You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
605 lines
17 KiB
605 lines
17 KiB
package rpc
|
|
|
|
import (
|
|
"bytes"
|
|
"context"
|
|
"errors"
|
|
"fmt"
|
|
"time"
|
|
|
|
"github.com/gogo/protobuf/proto"
|
|
|
|
abci "github.com/tendermint/tendermint/abci/types"
|
|
"github.com/tendermint/tendermint/crypto/merkle"
|
|
tmbytes "github.com/tendermint/tendermint/libs/bytes"
|
|
tmmath "github.com/tendermint/tendermint/libs/math"
|
|
service "github.com/tendermint/tendermint/libs/service"
|
|
rpcclient "github.com/tendermint/tendermint/rpc/client"
|
|
ctypes "github.com/tendermint/tendermint/rpc/core/types"
|
|
rpctypes "github.com/tendermint/tendermint/rpc/jsonrpc/types"
|
|
"github.com/tendermint/tendermint/types"
|
|
)
|
|
|
|
var errNegOrZeroHeight = errors.New("negative or zero height")
|
|
|
|
// KeyPathFunc builds a merkle path out of the given path and key.
|
|
type KeyPathFunc func(path string, key []byte) (merkle.KeyPath, error)
|
|
|
|
// LightClient is an interface that contains functionality needed by Client from the light client.
|
|
type LightClient interface {
|
|
ChainID() string
|
|
VerifyLightBlockAtHeight(ctx context.Context, height int64, now time.Time) (*types.LightBlock, error)
|
|
TrustedLightBlock(height int64) (*types.LightBlock, error)
|
|
}
|
|
|
|
// Client is an RPC client, which uses light#Client to verify data (if it can
|
|
// be proved!). merkle.DefaultProofRuntime is used to verify values returned by
|
|
// ABCIQuery.
|
|
type Client struct {
|
|
service.BaseService
|
|
|
|
next rpcclient.Client
|
|
lc LightClient
|
|
// Proof runtime used to verify values returned by ABCIQuery
|
|
prt *merkle.ProofRuntime
|
|
keyPathFn KeyPathFunc
|
|
}
|
|
|
|
var _ rpcclient.Client = (*Client)(nil)
|
|
|
|
// Option allow you to tweak Client.
|
|
type Option func(*Client)
|
|
|
|
// KeyPathFn option can be used to set a function, which parses a given path
|
|
// and builds the merkle path for the prover. It must be provided if you want
|
|
// to call ABCIQuery or ABCIQueryWithOptions.
|
|
func KeyPathFn(fn KeyPathFunc) Option {
|
|
return func(c *Client) {
|
|
c.keyPathFn = fn
|
|
}
|
|
}
|
|
|
|
// NewClient returns a new client.
|
|
func NewClient(next rpcclient.Client, lc LightClient, opts ...Option) *Client {
|
|
c := &Client{
|
|
next: next,
|
|
lc: lc,
|
|
prt: merkle.DefaultProofRuntime(),
|
|
}
|
|
c.BaseService = *service.NewBaseService(nil, "Client", c)
|
|
for _, o := range opts {
|
|
o(c)
|
|
}
|
|
return c
|
|
}
|
|
|
|
func (c *Client) OnStart() error {
|
|
if !c.next.IsRunning() {
|
|
return c.next.Start()
|
|
}
|
|
return nil
|
|
}
|
|
|
|
func (c *Client) OnStop() {
|
|
if c.next.IsRunning() {
|
|
if err := c.next.Stop(); err != nil {
|
|
c.Logger.Error("Error stopping on next", "err", err)
|
|
}
|
|
}
|
|
}
|
|
|
|
func (c *Client) Status(ctx context.Context) (*ctypes.ResultStatus, error) {
|
|
return c.next.Status(ctx)
|
|
}
|
|
|
|
func (c *Client) ABCIInfo(ctx context.Context) (*ctypes.ResultABCIInfo, error) {
|
|
return c.next.ABCIInfo(ctx)
|
|
}
|
|
|
|
// ABCIQuery requests proof by default.
