|
package types
|
|
|
|
import (
|
|
"bytes"
|
|
"fmt"
|
|
"math"
|
|
"math/big"
|
|
"sort"
|
|
"strings"
|
|
|
|
"github.com/tendermint/tendermint/crypto/merkle"
|
|
cmn "github.com/tendermint/tendermint/libs/common"
|
|
)
|
|
|
|
// The maximum allowed total voting power.
|
|
// It needs to be sufficiently small to, in all cases::
|
|
// 1. prevent clipping in incrementProposerPriority()
|
|
// 2. let (diff+diffMax-1) not overflow in IncrementPropposerPriotity()
|
|
// (Proof of 1 is tricky, left to the reader).
|
|
// It could be higher, but this is sufficiently large for our purposes,
|
|
// and leaves room for defensive purposes.
|
|
const MaxTotalVotingPower = int64(math.MaxInt64) / 8
|
|
|
|
// ValidatorSet represent a set of *Validator at a given height.
|
|
// The validators can be fetched by address or index.
|
|
// The index is in order of .Address, so the indices are fixed
|
|
// for all rounds of a given blockchain height.
|
|
// On the other hand, the .ProposerPriority of each validator and
|
|
// the designated .GetProposer() of a set changes every round,
|
|
// upon calling .IncrementProposerPriority().
|
|
// NOTE: Not goroutine-safe.
|
|
// NOTE: All get/set to validators should copy the value for safety.
|
|
type ValidatorSet struct {
|
|
// NOTE: persisted via reflect, must be exported.
|
|
Validators []*Validator `json:"validators"`
|
|
Proposer *Validator `json:"proposer"`
|
|
|
|
// cached (unexported)
|
|
totalVotingPower int64
|
|
}
|
|
|
|
// NewValidatorSet initializes a ValidatorSet by copying over the
|
|
// values from `valz`, a list of Validators. If valz is nil or empty,
|
|
// the new ValidatorSet will have an empty list of Validators.
|
|
func NewValidatorSet(valz []*Validator) *ValidatorSet {
|
|
validators := make([]*Validator, len(valz))
|
|
for i, val := range valz {
|
|
validators[i] = val.Copy()
|
|
}
|
|
sort.Sort(ValidatorsByAddress(validators))
|
|
vals := &ValidatorSet{
|
|
Validators: validators,
|
|
}
|
|
if len(valz) > 0 {
|
|
vals.IncrementProposerPriority(1)
|
|
}
|
|
|
|
return vals
|
|
}
|
|
|
|
// Nil or empty validator sets are invalid.
|
|
func (vals *ValidatorSet) IsNilOrEmpty() bool {
|
|
return vals == nil || len(vals.Validators) == 0
|
|
}
|
|
|
|
// Increment ProposerPriority and update the proposer on a copy, and return it.
|
|
func (vals *ValidatorSet) CopyIncrementProposerPriority(times int) *ValidatorSet {
|
|
copy := vals.Copy()
|
|
copy.IncrementProposerPriority(times)
|
|
return copy
|
|
}
|
|
|
|
// IncrementProposerPriority increments ProposerPriority of each validator and updates the
|
|
// proposer. Panics if validator set is empty.
|
|
// `times` must be positive.
|
|
func (vals *ValidatorSet) IncrementProposerPriority(times int) {
|
|
if times <= 0 {
|
|
panic("Cannot call IncrementProposerPriority with non-positive times")
|
|
}
|
|
|
|
// Cap the difference between priorities to be proportional to 2*totalPower by
|
|
// re-normalizing priorities, i.e., rescale all priorities by multiplying with:
|
|
// 2*totalVotingPower/(maxPriority - minPriority)
|
|
diffMax := 2 * vals.TotalVotingPower()
|
|
vals.RescalePriorities(diffMax)
|
|
|
|
var proposer *Validator
|
|
// call IncrementProposerPriority(1) times times:
|
|
for i := 0; i < times; i++ {
|
|
proposer = vals.incrementProposerPriority()
|
|
}
|
|
vals.shiftByAvgProposerPriority()
|
|
|
|
vals.Proposer = proposer
|
|
}
|
|
|
|
func (vals *ValidatorSet) RescalePriorities(diffMax int64) {
|
|
// NOTE: This check is merely a sanity check which could be
|
|
// removed if all tests would init. voting power appropriately;
|
|
// i.e. diffMax should always be > 0
|
|
if diffMax <= 0 {
|
|
return
|
|
}
|
|
|
|
// Caculating ceil(diff/diffMax):
|
|
// Re-normalization is performed by dividing by an integer for simplicity.
