1 files changed, 55 insertions, 0 deletions
diff --git a/whisper/whisperv6/topic.go b/whisper/whisperv6/topic.go
new file mode 100644
index 000000000..5ef7f6939
--- /dev/null
+++ b/whisper/whisperv6/topic.go
@@ -0,0 +1,55 @@
+// Copyright 2016 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// Contains the Whisper protocol Topic element.
+
+package whisperv6
+
+import (
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/hexutil"
+)
+
+// Topic represents a cryptographically secure, probabilistic partial
+// classifications of a message, determined as the first (left) 4 bytes of the
+// SHA3 hash of some arbitrary data given by the original author of the message.
+type TopicType [TopicLength]byte
+
+func BytesToTopic(b []byte) (t TopicType) {
+	sz := TopicLength
+	if x := len(b); x < TopicLength {
+		sz = x
+	}
+	for i := 0; i < sz; i++ {
+		t[i] = b[i]
+	}
+	return t
+}
+
+// String converts a topic byte array to a string representation.
+func (topic *TopicType) String() string {
+	return string(common.ToHex(topic[:]))
+}
+
+// MarshalText returns the hex representation of t.
+func (t TopicType) MarshalText() ([]byte, error) {
+	return hexutil.Bytes(t[:]).MarshalText()
+}
+
+// UnmarshalText parses a hex representation to a topic.
+func (t *TopicType) UnmarshalText(input []byte) error {
+	return hexutil.UnmarshalFixedText("Topic", input, t[:])
+}