Improving the performance of ByteString.decodeString, and adding base64

* Improving the performance of ByteString.decodeString, and adding ByteString.encodeBase64 and ByteString.decodeBase64
* ByteString.take should return itself whenever possible
* Implementing fallback for the rare case where the JDKs Base64 returns a non-array-backed ByteBuffer
* Adding mima excludes for encodeBase64/decodeBase64

akka-actor-tests/src/test/scala/akka/util/ByteStringSpec.scala

@@ -788,6 +788,20 @@ class ByteStringSpec extends AnyWordSpec with Matchers with Checkers {
         }
       }
 
+      "taking its own length" in {
+        check { b: ByteString =>
+          b.take(b.length) eq b
+        }
+      }
+
+      "created from and decoding to Base64" in {
+        check { a: ByteString =>
+          val encoded = a.encodeBase64
+          encoded == ByteString(java.util.Base64.getEncoder.encode(a.toArray)) &&
+          encoded.decodeBase64 == a
+        }
+      }
+
       "compacting" in {
         check { a: ByteString =>
           val wasCompact = a.isCompact

akka-actor/src/main/mima-filters/2.6.3.backwards.excludes/pr-28663-wip-bytestring-improvements-√.excludes

@@ -0,0 +1,2 @@
+ProblemFilters.exclude[ReversedMissingMethodProblem]("akka.util.ByteString.decodeBase64")
+ProblemFilters.exclude[ReversedMissingMethodProblem]("akka.util.ByteString.encodeBase64")

akka-actor/src/main/scala-2.13+/akka/util/ByteString.scala

@@ -8,6 +8,7 @@ import java.io.{ ObjectInputStream, ObjectOutputStream }
 import java.nio.{ ByteBuffer, ByteOrder }
 import java.lang.{ Iterable => JIterable }
 import java.nio.charset.{ Charset, StandardCharsets }
+import java.util.Base64
 
 import scala.annotation.{ tailrec, varargs }
 import scala.collection.mutable.{ Builder, WrappedArray }
@@ -196,6 +197,12 @@ object ByteString {
     override def decodeString(charset: Charset): String =
       if (isEmpty) "" else new String(bytes, charset)
 
+    override def decodeBase64: ByteString =
+      if (isEmpty) this else ByteString1C(Base64.getDecoder.decode(bytes))
+
+    override def encodeBase64: ByteString =
+      if (isEmpty) this else ByteString1C(Base64.getEncoder.encode(bytes))
+
     override def ++(that: ByteString): ByteString = {
       if (that.isEmpty) this
       else if (this.isEmpty) that
@@ -204,6 +211,7 @@ object ByteString {
 
     override def take(n: Int): ByteString =
       if (n <= 0) ByteString.empty
+      else if (n >= length) this
       else toByteString1.take(n)
 
     override def dropRight(n: Int): ByteString =
@@ -361,10 +369,34 @@ object ByteString {
     def asByteBuffers: scala.collection.immutable.Iterable[ByteBuffer] = List(asByteBuffer)
 
     override def decodeString(charset: String): String =
-      new String(if (length == bytes.length) bytes else toArray, charset)
+      if (isEmpty) ""
+      else new String(bytes, startIndex, length, charset)
 
     override def decodeString(charset: Charset): String = // avoids Charset.forName lookup in String internals
-      new String(if (length == bytes.length) bytes else toArray, charset)
+      if (isEmpty) ""
+      else new String(bytes, startIndex, length, charset)
+
+    override def decodeBase64: ByteString =
+      if (isEmpty) this
+      else if (isCompact) ByteString1C(Base64.getDecoder.decode(bytes))
+      else {
+        val dst = Base64.getDecoder.decode(ByteBuffer.wrap(bytes, startIndex, length))
+        if (dst.hasArray) {
+          if (dst.array.length == dst.remaining) ByteString1C(dst.array)
+          else ByteString1(dst.array, dst.arrayOffset + dst.position, dst.remaining)
+        } else CompactByteString(dst)
+      }
+
+    override def encodeBase64: ByteString =
+      if (isEmpty) this
+      else if (isCompact) ByteString1C(Base64.getEncoder.encode(bytes))
+      else {
+        val dst = Base64.getEncoder.encode(ByteBuffer.wrap(bytes, startIndex, length))
+        if (dst.hasArray) {
+          if (dst.array.length == dst.remaining) ByteString1C(dst.array)
+          else ByteString1(dst.array, dst.arrayOffset + dst.position, dst.remaining)
+        } else CompactByteString(dst)
+      }
 
     def ++(that: ByteString): ByteString = {
       if (that.isEmpty) this
@@ -535,6 +567,10 @@ object ByteString {
 
     def decodeString(charset: Charset): String = compact.decodeString(charset)
 
+    override def decodeBase64: ByteString = compact.decodeBase64
+
+    override def encodeBase64: ByteString = compact.encodeBase64
+
     private[akka] def writeToOutputStream(os: ObjectOutputStream): Unit = {
       os.writeInt(bytestrings.length)
       bytestrings.foreach(_.writeToOutputStream(os))
@@ -887,6 +923,17 @@ sealed abstract class ByteString
    */
   def decodeString(charset: Charset): String
 