|
|
// NOTE: This may make debugging priority issues easier as well.
|
|
diff := computeMaxMinPriorityDiff(vals)
|
|
ratio := (diff + diffMax - 1) / diffMax
|
|
if ratio > 1 {
|
|
for _, val := range vals.Validators {
|
|
val.ProposerPriority /= ratio
|
|
}
|
|
}
|
|
}
|
|
|
|
func (vals *ValidatorSet) incrementProposerPriority() *Validator {
|
|
for _, val := range vals.Validators {
|
|
// Check for overflow for sum.
|
|
newPrio := safeAddClip(val.ProposerPriority, val.VotingPower)
|
|
val.ProposerPriority = newPrio
|
|
}
|
|
// Decrement the validator with most ProposerPriority:
|
|
mostest := vals.getValWithMostPriority()
|
|
// mind underflow
|
|
mostest.ProposerPriority = safeSubClip(mostest.ProposerPriority, vals.TotalVotingPower())
|
|
|
|
return mostest
|
|
}
|
|
|
|
// should not be called on an empty validator set
|
|
func (vals *ValidatorSet) computeAvgProposerPriority() int64 {
|
|
n := int64(len(vals.Validators))
|
|
sum := big.NewInt(0)
|
|
for _, val := range vals.Validators {
|
|
sum.Add(sum, big.NewInt(val.ProposerPriority))
|
|
}
|
|
avg := sum.Div(sum, big.NewInt(n))
|
|
if avg.IsInt64() {
|
|
return avg.Int64()
|
|
}
|
|
|
|
// this should never happen: each val.ProposerPriority is in bounds of int64
|
|
panic(fmt.Sprintf("Cannot represent avg ProposerPriority as an int64 %v", avg))
|
|
}
|
|
|
|
// compute the difference between the max and min ProposerPriority of that set
|
|
func computeMaxMinPriorityDiff(vals *ValidatorSet) int64 {
|
|
max := int64(math.MinInt64)
|
|
min := int64(math.MaxInt64)
|
|
for _, v := range vals.Validators {
|
|
if v.ProposerPriority < min {
|
|
min = v.ProposerPriority
|
|
}
|
|
if v.ProposerPriority > max {
|
|
max = v.ProposerPriority
|
|
}
|
|
}
|
|
diff := max - min
|
|
if diff < 0 {
|
|
return -1 * diff
|
|
} else {
|
|
return diff
|
|
}
|
|
}
|
|
|
|
func (vals *ValidatorSet) getValWithMostPriority() *Validator {
|
|
var res *Validator
|
|
for _, val := range vals.Validators {
|
|
res = res.CompareProposerPriority(val)
|
|
}
|
|
return res
|
|
}
|
|
|
|
func (vals *ValidatorSet) shiftByAvgProposerPriority() {
|
|
avgProposerPriority := vals.computeAvgProposerPriority()
|
|
for _, val := range vals.Validators {
|
|
val.ProposerPriority = safeSubClip(val.ProposerPriority, avgProposerPriority)
|
|
}
|
|
}
|
|
|
|
// Copy each validator into a new ValidatorSet
|
|
func (vals *ValidatorSet) Copy() *ValidatorSet {
|
|
validators := make([]*Validator, len(vals.Validators))
|
|
for i, val := range vals.Validators {
|
|
// NOTE: must copy, since IncrementProposerPriority updates in place.
|
|
validators[i] = val.Copy()
|
|
}
|
|
return &ValidatorSet{
|
|
Validators: validators,
|
|
Proposer: vals.Proposer,
|
|
totalVotingPower: vals.totalVotingPower,
|
|
}
|
|
}
|
|
|
|
// HasAddress returns true if address given is in the validator set, false -
|
|
// otherwise.
|
|
func (vals *ValidatorSet) HasAddress(address []byte) bool {
|
|
idx := sort.Search(len(vals.Validators), func(i int) bool {
|
|
return bytes.Compare(address, vals.Validators[i].Address) <= 0
|
|
})
|
|
return idx < len(vals.Validators) && bytes.Equal(vals.Validators[idx].Address, address)
|
|
}
|
|
|
|
// GetByAddress returns an index of the validator with address and validator
|
|
// itself if found. Otherwise, -1 and nil are returned.