|
|
func (c *Client) ABCIQuery(ctx context.Context, path string, data tmbytes.HexBytes) (*ctypes.ResultABCIQuery, error) {
|
|
return c.ABCIQueryWithOptions(ctx, path, data, rpcclient.DefaultABCIQueryOptions)
|
|
}
|
|
|
|
// ABCIQueryWithOptions returns an error if opts.Prove is false.
|
|
func (c *Client) ABCIQueryWithOptions(ctx context.Context, path string, data tmbytes.HexBytes,
|
|
opts rpcclient.ABCIQueryOptions) (*ctypes.ResultABCIQuery, error) {
|
|
|
|
// always request the proof
|
|
opts.Prove = true
|
|
|
|
res, err := c.next.ABCIQueryWithOptions(ctx, path, data, opts)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
resp := res.Response
|
|
|
|
// Validate the response.
|
|
if resp.IsErr() {
|
|
return nil, fmt.Errorf("err response code: %v", resp.Code)
|
|
}
|
|
if len(resp.Key) == 0 {
|
|
return nil, errors.New("empty key")
|
|
}
|
|
if resp.ProofOps == nil || len(resp.ProofOps.Ops) == 0 {
|
|
return nil, errors.New("no proof ops")
|
|
}
|
|
if resp.Height <= 0 {
|
|
return nil, errNegOrZeroHeight
|
|
}
|
|
|
|
// Update the light client if we're behind.
|
|
// NOTE: AppHash for height H is in header H+1.
|
|
l, err := c.updateLightClientIfNeededTo(ctx, resp.Height+1)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// Validate the value proof against the trusted header.
|
|
if resp.Value != nil {
|
|
// 1) build a Merkle key path from path and resp.Key
|
|
if c.keyPathFn == nil {
|
|
return nil, errors.New("please configure Client with KeyPathFn option")
|
|
}
|
|
|
|
kp, err := c.keyPathFn(path, resp.Key)
|
|
if err != nil {
|
|
return nil, fmt.Errorf("can't build merkle key path: %w", err)
|
|
}
|
|
|
|
// 2) verify value
|
|
err = c.prt.VerifyValue(resp.ProofOps, l.AppHash, kp.String(), resp.Value)
|
|
if err != nil {
|
|
return nil, fmt.Errorf("verify value proof: %w", err)
|
|
}
|
|
} else { // OR validate the absence proof against the trusted header.
|
|
err = c.prt.VerifyAbsence(resp.ProofOps, l.AppHash, string(resp.Key))
|
|
if err != nil {
|
|
return nil, fmt.Errorf("verify absence proof: %w", err)
|
|
}
|
|
}
|
|
|
|
return &ctypes.ResultABCIQuery{Response: resp}, nil
|
|
}
|
|
|
|
func (c *Client) BroadcastTxCommit(ctx context.Context, tx types.Tx) (*ctypes.ResultBroadcastTxCommit, error) {
|
|
return c.next.BroadcastTxCommit(ctx, tx)
|
|
}
|
|
|
|
func (c *Client) BroadcastTxAsync(ctx context.Context, tx types.Tx) (*ctypes.ResultBroadcastTx, error) {
|
|
return c.next.BroadcastTxAsync(ctx, tx)
|
|
}
|
|
|
|
func (c *Client) BroadcastTxSync(ctx context.Context, tx types.Tx) (*ctypes.ResultBroadcastTx, error) {
|
|
return c.next.BroadcastTxSync(ctx, tx)
|
|
}
|
|
|
|
func (c *Client) UnconfirmedTxs(ctx context.Context, limit *int) (*ctypes.ResultUnconfirmedTxs, error) {
|
|
return c.next.UnconfirmedTxs(ctx, limit)
|
|
}
|
|
|
|
func (c *Client) NumUnconfirmedTxs(ctx context.Context) (*ctypes.ResultUnconfirmedTxs, error) {
|
|
return c.next.NumUnconfirmedTxs(ctx)
|
|
}
|
|
|
|
func (c *Client) CheckTx(ctx context.Context, tx types.Tx) (*ctypes.ResultCheckTx, error) {
|
|
return c.next.CheckTx(ctx, tx)
|
|
}
|
|
|
|
func (c *Client) NetInfo(ctx context.Context) (*ctypes.ResultNetInfo, error) {
|
|
return c.next.NetInfo(ctx)
|
|
}
|
|
|
|
func (c *Client) DumpConsensusState(ctx context.Context) (*ctypes.ResultDumpConsensusState, error) {
|
|
return c.next.DumpConsensusState(ctx)
|
|
}
|
|
|
|
func (c *Client) ConsensusState(ctx context.Context) (*ctypes.ResultConsensusState, error) {
|
|
return c.next.ConsensusState(ctx)
|
|
}
|
|
|
|
func (c *Client) ConsensusParams(ctx context.Context, height *int64) (*ctypes.ResultConsensusParams, error) {
|
|
res, err := c.next.ConsensusParams(ctx, height)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// Validate res.
