// 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()
// Calculate the total difficulty of the header
ptd := self.GetTd(header.ParentHash)
if ptd == nil {
return ParentError(header.ParentHash)
}
localTd := self.GetTd(self.currentHeader.Hash())
externTd := new(big.Int).Add(header.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) {
// Delete any canonical number assignments above the new head
for i := header.Number.Uint64() + 1; GetCanonicalHash(self.chainDb, i) != (common.Hash{}); i++ {
DeleteCanonicalHash(self.chainDb, i)
}
// Overwrite any stale canonical number assignments
head := self.GetHeader(header.ParentHash)
for GetCanonicalHash(self.chainDb, head.Number.Uint64()) != head.Hash() {
WriteCanonicalHash(self.chainDb, head.Hash(), head.Number.Uint64())
head = self.GetHeader(head.ParentHash)
}
// Extend the canonical chain with the new header
if err := WriteCanonicalHash(self.chainDb, header.Hash(), header.Number.Uint64()); err != nil {
glog.Fatalf("failed to insert header number: %v", err)
}
if err := WriteHeadHeaderHash(self.chainDb, header.Hash()); err != nil {
glog.Fatalf("failed to insert head header hash: %v", err)
}
self.currentHeader = types.CopyHeader(header)
}
// Irrelevant of the canonical status, write the header itself to the database
if err := WriteTd(self.chainDb, header.Hash(), externTd); err != nil {
glog.Fatalf("failed to write header total difficulty: %v", err)
}
if err := WriteHeader(self.chainDb, header); err != nil {
glog.Fatalf("filed to write header contents: %v", err)
}
return nil
}
// 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()
// Calculate the total difficulty of the header
ptd := self.GetTd(header.ParentHash)
if ptd == nil {
return ParentError(header.ParentHash)
}
td := new(big.Int).Add(header.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
if td.Cmp(self.GetTd(self.currentHeader.Hash())) > 0 {
// Delete any canonical number assignments above the new head
for i := header.Number.Uint64() + 1; GetCanonicalHash(self.chainDb, i) != (common.Hash{}); i++ {
DeleteCanonicalHash(self.chainDb, i)
}
// Overwrite any stale canonical number assignments
head := self.GetHeader(header.ParentHash)
for GetCanonicalHash(self.chainDb, head.Number.Uint64()) != head.Hash() {
WriteCanonicalHash(self.chainDb, head.Hash(), head.Number.Uint64())
head = self.GetHeader(head.ParentHash)
}
// Extend the canonical chain with the new header
if err := WriteCanonicalHash(self.chainDb, header.Hash(), header.Number.Uint64()); err != nil {
glog.Fatalf("failed to insert header number: %v", err)
}
if err := WriteHeadHeaderHash(self.chainDb, header.Hash()); err != nil {
glog.Fatalf("failed to insert head header hash: %v", err)
}
self.currentHeader = types.CopyHeader(header)
}
// Irrelevant of the canonical status, write the header itself to the database
if err := WriteTd(self.chainDb, header.Hash(), td); err != nil {
glog.Fatalf("failed to write header total difficulty: %v", err)
}
if err := WriteHeader(self.chainDb, header); err != nil {
glog.Fatalf("filed to write header contents: %v", err)
}
return nil
}
// 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 (hc *HeaderChain) WriteHeader(header *types.Header) (status WriteStatus, err error) {
// Cache some values to prevent constant recalculation
var (
hash = header.Hash()
number = header.Number.Uint64()
)
// Calculate the total difficulty of the header
ptd := hc.GetTd(header.ParentHash)
if ptd == nil {
return NonStatTy, ParentError(header.ParentHash)
}
localTd := hc.GetTd(hc.currentHeaderHash)
externTd := new(big.Int).Add(header.Difficulty, ptd)
// Irrelevant of the canonical status, write the td and header to the database
if err := hc.WriteTd(hash, externTd); err != nil {
glog.Fatalf("failed to write header total difficulty: %v", err)
}
if err := WriteHeader(hc.chainDb, header); err != nil {
glog.Fatalf("failed to write header contents: %v", err)
}
// 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) {
// Delete any canonical number assignments above the new head
for i := number + 1; GetCanonicalHash(hc.chainDb, i) != (common.Hash{}); i++ {
DeleteCanonicalHash(hc.chainDb, i)
}
// Overwrite any stale canonical number assignments
var (
headHash = header.ParentHash
headHeader = hc.GetHeader(headHash)
headNumber = headHeader.Number.Uint64()
)
for GetCanonicalHash(hc.chainDb, headNumber) != headHash {
WriteCanonicalHash(hc.chainDb, headHash, headNumber)
headHash = headHeader.ParentHash
headHeader = hc.GetHeader(headHash)
headNumber = headHeader.Number.Uint64()
}
// Extend the canonical chain with the new header
if err := WriteCanonicalHash(hc.chainDb, hash, number); err != nil {
glog.Fatalf("failed to insert header number: %v", err)
}
if err := WriteHeadHeaderHash(hc.chainDb, hash); err != nil {
glog.Fatalf("failed to insert head header hash: %v", err)
}
hc.currentHeaderHash, hc.currentHeader = hash, types.CopyHeader(header)
status = CanonStatTy
} else {
status = SideStatTy
}
hc.headerCache.Add(hash, header)
return
}
