/*!
* sigcache.js - signature cache for bcoin
* Copyright (c) 2014-2017, Christopher Jeffrey (MIT License).
* https://github.com/bcoin-org/bcoin
*/
'use strict';
const assert = require('bsert');
const {BufferMap} = require('buffer-map');
const secp256k1 = require('bcrypto/lib/secp256k1');
/**
* Signature cache.
* @alias module:script.SigCache
* @property {Number} size
* @property {Hash[]} keys
* @property {Object} valid
*/
class SigCache {
/**
* Create a signature cache.
* @constructor
* @param {Number} [size=10000]
*/
constructor(size) {
if (size == null)
size = 10000;
assert((size >>> 0) === size);
this.size = size;
this.keys = [];
this.valid = new BufferMap();
}
/**
* Resize the sigcache.
* @param {Number} size
*/
resize(size) {
assert((size >>> 0) === size);
this.size = size;
this.keys.length = 0;
this.valid.clear();
}
/**
* Add item to the sigcache.
* Potentially evict a random member.
* @param {Hash} msg - Sig hash.
* @param {Buffer} sig
* @param {Buffer} key
*/
add(msg, sig, key) {
if (this.size === 0)
return;
this.valid.set(msg, new SigCacheEntry(sig, key));
if (this.keys.length >= this.size) {
const i = Math.floor(Math.random() * this.keys.length);
const k = this.keys[i];
this.valid.delete(k);
this.keys[i] = msg;
} else {
this.keys.push(msg);
}
}
/**
* Test whether the sig exists.
* @param {Hash} msg - Sig hash.
* @param {Buffer} sig
* @param {Buffer} key
* @returns {Boolean}
*/
has(msg, sig, key) {
const entry = this.valid.get(msg);
if (!entry)
return false;
return entry.equals(sig, key);
}
/**
* Verify a signature, testing
* it against the cache first.
* @param {Buffer} msg
* @param {Buffer} sig
* @param {Buffer} key
* @returns {Boolean}
*/
verify(msg, sig, key) {
if (this.size === 0)
return secp256k1.verifyDER(msg, sig, key);
if (this.has(msg, sig, key))
return true;
const result = secp256k1.verifyDER(msg, sig, key);
if (!result)
return false;
this.add(msg, sig, key);
return true;
}
}
/**
* Signature Cache Entry
* @ignore
* @property {Buffer} sig
* @property {Buffer} key
*/
class SigCacheEntry {
/**
* Create a cache entry.
* @constructor
* @param {Buffer} sig
* @param {Buffer} key
*/
constructor(sig, key) {
this.sig = Buffer.from(sig);
this.key = Buffer.from(key);
}
/**
* Compare an entry to a sig and key.
* @param {Buffer} sig
* @param {Buffer} key
* @returns {Boolean}
*/
equals(sig, key) {
return this.sig.equals(sig) && this.key.equals(key);
}
}
/*
* Expose
*/
module.exports = SigCache;