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// 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 mru
import (
"bytes"
"context"
"time"
"github.com/ethereum/go-ethereum/swarm/storage"
)
const (
defaultStoreTimeout = 4000 * time.Millisecond
hasherCount = 8
resourceHashAlgorithm = storage.SHA3Hash
defaultRetrieveTimeout = 100 * time.Millisecond
)
// resource caches resource data and the metadata of its root chunk.
type resource struct {
resourceUpdate
ResourceMetadata
*bytes.Reader
lastKey storage.Address
updated time.Time
}
func (r *resource) Context() context.Context {
return context.TODO()
}
// TODO Expire content after a defined period (to force resync)
func (r *resource) isSynced() bool {
return !r.updated.IsZero()
}
// implements storage.LazySectionReader
func (r *resource) Size(ctx context.Context, _ chan bool) (int64, error) {
if !r.isSynced() {
return 0, NewError(ErrNotSynced, "Not synced")
}
return int64(len(r.resourceUpdate.data)), nil
}
//returns the resource's human-readable name
func (r *resource) Name() string {
return r.ResourceMetadata.Name
}
// Helper function to calculate the next update period number from the current time, start time and frequency
func getNextPeriod(start uint64, current uint64, frequency uint64) (uint32, error) {
if current < start {
return 0, NewErrorf(ErrInvalidValue, "given current time value %d < start time %d", current, start)
}
if frequency == 0 {
return 0, NewError(ErrInvalidValue, "frequency is 0")
}
timeDiff := current - start
period := timeDiff / frequency
return uint32(period + 1), nil
}
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