From e04682514578feecdab6314696371a187dd030b6 Mon Sep 17 00:00:00 2001
From: Christopher Jeffrey <chjjeffrey@gmail.com>
Date: Sat, 2 Jul 2016 07:09:22 -0700
Subject: [PATCH] sigcache.

---
 lib/bcoin/sigcache.js | 141 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 141 insertions(+)
 create mode 100644 lib/bcoin/sigcache.js

diff --git a/lib/bcoin/sigcache.js b/lib/bcoin/sigcache.js
new file mode 100644
index 00000000..afe75468
--- /dev/null
+++ b/lib/bcoin/sigcache.js
@@ -0,0 +1,141 @@
+/*!
+ * sigcache.js - signature cache for bcoin
+ * Copyright (c) 2014-2016, Christopher Jeffrey (MIT License).
+ * https://github.com/bcoin-org/bcoin
+ */
+
+'use strict';
+
+var bcoin = require('./env');
+var utils = bcoin.utils;
+var assert = utils.assert;
+
+/**
+ * Signature cache.
+ * @constructor
+ * @param {Number} [size=50000]
+ * @property {Number} size
+ * @property {Hash[]} keys
+ * @property {Object} valid
+ */
+
+function SigCache(size) {
+  if (!(this instanceof SigCache))
+    return new SigCache(size);
+
+  if (size == null)
+    size = 10000;
+
+  assert(utils.isNumber(size));
+  assert(size >= 0);
+
+  this.size = size;
+  this.keys = [];
+  this.valid = {};
+}
+
+/**
+ * Add item to the sigcache.
+ * Potentially evict a random member.
+ * @param {Hash} hash - Sig hash.
+ * @param {Buffer} sig
+ * @param {Buffer} key
+ */
+
+SigCache.prototype.add = function add(hash, sig, key) {
+  var index, key;
+
+  if (this.size === 0)
+    return;
+
+  this.valid[hash] = new SigCacheEntry(sig, key);
+
+  if (this.keys.length === this.size) {
+    index = Math.floor(Math.random() * this.keys.length);
+    key = this.keys[index];
+    delete this.valid[key];
+    this.keys[index] = hash;
+  } else {
+    this.keys.push(hash);
+  }
+};
+
+/**
+ * Test whether the sig exists.
+ * @param {Hash} hash - Sig hash.
+ * @param {Buffer} sig
+ * @param {Buffer} key
+ * @returns {Boolean}
+ */
+
+SigCache.prototype.has = function has(hash, sig, key) {
+  var entry = this.valid[hash];
+
+  if (!entry)
+    return false;
+
+  return entry.equal(sig, key);
+};
+
+/**
+ * Verify a signature, testing
+ * it against the cache first.
+ * @param {Buffer} msg
+ * @param {Buffer} sig
+ * @param {Buffer} key
+ * @param {Boolean?} historical
+ * @param {Boolean?} high
+ * @returns {Boolean}
+ */
+
+SigCache.prototype.verify = function verify(msg, sig, key, historical, high) {
+  var hash, result;
+
+  if (historical || this.size === 0)
+    return bcoin.ec.verify(msg, sig, key, historical, high);
+
+  hash = msg.toString('hex');
+
+  if (this.has(hash, sig, key))
+    return true;
+
+  result = bcoin.ec.verify(msg, sig, key, historical, high);
+
+  if (!result)
+    return false;
+
+  this.add(hash, sig, key);
+
+  return true;
+};
+
+/**
+ * Signature cache entry.
+ * @constructor
+ * @param {Buffer} sig
+ * @param {Buffer} key
+ * @property {Buffer} sig
+ * @property {Buffer} key
+ */
+
+function SigCacheEntry(sig, key) {
+  this.sig = sig;
+  this.key = key;
+}
+
+/**
+ * Compare an entry to a sig and key.
+ * @param {Buffer} sig
+ * @param {Buffer} key
+ * @returns {Boolean}
+ */
+
+SigCacheEntry.prototype.equal = function equal(sig, key) {
+  return utils.equal(this.sig, sig) && utils.equal(this.key, key);
+};
+
+/*
+ * Expose
+ */
+
+module.exports = SigCache;