init

.gitignore

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+.idea
+target

LICENSE

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+MIT License
+
+Copyright (c) 2018 Chang Liu
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# varint
+
+[![standard-readme compliant](https://img.shields.io/badge/standard--readme-OK-green.svg?style=flat-square)](https://github.com/RichardLitt/standard-readme)
+
+> Scala Implementation of [Varint](https://github.com/multiformats/unsigned-varint).
+
+## Table of Contents
+
+- [Install](#install)
+- [Usage](#usage)
+- [API](#api)
+- [Maintainers](#maintainers)
+- [Contribute](#contribute)
+- [License](#license)
+
+## Install
+
+```
+```
+
+## Usage
+
+```
+```
+
+## API
+
+## Maintainers
+
+[@fluency03](https://github.com/fluency03)
+
+## Contribute
+
+PRs accepted.
+
+Small note: If editing the README, please conform to the [standard-readme](https://github.com/RichardLitt/standard-readme) specification.
+
+## License
+
+MIT © 2018 Chang Liu

build.sbt

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+name := "varint"
+
+version := "0.0.1"
+
+organization := "com.github.fluency03"
+organizationName := "fluency03"
+organizationHomepage := Some(url("https://github.com/fluency03"))
+
+scalaVersion := "2.12.7"
+
+val scalaTestVersion = "3.0.5"
+
+val testDependencies = Seq(
+  "org.scalactic" %% "scalactic" % scalaTestVersion,
+  "org.scalatest" %% "scalatest" % scalaTestVersion % Test
+)
+
+libraryDependencies ++= testDependencies
+
+sonatypeProfileName := "com.github.fluency03"
+
+publishMavenStyle := true
+
+publishTo := {
+  val nexus = "https://oss.sonatype.org/"
+  if (isSnapshot.value)
+    Some("snapshots" at nexus + "content/repositories/snapshots")
+  else
+    Some("releases"  at nexus + "service/local/staging/deploy/maven2")
+}
+
+scmInfo := Some(
+  ScmInfo(
+    url("https://github.com/fluency03/varint"),
+    "scm:git@github.com:fluency03/varint.git"
+  )
+)
+
+developers := List(
+  Developer(
+    id  = "fluency03",
+    name = "Chang Liu",
+    email = "fluency.03@gmail.com",
+    url = url("https://github.com/fluency03")
+  )
+)
+
+description := "Scala Implementation of Varint."
+
+licenses := Seq("MIT" -> url("https://raw.githubusercontent.com/fluency03/varint/master/LICENSE"))
+
+homepage := Some(url("https://github.com/fluency03/varint"))
+
+pomIncludeRepository := { _ => false }

project/build.properties

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+sbt.version = 1.2.6

project/plugins.sbt

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+addSbtPlugin("com.jsuereth" % "sbt-pgp" % "2.0.0-M2")
+addSbtPlugin("org.xerial.sbt" % "sbt-sonatype" % "2.0")

src/main/scala/com/github/fluency03/varint/Varint.scala

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+package com.github.fluency03.varint
+
+import scala.annotation.tailrec
+
+object Varint {
+
+  val MSB = 0x80
+  val LOW_7_BITS = 0x7F
+  val INT_REST_BITES = 0xFFFFFF80
+  val LONG_REST_BITES = 0xFFFFFFFFFFFFFF80L
+
+  // TODO (fluency03): set max size
+
+  def encodeInt(num: Int): Array[Byte] = {
+    @tailrec
+    def rec(value: Int, acc: Array[Byte]): Array[Byte] =
+      if ((value & INT_REST_BITES) == 0) acc :+ (value & LOW_7_BITS).toByte
+      else rec(value >>> 7, acc :+ ((value & LOW_7_BITS) | MSB).toByte)
+
+    rec(num, Array())
+  }
+
+  def encodeLong(num: Long): Array[Byte] = {
+    @tailrec
+    def rec(value: Long, acc: Array[Byte]): Array[Byte] =
+      if ((value & LONG_REST_BITES) == 0) acc :+ (value & LOW_7_BITS).toByte
+      else rec(value >>> 7, acc :+ ((value & LOW_7_BITS) | MSB).toByte)
+
+    rec(num, Array())
+  }
+
+
+  def decodeToInt(bytes: Array[Byte]): Int = {
+    @tailrec
+    def rec(index: Int, shift: Int, acc: Int): Int =
+      if (index >= bytes.length || (bytes(index) & MSB) == 0) acc | (bytes(index) << shift)
+      else rec(index + 1, shift + 7, acc | ((bytes(index) & LOW_7_BITS) << shift))
+
+    rec(0, 0, 0)
+  }
+
+  def decodeToLong(bytes: Array[Byte]): Long = {
+    @tailrec
+    def rec(index: Int, shift: Long, acc: Long): Long =
+      if (index >= bytes.length || (bytes(index) & MSB) == 0) acc | (bytes(index).toLong << shift)
+      else rec(index + 1, shift + 7, acc | ((bytes(index).toLong & LOW_7_BITS) << shift))
+
+    rec(0, 0L, 0L)
+  }
+
+}

src/test/scala/com/github/fluency03/varint/VarintTest.scala

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+package com.github.fluency03.varint
+
+import org.scalatest.{FlatSpec, Matchers}
+
+class VarintTest extends FlatSpec with Matchers {
+
+  val rand = new scala.util.Random
+
+  it should "encode an Int to Varint Bytes and decode it back." in {
+    for (i <- 1 to 100) {
+      val num = rand.nextInt(Int.MaxValue)
+      Varint.decodeToInt(Varint.encodeInt(num)) shouldBe num
+    }
+
+    Varint.encodeInt(300) shouldBe Array(0xac.toByte, 0x02.toByte)
+  }
+
+  it should "encode an Long to Varint Bytes and decode it back." in {
+    for (i <- 1 to 200) {
+      val num = rand.nextLong
+      if (num > 0) Varint.decodeToLong(Varint.encodeLong(num)) shouldBe num
+    }
+
+    Varint.decodeToLong(Varint.encodeLong(278734309057836877L)) shouldBe 278734309057836877L
+    Varint.decodeToLong(Varint.encodeLong(100L)) shouldBe 100L
+    Varint.decodeToLong(Varint.encodeLong(10000000000L)) shouldBe 10000000000L
+  }
+
+}