aboutsummaryrefslogtreecommitdiffstats
path: root/core/blockchain.go
blob: 55034d9de0b8771b70d0a352b359e843242bee73 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
// Copyright 2014 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 core implements the Ethereum consensus protocol.
package core

import (
    "errors"
    "fmt"
    "io"
    "math/big"
    mrand "math/rand"
    "runtime"
    "sync"
    "sync/atomic"
    "time"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/core/state"
    "github.com/ethereum/go-ethereum/core/types"
    "github.com/ethereum/go-ethereum/core/vm"
    "github.com/ethereum/go-ethereum/crypto"
    "github.com/ethereum/go-ethereum/ethdb"
    "github.com/ethereum/go-ethereum/event"
    "github.com/ethereum/go-ethereum/logger"
    "github.com/ethereum/go-ethereum/logger/glog"
    "github.com/ethereum/go-ethereum/metrics"
    "github.com/ethereum/go-ethereum/pow"
    "github.com/ethereum/go-ethereum/rlp"
    "github.com/ethereum/go-ethereum/trie"
    "github.com/hashicorp/golang-lru"
)

var (
    chainlogger = logger.NewLogger("CHAIN")
    jsonlogger  = logger.NewJsonLogger()

    blockInsertTimer = metrics.NewTimer("chain/inserts")

    ErrNoGenesis = errors.New("Genesis not found in chain")
)

const (
    headerCacheLimit    = 512
    bodyCacheLimit      = 256
    tdCacheLimit        = 1024
    blockCacheLimit     = 256
    maxFutureBlocks     = 256
    maxTimeFutureBlocks = 30
    // must be bumped when consensus algorithm is changed, this forces the upgradedb
    // command to be run (forces the blocks to be imported again using the new algorithm)
    BlockChainVersion = 3
)

// BlockChain represents the canonical chain given a database with a genesis
// block. The Blockchain manages chain imports, reverts, chain reorganisations.
//
// Importing blocks in to the block chain happens according to the set of rules
// defined by the two stage Validator. Processing of blocks is done using the
// Processor which processes the included transaction. The validation of the state
// is done in the second part of the Validator. Failing results in aborting of
// the import.
//
// The BlockChain also helps in returning blocks from **any** chain included
// in the database as well as blocks that represents the canonical chain. It's
// important to note that GetBlock can return any block and does not need to be
// included in the canonical one where as GetBlockByNumber always represents the
// canonical chain.
type BlockChain struct {
    hc           *HeaderChain
    chainDb      ethdb.Database
    eventMux     *event.TypeMux
    genesisBlock *types.Block

    mu      sync.RWMutex // global mutex for locking chain operations
    chainmu sync.RWMutex // blockchain insertion lock
    procmu  sync.RWMutex // block processor lock

    checkpoint       int          // checkpoint counts towards the new checkpoint
    currentBlock     *types.Block // Current head of the block chain
    currentFastBlock *types.Block // Current head of the fast-sync chain (may be above the block chain!)

    bodyCache    *lru.Cache // Cache for the most recent block bodies
    bodyRLPCache *lru.Cache // Cache for the most recent block bodies in RLP encoded format
    blockCache   *lru.Cache // Cache for the most recent entire blocks
    futureBlocks *lru.Cache // future blocks are blocks added for later processing

    quit    chan struct{} // blockchain quit channel
    running int32         // running must be called automically
    // procInterrupt must be atomically called
    procInterrupt int32          // interrupt signaler for block processing
    wg            sync.WaitGroup // chain processing wait group for shutting down

    pow       pow.PoW
    processor Processor // block processor interface
    validator Validator // block and state validator interface
}

// NewBlockChain returns a fully initialised block chain using information
// available in the database. It initialiser the default Ethereum Validator and
// Processor.
func NewBlockChain(chainDb ethdb.Database, pow pow.PoW, mux *event.TypeMux) (*BlockChain, error) {
    bodyCache, _ := lru.New(bodyCacheLimit)
    bodyRLPCache, _ := lru.New(bodyCacheLimit)
    blockCache, _ := lru.New(blockCacheLimit)
    futureBlocks, _ := lru.New(maxFutureBlocks)

    bc := &BlockChain{
        chainDb:      chainDb,
        eventMux:     mux,
        quit:         make(chan struct{}),
        bodyCache:    bodyCache,
        bodyRLPCache: bodyRLPCache,
        blockCache:   blockCache,
        futureBlocks: futureBlocks,
        pow:          pow,
    }
    bc.SetValidator(NewBlockValidator(bc, pow))
    bc.SetProcessor(NewStateProcessor(bc))

    gv := func() HeaderValidator { return bc.Validator() }
    var err error
    bc.hc, err = NewHeaderChain(chainDb, gv, bc.getProcInterrupt)
    if err != nil {
        return nil, err
    }

    bc.genesisBlock = bc.GetBlockByNumber(0)
    if bc.genesisBlock == nil {
        bc.genesisBlock, err = WriteDefaultGenesisBlock(chainDb)
        if err != nil {
            return nil, err
        }
        glog.V(logger.Info).Infoln("WARNING: Wrote default ethereum genesis block")
    }
    if err := bc.loadLastState(); err != nil {
        return nil, err
    }
    // Check the current state of the block hashes and make sure that we do not have any of the bad blocks in our chain
    for hash, _ := range BadHashes {
        if header := bc.GetHeader(hash); header != nil {
            glog.V(logger.Error).Infof("Found bad hash, rewinding chain to block #%d [%x…]", header.Number, header.ParentHash[:4])
            bc.SetHead(header.Number.Uint64() - 1)
            glog.V(logger.Error).Infoln("Chain rewind was successful, resuming normal operation")
        }
    }
    // Take ownership of this particular state
    go bc.update()
    return bc, nil
}

func (self *BlockChain) getProcInterrupt() bool {
    return atomic.LoadInt32(&self.procInterrupt) == 1
}

