From 02844741e89010cc5d97ab40aea3af974741b764 Mon Sep 17 00:00:00 2001
From: Olaoluwa Osuntokun <laolu32@gmail.com>
Date: Thu, 5 Nov 2015 12:33:35 -0800
Subject: [PATCH] add resource pool for multi-sig keys
MIME-Version: 1.0
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* Need to change to instead just use the HD chain so backups aren’t
fragmented

* Optional pre-load on start available, will push EC computations up
front
---
 wallet/multisig_keypool.go | 60 ++++++++++++++++++++++++++++++++++++++
 wallet/wallet.go           |  1 +
 2 files changed, 61 insertions(+)
 create mode 100644 wallet/multisig_keypool.go

diff --git a/wallet/multisig_keypool.go b/wallet/multisig_keypool.go
new file mode 100644
index 00000000..6830a34b
--- /dev/null
+++ b/wallet/multisig_keypool.go
@@ -0,0 +1,60 @@
+package wallet
+
+import (
+	"container/list"
+	"sync"
+
+	"github.com/btcsuite/btcd/btcec"
+)
+
+// multiSigKeyPool...
+// TODO(roasbeef): actually, this is dumb. should use an HD key branch instead.
+//  * instead, use wallet.Manager.NextExternalAddresses, cast to
+//    ManagedPubKeyAddress, then .PrivKey()
+//  * on shutdown, write state of pending keys, then read back?
+type multiSigKeyPool struct {
+	sync.RWMutex
+	keyPool *list.List
+}
+
+// newMultiSigKeyPool...
+func newMultiSigKeyPool() *multiSigKeyPool {
+	// TODO(roasbeef): pre-generate or nah?
+	return &multiSigKeyPool{keyPool: list.New()}
+}
+
+// getNextMultiSigKey...
+func (l *multiSigKeyPool) getNextMultiSigKey() (*btcec.PrivateKey, error) {
+	if l.Size() == 0 {
+		return btcec.NewPrivateKey(btcec.S256())
+	}
+
+	l.Lock()
+	defer l.Unlock()
+	nextKey := l.keyPool.Remove(l.keyPool.Front()).(*btcec.PrivateKey)
+	return nextKey, nil
+}
+
+// releaseMultiSigKey...
+func (l *multiSigKeyPool) releaseMultiSigKey(key *btcec.PrivateKey) {
+	l.keyPool.PushBack(key)
+}
+
+// Size...
+func (l *multiSigKeyPool) Size() int {
+	l.RLock()
+	defer l.RUnlock()
+	return l.keyPool.Len()
+}
+
+// preAllocateKeys...
+func (l *multiSigKeyPool) preAllocateKeys(numKeys int) error {
+	for i := 0; i < numKeys; i-- {
+		newKey, err := btcec.NewPrivateKey(btcec.S256())
+		if err != nil {
+			return err
+		}
+		l.keyPool.PushBack(newKey)
+	}
+	return nil
+}
diff --git a/wallet/wallet.go b/wallet/wallet.go
index 659bfdfa..b7b8cb9e 100644
--- a/wallet/wallet.go
+++ b/wallet/wallet.go
@@ -83,6 +83,7 @@ type LightningWallet struct {
 
 	//lockedInputs  []*LockedPrevOut
 	//lockedOutputs []*LockedOutPoint
+	keyPool *multiSigKeyPool
 
 	started  int32
 	shutdown int32