whisper: minor refactoring

whisper/whisperv6/envelope.go

@@ -51,6 +51,7 @@ type Envelope struct {
 
 // size returns the size of envelope as it is sent (i.e. public fields only)
 func (e *Envelope) size() int {
+	const EnvelopeHeaderLength = 20
 	return EnvelopeHeaderLength + len(e.Data)
 }
 

whisper/whisperv6/whisper.go

@@ -1067,3 +1067,12 @@ func addBloom(a, b []byte) []byte {
 	}
 	return c
 }
+
+func isBloomFilterEqual(a, b []byte) bool {
+	for i := 0; i < bloomFilterSize; i++ {
+		if a[i] != b[i] {
+			return false
+		}
+	}
+	return true
+}