Varint class

...will be useful in transactions. Note that we already have a primitive
understanding of Varints in the BufferReader and BufferWriter classes. However,
the new Varint class is a varint object which actually depends on BufferReader
and BufferWriter for reading and writing varints. This class is for keeping
track of the raw buffer that is read in from a buffer.

lib/varint.js

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+var BufferWriter = require('./bufferwriter');
+var BufferReader = require('./bufferreader');
+var BN = require('./bn');
+
+var Varint = function Varint(buf) {
+  if (!(this instanceof Varint))
+    return new Varint(buf);
+  if (Buffer.isBuffer(buf)) {
+    this.buf = buf;
+  } else if (typeof buf === 'number') {
+    var num = buf;
+    this.fromNumber(num);
+  } else if (buf) {
+    var obj = buf;
+    this.set(obj);
+  }
+};
+
+Varint.prototype.set = function(obj) {
+  this.buf = obj.buf || this.buf;
+  return this;
+};
+
+Varint.prototype.fromBuffer = function(buf) {
+  this.buf = buf;
+  return this;
+};
+
+Varint.prototype.fromBufferReader = function(br) {
+  this.buf = br.readVarintBuf();
+  return this;
+};
+
+Varint.prototype.fromNumber = function(num) {
+  this.buf = BufferWriter().writeVarintNum(num).concat();
+  return this;
+};
+
+Varint.prototype.toBuffer = function() {
+  return this.buf;
+};
+
+Varint.prototype.toNumber = function() {
+  return BufferReader(this.buf).readVarintNum();
+};
+
+module.exports = Varint;

test/varint.js

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+var should = require('chai').should();
+var BufferReader = require('../lib/bufferreader');
+var BufferWriter = require('../lib/bufferwriter');
+var Varint = require('../lib/varint');
+
+describe('Varint', function() {
+
+  it('should make a new varint', function() {
+    var buf = new Buffer('00', 'hex');
+    var varint = new Varint(buf);
+    should.exist(varint);
+    varint.buf.toString('hex').should.equal('00');
+    varint = Varint(buf);
+    should.exist(varint);
+    varint.buf.toString('hex').should.equal('00');
+  });
+
+  describe('#set', function() {
+    
+    it('should set a buffer', function() {
+      var buf = new Buffer('00', 'hex');
+      var varint = Varint().set({buf: buf});
+      varint.buf.toString('hex').should.equal('00');
+      varint.set({});
+      varint.buf.toString('hex').should.equal('00');
+    });
+
+  });
+
+  describe('#fromBuffer', function() {
+    
+    it('should set a buffer', function() {
+      var buf = BufferWriter().writeVarintNum(5).concat();
+      var varint = Varint().fromBuffer(buf);
+      varint.toNumber().should.equal(5);
+    });
+
+  });
+
+  describe('#fromBufferReader', function() {
+    
+    it('should set a buffer reader', function() {
+      var buf = BufferWriter().writeVarintNum(5).concat();
+      var br = BufferReader(buf);
+      var varint = Varint().fromBufferReader(br);
+      varint.toNumber().should.equal(5);
+    });
+
+  });
+
+  describe('#fromNumber', function() {
+    
+    it('should set a number', function() {
+      var varint = Varint().fromNumber(5);
+      varint.toNumber().should.equal(5);
+    });
+
+  });
+
+  describe('#toBuffer', function() {
+    
+    it('should return a buffer', function() {
+      buf = BufferWriter().writeVarintNum(5).concat();
+      var varint = Varint(buf);
+      varint.toBuffer().toString('hex').should.equal(buf.toString('hex'));
+    });
+
+  });
+
+  describe('#toNumber', function() {
+    
+    it('should return a buffer', function() {
+      var varint = Varint(5);
+      varint.toNumber().should.equal(5);
+    });
+
+  });
+
+});