|
|
func (vals *ValidatorSet) GetByAddress(address []byte) (index int, val *Validator) {
|
|
idx := sort.Search(len(vals.Validators), func(i int) bool {
|
|
return bytes.Compare(address, vals.Validators[i].Address) <= 0
|
|
})
|
|
if idx < len(vals.Validators) && bytes.Equal(vals.Validators[idx].Address, address) {
|
|
return idx, vals.Validators[idx].Copy()
|
|
}
|
|
return -1, nil
|
|
}
|
|
|
|
// GetByIndex returns the validator's address and validator itself by index.
|
|
// It returns nil values if index is less than 0 or greater or equal to
|
|
// len(ValidatorSet.Validators).
|
|
func (vals *ValidatorSet) GetByIndex(index int) (address []byte, val *Validator) {
|
|
if index < 0 || index >= len(vals.Validators) {
|
|
return nil, nil
|
|
}
|
|
val = vals.Validators[index]
|
|
return val.Address, val.Copy()
|
|
}
|
|
|
|
// Size returns the length of the validator set.
|
|
func (vals *ValidatorSet) Size() int {
|
|
return len(vals.Validators)
|
|
}
|
|
|
|
// TotalVotingPower returns the sum of the voting powers of all validators.
|
|
func (vals *ValidatorSet) TotalVotingPower() int64 {
|
|
if vals.totalVotingPower == 0 {
|
|
sum := int64(0)
|
|
for _, val := range vals.Validators {
|
|
// mind overflow
|
|
sum = safeAddClip(sum, val.VotingPower)
|
|
}
|
|
if sum > MaxTotalVotingPower {
|
|
panic(fmt.Sprintf(
|
|
"Total voting power should be guarded to not exceed %v; got: %v",
|
|
MaxTotalVotingPower,
|
|
sum))
|
|
}
|
|
vals.totalVotingPower = sum
|
|
}
|
|
return vals.totalVotingPower
|
|
}
|
|
|
|
// GetProposer returns the current proposer. If the validator set is empty, nil
|
|
// is returned.
|
|
func (vals *ValidatorSet) GetProposer() (proposer *Validator) {
|
|
if len(vals.Validators) == 0 {
|
|
return nil
|
|
}
|
|
if vals.Proposer == nil {
|
|
vals.Proposer = vals.findProposer()
|
|
}
|
|
return vals.Proposer.Copy()
|
|
}
|
|
|
|
func (vals *ValidatorSet) findProposer() *Validator {
|
|
var proposer *Validator
|
|
for _, val := range vals.Validators {
|
|
if proposer == nil || !bytes.Equal(val.Address, proposer.Address) {
|
|
proposer = proposer.CompareProposerPriority(val)
|
|
}
|
|
}
|
|
return proposer
|
|
}
|
|
|
|
// Hash returns the Merkle root hash build using validators (as leaves) in the
|
|
// set.
|
|
func (vals *ValidatorSet) Hash() []byte {
|
|
if len(vals.Validators) == 0 {
|
|
return nil
|
|
}
|
|
bzs := make([][]byte, len(vals.Validators))
|
|
for i, val := range vals.Validators {
|
|
bzs[i] = val.Bytes()
|
|
}
|
|
return merkle.SimpleHashFromByteSlices(bzs)
|
|
}
|
|
|
|
// Add adds val to the validator set and returns true. It returns false if val
|
|
// is already in the set.
|
|
func (vals *ValidatorSet) Add(val *Validator) (added bool) {
|
|
val = val.Copy()
|
|
idx := sort.Search(len(vals.Validators), func(i int) bool {
|
|
return bytes.Compare(val.Address, vals.Validators[i].Address) <= 0
|
|
})
|
|
if idx >= len(vals.Validators) {
|
|
vals.Validators = append(vals.Validators, val)
|
|
// Invalidate cache
|
|
vals.Proposer = nil
|
|
vals.totalVotingPower = 0
|
|
return true
|
|
} else if bytes.Equal(vals.Validators[idx].Address, val.Address) {
|
|
return false
|
|
} else {
|
|
newValidators := make([]*Validator, len(vals.Validators)+1)
|
|
copy(newValidators[:idx], vals.Validators[:idx])
|
|
newValidators[idx] = val
|
|
copy(newValidators[idx+1:], vals.Validators[idx:])
|
|
vals.Validators = newValidators
|
|
// Invalidate cache
|
|
vals.Proposer = nil
|
|
vals.totalVotingPower = 0
|
|
return true
|
|
}
|
|
}
|
|
|
|
// Update updates the ValidatorSet by copying in the val.
