blockchain: Return uint256 from chain work method.

This modifies the method that returns the total cumulative work for a
given block to return a more efficient uint256 instead of a big integer
and updates all consumers accordingly.

internal/blockchain/chain.go

@@ -11,7 +11,6 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"math/big"
 	"sync"
 	"time"
 
@@ -463,13 +462,13 @@ func (b *BlockChain) HaveBlock(hash *chainhash.Hash) bool {
 
 // ChainWork returns the total work up to and including the block of the
 // provided block hash.
-func (b *BlockChain) ChainWork(hash *chainhash.Hash) (*big.Int, error) {
+func (b *BlockChain) ChainWork(hash *chainhash.Hash) (uint256.Uint256, error) {
 	node := b.index.LookupNode(hash)
 	if node == nil {
-		return nil, unknownBlockError(hash)
+		return uint256.Uint256{}, unknownBlockError(hash)
 	}
 
-	return node.workSum.ToBig(), nil
+	return node.workSum, nil
 }
 
 // TipGeneration returns the entire generation of blocks stemming from the

internal/netsync/manager.go

@@ -23,6 +23,7 @@ import (
 	"github.com/decred/dcrd/internal/blockchain"
 	"github.com/decred/dcrd/internal/mempool"
 	"github.com/decred/dcrd/internal/progresslog"
+	"github.com/decred/dcrd/math/uint256"
 	peerpkg "github.com/decred/dcrd/peer/v3"
 	"github.com/decred/dcrd/wire"
 )
@@ -272,6 +273,14 @@ type SyncManager struct {
 	// creation time and treated as immutable after that.
 	cfg Config
 
+	// minKnownWork houses the minimum known work from the associated network
+	// params converted to a uint256 so the conversion only needs to be
+	// performed once when the sync manager is initialized.  Ideally, the chain
+	// params should be updated to use the new type, but that will be a major
+	// version bump, so a one-time conversion is a good tradeoff in the mean
+	// time.
+	minKnownWork *uint256.Uint256
+
 	rejectedTxns    *apbf.Filter
 	requestedTxns   map[chainhash.Hash]struct{}
 	requestedBlocks map[chainhash.Hash]struct{}
@@ -1094,10 +1103,9 @@ func (m *SyncManager) handleHeadersMsg(hmsg *headersMsg) {
 	isChainCurrent := chain.IsCurrent()
 	receivedMaxHeaders := len(headers) == wire.MaxBlockHeadersPerMsg
 	if !isChainCurrent && !peer.Inbound() && !receivedMaxHeaders {
-		minKnownWork := m.cfg.ChainParams.MinKnownChainWork
-		if minKnownWork != nil {
+		if m.minKnownWork != nil {
 			workSum, err := chain.ChainWork(finalReceivedHash)
-			if err == nil && workSum.Cmp(minKnownWork) < 0 {
+			if err == nil && workSum.Lt(m.minKnownWork) {
 				log.Debugf("Best known chain for peer %s has too little "+
 					"cumulative work -- disconnecting", peer)
 				peer.Disconnect()
@@ -1771,12 +1779,23 @@ type Config struct {
 // New returns a new network chain synchronization manager.  Use Run to begin
 // processing asynchronous events.
 func New(config *Config) *SyncManager {
+	// Convert the minimum known work to a uint256 when it exists.  Ideally, the
+	// chain params should be updated to use the new type, but that will be a
+	// major version bump, so a one-time conversion is a good tradeoff in the
+	// mean time.
+	var minKnownWork *uint256.Uint256
+	minKnownWorkBig := config.ChainParams.MinKnownChainWork
+	if minKnownWorkBig != nil {
+		minKnownWork = new(uint256.Uint256).SetBig(minKnownWorkBig)
+	}
+
 	return &SyncManager{
 		cfg:             *config,
 		rejectedTxns:    apbf.NewFilter(maxRejectedTxns, rejectedTxnsFPRate),
 		requestedTxns:   make(map[chainhash.Hash]struct{}),
 		requestedBlocks: make(map[chainhash.Hash]struct{}),
 		peers:           make(map[*peerpkg.Peer]*syncMgrPeer),
+		minKnownWork:    minKnownWork,
 		hdrSyncState:    makeHeaderSyncState(),
 		progressLogger:  progresslog.New("Processed", log),
 		msgChan:         make(chan interface{}, config.MaxPeers*3),

internal/rpcserver/interface.go

@@ -6,7 +6,6 @@ package rpcserver
 
 import (
 	"context"
-	"math/big"
 	"net"
 	"time"
 
@@ -19,6 +18,7 @@ import (
 	"github.com/decred/dcrd/internal/blockchain/indexers"
 	"github.com/decred/dcrd/internal/mempool"
 	"github.com/decred/dcrd/internal/mining"
+	"github.com/decred/dcrd/math/uint256"
 	"github.com/decred/dcrd/peer/v3"
 	"github.com/decred/dcrd/rpc/jsonrpc/types/v4"
 	"github.com/decred/dcrd/txscript/v4/stdaddr"
@@ -246,7 +246,7 @@ type Chain interface {
 
 	// ChainWork returns the total work up to and including the block of the
 	// provided block hash.
-	ChainWork(hash *chainhash.Hash) (*big.Int, error)
+	ChainWork(hash *chainhash.Hash) (uint256.Uint256, error)
 
 	// CheckLiveTicket returns whether or not a ticket exists in the live ticket
 	// treap of the best node.

