github.com/xxRanger/go-ethereum@v1.8.23/swarm/storage/feed/cacheentry.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 feed
    18  
    19  import (
    20  	"bytes"
    21  	"context"
    22  	"time"
    23  
    24  	"github.com/ethereum/go-ethereum/swarm/storage"
    25  )
    26  
    27  const (
    28  	hasherCount            = 8
    29  	feedsHashAlgorithm     = storage.SHA3Hash
    30  	defaultRetrieveTimeout = 100 * time.Millisecond
    31  )
    32  
    33  // cacheEntry caches the last known update of a specific Swarm feed.
    34  type cacheEntry struct {
    35  	Update
    36  	*bytes.Reader
    37  	lastKey storage.Address
    38  }
    39  
    40  // implements storage.LazySectionReader
    41  func (r *cacheEntry) Size(ctx context.Context, _ chan bool) (int64, error) {
    42  	return int64(len(r.Update.data)), nil
    43  }
    44  
    45  //returns the feed's topic
    46  func (r *cacheEntry) Topic() Topic {
    47  	return r.Feed.Topic
    48  }