market: implement MarketTunnel

This implements Market.MidGap and Market.CoinLocked, and adds a CoinLocker.

swap: Create LockableAsset and use in the coins map.
LockOrdersCoins separates orders by locked asset coins internally.
Unlock coins in Swapper.revoke and in processBlock for completed matches.

book: Use a mutex for atomic buy and sell operations (i.e. Buys()).

pg: Add ActiveOrderCoins to retrieve coins for active orders.
Also, fix shallow copy and avoid buffer reuse in (*dbCoins).Scan.

CI: Add structcheck and replace gofmt with goimports.

matcher: add doneOK output, where doneOK = passed - booked
Fix passed not including unmatched standing orders.

.github/workflows/go.yml

@@ -25,7 +25,7 @@ jobs:
           GO111MODULE: "on"
         run: |
           export PATH=${PATH}:$(go env GOPATH)/bin
-          golangci-lint run --disable-all --deadline=10m --enable=gofmt --enable=gosimple --enable=unconvert --enable=ineffassign --enable=govet
+          golangci-lint run --disable-all --deadline=10m --enable=goimports --enable=gosimple --enable=unconvert --enable=ineffassign --enable=govet --enable=structcheck
       - name: Test
         env:
           GO111MODULE: "on"

dex/order/order.go

@@ -153,23 +153,41 @@ type Order interface {
 	// Quote returns the unique integer identifier of the quote asset as defined
 	// in the asset package.
 	Quote() uint32
+
+	// IsSell indicates if the order is selling the base asset (false indicates
+	// selling the quote asset). This helps identify the asset of the backing
+	// coins returned by CoinIDs(). Note that a cancel order will return false.
+	IsSell() bool
+
+	// Coins returns the backing coins of either base or quote asset depending
+	// on IsSell.
+	//
+	// TODO!!! The orders must be updated to track the current backing coins,
+	// not just the original backing coins. This is critical for partially
+	// filled orders where each fill creates change that must then be tracked as
+	// the new backing coins.
+	CoinIDs() []CoinID
 }
 
 // zeroTime is the Unix time for a Time where IsZero() == true.
 var zeroTime = time.Time{}.Unix()
 
 // An order's ID is computed as the Blake-256 hash of the serialized order.
 func calcOrderID(order Order) OrderID {
-	stime := order.Time()
-	if stime == zeroTime {
+	sTime := order.Time()
+	if sTime == zeroTime {
 		panic("Order's ServerTime is unset")
 	}
 	return blake256.Sum256(order.Serialize())
 }
 
-// CoinID identifies value on the blockchain.
+// CoinID should be used to wrap a []byte so that it may be used as a map key.
 type CoinID []byte
 
+func (c CoinID) String() string {
+	return hex.EncodeToString(c)
+}
+
 // Prefix is the order prefix containing data fields common to all orders.
 type Prefix struct {
 	AccountID  account.AccountID
@@ -359,6 +377,16 @@ func (o *MarketOrder) Remaining() uint64 {
 	return o.Quantity - o.Filled
 }
 
+// IsSell indicates if the order is selling the base asset.
+func (o *MarketOrder) IsSell() bool {
+	return o.Sell
+}
+
+// CoinIDs returns the order's backing coins.
+func (o *MarketOrder) CoinIDs() []CoinID {
+	return o.Coins
+}
+
 // Ensure MarketOrder is an Order.
 var _ Order = (*MarketOrder)(nil)
 
@@ -434,6 +462,11 @@ func (o *LimitOrder) Price() uint64 {
 	return o.Rate
 }
 
+// IsSell indicates if the order is selling the base asset.
+func (o *LimitOrder) IsSell() bool {
+	return o.Sell
+}
+
 // CancelOrder defines a cancel order in terms of an order Prefix and the ID of
 // the order to be canceled.
 type CancelOrder struct {
@@ -497,5 +530,15 @@ func (o *CancelOrder) FilledAmt() uint64 {
 	return 0
 }
 
+// IsSell is always false for a CancelOrder.
+func (o *CancelOrder) IsSell() bool {
+	return false
+}
+
+// CoinIDs always returns a nil slice for a CancelOrder.
+func (o *CancelOrder) CoinIDs() []CoinID {
+	return nil
+}
+
 // Ensure CancelOrder is an Order.
 var _ Order = (*CancelOrder)(nil)

server/asset/btc/btc_test.go

@@ -550,7 +550,6 @@ func testMakeMsgTx(segwit bool) *testMsgTx {
 
 type testMsgTxSwap struct {
 	tx        *wire.MsgTx
-	vout      uint32
 	contract  []byte
 	recipient btcutil.Address
 }

server/asset/dcr/dcr_test.go

@@ -439,7 +439,6 @@ func testMsgTxRegular(sigType dcrec.SignatureType) *testMsgTx {
 // Information about a swap contract.
 type testMsgTxSwap struct {
 	tx        *wire.MsgTx
-	vout      uint32
 	contract  []byte
 	recipient dcrutil.Address
 }

server/book/book.go

@@ -5,6 +5,8 @@
 package book
 
 import (
+	"sync"
+
 	"decred.org/dcrdex/dex/order"
 )
 
@@ -21,6 +23,7 @@ const (
 // allow constant time access to the best orders, and log time insertion and
 // removal of orders.
 type Book struct {
+	mtx     sync.RWMutex
 	lotSize uint64
 	buys    *OrderPQ
 	sells   *OrderPQ
@@ -44,8 +47,10 @@ func New(lotSize uint64, halfCapacity ...uint32) *Book {
 // Realloc changes the capacity of the order book given the specified capacity
 // of both buy and sell sides of the book.
 func (b *Book) Realloc(newHalfCap uint32) {
+	b.mtx.Lock()
 	b.buys.Realloc(newHalfCap)
 	b.sells.Realloc(newHalfCap)
+	b.mtx.Unlock()
 }
 
 // LotSize returns the Book's configured lot size in atoms of the base asset.
@@ -75,6 +80,16 @@ func (b *Book) BestBuy() *order.LimitOrder {
 	return b.buys.PeekBest()
 }
 
+// Best returns pointers to the best buy and sell order in the order book. The
+// orders are NOT removed from the book.
+func (b *Book) Best() (bestBuy, bestSell *order.LimitOrder) {
+	b.mtx.RLock()
+	bestBuy = b.buys.PeekBest()
+	bestSell = b.sells.PeekBest()
+	b.mtx.RUnlock()
+	return
+}
+
 // Insert attempts to insert the provided order into the order book, returning a
 // boolean indicating if the insertion was successful. If the order is not an
 // integer multiple of the Book's lot size, the order will not be inserted.
@@ -84,6 +99,8 @@ func (b *Book) Insert(o *order.LimitOrder) bool {
 			"quantity that is not a multiple of lot size.")
 		return false
 	}
+	b.mtx.Lock()
+	defer b.mtx.Unlock()
 	if o.Sell {
 		return b.sells.Insert(o)
 	}
@@ -93,6 +110,8 @@ func (b *Book) Insert(o *order.LimitOrder) bool {
 // Remove attempts to remove the order with the given OrderID from the book.
 func (b *Book) Remove(oid order.OrderID) (*order.LimitOrder, bool) {
 	uid := oid.String()
+	b.mtx.Lock()
+	defer b.mtx.Unlock()
 	if removed, ok := b.sells.RemoveOrderUID(uid); ok {
 		return removed, true
 	}