add offset & exception in case of invalid input bytes

README.md

@@ -1,5 +1,7 @@
 # varint
 
+[![Latest release](https://img.shields.io/github/release/fluency03/varint.svg)](https://github.com/fluency03/varint/releases/latest)
+[![Maven Central](https://img.shields.io/maven-central/v/com.github.fluency03/varint_2.12.svg?label=Maven%20Central)](https://search.maven.org/search?q=g:%22com.github.fluency03%22%20AND%20a:%22varint_2.12%22)
 [![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).
@@ -15,7 +17,20 @@
 
 ## Install
 
+#### Maven
+
+```xml
+<dependency>
+  <groupId>com.github.fluency03</groupId>
+  <artifactId>varint_2.12</artifactId>
+  <version>{latestVersion}</version>
+</dependency>
 ```
+
+#### sbt
+
+```scala
+libraryDependencies += "com.github.fluency03" % "varint_2.12" % {latestVersion}
 ```
 
 ## Usage

build.sbt

@@ -1,6 +1,6 @@
 name := "varint"
 
-version := "0.0.1"
+version := "0.0.2"
 
 organization := "com.github.fluency03"
 organizationName := "fluency03"

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

@@ -9,8 +9,6 @@ object Varint {
   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] =
@@ -29,23 +27,38 @@ object Varint {
     rec(num, Array())
   }
 
+  def decodeToInt(bytes: Array[Byte]): (Int, Int) = decodeToInt(bytes, 0)
 
-  def decodeToInt(bytes: Array[Byte]): Int = {
+  def decodeToInt(bytes: Array[Byte], offset: Int): (Int, Int) = {
     @tailrec
-    def rec(index: Int, shift: Int, acc: Int): Int =
-      if (index >= bytes.length || (bytes(index) & MSB) == 0) acc | (bytes(index) << shift)
+    def rec(index: Int, shift: Int, acc: Int): (Int, Int) =
+      if (index >= bytes.length) throw new IllegalArgumentException("Cannot find the ending Byte.")
+      else if ((bytes(index) & MSB) == 0) (acc | (bytes(index) << shift), index + 1 - offset)
       else rec(index + 1, shift + 7, acc | ((bytes(index) & LOW_7_BITS) << shift))
 
-    rec(0, 0, 0)
+    rec(offset, 0, 0)
   }
 
-  def decodeToLong(bytes: Array[Byte]): Long = {
+  def decodeToLong(bytes: Array[Byte]): (Long, Int) = decodeToLong(bytes, 0)
+
+  def decodeToLong(bytes: Array[Byte], offset: Int): (Long, Int) = {
     @tailrec
-    def rec(index: Int, shift: Long, acc: Long): Long =
-      if (index >= bytes.length || (bytes(index) & MSB) == 0) acc | (bytes(index).toLong << shift)
+    def rec(index: Int, shift: Long, acc: Long): (Long, Int) =
+      if (index >= bytes.length) throw new IllegalArgumentException("Cannot find the ending Byte.")
+      else if ((bytes(index) & MSB) == 0) (acc | (bytes(index).toLong << shift), index + 1 - offset)
       else rec(index + 1, shift + 7, acc | ((bytes(index).toLong & LOW_7_BITS) << shift))
 
-    rec(0, 0L, 0L)
+    rec(offset, 0L, 0L)
+  }
+
+  def extractLength(bytes: Array[Byte], offset: Int): Int = {
+    @tailrec
+    def rec(index: Int): Int =
+      if (index >= bytes.length) 0
+      else if ((bytes(index) & MSB) == 0) index + 1 - offset
+      else rec(index + 1)
+
+    rec(offset)
   }
 
 }

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

@@ -9,7 +9,7 @@ class VarintTest extends FlatSpec with Matchers {
   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.decodeToInt(Varint.encodeInt(num))._1 shouldBe num
     }
 
     Varint.encodeInt(300) shouldBe Array(0xac.toByte, 0x02.toByte)
@@ -18,12 +18,43 @@ class VarintTest extends FlatSpec with Matchers {
   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
+      if (num > 0) Varint.decodeToLong(Varint.encodeLong(num))._1 shouldBe num
     }
 
-    Varint.decodeToLong(Varint.encodeLong(278734309057836877L)) shouldBe 278734309057836877L
-    Varint.decodeToLong(Varint.encodeLong(100L)) shouldBe 100L
-    Varint.decodeToLong(Varint.encodeLong(10000000000L)) shouldBe 10000000000L
+    Varint.decodeToLong(Varint.encodeLong(278734309057836877L))._1 shouldBe 278734309057836877L
+    Varint.decodeToLong(Varint.encodeLong(100L))._1 shouldBe 100L
+    Varint.decodeToLong(Varint.encodeLong(10000000000L))._1 shouldBe 10000000000L
+  }
+
+  it should "throw exception if the given bytes is not Varint bytes." in {
+    the [IllegalArgumentException] thrownBy {
+      Varint.decodeToInt(Array())
+    } should have message "Cannot find the ending Byte."
+
+    the [IllegalArgumentException] thrownBy {
+      Varint.decodeToInt(Array(0xff.toByte))
+    } should have message "Cannot find the ending Byte."
+
+    the [IllegalArgumentException] thrownBy {
+      Varint.decodeToInt(Array(0xff.toByte, 0x8f.toByte))
+    } should have message "Cannot find the ending Byte."
+
+    the [IllegalArgumentException] thrownBy {
+      Varint.decodeToInt(Array(0x8f.toByte))
+    } should have message "Cannot find the ending Byte."
+  }
+
+  it should "be able to extract the valid length of Varint from bytes, given offset." in {
+    Varint.extractLength(Array(), 0) shouldBe 0
+    Varint.extractLength(Array(), 1) shouldBe 0
+    Varint.extractLength(Array(0xff.toByte), 0) shouldBe 0
+    Varint.extractLength(Array(0xff.toByte, 0x8f.toByte), 0) shouldBe 0
+    Varint.extractLength(Array(0x8f.toByte), 0) shouldBe 0
+
+    Varint.extractLength(Array(0xff.toByte, 0x0f.toByte), 0) shouldBe 2
+    Varint.extractLength(Array(0xff.toByte, 0x0f.toByte), 1) shouldBe 1
+    Varint.extractLength(Array(0xff.toByte, 0xff.toByte, 0x8f.toByte, 0x8f.toByte, 0x0f.toByte), 0) shouldBe 5
+    Varint.extractLength(Array(0x80.toByte, 0x80.toByte, 0x8f.toByte, 0x82.toByte, 0x01.toByte), 2) shouldBe 3
   }
 
 }