Have ArrayCharSequence reuse its Array.

Your know, for performance.  Closes SI-5641.

1 files changed, 20 insertions, 5 deletions

diff --git a/src/library/scala/runtime/SeqCharSequence.scala b/src/library/scala/runtime/SeqCharSequence.scala
index 7f7bca789f..6bf88e0729 100644
--- a/src/library/scala/runtime/SeqCharSequence.scala
+++ b/src/library/scala/runtime/SeqCharSequence.scala
@@ -17,9 +17,24 @@ final class SeqCharSequence(val xs: collection.IndexedSeq[Char]) extends CharSeq
   override def toString = xs.mkString("")
 }
 
-final class ArrayCharSequence(val xs: Array[Char]) extends CharSequence {
-  def length: Int                                     = xs.length
-  def charAt(index: Int): Char                        = xs(index)
-  def subSequence(start: Int, end: Int): CharSequence = new ArrayCharSequence(copyOfRange(xs, math.max(0, start), math.min(xs.length, end)))
-  override def toString = xs.mkString("")
+final class ArrayCharSequence(val xs: Array[Char], start: Int, end: Int) extends CharSequence {
+  def this(xs: Array[Char]) = this(xs, 0, xs.length)
+
+  def length: Int = math.max(0, end - start)
+  def charAt(index: Int): Char = {
+    if (0 <= index && index < length)
+      xs(start + index)
+    else throw new ArrayIndexOutOfBoundsException(index)
+  }
+  def subSequence(start0: Int, end0: Int): CharSequence = {
+    if (start0 < 0) throw new ArrayIndexOutOfBoundsException(start0)
+    else if (end0 > length) throw new ArrayIndexOutOfBoundsException(end0)
+    else if (end0 <= start0) new ArrayCharSequence(xs, 0, 0)
+    else {
+      val newlen = end0 - start0
+      val start1 = start + start0
+      new ArrayCharSequence(xs, start1, start1 + newlen)
+    }
+  }
+  override def toString = xs drop start take length mkString ""
 }