|
|
if err := types.ValidateConsensusParams(res.ConsensusParams); err != nil {
|
|
return nil, err
|
|
}
|
|
if res.BlockHeight <= 0 {
|
|
return nil, errNegOrZeroHeight
|
|
}
|
|
|
|
// Update the light client if we're behind.
|
|
l, err := c.updateLightClientIfNeededTo(ctx, res.BlockHeight)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// Verify hash.
|
|
if cH, tH := types.HashConsensusParams(res.ConsensusParams), l.ConsensusHash; !bytes.Equal(cH, tH) {
|
|
return nil, fmt.Errorf("params hash %X does not match trusted hash %X",
|
|
cH, tH)
|
|
}
|
|
|
|
return res, nil
|
|
}
|
|
|
|
func (c *Client) Health(ctx context.Context) (*ctypes.ResultHealth, error) {
|
|
return c.next.Health(ctx)
|
|
}
|
|
|
|
// BlockchainInfo calls rpcclient#BlockchainInfo and then verifies every header
|
|
// returned.
|
|
func (c *Client) BlockchainInfo(ctx context.Context, minHeight, maxHeight int64) (*ctypes.ResultBlockchainInfo, error) {
|
|
res, err := c.next.BlockchainInfo(ctx, minHeight, maxHeight)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// Validate res.
|
|
for i, meta := range res.BlockMetas {
|
|
if meta == nil {
|
|
return nil, fmt.Errorf("nil block meta %d", i)
|
|
}
|
|
if err := meta.ValidateBasic(); err != nil {
|
|
return nil, fmt.Errorf("invalid block meta %d: %w", i, err)
|
|
}
|
|
}
|
|
|
|
// Update the light client if we're behind.
|
|
if len(res.BlockMetas) > 0 {
|
|
lastHeight := res.BlockMetas[len(res.BlockMetas)-1].Header.Height
|
|
if _, err := c.updateLightClientIfNeededTo(ctx, lastHeight); err != nil {
|
|
return nil, err
|
|
}
|
|
}
|
|
|
|
// Verify each of the BlockMetas.
|
|
for _, meta := range res.BlockMetas {
|
|
h, err := c.lc.TrustedLightBlock(meta.Header.Height)
|
|
if err != nil {
|
|
return nil, fmt.Errorf("trusted header %d: %w", meta.Header.Height, err)
|
|
}
|
|
if bmH, tH := meta.Header.Hash(), h.Hash(); !bytes.Equal(bmH, tH) {
|
|
return nil, fmt.Errorf("block meta header %X does not match with trusted header %X",
|
|
bmH, tH)
|
|
}
|
|
}
|
|
|
|
return res, nil
|
|
}
|
|
|
|
func (c *Client) Genesis(ctx context.Context) (*ctypes.ResultGenesis, error) {
|
|
return c.next.Genesis(ctx)
|
|
}
|
|
|
|
// Block calls rpcclient#Block and then verifies the result.
