1 files changed, 91 insertions, 0 deletions
diff --git a/swarm/storage/feeds/lookup/epoch.go b/swarm/storage/feeds/lookup/epoch.go
new file mode 100644
index 000000000..bafe95477
--- /dev/null
+++ b/swarm/storage/feeds/lookup/epoch.go
@@ -0,0 +1,91 @@
+// Copyright 2018 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/>.
+
+package lookup
+
+import (
+	"encoding/binary"
+	"errors"
+	"fmt"
+)
+
+// Epoch represents a time slot at a particular frequency level
+type Epoch struct {
+	Time  uint64 `json:"time"`  // Time stores the time at which the update or lookup takes place
+	Level uint8  `json:"level"` // Level indicates the frequency level as the exponent of a power of 2
+}
+
+// EpochID is a unique identifier for an Epoch, based on its level and base time.
+type EpochID [8]byte
+
+// EpochLength stores the serialized binary length of an Epoch
+const EpochLength = 8
+
+// MaxTime contains the highest possible time value an Epoch can handle
+const MaxTime uint64 = (1 << 56) - 1
+
+// Base returns the base time of the Epoch
+func (e *Epoch) Base() uint64 {
+	return getBaseTime(e.Time, e.Level)
+}
+
+// ID Returns the unique identifier of this epoch
+func (e *Epoch) ID() EpochID {
+	base := e.Base()
+	var id EpochID
+	binary.LittleEndian.PutUint64(id[:], base)
+	id[7] = e.Level
+	return id
+}
+
+// MarshalBinary implements the encoding.BinaryMarshaller interface
+func (e *Epoch) MarshalBinary() (data []byte, err error) {
+	b := make([]byte, 8)
+	binary.LittleEndian.PutUint64(b[:], e.Time)
+	b[7] = e.Level
+	return b, nil
+}
+
+// UnmarshalBinary implements the encoding.BinaryUnmarshaller interface
+func (e *Epoch) UnmarshalBinary(data []byte) error {
+	if len(data) != EpochLength {
+		return errors.New("Invalid data unmarshalling Epoch")
+	}
+	b := make([]byte, 8)
+	copy(b, data)
+	e.Level = b[7]
+	b[7] = 0
+	e.Time = binary.LittleEndian.Uint64(b)
+	return nil
+}
+
+// After returns true if this epoch occurs later or exactly at the other epoch.
+func (e *Epoch) After(epoch Epoch) bool {
+	if e.Time == epoch.Time {
+		return e.Level < epoch.Level
+	}
+	return e.Time >= epoch.Time
+}
+
+// Equals compares two epochs and returns true if they refer to the same time period.
+func (e *Epoch) Equals(epoch Epoch) bool {
+	return e.Level == epoch.Level && e.Base() == epoch.Base()
+}
+
+// String implements the Stringer interface.
+func (e *Epoch) String() string {
+	return fmt.Sprintf("Epoch{Time:%d, Level:%d}", e.Time, e.Level)
+}