From 9407e27529647775fb78e88b4888041dcb4a27a3 Mon Sep 17 00:00:00 2001
From: Kagami Hiiragi <kagami@genshiken.org>
Date: Thu, 8 Jan 2015 16:47:29 +0300
Subject: [PATCH] Check a POW

---
 lib/address.js |  4 ++--
 lib/pow.js     | 45 +++++++++++++++++++++++++++++++++++++++++++--
 lib/structs.js |  2 +-
 test.js        |  6 ++++++
 4 files changed, 52 insertions(+), 5 deletions(-)

diff --git a/lib/address.js b/lib/address.js
index ce247ef..d798497 100644
--- a/lib/address.js
+++ b/lib/address.js
@@ -91,8 +91,8 @@ function keys2ripe(signKey, encKey) {
   } else {
     encPublicKey = encKey;
   }
-  var concat = Buffer.concat([signPublicKey, encPublicKey]);
-  return bmcrypto.ripemd160(bmcrypto.sha512(concat));
+  var dataToHash = Buffer.concat([signPublicKey, encPublicKey]);
+  return bmcrypto.ripemd160(bmcrypto.sha512(dataToHash));
 }
 
 /**
diff --git a/lib/pow.js b/lib/pow.js
index 622c134..a05ceb0 100644
--- a/lib/pow.js
+++ b/lib/pow.js
@@ -6,6 +6,7 @@
 
 "use strict";
 
+var bmcrypto = require("./crypto");
 var platform = require("./platform");
 
 var DEFAULT_TRIALS_PER_BYTE = 1000;
@@ -13,11 +14,13 @@ var DEFAULT_EXTRA_BYTES = 1000;
 
 /**
  * Calculate target
- * @param {{ttl: number, payloadLength: number}} opts - Target options
+ * @param {Object} opts - Target options
  * @return {number} Target.
  */
+// TODO(Kagami): Find a way how to document object params properly.
 // Just a wrapper around platform-specific implementation.
 exports.getTarget = function(opts) {
+  var payloadLength = opts.payloadLength || opts.payload.length;
   var nonceTrialsPerByte = opts.nonceTrialsPerByte;
   // Automatically raise lower values per spec.
   if (!nonceTrialsPerByte || nonceTrialsPerByte < DEFAULT_TRIALS_PER_BYTE) {
@@ -29,8 +32,46 @@ exports.getTarget = function(opts) {
   }
   return platform.getTarget({
     ttl: opts.ttl,
-    payloadLength: opts.payloadLength,
+    payloadLength: payloadLength,
     nonceTrialsPerByte: nonceTrialsPerByte,
     payloadLengthExtraBytes: payloadLengthExtraBytes,
   });
 };
+
+/**
+ * Check a POW.
+ * @param {Object} opts - Proof of work options
+ * @return {boolean} Is the proof of work sufficient.
+ */
+exports.check = function(opts) {
+  var initialHash;
+  var nonce;
+  if (opts.data) {
+    nonce = opts.data.slice(0, 8);
+    initialHash = bmcrypto.sha512(opts.data.slice(8));
+  } else {
+    if (typeof opts.nonce === "number") {
+      nonce = new Buffer(8);
+      // High 32 bits.
+      nonce.writeUInt32BE(Math.floor(opts.nonce / 4294967296), 0, true);
+      // Low 32 bits.
+      nonce.writeUInt32BE(opts.nonce % 4294967296, 4, true);
+    } else {
+      nonce = opts.nonce;
+    }
+    initialHash = opts.initialHash;
+  }
+  var targetHi = Math.floor(opts.target / 4294967296);
+  var targetLo = opts.target % 4294967296;
+  var dataToHash = Buffer.concat([nonce, initialHash]);
+  var resultHash = bmcrypto.sha512(bmcrypto.sha512(dataToHash));
+  var trialHi = resultHash.readUInt32BE(0, true);
+  if (trialHi > targetHi) {
+    return false;
+  } else if (trialHi < targetHi) {
+    return true;
+  } else {
+    var trialLo = resultHash.readUInt32BE(4, true);
+    return trialLo <= targetLo;
+  }
+};
diff --git a/lib/structs.js b/lib/structs.js
index 49bdc88..9b4373d 100644
--- a/lib/structs.js
+++ b/lib/structs.js
@@ -173,7 +173,7 @@ var var_int = exports.var_int = {
       targetStart = 1 + (8 - value.length);
       value.copy(buf, targetStart);
     } else {
-      throw new Error("Value encode error");
+      throw new Error("Unknown value type");
     }
     return buf;
   },
diff --git a/test.js b/test.js
index bc2a726..7c65395 100644
--- a/test.js
+++ b/test.js
@@ -272,6 +272,12 @@ describe("POW", function() {
     expect(POW.getTarget({ttl: 2418984, payloadLength: 628, nonceTrialsPerByte: 1000, payloadLengthExtraBytes: 1000})).to.equal(297422593171);
     expect(POW.getTarget({ttl: 86400, payloadLength: 628})).to.equal(4864647698763);
   });
+
+  it("should check a POW", function() {
+    expect(POW.check({nonce: 21997550, target: 297422593171, initialHash: Buffer("8ff2d685db89a0af2e3dbfd3f700ae96ef4d9a1eac72fd778bbb368c7510cddda349e03207e1c4965bd95c6f7265e8f1a481a08afab3874eaafb9ade09a10880", "hex")})).to.be.true;
+    expect(POW.check({nonce: 3122437, target: 4864647698763, initialHash: Buffer("8ff2d685db89a0af2e3dbfd3f700ae96ef4d9a1eac72fd778bbb368c7510cddda349e03207e1c4965bd95c6f7265e8f1a481a08afab3874eaafb9ade09a10880", "hex")})).to.be.true;
+    expect(POW.check({nonce: 3122436, target: 4864647698763, initialHash: Buffer("8ff2d685db89a0af2e3dbfd3f700ae96ef4d9a1eac72fd778bbb368c7510cddda349e03207e1c4965bd95c6f7265e8f1a481a08afab3874eaafb9ade09a10880", "hex")})).to.be.false;
+  });
 });
 
 describe("High-level classes", function() {