|
|
func (c *Client) Block(ctx context.Context, height *int64) (*ctypes.ResultBlock, error) {
|
|
res, err := c.next.Block(ctx, height)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// Validate res.
|
|
if err := res.BlockID.ValidateBasic(); err != nil {
|
|
return nil, err
|
|
}
|
|
if err := res.Block.ValidateBasic(); err != nil {
|
|
return nil, err
|
|
}
|
|
if bmH, bH := res.BlockID.Hash, res.Block.Hash(); !bytes.Equal(bmH, bH) {
|
|
return nil, fmt.Errorf("blockID %X does not match with block %X",
|
|
bmH, bH)
|
|
}
|
|
|
|
// Update the light client if we're behind.
|
|
l, err := c.updateLightClientIfNeededTo(ctx, res.Block.Height)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// Verify block.
|
|
if bH, tH := res.Block.Hash(), l.Hash(); !bytes.Equal(bH, tH) {
|
|
return nil, fmt.Errorf("block header %X does not match with trusted header %X",
|
|
bH, tH)
|
|
}
|
|
|
|
return res, nil
|
|
}
|
|
|
|
// BlockByHash calls rpcclient#BlockByHash and then verifies the result.
|
|
func (c *Client) BlockByHash(ctx context.Context, hash []byte) (*ctypes.ResultBlock, error) {
|
|
res, err := c.next.BlockByHash(ctx, hash)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// Validate res.
|
|
if err := res.BlockID.ValidateBasic(); err != nil {
|
|
return nil, err
|
|
}
|
|
if err := res.Block.ValidateBasic(); err != nil {
|
|
return nil, err
|
|
}
|
|
if bmH, bH := res.BlockID.Hash, res.Block.Hash(); !bytes.Equal(bmH, bH) {
|
|
return nil, fmt.Errorf("blockID %X does not match with block %X",
|
|
bmH, bH)
|
|
}
|
|
|
|
// Update the light client if we're behind.
|
|
l, err := c.updateLightClientIfNeededTo(ctx, res.Block.Height)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// Verify block.
|
|
if bH, tH := res.Block.Hash(), l.Hash(); !bytes.Equal(bH, tH) {
|
|
return nil, fmt.Errorf("block header %X does not match with trusted header %X",
|
|
bH, tH)
|
|
}
|
|
|
|
return res, nil
|
|
}
|
|
|
|
// BlockResults returns the block results for the given height. If no height is
|
|
// provided, the results of the block preceding the latest are returned.
|
|
func (c *Client) BlockResults(ctx context.Context, height *int64) (*ctypes.ResultBlockResults, error) {
|
|
var h int64
|
|
if height == nil {
|
|
res, err := c.next.Status(ctx)
|
|
if err != nil {
|
|
return nil, fmt.Errorf("can't get latest height: %w", err)
|
|
}
|
|
// Can't return the latest block results here because we won't be able to
|
|
// prove them. Return the results for the previous block instead.
|
|
h = res.SyncInfo.LatestBlockHeight - 1
|
|
} else {
|
|
h = *height
|
|
}
|
|
|
|
res, err := c.next.BlockResults(ctx, &h)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// Validate res.
|
|
if res.Height <= 0 {
|
|
return nil, errNegOrZeroHeight
|
|
}
|
|
|
|
// Update the light client if we're behind.
|
|
trustedBlock, err := c.updateLightClientIfNeededTo(ctx, h+1)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// proto-encode BeginBlock events
|
|
bbeBytes, err := proto.Marshal(&abci.ResponseBeginBlock{
|
|
Events: res.BeginBlockEvents,
|
|
})
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// Build a Merkle tree of proto-encoded DeliverTx results and get a hash.
|
|
results := types.NewResults(res.TxsResults)
|
|
|
|
// proto-encode EndBlock events.
|
|
ebeBytes, err := proto.Marshal(&abci.ResponseEndBlock{
|
|
Events: res.EndBlockEvents,
|
|
})
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// Build a Merkle tree out of the above 3 binary slices.
