From e6d4e4c029fcdf086d1a0d154e3e538a82ba6b4e Mon Sep 17 00:00:00 2001
From: Kagami Hiiragi <kagami@genshiken.org>
Date: Mon, 5 Jan 2015 02:40:52 +0300
Subject: [PATCH] Bitfields encoding/decoding

---
 README.md      |  4 +--
 lib/structs.js | 78 ++++++++++++++++++++++++++++++++++++++++++++++----
 test.js        | 42 ++++++++++++++++++++++++---
 3 files changed, 112 insertions(+), 12 deletions(-)

diff --git a/README.md b/README.md
index 1987e3b..6d37c93 100644
--- a/README.md
+++ b/README.md
@@ -33,8 +33,8 @@ API documentation is available [here](https://bitchan.github.io/bitmessage/docs/
   - [ ] net_addr
   - [ ] encrypted
   - [x] message encodings
-  - [ ] service features
-  - [ ] pubkey features
+  - [x] service features
+  - [x] pubkey features
 - [ ] Message types
   - [ ] version
   - [ ] verack
diff --git a/lib/structs.js b/lib/structs.js
index 07f5c30..ae13c98 100644
--- a/lib/structs.js
+++ b/lib/structs.js
@@ -251,18 +251,84 @@ exports.var_int_list = {
   },
 };
 
-exports.messageEncodings = Object.create(var_int);
-Object.assign(exports.messageEncodings, {
+/**
+ * Message encodings. Extends {@link var_int} by adding known encoding type
+ * constants.
+ * @see {@link https://bitmessage.org/wiki/Protocol_specification#Message_Encodings}
+ */
+exports.messageEncodings = Object.assign(Object.create(var_int), {
+  /**
+   * Any data with this number may be ignored. The sending node might
+   * simply be sharing its public key with you.
+   */
   IGNORE: 0,
+  /**
+   * UTF-8. No 'Subject' or 'Body' sections. Useful for simple strings
+   * of data, like URIs or magnet links.
+   */
   TRIVIAL: 1,
+  /**
+   * UTF-8. Uses 'Subject' and 'Body' sections. No MIME is used.
+   */
   SIMPLE: 2,
 });
 
-exports.serviceFeatures = {
-  NODE_NETWORK: 1,
+// Creates bitfield class of the specified size.
+var bitfield = function(size) {
+  var bytesize = size / 8;
+  return {
+    decode: function(buf) {
+      assert(buf.length === bytesize, "Bad buffer size");
+      var features = [];
+      var index;
+      for (var i = 0; i < size; i++) {
+        index = bytesize - Math.floor(i / 8) - 1;
+        if ((buf[index] & (1 << (i % 8))) !== 0) {  // jshint ignore:line
+          features.push(i);
+        }
+      }
+      return features;
+    },
+
+    encode: function(features) {
+      var buf = new Buffer(bytesize);
+      buf.fill(0);
+      features.forEach(function(feature) {
+        assert(feature >= 0, "Bad feature");
+        assert(feature <= (size - 1), "Bad feature");
+        var index = bytesize - Math.floor(feature / 8) - 1;
+        buf[index] |= 1 << (feature % 8);  // jshint ignore:line
+      });
+      return buf;
+    },
+  };
 };
 
-exports.pubkeyFeatures = {
+/**
+ * Service bitfield features. Implements encoding/decoding for a 8-byte
+ * buffer object.
+ * @see {@link https://bitmessage.org/wiki/Protocol_specification#version}
+ */
+exports.serviceFeatures = Object.assign(bitfield(64), {
+  /** This is a normal network node. */
+  NODE_NETWORK: 0,
+});
+
+/**
+ * Pubkey bitfield features. Implements encoding/decoding for a 4-byte
+ * buffer object.
+ * @see {@link https://bitmessage.org/wiki/Protocol_specification#Pubkey_bitfield_features}
+ */
+exports.pubkeyFeatures = Object.assign(bitfield(32), {
+  /**
+   * Receiving node expects that the RIPE hash encoded in their address
+   * preceedes the encrypted message data of msg messages bound for
+   * them.
+   */
   INCLUDE_DESTINATION: 30,
+  /**
+   * If true, the receiving node does send acknowledgements (rather than
+   * dropping them).
+   */
   DOES_ACK: 31,
-};
+});
diff --git a/test.js b/test.js
index b741f22..b6d9148 100644
--- a/test.js
+++ b/test.js
@@ -5,10 +5,14 @@ var allTests = typeof window === "undefined" ?
 
 var bmcrypto = require("./lib/crypto");
 var bitmessage = require("./lib");
-var message = bitmessage.structs.message;
-var var_int = bitmessage.structs.var_int;
-var var_str = bitmessage.structs.var_str;
-var var_int_list = bitmessage.structs.var_int_list;
+var structs = bitmessage.structs;
+var message = structs.message;
+var var_int = structs.var_int;
+var var_str = structs.var_str;
+var var_int_list = structs.var_int_list;
+var messageEncodings = structs.messageEncodings;
+var serviceFeatures = structs.serviceFeatures;
+var pubkeyFeatures = structs.pubkeyFeatures;
 var WIF = bitmessage.WIF;
 var Address = bitmessage.Address;
 
@@ -166,6 +170,36 @@ describe("Common structures", function() {
       expect(var_int_list.encode([1, 1024, 1125899906842624, 40000, 100000]).toString("hex")).to.equal("0501fd0400ff0004000000000000fd9c40fe000186a0");
     });
   });
+
+  describe("Message encodings", function() {
+    it("should decode", function() {
+      expect(messageEncodings.decode(Buffer([2])).value).to.equal(messageEncodings.SIMPLE);
+    });
+
+    it("should encode", function() {
+      expect(messageEncodings.encode(messageEncodings.SIMPLE).toString("hex")).to.equal("02");
+    });
+  });
+
+  describe("Service features", function() {
+    it("should decode", function() {
+      expect(serviceFeatures.decode(Buffer("0000000000000001", "hex"))).to.have.members([serviceFeatures.NODE_NETWORK]);
+    });
+
+    it("should encode", function() {
+      expect(serviceFeatures.encode([serviceFeatures.NODE_NETWORK]).toString("hex")).to.equal("0000000000000001");
+    });
+  });
+
+  describe("Pubkey features", function() {
+    it("should decode", function() {
+      expect(pubkeyFeatures.decode(Buffer("c0000000", "hex"))).to.have.members([pubkeyFeatures.DOES_ACK, pubkeyFeatures.INCLUDE_DESTINATION]);
+    });
+
+    it("should encode", function() {
+      expect(pubkeyFeatures.encode([pubkeyFeatures.INCLUDE_DESTINATION, pubkeyFeatures.DOES_ACK]).toString("hex")).to.equal("c0000000");
+    });
+  });
 });
 
 describe("WIF", function() {