Have ArrayCharSequence reuse its Array.

Your know, for performance.  Closes SI-5641.

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 ""
 }

test/files/run/array-charSeq.check

@@ -0,0 +1,248 @@
+
+[check 'abcdefghi'] len = 9
+sub(0, 9) == 'abcdefghi'
+sub(0, 0) == ''
+sub(1, 9) == 'bcdefghi'
+sub(0, 1) == 'a'
+sub(2, 9) == 'cdefghi'
+sub(0, 2) == 'ab'
+sub(3, 9) == 'defghi'
+sub(0, 3) == 'abc'
+sub(4, 9) == 'efghi'
+sub(0, 4) == 'abcd'
+sub(5, 9) == 'fghi'
+sub(0, 5) == 'abcde'
+sub(6, 9) == 'ghi'
+sub(0, 6) == 'abcdef'
+sub(7, 9) == 'hi'
+sub(0, 7) == 'abcdefg'
+sub(8, 9) == 'i'
+sub(0, 8) == 'abcdefgh'
+
+[check 'bcdefgh'] len = 7
+sub(0, 7) == 'bcdefgh'
+sub(0, 0) == ''
+sub(1, 7) == 'cdefgh'
+sub(0, 1) == 'b'
+sub(2, 7) == 'defgh'
+sub(0, 2) == 'bc'
+sub(3, 7) == 'efgh'
+sub(0, 3) == 'bcd'
+sub(4, 7) == 'fgh'
+sub(0, 4) == 'bcde'
+sub(5, 7) == 'gh'
+sub(0, 5) == 'bcdef'
+sub(6, 7) == 'h'
+sub(0, 6) == 'bcdefg'
+
+[check 'cdefg'] len = 5
+sub(0, 5) == 'cdefg'
+sub(0, 0) == ''
+sub(1, 5) == 'defg'
+sub(0, 1) == 'c'
+sub(2, 5) == 'efg'
+sub(0, 2) == 'cd'
+sub(3, 5) == 'fg'
+sub(0, 3) == 'cde'
+sub(4, 5) == 'g'
+sub(0, 4) == 'cdef'
+
+[check 'def'] len = 3
+sub(0, 3) == 'def'
+sub(0, 0) == ''
+sub(1, 3) == 'ef'
+sub(0, 1) == 'd'
+sub(2, 3) == 'f'
+sub(0, 2) == 'de'
+
+[check 'e'] len = 1
+sub(0, 1) == 'e'
+sub(0, 0) == ''
+
+[check 'abcdefgh'] len = 8
+sub(0, 8) == 'abcdefgh'
+sub(0, 0) == ''
+sub(1, 8) == 'bcdefgh'
+sub(0, 1) == 'a'
+sub(2, 8) == 'cdefgh'
+sub(0, 2) == 'ab'
+sub(3, 8) == 'defgh'
+sub(0, 3) == 'abc'
+sub(4, 8) == 'efgh'
+sub(0, 4) == 'abcd'
+sub(5, 8) == 'fgh'
+sub(0, 5) == 'abcde'
+sub(6, 8) == 'gh'
+sub(0, 6) == 'abcdef'
+sub(7, 8) == 'h'
+sub(0, 7) == 'abcdefg'
+
+[check 'bcdefg'] len = 6
+sub(0, 6) == 'bcdefg'
+sub(0, 0) == ''
+sub(1, 6) == 'cdefg'
+sub(0, 1) == 'b'
+sub(2, 6) == 'defg'
+sub(0, 2) == 'bc'
+sub(3, 6) == 'efg'
+sub(0, 3) == 'bcd'
+sub(4, 6) == 'fg'
+sub(0, 4) == 'bcde'
+sub(5, 6) == 'g'
+sub(0, 5) == 'bcdef'
+
+[check 'cdef'] len = 4
+sub(0, 4) == 'cdef'
+sub(0, 0) == ''
+sub(1, 4) == 'def'
+sub(0, 1) == 'c'
+sub(2, 4) == 'ef'
+sub(0, 2) == 'cd'
+sub(3, 4) == 'f'
+sub(0, 3) == 'cde'
+
+[check 'de'] len = 2
+sub(0, 2) == 'de'
+sub(0, 0) == ''
+sub(1, 2) == 'e'
+sub(0, 1) == 'd'
+
+[check ''] len = 0
+
+[check 'abcdefg'] len = 7
+sub(0, 7) == 'abcdefg'
+sub(0, 0) == ''
+sub(1, 7) == 'bcdefg'
+sub(0, 1) == 'a'
+sub(2, 7) == 'cdefg'
+sub(0, 2) == 'ab'
+sub(3, 7) == 'defg'
+sub(0, 3) == 'abc'
+sub(4, 7) == 'efg'
+sub(0, 4) == 'abcd'
+sub(5, 7) == 'fg'
+sub(0, 5) == 'abcde'
+sub(6, 7) == 'g'
+sub(0, 6) == 'abcdef'
+
+[check 'bcdef'] len = 5
+sub(0, 5) == 'bcdef'
+sub(0, 0) == ''
+sub(1, 5) == 'cdef'
+sub(0, 1) == 'b'
+sub(2, 5) == 'def'
+sub(0, 2) == 'bc'
+sub(3, 5) == 'ef'
+sub(0, 3) == 'bcd'