// loadLastState loads the last known chain state from the database. This method
// assumes that the chain manager mutex is held.
func (self *BlockChain) loadLastState() error {
    // Restore the last known head block
    head := GetHeadBlockHash(self.chainDb)
    if head == (common.Hash{}) {
        // Corrupt or empty database, init from scratch
        self.Reset()
    } else {
        if block := self.GetBlock(head); block != nil {
            // Block found, set as the current head
            self.currentBlock = block
        } else {
            // Corrupt or empty database, init from scratch
            self.Reset()
        }
    }
    // Restore the last known head header
    currentHeader := self.currentBlock.Header()
    if head := GetHeadHeaderHash(self.chainDb); head != (common.Hash{}) {
        if header := self.GetHeader(head); header != nil {
            currentHeader = header
        }
    }
    self.hc.SetCurrentHeader(currentHeader)
    // Restore the last known head fast block
    self.currentFastBlock = self.currentBlock
    if head := GetHeadFastBlockHash(self.chainDb); head != (common.Hash{}) {
        if block := self.GetBlock(head); block != nil {
            self.currentFastBlock = block
        }
    }
    // Issue a status log and return
    headerTd := self.GetTd(self.hc.CurrentHeader().Hash())
    blockTd := self.GetTd(self.currentBlock.Hash())
    fastTd := self.GetTd(self.currentFastBlock.Hash())

    glog.V(logger.Info).Infof("Last header: #%d [%x…] TD=%v", self.hc.CurrentHeader().Number, self.hc.CurrentHeader().Hash().Bytes()[:4], headerTd)
    glog.V(logger.Info).Infof("Last block: #%d [%x…] TD=%v", self.currentBlock.Number(), self.currentBlock.Hash().Bytes()[:4], blockTd)
    glog.V(logger.Info).Infof("Fast block: #%d [%x…] TD=%v", self.currentFastBlock.Number(), self.currentFastBlock.Hash().Bytes()[:4], fastTd)

    return nil
}

// SetHead rewinds the local chain to a new head. In the case of headers, everything
// above the new head will be deleted and the new one set. In the case of blocks
// though, the head may be further rewound if block bodies are missing (non-archive
// nodes after a fast sync).
func (bc *BlockChain) SetHead(head uint64) {
    bc.mu.Lock()
    defer bc.mu.Unlock()

    delFn := func(hash common.Hash) {
        DeleteBody(bc.chainDb, hash)
    }
    bc.hc.SetHead(head, delFn)

    // Clear out any stale content from the caches
    bc.bodyCache.Purge()
    bc.bodyRLPCache.Purge()
    bc.blockCache.Purge()
    bc.futureBlocks.Purge()

    // Update all computed fields to the new head
    if bc.currentBlock != nil && bc.hc.CurrentHeader().Number.Uint64() < bc.currentBlock.NumberU64() {
        bc.currentBlock = bc.GetBlock(bc.hc.CurrentHeader().Hash())
    }
    if bc.currentFastBlock != nil && bc.hc.CurrentHeader().Number.Uint64() < bc.currentFastBlock.NumberU64() {
        bc.currentFastBlock = bc.GetBlock(bc.hc.CurrentHeader().Hash())
    }

    if bc.currentBlock == nil {
        bc.currentBlock = bc.genesisBlock
    }
    if bc.currentFastBlock == nil {
        bc.currentFastBlock = bc.genesisBlock
    }

    if err := WriteHeadBlockHash(bc.chainDb, bc.currentBlock.Hash()); err != nil {
        glog.Fatalf("failed to reset head block hash: %v", err)
    }
    if err := WriteHeadFastBlockHash(bc.chainDb, bc.currentFastBlock.Hash()); err != nil {
        glog.Fatalf("failed to reset head fast block hash: %v", err)
    }
    bc.loadLastState()
}

// FastSyncCommitHead sets the current head block to the one defined by the hash
// irrelevant what the chain contents were prior.
func (self *BlockChain) FastSyncCommitHead(hash common.Hash) error {
    // Make sure that both the block as well at its state trie exists
    block := self.GetBlock(hash)
    if block == nil {
        return fmt.Errorf("non existent block [%x…]", hash[:4])
    }
    if _, err := trie.NewSecure(block.Root(), self.chainDb); err != nil {
        return err
    }
    // If all checks out, manually set the head block
    self.mu.Lock()
    self.currentBlock = block
    self.mu.Unlock()

    glog.V(logger.Info).Infof("committed block #%d [%x…] as new head", block.Number(), hash[:4])
    return nil
}

