92 lines
2.8 KiB
Go
92 lines
2.8 KiB
Go
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// Copyright 2018 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package lookup
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import (
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"encoding/binary"
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"errors"
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"fmt"
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)
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// Epoch represents a time slot at a particular frequency level
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type Epoch struct {
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Time uint64 `json:"time"` // Time stores the time at which the update or lookup takes place
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Level uint8 `json:"level"` // Level indicates the frequency level as the exponent of a power of 2
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}
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// EpochID is a unique identifier for an Epoch, based on its level and base time.
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type EpochID [8]byte
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// EpochLength stores the serialized binary length of an Epoch
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const EpochLength = 8
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// MaxTime contains the highest possible time value an Epoch can handle
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const MaxTime uint64 = (1 << 56) - 1
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// Base returns the base time of the Epoch
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func (e *Epoch) Base() uint64 {
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return getBaseTime(e.Time, e.Level)
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}
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// ID Returns the unique identifier of this epoch
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func (e *Epoch) ID() EpochID {
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base := e.Base()
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var id EpochID
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binary.LittleEndian.PutUint64(id[:], base)
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id[7] = e.Level
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return id
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}
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// MarshalBinary implements the encoding.BinaryMarshaller interface
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func (e *Epoch) MarshalBinary() (data []byte, err error) {
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b := make([]byte, 8)
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binary.LittleEndian.PutUint64(b[:], e.Time)
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b[7] = e.Level
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return b, nil
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}
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// UnmarshalBinary implements the encoding.BinaryUnmarshaller interface
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func (e *Epoch) UnmarshalBinary(data []byte) error {
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if len(data) != EpochLength {
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return errors.New("Invalid data unmarshalling Epoch")
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}
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b := make([]byte, 8)
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copy(b, data)
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e.Level = b[7]
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b[7] = 0
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e.Time = binary.LittleEndian.Uint64(b)
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return nil
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}
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// After returns true if this epoch occurs later or exactly at the other epoch.
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func (e *Epoch) After(epoch Epoch) bool {
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if e.Time == epoch.Time {
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return e.Level < epoch.Level
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}
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return e.Time >= epoch.Time
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}
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// Equals compares two epochs and returns true if they refer to the same time period.
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func (e *Epoch) Equals(epoch Epoch) bool {
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return e.Level == epoch.Level && e.Base() == epoch.Base()
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}
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// String implements the Stringer interface.
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func (e *Epoch) String() string {
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return fmt.Sprintf("Epoch{Time:%d, Level:%d}", e.Time, e.Level)
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}
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