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author | Paul Phillips <paulp@improving.org> | 2012-09-30 09:43:51 -0700 |
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committer | Paul Phillips <paulp@improving.org> | 2012-09-30 09:59:19 -0700 |
commit | d16326a7b679ec7877ff6b5223d2176f8a651b70 (patch) | |
tree | 6857acfbd9f821f1a069d7025d71614eb2063f1c /src/library | |
parent | 2e14b0771569b4fb6cd0273e1480f69c18743832 (diff) | |
download | scala-d16326a7b679ec7877ff6b5223d2176f8a651b70.tar.gz scala-d16326a7b679ec7877ff6b5223d2176f8a651b70.tar.bz2 scala-d16326a7b679ec7877ff6b5223d2176f8a651b70.zip |
Fix for SI-6452, leak in ListBuffer.
The private var which holds a pointer to the end
of the list was not cleared even when the length of the
buffer was reduced to 0.
Diffstat (limited to 'src/library')
-rw-r--r-- | src/library/scala/collection/mutable/ListBuffer.scala | 44 |
1 files changed, 31 insertions, 13 deletions
diff --git a/src/library/scala/collection/mutable/ListBuffer.scala b/src/library/scala/collection/mutable/ListBuffer.scala index cd743999bc..bced92e663 100644 --- a/src/library/scala/collection/mutable/ListBuffer.scala +++ b/src/library/scala/collection/mutable/ListBuffer.scala @@ -56,12 +56,18 @@ final class ListBuffer[A] import scala.collection.Traversable import scala.collection.immutable.ListSerializeEnd + /** Expected invariants: + * If start.isEmpty, last0 == null + * If start.nonEmpty, last0 != null + * If len == 0, start.isEmpty + * If len > 0, start.nonEmpty + */ private var start: List[A] = Nil private var last0: ::[A] = _ private var exported: Boolean = false private var len = 0 - protected def underlying: immutable.Seq[A] = start + protected def underlying: List[A] = start private def writeObject(out: ObjectOutputStream) { // write start @@ -133,7 +139,7 @@ final class ListBuffer[A] if (exported) copy() if (n == 0) { val newElem = new :: (x, start.tail); - if (last0 eq start) { + if ((last0 eq null) || (last0 eq start)) { last0 = newElem } start = newElem @@ -162,7 +168,7 @@ final class ListBuffer[A] */ def += (x: A): this.type = { if (exported) copy() - if (start.isEmpty) { + if (isEmpty) { last0 = new :: (x, Nil) start = last0 } else { @@ -184,6 +190,7 @@ final class ListBuffer[A] */ def clear() { start = Nil + last0 = null exported = false len = 0 } @@ -197,7 +204,7 @@ final class ListBuffer[A] def +=: (x: A): this.type = { if (exported) copy() val newElem = new :: (x, start) - if (start.isEmpty) last0 = newElem + if (isEmpty) last0 = newElem start = newElem len += 1 this @@ -219,7 +226,7 @@ final class ListBuffer[A] if (n == 0) { while (!elems.isEmpty) { val newElem = new :: (elems.head, start) - if (start.isEmpty) last0 = newElem + if (isEmpty) last0 = newElem start = newElem elems = elems.tail } @@ -243,6 +250,15 @@ final class ListBuffer[A] } } + /** Reduce the length of the buffer, and null out last0 + * if this reduces the length to 0. + */ + private def reduceLengthBy(num: Int) { + len -= num + if (len <= 0) // obviously shouldn't be < 0, but still better not to leak + last0 = null + } + /** Removes a given number of elements on a given index position. May take * time linear in the buffer size. * @@ -274,7 +290,7 @@ final class ListBuffer[A] c -= 1 } } - len -= count1 + reduceLengthBy(count1) } // Implementation of abstract method in Builder @@ -285,7 +301,7 @@ final class ListBuffer[A] * copied lazily, the first time it is mutated. */ override def toList: List[A] = { - exported = !start.isEmpty + exported = !isEmpty start } @@ -296,7 +312,7 @@ final class ListBuffer[A] * @param xs the list to which elements are prepended */ def prependToList(xs: List[A]): List[A] = { - if (start.isEmpty) xs + if (isEmpty) xs else { if (exported) copy() last0.tl = xs @@ -331,7 +347,7 @@ final class ListBuffer[A] if (last0 eq cursor.tail) last0 = cursor.asInstanceOf[::[A]] cursor.asInstanceOf[::[A]].tl = cursor.tail.tail } - len -= 1 + reduceLengthBy(1) old } @@ -343,11 +359,12 @@ final class ListBuffer[A] */ override def -= (elem: A): this.type = { if (exported) copy() - if (start.isEmpty) {} + if (isEmpty) {} else if (start.head == elem) { start = start.tail - len -= 1 - } else { + reduceLengthBy(1) + } + else { var cursor = start while (!cursor.tail.isEmpty && cursor.tail.head != elem) { cursor = cursor.tail @@ -357,7 +374,7 @@ final class ListBuffer[A] if (z.tl == last0) last0 = z z.tl = cursor.tail.tail - len -= 1 + reduceLengthBy(1) } } this @@ -397,6 +414,7 @@ final class ListBuffer[A] /** Copy contents of this buffer */ private def copy() { + if (isEmpty) return var cursor = start val limit = last0.tail clear() |