// GasLimit returns the gas limit of the current HEAD block.
func (self *BlockChain) GasLimit() *big.Int {
    self.mu.RLock()
    defer self.mu.RUnlock()

    return self.currentBlock.GasLimit()
}

// LastBlockHash return the hash of the HEAD block.
func (self *BlockChain) LastBlockHash() common.Hash {
    self.mu.RLock()
    defer self.mu.RUnlock()

    return self.currentBlock.Hash()
}

// CurrentBlock retrieves the current head block of the canonical chain. The
// block is retrieved from the blockchain's internal cache.
func (self *BlockChain) CurrentBlock() *types.Block {
    self.mu.RLock()
    defer self.mu.RUnlock()

    return self.currentBlock
}

// CurrentFastBlock retrieves the current fast-sync head block of the canonical
// chain. The block is retrieved from the blockchain's internal cache.
func (self *BlockChain) CurrentFastBlock() *types.Block {
    self.mu.RLock()
    defer self.mu.RUnlock()

    return self.currentFastBlock
}

// Status returns status information about the current chain such as the HEAD Td,
// the HEAD hash and the hash of the genesis block.
func (self *BlockChain) Status() (td *big.Int, currentBlock common.Hash, genesisBlock common.Hash) {
    self.mu.RLock()
    defer self.mu.RUnlock()

    return self.GetTd(self.currentBlock.Hash()), self.currentBlock.Hash(), self.genesisBlock.Hash()
}

// SetProcessor sets the processor required for making state modifications.
func (self *BlockChain) SetProcessor(processor Processor) {
    self.procmu.Lock()
    defer self.procmu.Unlock()
    self.processor = processor
}

// SetValidator sets the validator which is used to validate incoming blocks.
func (self *BlockChain) SetValidator(validator Validator) {
    self.procmu.Lock()
    defer self.procmu.Unlock()
    self.validator = validator
}

// Validator returns the current validator.
func (self *BlockChain) Validator() Validator {
    self.procmu.RLock()
    defer self.procmu.RUnlock()
    return self.validator
}

// Processor returns the current processor.
func (self *BlockChain) Processor() Processor {
    self.procmu.RLock()
    defer self.procmu.RUnlock()
    return self.processor
}

// AuxValidator returns the auxiliary validator (Proof of work atm)
func (self *BlockChain) AuxValidator() pow.PoW { return self.pow }

// State returns a new mutable state based on the current HEAD block.
func (self *BlockChain) State() (*state.StateDB, error) {
    return state.New(self.CurrentBlock().Root(), self.chainDb)
}

// Reset purges the entire blockchain, restoring it to its genesis state.
func (bc *BlockChain) Reset() {
    bc.ResetWithGenesisBlock(bc.genesisBlock)
}

// ResetWithGenesisBlock purges the entire blockchain, restoring it to the
// specified genesis state.
func (bc *BlockChain) ResetWithGenesisBlock(genesis *types.Block) {
    // Dump the entire block chain and purge the caches
    bc.SetHead(0)

    bc.mu.Lock()
    defer bc.mu.Unlock()

    // Prepare the genesis block and reinitialise the chain
    if err := bc.hc.WriteTd(genesis.Hash(), genesis.Difficulty()); err != nil {
        glog.Fatalf("failed to write genesis block TD: %v", err)
    }
    if err := WriteBlock(bc.chainDb, genesis); err != nil {
        glog.Fatalf("failed to write genesis block: %v", err)
    }
    bc.genesisBlock = genesis
    bc.insert(bc.genesisBlock)
    bc.currentBlock = bc.genesisBlock
    bc.hc.SetGenesis(bc.genesisBlock.Header())
    bc.hc.SetCurrentHeader(bc.genesisBlock.Header())
    bc.currentFastBlock = bc.genesisBlock
}

// Export writes the active chain to the given writer.
func (self *BlockChain) Export(w io.Writer) error {
    if err := self.ExportN(w, uint64(0), self.currentBlock.NumberU64()); err != nil {
        return err
    }
    return nil
}

// ExportN writes a subset of the active chain to the given writer.
func (self *BlockChain) ExportN(w io.Writer, first uint64, last uint64) error {
    self.mu.RLock()
    defer self.mu.RUnlock()

    if first > last {
        return fmt.Errorf("export failed: first (%d) is greater than last (%d)", first, last)
    }

    glog.V(logger.Info).Infof("exporting %d blocks...\n", last-first+1)

    for nr := first; nr <= last; nr++ {
        block := self.GetBlockByNumber(nr)
        if block == nil {
            return fmt.Errorf("export failed on #%d: not found", nr)
        }

        if err := block.EncodeRLP(w); err != nil {
            return err
        }
    }

    return nil
}

// insert injects a new head block into the current block chain. This method
// assumes that the block is indeed a true head. It will also reset the head
// header and the head fast sync block to this very same block if they are older
// or if they are on a different side chain.
//
// Note, this function assumes that the `mu` mutex is held!
func (bc *BlockChain) insert(block *types.Block) {
    // If the block is on a side chain or an unknown one, force other heads onto it too
    updateHeads := GetCanonicalHash(bc.chainDb, block.NumberU64()) != block.Hash()

    // Add the block to the canonical chain number scheme and mark as the head
    if err := WriteCanonicalHash(bc.chainDb, block.Hash(), block.NumberU64()); err != nil {
        glog.Fatalf("failed to insert block number: %v", err)
    }
    if err := WriteHeadBlockHash(bc.chainDb, block.Hash()); err != nil {
        glog.Fatalf("failed to insert head block hash: %v", err)
    }
    bc.currentBlock = block

    // If the block is better than out head or is on a different chain, force update heads
    if updateHeads {
        bc.hc.SetCurrentHeader(block.Header())

        if err := WriteHeadFastBlockHash(bc.chainDb, block.Hash()); err != nil {
            glog.Fatalf("failed to insert head fast block hash: %v", err)
        }
        bc.currentFastBlock = block
    }
}

// Accessors
func (bc *BlockChain) Genesis() *types.Block {
    return bc.genesisBlock
}