|
|
// If the val is not found, it returns false; otherwise,
|
|
// it returns true. The val.ProposerPriority field is ignored
|
|
// and unchanged by this method.
|
|
func (vals *ValidatorSet) Update(val *Validator) (updated bool) {
|
|
index, sameVal := vals.GetByAddress(val.Address)
|
|
if sameVal == nil {
|
|
return false
|
|
}
|
|
// Overwrite the ProposerPriority so it doesn't change.
|
|
// During block execution, the val passed in here comes
|
|
// from ABCI via PB2TM.ValidatorUpdates. Since ABCI
|
|
// doesn't know about ProposerPriority, PB2TM.ValidatorUpdates
|
|
// uses the default value of 0, which would cause issues for
|
|
// proposer selection every time a validator's voting power changes.
|
|
val.ProposerPriority = sameVal.ProposerPriority
|
|
vals.Validators[index] = val.Copy()
|
|
// Invalidate cache
|
|
vals.Proposer = nil
|
|
vals.totalVotingPower = 0
|
|
return true
|
|
}
|
|
|
|
// Remove deletes the validator with address. It returns the validator removed
|
|
// and true. If returns nil and false if validator is not present in the set.
|
|
func (vals *ValidatorSet) Remove(address []byte) (val *Validator, removed bool) {
|
|
idx := sort.Search(len(vals.Validators), func(i int) bool {
|
|
return bytes.Compare(address, vals.Validators[i].Address) <= 0
|
|
})
|
|
if idx >= len(vals.Validators) || !bytes.Equal(vals.Validators[idx].Address, address) {
|
|
return nil, false
|
|
}
|
|
removedVal := vals.Validators[idx]
|
|
newValidators := vals.Validators[:idx]
|
|
if idx+1 < len(vals.Validators) {
|
|
newValidators = append(newValidators, vals.Validators[idx+1:]...)
|
|
}
|
|
vals.Validators = newValidators
|
|
// Invalidate cache
|
|
vals.Proposer = nil
|
|
vals.totalVotingPower = 0
|
|
return removedVal, true
|
|
}
|
|
|
|
// Iterate will run the given function over the set.
|
|
func (vals *ValidatorSet) Iterate(fn func(index int, val *Validator) bool) {
|
|
for i, val := range vals.Validators {
|
|
stop := fn(i, val.Copy())
|
|
if stop {
|
|
break
|
|
}
|
|
}
|
|
}
|
|
|
|
// Verify that +2/3 of the set had signed the given signBytes.
|
|
func (vals *ValidatorSet) VerifyCommit(chainID string, blockID BlockID, height int64, commit *Commit) error {
|
|
|
|
if err := commit.ValidateBasic(); err != nil {
|
|
return err
|
|
}
|
|
if vals.Size() != len(commit.Precommits) {
|
|
return fmt.Errorf("Invalid commit -- wrong set size: %v vs %v", vals.Size(), len(commit.Precommits))
|
|
}
|
|
if height != commit.Height() {
|
|
return fmt.Errorf("Invalid commit -- wrong height: %v vs %v", height, commit.Height())
|
|
}
|
|
if !blockID.Equals(commit.BlockID) {
|
|
return fmt.Errorf("Invalid commit -- wrong block id: want %v got %v",
|
|
blockID, commit.BlockID)
|
|
}
|
|
|
|
talliedVotingPower := int64(0)
|
|
|
|
for idx, precommit := range commit.Precommits {
|
|
if precommit == nil {
|
|
continue // OK, some precommits can be missing.
|
|
}
|
|
_, val := vals.GetByIndex(idx)
|
|
// Validate signature.
|
|
precommitSignBytes := commit.VoteSignBytes(chainID, precommit)
|
|
if !val.PubKey.VerifyBytes(precommitSignBytes, precommit.Signature) {
|
|
return fmt.Errorf("Invalid commit -- invalid signature: %v", precommit)
|
|
}
|
|
// Good precommit!