internal/rpcserver/rpcserverhandlers_test.go

@@ -40,6 +40,7 @@ import (
 	"github.com/decred/dcrd/internal/mempool"
 	"github.com/decred/dcrd/internal/mining"
 	"github.com/decred/dcrd/internal/version"
+	"github.com/decred/dcrd/math/uint256"
 	"github.com/decred/dcrd/peer/v3"
 	"github.com/decred/dcrd/rpc/jsonrpc/types/v4"
 	"github.com/decred/dcrd/txscript/v4"
@@ -144,7 +145,7 @@ type testRPCChain struct {
 	blockHeightByHashErr          error
 	calcWantHeight                int64
 	chainTips                     []blockchain.ChainTipInfo
-	chainWork                     *big.Int
+	chainWork                     uint256.Uint256
 	chainWorkErr                  error
 	checkLiveTicket               bool
 	checkLiveTickets              []bool
@@ -241,7 +242,7 @@ func (c *testRPCChain) ChainTips() []blockchain.ChainTipInfo {
 
 // ChainWork returns returns a mocked total work up to and including the block
 // of the provided block hash.
-func (c *testRPCChain) ChainWork(hash *chainhash.Hash) (*big.Int, error) {
+func (c *testRPCChain) ChainWork(hash *chainhash.Hash) (uint256.Uint256, error) {
 	return c.chainWork, c.chainWorkErr
 }
 
@@ -1272,6 +1273,19 @@ func hexToBytes(s string) []byte {
 	return b
 }
 
+// hexToUint256 interprets the passed hex string as a 256-bit big-endian
+// unsigned integer and returns the resulting uint256.  It will panic if there
+// is an error.  This is only provided for the hard-coded constants so errors in
+// the source code can be detected. It will only (and must only) be called with
+// hard-coded values.
+func hexToUint256(s string) uint256.Uint256 {
+	b, err := hex.DecodeString(s)
+	if err != nil {
+		panic("invalid hex in source file: " + s)
+	}
+	return *new(uint256.Uint256).SetByteSlice(b)
+}
+
 // hexToMsgTx converts the passed hex string into a wire.MsgTx and will panic if
 // there is an error.  This is only provided for hard-coded constants so errors
 // in the source code can be detected.  It will only (and must only) be called
@@ -1416,7 +1430,7 @@ func defaultMockRPCChain() *testRPCChain {
 	headerByHashFn := func() wire.BlockHeader { return blkHeader }
 	blkHash := blk.Hash()
 	blkHeight := blk.Height()
-	chainWork, _ := new(big.Int).SetString("0e805fb85284503581c57c", 16)
+	chainWork := hexToUint256("0e805fb85284503581c57c")
 	return &testRPCChain{
 		bestSnapshot: &blockchain.BestState{
 			Hash:           *blkHash,
@@ -3579,8 +3593,7 @@ func TestHandleGetBlockchainInfo(t *testing.T) {
 			}
 			chain.bestHeaderHash = *hash
 			chain.bestHeaderHeight = 463073
-			chain.chainWork = big.NewInt(0).SetBytes([]byte{0x11, 0x5d, 0x28, 0x33, 0x84,
-				0x90, 0x90, 0xb0, 0x02, 0x65, 0x06})
+			chain.chainWork = hexToUint256("115d2833849090b0026506")
 			chain.isCurrent = false
 			chain.maxBlockSize = 393216
 			chain.stateLastChangedHeight = int64(149248)
@@ -3619,8 +3632,7 @@ func TestHandleGetBlockchainInfo(t *testing.T) {
 				Hash:     *genesisHash,
 				PrevHash: *genesisPrevHash,
 			}
-			chain.chainWork = big.NewInt(0).SetBytes([]byte{0x80, 0x00, 0x40, 0x00, 0x20,
-				0x00})
+			chain.chainWork = hexToUint256("800040002000")
 			chain.isCurrent = false
 			chain.maxBlockSize = 393216
 			chain.nextThresholdState = blockchain.ThresholdStateTuple{
@@ -3681,8 +3693,7 @@ func TestHandleGetBlockchainInfo(t *testing.T) {
 				Hash:     *hash,
 				PrevHash: *prevHash,
 			}
-			chain.chainWork = big.NewInt(0).SetBytes([]byte{0x11, 0x5d, 0x28, 0x33, 0x84,
-				0x90, 0x90, 0xb0, 0x02, 0x65, 0x06})
+			chain.chainWork = hexToUint256("115d2833849090b0026506")
 			chain.maxBlockSizeErr = errors.New("could not fetch max block size")
 			return chain
 		}(),
@@ -3700,8 +3711,7 @@ func TestHandleGetBlockchainInfo(t *testing.T) {
 				Hash:     *hash,
 				PrevHash: *prevHash,
 			}
-			chain.chainWork = big.NewInt(0).SetBytes([]byte{0x11, 0x5d, 0x28, 0x33, 0x84,
-				0x90, 0x90, 0xb0, 0x02, 0x65, 0x06})
+			chain.chainWork = hexToUint256("115d2833849090b0026506")
 			chain.maxBlockSize = 393216
 			chain.nextThresholdStateErr = errors.New("could not fetch threshold state")
 			return chain
@@ -3720,8 +3730,7 @@ func TestHandleGetBlockchainInfo(t *testing.T) {
 				Hash:     *hash,
 				PrevHash: *prevHash,
 			}
-			chain.chainWork = big.NewInt(0).SetBytes([]byte{0x11, 0x5d, 0x28, 0x33, 0x84,
-				0x90, 0x90, 0xb0, 0x02, 0x65, 0x06})
+			chain.chainWork = hexToUint256("115d2833849090b0026506")
 			chain.maxBlockSize = 393216
 			chain.stateLastChangedHeightErr = errors.New("could not fetch state last changed")
 			return chain