// GetBody retrieves a block body (transactions and uncles) from the database by
// hash, caching it if found.
func (self *BlockChain) GetBody(hash common.Hash) *types.Body {
    // Short circuit if the body's already in the cache, retrieve otherwise
    if cached, ok := self.bodyCache.Get(hash); ok {
        body := cached.(*types.Body)
        return body
    }
    body := GetBody(self.chainDb, hash)
    if body == nil {
        return nil
    }
    // Cache the found body for next time and return
    self.bodyCache.Add(hash, body)
    return body
}

// GetBodyRLP retrieves a block body in RLP encoding from the database by hash,
// caching it if found.
func (self *BlockChain) GetBodyRLP(hash common.Hash) rlp.RawValue {
    // Short circuit if the body's already in the cache, retrieve otherwise
    if cached, ok := self.bodyRLPCache.Get(hash); ok {
        return cached.(rlp.RawValue)
    }
    body := GetBodyRLP(self.chainDb, hash)
    if len(body) == 0 {
        return nil
    }
    // Cache the found body for next time and return
    self.bodyRLPCache.Add(hash, body)
    return body
}

// HasBlock checks if a block is fully present in the database or not, caching
// it if present.
func (bc *BlockChain) HasBlock(hash common.Hash) bool {
    return bc.GetBlock(hash) != nil
}

// HasBlockAndState checks if a block and associated state trie is fully present
// in the database or not, caching it if present.
func (bc *BlockChain) HasBlockAndState(hash common.Hash) bool {
    // Check first that the block itself is known
    block := bc.GetBlock(hash)
    if block == nil {
        return false
    }
    // Ensure the associated state is also present
    _, err := state.New(block.Root(), bc.chainDb)
    return err == nil
}

// GetBlock retrieves a block from the database by hash, caching it if found.
func (self *BlockChain) GetBlock(hash common.Hash) *types.Block {
    // Short circuit if the block's already in the cache, retrieve otherwise
    if block, ok := self.blockCache.Get(hash); ok {
        return block.(*types.Block)
    }
    block := GetBlock(self.chainDb, hash)
    if block == nil {
        return nil
    }
    // Cache the found block for next time and return
    self.blockCache.Add(block.Hash(), block)
    return block
}

// GetBlockByNumber retrieves a block from the database by number, caching it
// (associated with its hash) if found.
func (self *BlockChain) GetBlockByNumber(number uint64) *types.Block {
    hash := GetCanonicalHash(self.chainDb, number)
    if hash == (common.Hash{}) {
        return nil
    }
    return self.GetBlock(hash)
}

// [deprecated by eth/62]
// GetBlocksFromHash returns the block corresponding to hash and up to n-1 ancestors.
func (self *BlockChain) GetBlocksFromHash(hash common.Hash, n int) (blocks []*types.Block) {
    for i := 0; i < n; i++ {
        block := self.GetBlock(hash)
        if block == nil {
            break
        }
        blocks = append(blocks, block)
        hash = block.ParentHash()
    }
    return
}

// GetUnclesInChain retrieves all the uncles from a given block backwards until
// a specific distance is reached.
func (self *BlockChain) GetUnclesInChain(block *types.Block, length int) []*types.Header {
    uncles := []*types.Header{}
    for i := 0; block != nil && i < length; i++ {
        uncles = append(uncles, block.Uncles()...)
        block = self.GetBlock(block.ParentHash())
    }
    return uncles
}

// Stop stops the blockchain service. If any imports are currently in progress
// it will abort them using the procInterrupt.
func (bc *BlockChain) Stop() {
    if !atomic.CompareAndSwapInt32(&bc.running, 0, 1) {
        return
    }
    close(bc.quit)
    atomic.StoreInt32(&bc.procInterrupt, 1)

    bc.wg.Wait()

    glog.V(logger.Info).Infoln("Chain manager stopped")
}

func (self *BlockChain) procFutureBlocks() {
    blocks := make([]*types.Block, 0, self.futureBlocks.Len())
    for _, hash := range self.futureBlocks.Keys() {
        if block, exist := self.futureBlocks.Get(hash); exist {
            blocks = append(blocks, block.(*types.Block))
        }
    }
    if len(blocks) > 0 {
        types.BlockBy(types.Number).Sort(blocks)
        self.InsertChain(blocks)
    }
}

type WriteStatus byte

const (
    NonStatTy WriteStatus = iota
    CanonStatTy
    SplitStatTy
    SideStatTy
)

// Rollback is designed to remove a chain of links from the database that aren't
// certain enough to be valid.
func (self *BlockChain) Rollback(chain []common.Hash) {
    self.mu.Lock()
    defer self.mu.Unlock()

    for i := len(chain) - 1; i >= 0; i-- {
        hash := chain[i]

        if self.hc.CurrentHeader().Hash() == hash {
            self.hc.SetCurrentHeader(self.GetHeader(self.hc.CurrentHeader().ParentHash))
        }
        if self.currentFastBlock.Hash() == hash {
            self.currentFastBlock = self.GetBlock(self.currentFastBlock.ParentHash())
            WriteHeadFastBlockHash(self.chainDb, self.currentFastBlock.Hash())
        }
        if self.currentBlock.Hash() == hash {
            self.currentBlock = self.GetBlock(self.currentBlock.ParentHash())
            WriteHeadBlockHash(self.chainDb, self.currentBlock.Hash())
        }
    }
}

// InsertReceiptChain attempts to complete an already existing header chain with
// transaction and receipt data.
func (self *BlockChain) InsertReceiptChain(blockChain types.Blocks, receiptChain []types.Receipts) (int, error) {
    self.wg.Add(1)
    defer self.wg.Done()

