From affffb39b366321e47784e48c469da9584ceb92c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C3=A9ter=20Szil=C3=A1gyi?= <peterke@gmail.com>
Date: Tue, 9 Aug 2016 14:54:36 +0300
Subject: core/types, miner: switch over to the grouped tx sets

---
 core/types/transaction.go      | 79 +++++++++++++++++++++++++-----------------
 core/types/transaction_test.go | 11 +++++-
 2 files changed, 58 insertions(+), 32 deletions(-)

(limited to 'core')

diff --git a/core/types/transaction.go b/core/types/transaction.go
index af48e4d07..5bb599479 100644
--- a/core/types/transaction.go
+++ b/core/types/transaction.go
@@ -426,41 +426,58 @@ func (s *TxByPrice) Pop() interface{} {
 	return x
 }
 
-// SortByPriceAndNonce sorts the transactions by price in such a way that the
-// nonce orderings within a single account are maintained.
-//
-// Note, this is not as trivial as it seems from the first look as there are three
-// different criteria that need to be taken into account (price, nonce, account
-// match), which cannot be done with any plain sorting method, as certain items
-// cannot be compared without context.
+// TransactionsByPriceAndNonce represents a set of transactions that can return
+// transactions in a profit-maximising sorted order, while supporting removing
+// entire batches of transactions for non-executable accounts.
+type TransactionsByPriceAndNonce struct {
+	txs   map[common.Address]Transactions // Per account nonce-sorted list of transactions
+	heads TxByPrice                       // Next transaction for each unique account (price heap)
+}
+
+// NewTransactionsByPriceAndNonce creates a transaction set that can retrieve
+// price sorted transactions in a nonce-honouring way.
 //
-// This method first sorts the separates the list of transactions into individual
-// sender accounts and sorts them by nonce. After the account nonce ordering is
-// satisfied, the results are merged back together by price, always comparing only
-// the head transaction from each account. This is done via a heap to keep it fast.
-func SortByPriceAndNonce(txs map[common.Address]Transactions) Transactions {
+// Note, the input map is reowned so the caller should not interact any more with
+// if after providng it to the constructor.
+func NewTransactionsByPriceAndNonce(txs map[common.Address]Transactions) *TransactionsByPriceAndNonce {
 	// Initialize a price based heap with the head transactions
-	byPrice := make(TxByPrice, 0, len(txs))
+	heads := make(TxByPrice, 0, len(txs))
 	for acc, accTxs := range txs {
-		byPrice = append(byPrice, accTxs[0])
+		heads = append(heads, accTxs[0])
 		txs[acc] = accTxs[1:]
 	}
-	heap.Init(&byPrice)
-
-	// Merge by replacing the best with the next from the same account
-	var sorted Transactions
-	for len(byPrice) > 0 {
-		// Retrieve the next best transaction by price
-		best := heap.Pop(&byPrice).(*Transaction)
-
-		// Push in its place the next transaction from the same account
-		acc, _ := best.From() // we only sort valid txs so this cannot fail
-		if accTxs, ok := txs[acc]; ok && len(accTxs) > 0 {
-			heap.Push(&byPrice, accTxs[0])
-			txs[acc] = accTxs[1:]
-		}
-		// Accumulate the best priced transaction
-		sorted = append(sorted, best)
+	heap.Init(&heads)
+
+	// Assemble and return the transaction set
+	return &TransactionsByPriceAndNonce{
+		txs:   txs,
+		heads: heads,
+	}
+}
+
+// Peek returns the next transaction by price.
+func (t *TransactionsByPriceAndNonce) Peek() *Transaction {
+	if len(t.heads) == 0 {
+		return nil
+	}
+	return t.heads[0]
+}
+
+// Shift replaces the current best head with the next one from the same account.
+func (t *TransactionsByPriceAndNonce) Shift() {
+	acc, _ := t.heads[0].From() // we only sort valid txs so this cannot fail
+
+	if txs, ok := t.txs[acc]; ok && len(txs) > 0 {
+		t.heads[0], t.txs[acc] = txs[0], txs[1:]
+		heap.Fix(&t.heads, 0)
+	} else {
+		heap.Pop(&t.heads)
 	}
-	return sorted
+}
+
+// Pop removes the best transaction, *not* replacing it with the next one from
+// the same account. This should be used when a transaction cannot be executed
+// and hence all subsequent ones should be discarded from the same account.
+func (t *TransactionsByPriceAndNonce) Pop() {
+	heap.Pop(&t.heads)
 }
diff --git a/core/types/transaction_test.go b/core/types/transaction_test.go
index c6e6e3790..8b0b02c3e 100644
--- a/core/types/transaction_test.go
+++ b/core/types/transaction_test.go
@@ -137,7 +137,16 @@ func TestTransactionPriceNonceSort(t *testing.T) {
 		}
 	}
 	// Sort the transactions and cross check the nonce ordering
-	txs := SortByPriceAndNonce(groups)
+	txset := NewTransactionsByPriceAndNonce(groups)
+
+	txs := Transactions{}
+	for {
+		if tx := txset.Peek(); tx != nil {
+			txs = append(txs, tx)
+			txset.Shift()
+		}
+		break
+	}
 	for i, txi := range txs {
 		fromi, _ := txi.From()
 
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