|
|
rH := merkle.HashFromByteSlices([][]byte{bbeBytes, results.Hash(), ebeBytes})
|
|
|
|
// Verify block results.
|
|
if !bytes.Equal(rH, trustedBlock.LastResultsHash) {
|
|
return nil, fmt.Errorf("last results %X does not match with trusted last results %X",
|
|
rH, trustedBlock.LastResultsHash)
|
|
}
|
|
|
|
return res, nil
|
|
}
|
|
|
|
func (c *Client) Commit(ctx context.Context, height *int64) (*ctypes.ResultCommit, error) {
|
|
// Update the light client if we're behind and retrieve the light block at the requested height
|
|
l, err := c.updateLightClientIfNeededTo(ctx, *height)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
return &ctypes.ResultCommit{
|
|
SignedHeader: *l.SignedHeader,
|
|
CanonicalCommit: true,
|
|
}, nil
|
|
}
|
|
|
|
// Tx calls rpcclient#Tx method and then verifies the proof if such was
|
|
// requested.
|
|
func (c *Client) Tx(ctx context.Context, hash []byte, prove bool) (*ctypes.ResultTx, error) {
|
|
res, err := c.next.Tx(ctx, hash, prove)
|
|
if err != nil || !prove {
|
|
return res, err
|
|
}
|
|
|
|
// Validate res.
|
|
if res.Height <= 0 {
|
|
return nil, errNegOrZeroHeight
|
|
}
|
|
|
|
// Update the light client if we're behind.
|
|
l, err := c.updateLightClientIfNeededTo(ctx, res.Height)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// Validate the proof.
|
|
return res, res.Proof.Validate(l.DataHash)
|
|
}
|
|
|
|
func (c *Client) TxSearch(ctx context.Context, query string, prove bool, page, perPage *int, orderBy string) (
|
|
*ctypes.ResultTxSearch, error) {
|
|
return c.next.TxSearch(ctx, query, prove, page, perPage, orderBy)
|
|
}
|
|
|
|
// Validators fetches and verifies validators.
|
|
func (c *Client) Validators(ctx context.Context, height *int64, pagePtr, perPagePtr *int) (*ctypes.ResultValidators,
|
|
error) {
|
|
// Update the light client if we're behind and retrieve the light block at the requested height.
|
|
l, err := c.updateLightClientIfNeededTo(ctx, *height)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
totalCount := len(l.ValidatorSet.Validators)
|
|
perPage := validatePerPage(perPagePtr)
|
|
page, err := validatePage(pagePtr, perPage, totalCount)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
skipCount := validateSkipCount(page, perPage)
|
|
|
|
v := l.ValidatorSet.Validators[skipCount : skipCount+tmmath.MinInt(perPage, totalCount-skipCount)]
|
|
|
|
return &ctypes.ResultValidators{
|
|
BlockHeight: *height,
|
|
Validators: v,
|
|
Count: len(v),
|
|
Total: totalCount}, nil
|
|
}
|
|
|
|
func (c *Client) BroadcastEvidence(ctx context.Context, ev types.Evidence) (*ctypes.ResultBroadcastEvidence, error) {
|
|
return c.next.BroadcastEvidence(ctx, ev)
|
|
}
|
|
|
|
func (c *Client) Subscribe(ctx context.Context, subscriber, query string,
|
|
outCapacity ...int) (out <-chan ctypes.ResultEvent, err error) {
|
|
return c.next.Subscribe(ctx, subscriber, query, outCapacity...)
|
|
}
|
|
|
|
func (c *Client) Unsubscribe(ctx context.Context, subscriber, query string) error {
|
|
return c.next.Unsubscribe(ctx, subscriber, query)
|
|
}
|
|
|
|
func (c *Client) UnsubscribeAll(ctx context.Context, subscriber string) error {
|
|
return c.next.UnsubscribeAll(ctx, subscriber)
|
|
}
|
|
|
|
func (c *Client) updateLightClientIfNeededTo(ctx context.Context, height int64) (*types.LightBlock, error) {
|
|
l, err := c.lc.VerifyLightBlockAtHeight(ctx, height, time.Now())
|
|
if err != nil {
|
|
return nil, fmt.Errorf("failed to update light client to %d: %w", height, err)
|
|
}
|
|
return l, nil
|
|
}
|
|
|
|
func (c *Client) RegisterOpDecoder(typ string, dec merkle.OpDecoder) {
|
|
c.prt.RegisterOpDecoder(typ, dec)
|
|
}
|
|
|
|
// SubscribeWS subscribes for events using the given query and remote address as
|
|
// a subscriber, but does not verify responses (UNSAFE)!