    // Collect some import statistics to report on
    stats := struct{ processed, ignored int32 }{}
    start := time.Now()

    // Create the block importing task queue and worker functions
    tasks := make(chan int, len(blockChain))
    for i := 0; i < len(blockChain) && i < len(receiptChain); i++ {
        tasks <- i
    }
    close(tasks)

    errs, failed := make([]error, len(tasks)), int32(0)
    process := func(worker int) {
        for index := range tasks {
            block, receipts := blockChain[index], receiptChain[index]

            // Short circuit insertion if shutting down or processing failed
            if atomic.LoadInt32(&self.procInterrupt) == 1 {
                return
            }
            if atomic.LoadInt32(&failed) > 0 {
                return
            }
            // Short circuit if the owner header is unknown
            if !self.HasHeader(block.Hash()) {
                errs[index] = fmt.Errorf("containing header #%d [%x…] unknown", block.Number(), block.Hash().Bytes()[:4])
                atomic.AddInt32(&failed, 1)
                return
            }
            // Skip if the entire data is already known
            if self.HasBlock(block.Hash()) {
                atomic.AddInt32(&stats.ignored, 1)
                continue
            }
            // Compute all the non-consensus fields of the receipts
            transactions, logIndex := block.Transactions(), uint(0)
            for j := 0; j < len(receipts); j++ {
                // The transaction hash can be retrieved from the transaction itself
                receipts[j].TxHash = transactions[j].Hash()

                // The contract address can be derived from the transaction itself
                if MessageCreatesContract(transactions[j]) {
                    from, _ := transactions[j].From()
                    receipts[j].ContractAddress = crypto.CreateAddress(from, transactions[j].Nonce())
                }
                // The used gas can be calculated based on previous receipts
                if j == 0 {
                    receipts[j].GasUsed = new(big.Int).Set(receipts[j].CumulativeGasUsed)
                } else {
                    receipts[j].GasUsed = new(big.Int).Sub(receipts[j].CumulativeGasUsed, receipts[j-1].CumulativeGasUsed)
                }
                // The derived log fields can simply be set from the block and transaction
                for k := 0; k < len(receipts[j].Logs); k++ {
                    receipts[j].Logs[k].BlockNumber = block.NumberU64()
                    receipts[j].Logs[k].BlockHash = block.Hash()
                    receipts[j].Logs[k].TxHash = receipts[j].TxHash
                    receipts[j].Logs[k].TxIndex = uint(j)
                    receipts[j].Logs[k].Index = logIndex
                    logIndex++
                }
            }
            // Write all the data out into the database
            if err := WriteBody(self.chainDb, block.Hash(), &types.Body{block.Transactions(), block.Uncles()}); err != nil {
                errs[index] = fmt.Errorf("failed to write block body: %v", err)
                atomic.AddInt32(&failed, 1)
                glog.Fatal(errs[index])
                return
            }
            if err := WriteBlockReceipts(self.chainDb, block.Hash(), receipts); err != nil {
                errs[index] = fmt.Errorf("failed to write block receipts: %v", err)
                atomic.AddInt32(&failed, 1)
                glog.Fatal(errs[index])
                return
            }
            if err := WriteMipmapBloom(self.chainDb, block.NumberU64(), receipts); err != nil {
                errs[index] = fmt.Errorf("failed to write log blooms: %v", err)
                atomic.AddInt32(&failed, 1)
                glog.Fatal(errs[index])
                return
            }
            if err := WriteTransactions(self.chainDb, block); err != nil {
                errs[index] = fmt.Errorf("failed to write individual transactions: %v", err)
                atomic.AddInt32(&failed, 1)
                glog.Fatal(errs[index])
                return
            }
            if err := WriteReceipts(self.chainDb, receipts); err != nil {
                errs[index] = fmt.Errorf("failed to write individual receipts: %v", err)
                atomic.AddInt32(&failed, 1)
                glog.Fatal(errs[index])
                return
            }
            atomic.AddInt32(&stats.processed, 1)
        }
    }
    // Start as many worker threads as goroutines allowed
    pending := new(sync.WaitGroup)
    for i := 0; i < runtime.GOMAXPROCS(0); i++ {
        pending.Add(1)
        go func(id int) {
            defer pending.Done()
            process(id)
        }(i)
    }
    pending.Wait()

    // If anything failed, report
    if failed > 0 {
        for i, err := range errs {
            if err != nil {
                return i, err
            }
        }
    }
    if atomic.LoadInt32(&self.procInterrupt) == 1 {
        glog.V(logger.Debug).Infoln("premature abort during receipt chain processing")
        return 0, nil
    }
    // Update the head fast sync block if better
    self.mu.Lock()
    head := blockChain[len(errs)-1]
    if self.GetTd(self.currentFastBlock.Hash()).Cmp(self.GetTd(head.Hash())) < 0 {
        if err := WriteHeadFastBlockHash(self.chainDb, head.Hash()); err != nil {
            glog.Fatalf("failed to update head fast block hash: %v", err)
        }
        self.currentFastBlock = head
    }
    self.mu.Unlock()

    // Report some public statistics so the user has a clue what's going on
    first, last := blockChain[0], blockChain[len(blockChain)-1]
    glog.V(logger.Info).Infof("imported %d receipt(s) (%d ignored) in %v. #%d [%x… / %x…]", stats.processed, stats.ignored,
        time.Since(start), last.Number(), first.Hash().Bytes()[:4], last.Hash().Bytes()[:4])

    return 0, nil
}

// WriteBlock writes the block to the chain.
func (self *BlockChain) WriteBlock(block *types.Block) (status WriteStatus, err error) {
    self.wg.Add(1)
    defer self.wg.Done()

