1 files changed, 73 insertions, 0 deletions
diff --git a/ledger/onlinetopheap.go b/ledger/onlinetopheap.go
new file mode 100644
index 000000000..72a81d88a
--- /dev/null
+++ b/ledger/onlinetopheap.go
@@ -0,0 +1,73 @@
+// Copyright (C) 2019-2021 Algorand, Inc.
+// This file is part of go-algorand
+//
+// go-algorand is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as
+// published by the Free Software Foundation, either version 3 of the
+// License, or (at your option) any later version.
+//
+// go-algorand is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with go-algorand.  If not, see <https://www.gnu.org/licenses/>.
+
+package ledger
+
+import (
+	"bytes"
+
+	"github.com/algorand/go-algorand/ledger/ledgercore"
+)
+
+// onlineTopHeap implements heap.Interface for tracking top N online accounts.
+type onlineTopHeap struct {
+	accts []*ledgercore.OnlineAccount
+}
+
+// Len implements sort.Interface
+func (h *onlineTopHeap) Len() int {
+	return len(h.accts)
+}
+
+// Less implements sort.Interface
+func (h *onlineTopHeap) Less(i, j int) bool {
+	// For the heap, "less" means the element is returned earlier by Pop(),
+	// so we actually implement "greater-than" here.
+	ibal := h.accts[i].NormalizedOnlineBalance
+	jbal := h.accts[j].NormalizedOnlineBalance
+
+	if ibal > jbal {
+		return true
+	}
+	if ibal < jbal {
+		return false
+	}
+
+	bcmp := bytes.Compare(h.accts[i].Address[:], h.accts[j].Address[:])
+	if bcmp > 0 {
+		return true
+	}
+
+	return false
+}
+
+// Swap implements sort.Interface
+func (h *onlineTopHeap) Swap(i, j int) {
+	h.accts[i], h.accts[j] = h.accts[j], h.accts[i]
+}
+
+// Push implements heap.Interface
+func (h *onlineTopHeap) Push(x interface{}) {
+	h.accts = append(h.accts, x.(*ledgercore.OnlineAccount))
+}
+
+// Pop implements heap.Interface
+func (h *onlineTopHeap) Pop() interface{} {
+	res := h.accts[len(h.accts)-1]
+	h.accts[len(h.accts)-1] = nil
+	h.accts = h.accts[:len(h.accts)-1]
+	return res
+}