|
|
if blockID.Equals(precommit.BlockID) {
|
|
talliedVotingPower += val.VotingPower
|
|
} else {
|
|
// It's OK that the BlockID doesn't match. We include stray
|
|
// precommits to measure validator availability.
|
|
}
|
|
}
|
|
|
|
if talliedVotingPower > vals.TotalVotingPower()*2/3 {
|
|
return nil
|
|
}
|
|
return errTooMuchChange{talliedVotingPower, vals.TotalVotingPower()*2/3 + 1}
|
|
}
|
|
|
|
// VerifyFutureCommit will check to see if the set would be valid with a different
|
|
// validator set.
|
|
//
|
|
// vals is the old validator set that we know. Over 2/3 of the power in old
|
|
// signed this block.
|
|
//
|
|
// In Tendermint, 1/3 of the voting power can halt or fork the chain, but 1/3
|
|
// can't make arbitrary state transitions. You still need > 2/3 Byzantine to
|
|
// make arbitrary state transitions.
|
|
//
|
|
// To preserve this property in the light client, we also require > 2/3 of the
|
|
// old vals to sign the future commit at H, that way we preserve the property
|
|
// that if they weren't being truthful about the validator set at H (block hash
|
|
// -> vals hash) or about the app state (block hash -> app hash) we can slash
|
|
// > 2/3. Otherwise, the lite client isn't providing the same security
|
|
// guarantees.
|
|
//
|
|
// Even if we added a slashing condition that if you sign a block header with
|
|
// the wrong validator set, then we would only need > 1/3 of signatures from
|
|
// the old vals on the new commit, it wouldn't be sufficient because the new
|
|
// vals can be arbitrary and commit some arbitrary app hash.
|
|
//
|
|
// newSet is the validator set that signed this block. Only votes from new are
|
|
// sufficient for 2/3 majority in the new set as well, for it to be a valid
|
|
// commit.
|
|
//
|
|
// NOTE: This doesn't check whether the commit is a future commit, because the
|
|
// current height isn't part of the ValidatorSet. Caller must check that the
|
|
// commit height is greater than the height for this validator set.
|
|
func (vals *ValidatorSet) VerifyFutureCommit(newSet *ValidatorSet, chainID string,
|
|
blockID BlockID, height int64, commit *Commit) error {
|
|
oldVals := vals
|
|
|
|
// Commit must be a valid commit for newSet.
|
|
err := newSet.VerifyCommit(chainID, blockID, height, commit)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
|
|
// Check old voting power.
|
|
oldVotingPower := int64(0)
|
|
seen := map[int]bool{}
|
|
round := commit.Round()
|
|
|
|
for idx, precommit := range commit.Precommits {
|
|
if precommit == nil {
|
|
continue
|
|
}
|
|
if precommit.Height != height {
|
|
return cmn.NewError("Blocks don't match - %d vs %d", round, precommit.Round)
|
|
}
|
|
if precommit.Round != round {
|
|
return cmn.NewError("Invalid commit -- wrong round: %v vs %v", round, precommit.Round)
|
|
}
|
|
if precommit.Type != PrecommitType {
|
|
return cmn.NewError("Invalid commit -- not precommit @ index %v", idx)
|
|
}
|
|
// See if this validator is in oldVals.
|
|
idx, val := oldVals.GetByAddress(precommit.ValidatorAddress)
|
|
if val == nil || seen[idx] {
|
|
continue // missing or double vote...
|
|
}
|
|
seen[idx] = true
|
|
|
|
// Validate signature.
|
|
precommitSignBytes := commit.VoteSignBytes(chainID, precommit)
|
|
if !val.PubKey.VerifyBytes(precommitSignBytes, precommit.Signature) {
|
|
return cmn.NewError("Invalid commit -- invalid signature: %v", precommit)
|
|
}
|
|
// Good precommit!
|
|
if blockID.Equals(precommit.BlockID) {
|
|
oldVotingPower += val.VotingPower
|
|
} else {
|
|
// It's OK that the BlockID doesn't match. We include stray
|
|
// precommits to measure validator availability.