+sub(4, 5) == 'f'
+sub(0, 4) == 'bcde'
+
+[check 'cde'] len = 3
+sub(0, 3) == 'cde'
+sub(0, 0) == ''
+sub(1, 3) == 'de'
+sub(0, 1) == 'c'
+sub(2, 3) == 'e'
+sub(0, 2) == 'cd'
+
+[check 'd'] len = 1
+sub(0, 1) == 'd'
+sub(0, 0) == ''
+
+[check 'abcdef'] len = 6
+sub(0, 6) == 'abcdef'
+sub(0, 0) == ''
+sub(1, 6) == 'bcdef'
+sub(0, 1) == 'a'
+sub(2, 6) == 'cdef'
+sub(0, 2) == 'ab'
+sub(3, 6) == 'def'
+sub(0, 3) == 'abc'
+sub(4, 6) == 'ef'
+sub(0, 4) == 'abcd'
+sub(5, 6) == 'f'
+sub(0, 5) == 'abcde'
+
+[check 'bcde'] len = 4
+sub(0, 4) == 'bcde'
+sub(0, 0) == ''
+sub(1, 4) == 'cde'
+sub(0, 1) == 'b'
+sub(2, 4) == 'de'
+sub(0, 2) == 'bc'
+sub(3, 4) == 'e'
+sub(0, 3) == 'bcd'
+
+[check 'cd'] len = 2
+sub(0, 2) == 'cd'
+sub(0, 0) == ''
+sub(1, 2) == 'd'
+sub(0, 1) == 'c'
+
+[check ''] len = 0
+
+[check 'abcde'] len = 5
+sub(0, 5) == 'abcde'
+sub(0, 0) == ''
+sub(1, 5) == 'bcde'
+sub(0, 1) == 'a'
+sub(2, 5) == 'cde'
+sub(0, 2) == 'ab'
+sub(3, 5) == 'de'
+sub(0, 3) == 'abc'
+sub(4, 5) == 'e'
+sub(0, 4) == 'abcd'
+
+[check 'bcd'] len = 3
+sub(0, 3) == 'bcd'
+sub(0, 0) == ''
+sub(1, 3) == 'cd'
+sub(0, 1) == 'b'
+sub(2, 3) == 'd'
+sub(0, 2) == 'bc'
+
+[check 'c'] len = 1
+sub(0, 1) == 'c'
+sub(0, 0) == ''
+
+[check 'abcd'] len = 4
+sub(0, 4) == 'abcd'
+sub(0, 0) == ''
+sub(1, 4) == 'bcd'
+sub(0, 1) == 'a'
+sub(2, 4) == 'cd'
+sub(0, 2) == 'ab'
+sub(3, 4) == 'd'
+sub(0, 3) == 'abc'
+
+[check 'bc'] len = 2
+sub(0, 2) == 'bc'
+sub(0, 0) == ''
+sub(1, 2) == 'c'
+sub(0, 1) == 'b'
+
+[check ''] len = 0
+
+[check 'abc'] len = 3
+sub(0, 3) == 'abc'
+sub(0, 0) == ''
+sub(1, 3) == 'bc'
+sub(0, 1) == 'a'
+sub(2, 3) == 'c'
+sub(0, 2) == 'ab'
+
+[check 'b'] len = 1
+sub(0, 1) == 'b'
+sub(0, 0) == ''
+
+[check 'ab'] len = 2
+sub(0, 2) == 'ab'
+sub(0, 0) == ''
+sub(1, 2) == 'b'
+sub(0, 1) == 'a'
+
+[check ''] len = 0
+
+[check 'a'] len = 1
+sub(0, 1) == 'a'
+sub(0, 0) == ''

test/files/run/array-charSeq.scala

@@ -0,0 +1,27 @@
+object Test {
+  val arr = Array[Char]('a' to 'i': _*)
+  var xs: CharSequence = arr
+  val hash = xs.hashCode
+
+  def check(chars: CharSequence) {
+    println("\n[check '" + chars + "'] len = " + chars.length)
+    chars match {
+      case x: runtime.ArrayCharSequence => assert(x.xs eq arr, ((x.xs, arr)))
+      case x                            => assert(false, x)
+    }
+
+    0 until chars.length foreach { i =>
+      println("sub(%s, %s) == '%s'".format(i, chars.length, chars.subSequence(i, chars.length)))
+      println("sub(%s, %s) == '%s'".format(0, i, chars.subSequence(0, i)))
+    }
+    if (chars.length >= 2)
+      check(chars.subSequence(1, chars.length - 1))
+  }
+
+  def main(args: Array[String]): Unit = {
+    while (xs.length > 0) {
+      check(xs)
+      xs = xs.subSequence(0, xs.length - 1)
+    }
+  }
+}