    // Calculate the total difficulty of the block
    ptd := self.GetTd(block.ParentHash())
    if ptd == nil {
        return NonStatTy, ParentError(block.ParentHash())
    }

    localTd := self.GetTd(self.currentBlock.Hash())
    externTd := new(big.Int).Add(block.Difficulty(), ptd)

    // Make sure no inconsistent state is leaked during insertion
    self.mu.Lock()
    defer self.mu.Unlock()

    // If the total difficulty is higher than our known, add it to the canonical chain
    // Second clause in the if statement reduces the vulnerability to selfish mining.
    // Please refer to http://www.cs.cornell.edu/~ie53/publications/btcProcFC.pdf
    if externTd.Cmp(localTd) > 0 || (externTd.Cmp(localTd) == 0 && mrand.Float64() < 0.5) {
        // Reorganise the chain if the parent is not the head block
        if block.ParentHash() != self.currentBlock.Hash() {
            if err := self.reorg(self.currentBlock, block); err != nil {
                return NonStatTy, err
            }
        }
        // Insert the block as the new head of the chain
        self.insert(block)
        status = CanonStatTy
    } else {
        status = SideStatTy
    }
    // Irrelevant of the canonical status, write the block itself to the database
    if err := self.hc.WriteTd(block.Hash(), externTd); err != nil {
        glog.Fatalf("failed to write block total difficulty: %v", err)
    }
    if err := WriteBlock(self.chainDb, block); err != nil {
        glog.Fatalf("filed to write block contents: %v", err)
    }

    self.futureBlocks.Remove(block.Hash())

    return
}

// InsertChain will attempt to insert the given chain in to the canonical chain or, otherwise, create a fork. It an error is returned
// it will return the index number of the failing block as well an error describing what went wrong (for possible errors see core/errors.go).
func (self *BlockChain) InsertChain(chain types.Blocks) (int, error) {
    self.wg.Add(1)
    defer self.wg.Done()

    self.chainmu.Lock()
    defer self.chainmu.Unlock()

    // A queued approach to delivering events. This is generally
    // faster than direct delivery and requires much less mutex
    // acquiring.
    var (
        stats         struct{ queued, processed, ignored int }
        events        = make([]interface{}, 0, len(chain))
        coalescedLogs vm.Logs
        tstart        = time.Now()

        nonceChecked = make([]bool, len(chain))
    )

    // Start the parallel nonce verifier.
    nonceAbort, nonceResults := verifyNoncesFromBlocks(self.pow, chain)
    defer close(nonceAbort)

    txcount := 0
    for i, block := range chain {
        if atomic.LoadInt32(&self.procInterrupt) == 1 {
            glog.V(logger.Debug).Infoln("Premature abort during block chain processing")
            break
        }

        bstart := time.Now()
        // Wait for block i's nonce to be verified before processing
        // its state transition.
        for !nonceChecked[i] {
            r := <-nonceResults
            nonceChecked[r.index] = true
            if !r.valid {
                block := chain[r.index]
                return r.index, &BlockNonceErr{Hash: block.Hash(), Number: block.Number(), Nonce: block.Nonce()}
            }
        }

        if BadHashes[block.Hash()] {
            err := BadHashError(block.Hash())
            reportBlock(block, err)
            return i, err
        }
        // Stage 1 validation of the block using the chain's validator
        // interface.
        err := self.Validator().ValidateBlock(block)
        if err != nil {
            if IsKnownBlockErr(err) {
                stats.ignored++
                continue
            }

            if err == BlockFutureErr {
                // Allow up to MaxFuture second in the future blocks. If this limit
                // is exceeded the chain is discarded and processed at a later time
                // if given.
                max := big.NewInt(time.Now().Unix() + maxTimeFutureBlocks)
                if block.Time().Cmp(max) == 1 {
                    return i, fmt.Errorf("%v: BlockFutureErr, %v > %v", BlockFutureErr, block.Time(), max)
                }

                self.futureBlocks.Add(block.Hash(), block)
                stats.queued++
                continue
            }

            if IsParentErr(err) && self.futureBlocks.Contains(block.ParentHash()) {
                self.futureBlocks.Add(block.Hash(), block)
                stats.queued++
                continue
            }

            reportBlock(block, err)

            return i, err
        }

        // Create a new statedb using the parent block and report an
        // error if it fails.
        statedb, err := state.New(self.GetBlock(block.ParentHash()).Root(), self.chainDb)
        if err != nil {
            reportBlock(block, err)
            return i, err
        }
        // Process block using the parent state as reference point.
        receipts, logs, usedGas, err := self.processor.Process(block, statedb)
        if err != nil {
            reportBlock(block, err)
            return i, err
        }
        // Validate the state using the default validator
        err = self.Validator().ValidateState(block, self.GetBlock(block.ParentHash()), statedb, receipts, usedGas)
        if err != nil {
            reportBlock(block, err)
            return i, err
        }
        // Write state changes to database
        _, err = statedb.Commit()
        if err != nil {
            return i, err
        }

        // coalesce logs for later processing
        coalescedLogs = append(coalescedLogs, logs...)

