @@ const network = "udp4"
 
 const alpha = 3         // this is the constant alpha in the spec
 const nodeIDLength = 48 // bytes. this is the constant B in the spec
-const bucketSize = 20   // this is the constant k in the spec
+const bucketSize = 8    // this is the constant k in the spec
 
 const tExpire = 86400 * time.Second    // the time after which a key/value pair expires; this is a time-to-live (TTL) from the original publication date
 const tRefresh = 3600 * time.Second    // the time after which an otherwise unaccessed bucket must be refreshed
diff --git a/dht/routing_table.go b/dht/routing_table.go
index 32b86ab..138d310 100644
--- a/dht/routing_table.go
+++ b/dht/routing_table.go
@@ -135,12 +135,12 @@ func (rt *RoutingTable) FindClosest(target bitmap, count int) []*Node {
 	bucket := rt.buckets[prefixLength]
 	toSort = appendNodes(toSort, bucket.Front(), nil, target)
 
-	for i := 1; (prefixLength-i >= 0 || prefixLength+i < nodeIDLength*8) && len(toSort) < count; i++ {
+	for i := 1; (prefixLength-i >= 0 || prefixLength+i < numBuckets) && len(toSort) < count; i++ {
 		if prefixLength-i >= 0 {
 			bucket = rt.buckets[prefixLength-i]
 			toSort = appendNodes(toSort, bucket.Front(), nil, target)
 		}
-		if prefixLength+i < nodeIDLength*8 {
+		if prefixLength+i < numBuckets {
 			bucket = rt.buckets[prefixLength+i]
 			toSort = appendNodes(toSort, bucket.Front(), nil, target)
 		}