|
|
// TODO: verify data
|
|
func (c *Client) SubscribeWS(ctx *rpctypes.Context, query string) (*ctypes.ResultSubscribe, error) {
|
|
out, err := c.next.Subscribe(context.Background(), ctx.RemoteAddr(), query)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
go func() {
|
|
for {
|
|
select {
|
|
case resultEvent := <-out:
|
|
// We should have a switch here that performs a validation
|
|
// depending on the event's type.
|
|
ctx.WSConn.TryWriteRPCResponse(
|
|
rpctypes.NewRPCSuccessResponse(
|
|
rpctypes.JSONRPCStringID(fmt.Sprintf("%v#event", ctx.JSONReq.ID)),
|
|
resultEvent,
|
|
))
|
|
case <-c.Quit():
|
|
return
|
|
}
|
|
}
|
|
}()
|
|
|
|
return &ctypes.ResultSubscribe{}, nil
|
|
}
|
|
|
|
// UnsubscribeWS calls original client's Unsubscribe using remote address as a
|
|
// subscriber.
|
|
func (c *Client) UnsubscribeWS(ctx *rpctypes.Context, query string) (*ctypes.ResultUnsubscribe, error) {
|
|
err := c.next.Unsubscribe(context.Background(), ctx.RemoteAddr(), query)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
return &ctypes.ResultUnsubscribe{}, nil
|
|
}
|
|
|
|
// UnsubscribeAllWS calls original client's UnsubscribeAll using remote address
|
|
// as a subscriber.
|
|
func (c *Client) UnsubscribeAllWS(ctx *rpctypes.Context) (*ctypes.ResultUnsubscribe, error) {
|
|
err := c.next.UnsubscribeAll(context.Background(), ctx.RemoteAddr())
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
return &ctypes.ResultUnsubscribe{}, nil
|
|
}
|
|
|
|
// XXX: Copied from rpc/core/env.go
|
|
const (
|
|
// see README
|
|
defaultPerPage = 30
|
|
maxPerPage = 100
|
|
)
|
|
|
|
func validatePage(pagePtr *int, perPage, totalCount int) (int, error) {
|
|
if perPage < 1 {
|
|
panic(fmt.Sprintf("zero or negative perPage: %d", perPage))
|
|
}
|
|
|
|
if pagePtr == nil { // no page parameter
|
|
return 1, nil
|
|
}
|
|
|
|
pages := ((totalCount - 1) / perPage) + 1
|
|
if pages == 0 {
|
|
pages = 1 // one page (even if it's empty)
|
|
}
|
|
page := *pagePtr
|
|
if page <= 0 || page > pages {
|
|
return 1, fmt.Errorf("page should be within [1, %d] range, given %d", pages, page)
|
|
}
|
|
|
|
return page, nil
|
|
}
|
|
|
|
func validatePerPage(perPagePtr *int) int {
|
|
if perPagePtr == nil { // no per_page parameter
|
|
return defaultPerPage
|
|
}
|
|
|
|
perPage := *perPagePtr
|
|
if perPage < 1 {
|
|
return defaultPerPage
|
|
} else if perPage > maxPerPage {
|
|
return maxPerPage
|
|
}
|
|
return perPage
|
|
}
|
|
|
|
func validateSkipCount(page, perPage int) int {
|
|
skipCount := (page - 1) * perPage
|
|
if skipCount < 0 {
|
|
return 0
|
|
}
|
|
|
|
return skipCount
|
|
}
|