github.com/xxRanger/go-ethereum@v1.8.23/swarm/storage/feed/lookup/epoch.go (about)

     1  // Copyright 2018 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package lookup
    18  
    19  import (
    20  	"encoding/binary"
    21  	"errors"
    22  	"fmt"
    23  )
    24  
    25  // Epoch represents a time slot at a particular frequency level
    26  type Epoch struct {
    27  	Time  uint64 `json:"time"`  // Time stores the time at which the update or lookup takes place
    28  	Level uint8  `json:"level"` // Level indicates the frequency level as the exponent of a power of 2
    29  }
    30  
    31  // EpochID is a unique identifier for an Epoch, based on its level and base time.
    32  type EpochID [8]byte
    33  
    34  // EpochLength stores the serialized binary length of an Epoch
    35  const EpochLength = 8
    36  
    37  // MaxTime contains the highest possible time value an Epoch can handle
    38  const MaxTime uint64 = (1 << 56) - 1
    39  
    40  // Base returns the base time of the Epoch
    41  func (e *Epoch) Base() uint64 {
    42  	return getBaseTime(e.Time, e.Level)
    43  }
    44  
    45  // ID Returns the unique identifier of this epoch
    46  func (e *Epoch) ID() EpochID {
    47  	base := e.Base()
    48  	var id EpochID
    49  	binary.LittleEndian.PutUint64(id[:], base)
    50  	id[7] = e.Level
    51  	return id
    52  }
    53  
    54  // MarshalBinary implements the encoding.BinaryMarshaller interface
    55  func (e *Epoch) MarshalBinary() (data []byte, err error) {
    56  	b := make([]byte, 8)
    57  	binary.LittleEndian.PutUint64(b[:], e.Time)
    58  	b[7] = e.Level
    59  	return b, nil
    60  }
    61  
    62  // UnmarshalBinary implements the encoding.BinaryUnmarshaller interface
    63  func (e *Epoch) UnmarshalBinary(data []byte) error {
    64  	if len(data) != EpochLength {
    65  		return errors.New("Invalid data unmarshalling Epoch")
    66  	}
    67  	b := make([]byte, 8)
    68  	copy(b, data)
    69  	e.Level = b[7]
    70  	b[7] = 0
    71  	e.Time = binary.LittleEndian.Uint64(b)
    72  	return nil
    73  }
    74  
    75  // After returns true if this epoch occurs later or exactly at the other epoch.
    76  func (e *Epoch) After(epoch Epoch) bool {
    77  	if e.Time == epoch.Time {
    78  		return e.Level < epoch.Level
    79  	}
    80  	return e.Time >= epoch.Time
    81  }
    82  
    83  // Equals compares two epochs and returns true if they refer to the same time period.
    84  func (e *Epoch) Equals(epoch Epoch) bool {
    85  	return e.Level == epoch.Level && e.Base() == epoch.Base()
    86  }
    87  
    88  // String implements the Stringer interface.
    89  func (e *Epoch) String() string {
    90  	return fmt.Sprintf("Epoch{Time:%d, Level:%d}", e.Time, e.Level)
    91  }