|
|
}
|
|
}
|
|
|
|
if oldVotingPower <= oldVals.TotalVotingPower()*2/3 {
|
|
return errTooMuchChange{oldVotingPower, oldVals.TotalVotingPower()*2/3 + 1}
|
|
}
|
|
return nil
|
|
}
|
|
|
|
//-----------------
|
|
// ErrTooMuchChange
|
|
|
|
func IsErrTooMuchChange(err error) bool {
|
|
switch err_ := err.(type) {
|
|
case cmn.Error:
|
|
_, ok := err_.Data().(errTooMuchChange)
|
|
return ok
|
|
case errTooMuchChange:
|
|
return true
|
|
default:
|
|
return false
|
|
}
|
|
}
|
|
|
|
type errTooMuchChange struct {
|
|
got int64
|
|
needed int64
|
|
}
|
|
|
|
func (e errTooMuchChange) Error() string {
|
|
return fmt.Sprintf("Invalid commit -- insufficient old voting power: got %v, needed %v", e.got, e.needed)
|
|
}
|
|
|
|
//----------------
|
|
|
|
func (vals *ValidatorSet) String() string {
|
|
return vals.StringIndented("")
|
|
}
|
|
|
|
// String
|
|
func (vals *ValidatorSet) StringIndented(indent string) string {
|
|
if vals == nil {
|
|
return "nil-ValidatorSet"
|
|
}
|
|
var valStrings []string
|
|
vals.Iterate(func(index int, val *Validator) bool {
|
|
valStrings = append(valStrings, val.String())
|
|
return false
|
|
})
|
|
return fmt.Sprintf(`ValidatorSet{
|
|
%s Proposer: %v
|
|
%s Validators:
|
|
%s %v
|
|
%s}`,
|
|
indent, vals.GetProposer().String(),
|
|
indent,
|
|
indent, strings.Join(valStrings, "\n"+indent+" "),
|
|
indent)
|
|
|
|
}
|
|
|
|
//-------------------------------------
|
|
// Implements sort for sorting validators by address.
|
|
|
|
// Sort validators by address
|
|
type ValidatorsByAddress []*Validator
|
|
|
|
func (valz ValidatorsByAddress) Len() int {
|
|
return len(valz)
|
|
}
|
|
|
|
func (valz ValidatorsByAddress) Less(i, j int) bool {
|
|
return bytes.Compare(valz[i].Address, valz[j].Address) == -1
|
|
}
|
|
|
|
func (valz ValidatorsByAddress) Swap(i, j int) {
|
|
it := valz[i]
|
|
valz[i] = valz[j]
|
|
valz[j] = it
|
|
}
|
|
|
|
//----------------------------------------
|
|
// For testing
|
|
|
|
// RandValidatorSet returns a randomized validator set, useful for testing.
|
|
// NOTE: PrivValidator are in order.
|
|
// UNSTABLE
|
|
func RandValidatorSet(numValidators int, votingPower int64) (*ValidatorSet, []PrivValidator) {
|
|
valz := make([]*Validator, numValidators)
|
|
privValidators := make([]PrivValidator, numValidators)
|
|
for i := 0; i < numValidators; i++ {
|
|
val, privValidator := RandValidator(false, votingPower)
|
|
valz[i] = val
|
|
privValidators[i] = privValidator
|
|
}
|
|
vals := NewValidatorSet(valz)
|
|
sort.Sort(PrivValidatorsByAddress(privValidators))
|
|
return vals, privValidators
|
|
}
|
|
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
// Safe addition/subtraction
|
|
|
|
func safeAdd(a, b int64) (int64, bool) {
|
|
if b > 0 && a > math.MaxInt64-b {
|
|
return -1, true
|
|
} else if b < 0 && a < math.MinInt64-b {
|
|
return -1, true
|
|
}
|
|
return a + b, false
|
|
}
|
|
|
|
func safeSub(a, b int64) (int64, bool) {
|
|
if b > 0 && a < math.MinInt64+b {
|
|
return -1, true
|
|
} else if b < 0 && a > math.MaxInt64+b {
|
|
return -1, true
|
|
}
|
|
return a - b, false
|
|
}
|
|
|
|
func safeAddClip(a, b int64) int64 {
|
|
c, overflow := safeAdd(a, b)
|
|
if overflow {
|
|
if b < 0 {
|
|
return math.MinInt64
|
|
}
|
|
return math.MaxInt64
|
|
}
|
|
return c
|
|
}
|
|
|
|
func safeSubClip(a, b int64) int64 {
|
|
c, overflow := safeSub(a, b)
|
|
if overflow {
|
|
if b > 0 {
|
|
return math.MinInt64
|
|
}
|
|
return math.MaxInt64
|
|
}
|
|
return c
|
|
}
|