1 files changed, 71 insertions, 8 deletions
diff --git a/whisper/topic.go b/whisper/topic.go
index a965c7cc2..c47c94ae1 100644
--- a/whisper/topic.go
+++ b/whisper/topic.go
@@ -11,6 +11,8 @@ import "github.com/ethereum/go-ethereum/crypto"
 type Topic [4]byte
 
 // NewTopic creates a topic from the 4 byte prefix of the SHA3 hash of the data.
+//
+// Note, empty topics are considered the wildcard, and cannot be used in messages.
 func NewTopic(data []byte) Topic {
 	prefix := [4]byte{}
 	copy(prefix[:], crypto.Sha3(data)[:4])
@@ -48,14 +50,75 @@ func (self *Topic) String() string {
 	return string(self[:])
 }
 
-// TopicSet represents a hash set to check if a topic exists or not.
-type topicSet map[string]struct{}
+// topicMatcher is a filter expression to verify if a list of topics contained
+// in an arriving message matches some topic conditions. The topic matcher is
+// built up of a list of conditions, each of which must be satisfied by the
+// corresponding topic in the message. Each condition may require: a) an exact
+// topic match; b) a match from a set of topics; or c) a wild-card matching all.
+//
+// If a message contains more topics than required by the matcher, those beyond
+// the condition count are ignored and assumed to match.
+//
+// Consider the following sample topic matcher:
+//   sample := {
+//     {TopicA1, TopicA2, TopicA3},
+//     {TopicB},
+//     nil,
+//     {TopicD1, TopicD2}
+//   }
+// In order for a message to pass this filter, it should enumerate at least 4
+// topics, the first any of [TopicA1, TopicA2, TopicA3], the second mandatory
+// "TopicB", the third is ignored by the filter and the fourth either "TopicD1"
+// or "TopicD2". If the message contains further topics, the filter will match
+// them too.
+type topicMatcher struct {
+	conditions []map[Topic]struct{}
+}
+
+// newTopicMatcher create a topic matcher from a list of topic conditions.
+func newTopicMatcher(topics ...[]Topic) *topicMatcher {
+	matcher := make([]map[Topic]struct{}, len(topics))
+	for i, condition := range topics {
+		matcher[i] = make(map[Topic]struct{})
+		for _, topic := range condition {
+			matcher[i][topic] = struct{}{}
+		}
+	}
+	return &topicMatcher{conditions: matcher}
+}
 
-// NewTopicSet creates a topic hash set from a slice of topics.
-func newTopicSet(topics []Topic) topicSet {
-	set := make(map[string]struct{})
-	for _, topic := range topics {
-		set[topic.String()] = struct{}{}
+// newTopicMatcherFromBinary create a topic matcher from a list of binary conditions.
+func newTopicMatcherFromBinary(data ...[][]byte) *topicMatcher {
+	topics := make([][]Topic, len(data))
+	for i, condition := range data {
+		topics[i] = NewTopics(condition...)
+	}
+	return newTopicMatcher(topics...)
+}
+
+// newTopicMatcherFromStrings creates a topic matcher from a list of textual
+// conditions.
+func newTopicMatcherFromStrings(data ...[]string) *topicMatcher {
+	topics := make([][]Topic, len(data))
+	for i, condition := range data {
+		topics[i] = NewTopicsFromStrings(condition...)
+	}
+	return newTopicMatcher(topics...)
+}
+
+// Matches checks if a list of topics matches this particular condition set.
+func (self *topicMatcher) Matches(topics []Topic) bool {
+	// Mismatch if there aren't enough topics
+	if len(self.conditions) > len(topics) {
+		return false
+	}
+	// Check each topic condition for existence (skip wild-cards)
+	for i := 0; i < len(topics) && i < len(self.conditions); i++ {
+		if len(self.conditions[i]) > 0 {
+			if _, ok := self.conditions[i][topics[i]]; !ok {
+				return false
+			}
+		}
 	}
-	return topicSet(set)
+	return true
 }