        if err := WriteBlockReceipts(self.chainDb, block.Hash(), receipts); err != nil {
            return i, err
        }

        txcount += len(block.Transactions())
        // write the block to the chain and get the status
        status, err := self.WriteBlock(block)
        if err != nil {
            return i, err
        }

        switch status {
        case CanonStatTy:
            if glog.V(logger.Debug) {
                glog.Infof("[%v] inserted block #%d (%d TXs %v G %d UNCs) (%x...). Took %v\n", time.Now().UnixNano(), block.Number(), len(block.Transactions()), block.GasUsed(), len(block.Uncles()), block.Hash().Bytes()[0:4], time.Since(bstart))
            }
            events = append(events, ChainEvent{block, block.Hash(), logs})

            // This puts transactions in a extra db for rpc
            if err := WriteTransactions(self.chainDb, block); err != nil {
                return i, err
            }
            // store the receipts
            if err := WriteReceipts(self.chainDb, receipts); err != nil {
                return i, err
            }
            // Write map map bloom filters
            if err := WriteMipmapBloom(self.chainDb, block.NumberU64(), receipts); err != nil {
                return i, err
            }
        case SideStatTy:
            if glog.V(logger.Detail) {
                glog.Infof("inserted forked block #%d (TD=%v) (%d TXs %d UNCs) (%x...). Took %v\n", block.Number(), block.Difficulty(), len(block.Transactions()), len(block.Uncles()), block.Hash().Bytes()[0:4], time.Since(bstart))
            }
            events = append(events, ChainSideEvent{block, logs})

        case SplitStatTy:
            events = append(events, ChainSplitEvent{block, logs})
        }
        stats.processed++
    }

    if (stats.queued > 0 || stats.processed > 0 || stats.ignored > 0) && bool(glog.V(logger.Info)) {
        tend := time.Since(tstart)
        start, end := chain[0], chain[len(chain)-1]
        glog.Infof("imported %d block(s) (%d queued %d ignored) including %d txs in %v. #%v [%x / %x]\n", stats.processed, stats.queued, stats.ignored, txcount, tend, end.Number(), start.Hash().Bytes()[:4], end.Hash().Bytes()[:4])
    }
    go self.postChainEvents(events, coalescedLogs)

    return 0, nil
}

// reorgs takes two blocks, an old chain and a new chain and will reconstruct the blocks and inserts them
// to be part of the new canonical chain and accumulates potential missing transactions and post an
// event about them
func (self *BlockChain) reorg(oldBlock, newBlock *types.Block) error {
    var (
        newChain          types.Blocks
        oldChain          types.Blocks
        commonBlock       *types.Block
        oldStart          = oldBlock
        newStart          = newBlock
        deletedTxs        types.Transactions
        deletedLogs       vm.Logs
        deletedLogsByHash = make(map[common.Hash]vm.Logs)
        // collectLogs collects the logs that were generated during the
        // processing of the block that corresponds with the given hash.
        // These logs are later announced as deleted.
        collectLogs = func(h common.Hash) {
            // Coalesce logs
            receipts := GetBlockReceipts(self.chainDb, h)
            for _, receipt := range receipts {
                deletedLogs = append(deletedLogs, receipt.Logs...)

                deletedLogsByHash[h] = receipt.Logs
            }
        }
    )

    // first reduce whoever is higher bound
    if oldBlock.NumberU64() > newBlock.NumberU64() {
        // reduce old chain
        for oldBlock = oldBlock; oldBlock != nil && oldBlock.NumberU64() != newBlock.NumberU64(); oldBlock = self.GetBlock(oldBlock.ParentHash()) {
            oldChain = append(oldChain, oldBlock)
            deletedTxs = append(deletedTxs, oldBlock.Transactions()...)

            collectLogs(oldBlock.Hash())
        }
    } else {
        // reduce new chain and append new chain blocks for inserting later on
        for newBlock = newBlock; newBlock != nil && newBlock.NumberU64() != oldBlock.NumberU64(); newBlock = self.GetBlock(newBlock.ParentHash()) {
            newChain = append(newChain, newBlock)
        }
    }
    if oldBlock == nil {
        return fmt.Errorf("Invalid old chain")
    }
    if newBlock == nil {
        return fmt.Errorf("Invalid new chain")
    }

    numSplit := newBlock.Number()
    for {
        if oldBlock.Hash() == newBlock.Hash() {
            commonBlock = oldBlock
            break
        }

        oldChain = append(oldChain, oldBlock)
        newChain = append(newChain, newBlock)
        deletedTxs = append(deletedTxs, oldBlock.Transactions()...)
        collectLogs(oldBlock.Hash())

        oldBlock, newBlock = self.GetBlock(oldBlock.ParentHash()), self.GetBlock(newBlock.ParentHash())
        if oldBlock == nil {
            return fmt.Errorf("Invalid old chain")
        }
        if newBlock == nil {
            return fmt.Errorf("Invalid new chain")
        }
    }

    if glog.V(logger.Debug) {
        commonHash := commonBlock.Hash()
        glog.Infof("Chain split detected @ %x. Reorganising chain from #%v %x to %x", commonHash[:4], numSplit, oldStart.Hash().Bytes()[:4], newStart.Hash().Bytes()[:4])
    }

    var addedTxs types.Transactions
    // insert blocks. Order does not matter. Last block will be written in ImportChain itself which creates the new head properly
    for _, block := range newChain {
        // insert the block in the canonical way, re-writing history
        self.insert(block)
        // write canonical receipts and transactions
        if err := WriteTransactions(self.chainDb, block); err != nil {
            return err
        }
        receipts := GetBlockReceipts(self.chainDb, block.Hash())
        // write receipts
        if err := WriteReceipts(self.chainDb, receipts); err != nil {
            return err
        }
        // Write map map bloom filters
        if err := WriteMipmapBloom(self.chainDb, block.NumberU64(), receipts); err != nil {
            return err
        }
        addedTxs = append(addedTxs, block.Transactions()...)
    }