+  /*
+   * Returns a ByteString which is the binary representation of this ByteString
+   * if this ByteString is Base64-encoded.
+   */
+  def decodeBase64: ByteString
+
+  /**
+   * Returns a ByteString which is the Base64 representation of this ByteString
+   */
+  def encodeBase64: ByteString
+
   /**
    * map method that will automatically cast Int back into Byte.
    */

akka-actor/src/main/scala-2.13-/akka/util/ByteString.scala

@@ -7,6 +7,7 @@ package akka.util
 import java.io.{ ObjectInputStream, ObjectOutputStream }
 import java.nio.{ ByteBuffer, ByteOrder }
 import java.lang.{ Iterable => JIterable }
+import java.util.Base64
 
 import scala.annotation.{ tailrec, varargs }
 import scala.collection.IndexedSeqOptimized
@@ -193,6 +194,12 @@ object ByteString {
     override def decodeString(charset: Charset): String =
       if (isEmpty) "" else new String(bytes, charset)
 
+    override def decodeBase64: ByteString =
+      if (isEmpty) this else ByteString1C(Base64.getDecoder.decode(bytes))
+
+    override def encodeBase64: ByteString =
+      if (isEmpty) this else ByteString1C(Base64.getEncoder.encode(bytes))
+
     override def ++(that: ByteString): ByteString = {
       if (that.isEmpty) this
       else if (this.isEmpty) that
@@ -201,6 +208,7 @@ object ByteString {
 
     override def take(n: Int): ByteString =
       if (n <= 0) ByteString.empty
+      else if (n >= length) this
       else toByteString1.take(n)
 
     override def dropRight(n: Int): ByteString =
@@ -351,10 +359,34 @@ object ByteString {
     def asByteBuffers: scala.collection.immutable.Iterable[ByteBuffer] = List(asByteBuffer)
 
     override def decodeString(charset: String): String =
-      new String(if (length == bytes.length) bytes else toArray, charset)
+      if (isEmpty) ""
+      else new String(bytes, startIndex, length, charset)
 
     override def decodeString(charset: Charset): String = // avoids Charset.forName lookup in String internals
-      new String(if (length == bytes.length) bytes else toArray, charset)
+      if (isEmpty) ""
+      else new String(bytes, startIndex, length, charset)
+
+    override def decodeBase64: ByteString =
+      if (isEmpty) this
+      else if (isCompact) ByteString1C(Base64.getDecoder.decode(bytes))
+      else {
+        val dst = Base64.getDecoder.decode(ByteBuffer.wrap(bytes, startIndex, length))
+        if (dst.hasArray) {
+          if (dst.array.length == dst.remaining) ByteString1C(dst.array)
+          else ByteString1(dst.array, dst.arrayOffset + dst.position, dst.remaining)
+        } else CompactByteString(dst)
+      }
+
+    override def encodeBase64: ByteString =
+      if (isEmpty) this
+      else if (isCompact) ByteString1C(Base64.getEncoder.encode(bytes))
+      else {
+        val dst = Base64.getEncoder.encode(ByteBuffer.wrap(bytes, startIndex, length))
+        if (dst.hasArray) {
+          if (dst.array.length == dst.remaining) ByteString1C(dst.array)
+          else ByteString1(dst.array, dst.arrayOffset + dst.position, dst.remaining)
+        } else CompactByteString(dst)
+      }
 
     def ++(that: ByteString): ByteString = {
       if (that.isEmpty) this
@@ -517,6 +549,10 @@ object ByteString {
 
     def decodeString(charset: Charset): String = compact.decodeString(charset)
 
+    override def decodeBase64: ByteString = compact.decodeBase64
+
+    override def encodeBase64: ByteString = compact.encodeBase64
+
     private[akka] def writeToOutputStream(os: ObjectOutputStream): Unit = {
       os.writeInt(bytestrings.length)
       bytestrings.foreach(_.writeToOutputStream(os))
@@ -835,6 +871,17 @@ sealed abstract class ByteString extends IndexedSeq[Byte] with IndexedSeqOptimiz
    */
   def decodeString(charset: Charset): String
 
+  /*
+   * Returns a ByteString which is the binary representation of this ByteString
+   * if this ByteString is Base64-encoded.
+   */
+  def decodeBase64: ByteString
+
+  /**
+   * Returns a ByteString which is the Base64 representation of this ByteString
+   */
+  def encodeBase64: ByteString
+
   /**
    * map method that will automatically cast Int back into Byte.
    */
@@ -1237,8 +1284,7 @@ final class ByteStringBuilder extends Builder[Byte, ByteString] {
    * operations on the stream are forwarded to the builder.
    */
   def asOutputStream: java.io.OutputStream = new java.io.OutputStream {
-    def write(b: Int): Unit = builder += b.toByte
-
+    override def write(b: Int): Unit = builder += b.toByte
     override def write(b: Array[Byte], off: Int, len: Int): Unit = { builder.putBytes(b, off, len) }
   }