From b6db786098109ae8bc48a5101a8797bb7fff3326 Mon Sep 17 00:00:00 2001
From: Jack Grigg <jack@z.cash>
Date: Wed, 31 May 2017 15:42:48 +1200
Subject: [PATCH] Add readUInt64LE and writeUInt64LE from bitcoinjs-lib

---
 src/bufferutils.js             | 34 +++++++++++++++
 test/bufferutils.js            | 50 ++++++++++++++++++++++
 test/fixtures/bufferutils.json | 76 ++++++++++++++++++++++++++++++++++
 3 files changed, 160 insertions(+)
 create mode 100644 src/bufferutils.js
 create mode 100644 test/bufferutils.js
 create mode 100644 test/fixtures/bufferutils.json

diff --git a/src/bufferutils.js b/src/bufferutils.js
new file mode 100644
index 0000000..87a5454
--- /dev/null
+++ b/src/bufferutils.js
@@ -0,0 +1,34 @@
+/**
+ * Copyright (c) 2011-2016 bitcoinjs-lib contributors
+ */
+
+// https://github.com/feross/buffer/blob/master/index.js#L1127
+function verifuint (value, max) {
+  if (typeof value !== 'number') throw new Error('cannot write a non-number as a number')
+  if (value < 0) throw new Error('specified a negative value for writing an unsigned value')
+  if (value > max) throw new Error('RangeError: value out of range')
+  if (Math.floor(value) !== value) throw new Error('value has a fractional component')
+}
+
+function readUInt64LE (buffer, offset) {
+  var a = buffer.readUInt32LE(offset)
+  var b = buffer.readUInt32LE(offset + 4)
+  b *= 0x100000000
+
+  verifuint(b + a, 0x001fffffffffffff)
+
+  return b + a
+}
+
+function writeUInt64LE (buffer, value, offset) {
+  verifuint(value, 0x001fffffffffffff)
+
+  buffer.writeInt32LE(value & -1, offset)
+  buffer.writeUInt32LE(Math.floor(value / 0x100000000), offset + 4)
+  return offset + 8
+}
+
+module.exports = {
+  readUInt64LE: readUInt64LE,
+  writeUInt64LE: writeUInt64LE
+}
diff --git a/test/bufferutils.js b/test/bufferutils.js
new file mode 100644
index 0000000..414e843
--- /dev/null
+++ b/test/bufferutils.js
@@ -0,0 +1,50 @@
+/* global describe, it */
+
+var assert = require('assert')
+var bufferutils = require('../src/bufferutils')
+
+var fixtures = require('./fixtures/bufferutils.json')
+
+describe('bufferutils', function () {
+  describe('readUInt64LE', function () {
+    fixtures.valid.forEach(function (f) {
+      it('decodes ' + f.hex64 + ' correctly', function () {
+        var buffer = Buffer.from(f.hex64, 'hex')
+        var number = bufferutils.readUInt64LE(buffer, 0)
+
+        assert.strictEqual(number, f.dec)
+      })
+    })
+
+    fixtures.invalid.readUInt64LE.forEach(function (f) {
+      it('throws on ' + f.description, function () {
+        var buffer = Buffer.from(f.hex64, 'hex')
+
+        assert.throws(function () {
+          bufferutils.readUInt64LE(buffer, 0)
+        }, new RegExp(f.exception))
+      })
+    })
+  })
+
+  describe('writeUInt64LE', function () {
+    fixtures.valid.forEach(function (f) {
+      it('encodes ' + f.dec + ' correctly', function () {
+        var buffer = Buffer.alloc(8, 0)
+
+        bufferutils.writeUInt64LE(buffer, f.dec, 0)
+        assert.strictEqual(buffer.toString('hex'), f.hex64)
+      })
+    })
+
+    fixtures.invalid.readUInt64LE.forEach(function (f) {
+      it('throws on ' + f.description, function () {
+        var buffer = Buffer.alloc(8, 0)
+
+        assert.throws(function () {
+          bufferutils.writeUInt64LE(buffer, f.dec, 0)
+        }, new RegExp(f.exception))
+      })
+    })
+  })
+})
diff --git a/test/fixtures/bufferutils.json b/test/fixtures/bufferutils.json
new file mode 100644
index 0000000..0b82d50
--- /dev/null
+++ b/test/fixtures/bufferutils.json
@@ -0,0 +1,76 @@
+{
+  "valid": [
+    {
+      "dec": 0,
+      "hex64": "0000000000000000"
+    },
+    {
+      "dec": 1,
+      "hex64": "0100000000000000"
+    },
+    {
+      "dec": 252,
+      "hex64": "fc00000000000000"
+    },
+    {
+      "dec": 253,
+      "hex64": "fd00000000000000"
+    },
+    {
+      "dec": 254,
+      "hex64": "fe00000000000000"
+    },
+    {
+      "dec": 255,
+      "hex64": "ff00000000000000"
+    },
+    {
+      "dec": 65534,
+      "hex64": "feff000000000000"
+    },
+    {
+      "dec": 65535,
+      "hex64": "ffff000000000000"
+    },
+    {
+      "dec": 65536,
+      "hex64": "0000010000000000"
+    },
+    {
+      "dec": 65537,
+      "hex64": "0100010000000000"
+    },
+    {
+      "dec": 4294967295,
+      "hex64": "ffffffff00000000"
+    },
+    {
+      "dec": 4294967296,
+      "hex64": "0000000001000000"
+    },
+    {
+      "dec": 4294967297,
+      "hex64": "0100000001000000"
+    },
+    {
+      "dec": 9007199254740991,
+      "hex64": "ffffffffffff1f00"
+    }
+  ],
+  "invalid": {
+    "readUInt64LE": [
+      {
+        "description": "n === 2^53",
+        "exception": "RangeError: value out of range",
+        "hex64": "0000000000002000",
+        "dec": 9007199254740992
+      },
+      {
+        "description": "n > 2^53",
+        "exception": "RangeError: value out of range",
+        "hex64": "0100000000002000",
+        "dec": 9007199254740993
+      }
+    ]
+  }
+}