    // calculate the difference between deleted and added transactions
    diff := types.TxDifference(deletedTxs, addedTxs)
    // When transactions get deleted from the database that means the
    // receipts that were created in the fork must also be deleted
    for _, tx := range diff {
        DeleteReceipt(self.chainDb, tx.Hash())
        DeleteTransaction(self.chainDb, tx.Hash())
    }
    // Must be posted in a goroutine because of the transaction pool trying
    // to acquire the chain manager lock
    if len(diff) > 0 {
        go self.eventMux.Post(RemovedTransactionEvent{diff})
    }
    if len(deletedLogs) > 0 {
        go self.eventMux.Post(RemovedLogsEvent{deletedLogs})
    }

    if len(oldChain) > 0 {
        go func() {
            for _, block := range oldChain {
                self.eventMux.Post(ChainSideEvent{Block: block, Logs: deletedLogsByHash[block.Hash()]})
            }
        }()
    }

    return nil
}

// postChainEvents iterates over the events generated by a chain insertion and
// posts them into the event mux.
func (self *BlockChain) postChainEvents(events []interface{}, logs vm.Logs) {
    // post event logs for further processing
    self.eventMux.Post(logs)
    for _, event := range events {
        if event, ok := event.(ChainEvent); ok {
            // We need some control over the mining operation. Acquiring locks and waiting for the miner to create new block takes too long
            // and in most cases isn't even necessary.
            if self.LastBlockHash() == event.Hash {
                self.eventMux.Post(ChainHeadEvent{event.Block})
            }
        }
        // Fire the insertion events individually too
        self.eventMux.Post(event)
    }
}

func (self *BlockChain) update() {
    futureTimer := time.Tick(5 * time.Second)
    for {
        select {
        case <-futureTimer:
            self.procFutureBlocks()
        case <-self.quit:
            return
        }
    }
}

// reportBlock reports the given block and error using the canonical block
// reporting tool. Reporting the block to the service is handled in a separate
// goroutine.
func reportBlock(block *types.Block, err error) {
    if glog.V(logger.Error) {
        glog.Errorf("Bad block #%v (%s)\n", block.Number(), block.Hash().Hex())
        glog.Errorf("    %v", err)
    }
    go ReportBlock(block, err)
}

// InsertHeaderChain attempts to insert the given header chain in to the local
// chain, possibly creating a reorg. If an error is returned, it will return the
// index number of the failing header as well an error describing what went wrong.
//
// The verify parameter can be used to fine tune whether nonce verification
// should be done or not. The reason behind the optional check is because some
// of the header retrieval mechanisms already need to verfy nonces, as well as
// because nonces can be verified sparsely, not needing to check each.
func (self *BlockChain) InsertHeaderChain(chain []*types.Header, checkFreq int) (int, error) {
    // Make sure only one thread manipulates the chain at once
    self.chainmu.Lock()
    defer self.chainmu.Unlock()

    self.wg.Add(1)
    defer self.wg.Done()

    whFunc := func(header *types.Header) error {
        self.mu.Lock()
        defer self.mu.Unlock()

        _, err := self.hc.WriteHeader(header)
        return err
    }

    return self.hc.InsertHeaderChain(chain, checkFreq, whFunc)
}

// writeHeader writes a header into the local chain, given that its parent is
// already known. If the total difficulty of the newly inserted header becomes
// greater than the current known TD, the canonical chain is re-routed.
//
// Note: This method is not concurrent-safe with inserting blocks simultaneously
// into the chain, as side effects caused by reorganisations cannot be emulated
// without the real blocks. Hence, writing headers directly should only be done
// in two scenarios: pure-header mode of operation (light clients), or properly
// separated header/block phases (non-archive clients).
func (self *BlockChain) writeHeader(header *types.Header) error {
    self.wg.Add(1)
    defer self.wg.Done()

    self.mu.Lock()
    defer self.mu.Unlock()

    _, err := self.hc.WriteHeader(header)
    return err
}

// CurrentHeader retrieves the current head header of the canonical chain. The
// header is retrieved from the HeaderChain's internal cache.
func (self *BlockChain) CurrentHeader() *types.Header {
    self.mu.RLock()
    defer self.mu.RUnlock()

    return self.hc.CurrentHeader()
}

// GetTd retrieves a block's total difficulty in the canonical chain from the
// database by hash, caching it if found.
func (self *BlockChain) GetTd(hash common.Hash) *big.Int {
    return self.hc.GetTd(hash)
}

// GetHeader retrieves a block header from the database by hash, caching it if
// found.
func (self *BlockChain) GetHeader(hash common.Hash) *types.Header {
    return self.hc.GetHeader(hash)
}

// HasHeader checks if a block header is present in the database or not, caching
// it if present.
func (bc *BlockChain) HasHeader(hash common.Hash) bool {
    return bc.hc.HasHeader(hash)
}

// GetBlockHashesFromHash retrieves a number of block hashes starting at a given
// hash, fetching towards the genesis block.
func (self *BlockChain) GetBlockHashesFromHash(hash common.Hash, max uint64) []common.Hash {
    return self.hc.GetBlockHashesFromHash(hash, max)
}

// GetHeaderByNumber retrieves a block header from the database by number,
// caching it (associated with its hash) if found.
func (self *BlockChain) GetHeaderByNumber(number uint64) *types.Header {
    return self.hc.GetHeaderByNumber(number)
}