// verifyNonces starts a concurrent nonce verification, returning a quit channel
// to abort the operations and a results channel to retrieve the async checks.
func verifyNonces(checker pow.PoW, items []pow.Block) (chan<- struct{}, <-chan nonceCheckResult) {
// Spawn as many workers as allowed threads
workers := runtime.GOMAXPROCS(0)
if len(items) < workers {
workers = len(items)
}
// Create a task channel and spawn the verifiers
tasks := make(chan int, workers)
results := make(chan nonceCheckResult, len(items)) // Buffered to make sure all workers stop
for i := 0; i < workers; i++ {
go func() {
for index := range tasks {
results <- nonceCheckResult{index: index, valid: checker.Verify(items[index])}
}
}()
}
// Feed item indices to the workers until done or aborted
abort := make(chan struct{})
go func() {
defer close(tasks)
for i := range items {
select {
case tasks <- i:
continue
case <-abort:
return
}
}
}()
return abort, results
}
// Validates a header. Returns an error if the header is invalid.
//
// See YP section 4.3.4. "Block Header Validity"
func ValidateHeader(pow pow.PoW, header *types.Header, parent *types.Header, checkPow, uncle bool) error {
if big.NewInt(int64(len(header.Extra))).Cmp(params.MaximumExtraDataSize) == 1 {
return fmt.Errorf("Header extra data too long (%d)", len(header.Extra))
}
if uncle {
if header.Time.Cmp(common.MaxBig) == 1 {
return BlockTSTooBigErr
}
} else {
if header.Time.Cmp(big.NewInt(time.Now().Unix())) == 1 {
return BlockFutureErr
}
}
if header.Time.Cmp(parent.Time) != 1 {
return BlockEqualTSErr
}
expd := CalcDifficulty(header.Time.Uint64(), parent.Time.Uint64(), parent.Number, parent.Difficulty)
if expd.Cmp(header.Difficulty) != 0 {
return fmt.Errorf("Difficulty check failed for header %v, %v", header.Difficulty, expd)
}
a := new(big.Int).Set(parent.GasLimit)
a = a.Sub(a, header.GasLimit)
a.Abs(a)
b := new(big.Int).Set(parent.GasLimit)
b = b.Div(b, params.GasLimitBoundDivisor)
if !(a.Cmp(b) < 0) || (header.GasLimit.Cmp(params.MinGasLimit) == -1) {
return fmt.Errorf("GasLimit check failed for header %v (%v > %v)", header.GasLimit, a, b)
}
num := new(big.Int).Set(parent.Number)
num.Sub(header.Number, num)
if num.Cmp(big.NewInt(1)) != 0 {
return BlockNumberErr
}
if checkPow {
// Verify the nonce of the header. Return an error if it's not valid
if !pow.Verify(types.NewBlockWithHeader(header)) {
return &BlockNonceErr{header.Number, header.Hash(), header.Nonce.Uint64()}
}
}
return nil
}