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/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2006, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
// $Id$
package scala.collection.mutable
import Predef._
/**
*/
final class ListBuffer[A] extends Buffer[A] {
private var start: List[A] = Nil
private var last: ::[A] = _
private var exported: boolean = false
/** Prepend a single element to this buffer.
*
* @param x the element to prepend.
*/
def +: (x: A): Buffer[A] = {
if (exported) copy()
val newElem = new scala.:: (x, start)
if (start.isEmpty) last = newElem
start = newElem
this
}
/** Append a single element to this buffer.
*
* @param x the element to append.
*/
override def += (x: A): unit = {
if (exported) copy()
if (start.isEmpty) {
last = new scala.:: (x, Nil)
start = last
} else {
val last1 = last
last = new scala.:: (x, Nil)
last1.tl = last
}
}
/** Remove a single element from the buffer and return
* the identity of the buffer. Same as ``this -= x; this''
*
* @param x the element to remove.
*/
def - (x: A): Buffer[A] = { this -= x; this }
/** Remove a single element from this buffer.
*
* @param x the element to remove.
*/
override def -= (x: A): unit = {
if (exported) copy()
if (start.isEmpty) {}
else if (start.head == x) start = start.tail
else {
var cursor = start
while (!cursor.tail.isEmpty && cursor.tail.head != x)
cursor = cursor.tail
if (!cursor.tail.isEmpty)
cursor.asInstanceOf[scala.::[A]].tl = cursor.tail.tail
}
}
/** Converts this buffer to a list
*/
override def toList: List[A] = {
exported = !start.isEmpty
start
}
/** Prepends the elements of this buffer to a given list
*
* @param xs the list to which elements are prepended
*/
def prependToList(xs: List[A]): List[A] =
if (start.isEmpty) xs
else { last.tl = xs; toList }
/** Clears the buffer contents.
*/
def clear: unit = {
start = Nil
exported = false
}
/** Copy contents of this buffer */
private def copy() = {
var cursor = start
val limit = last.tail
clear
while (cursor ne limit) {
this += cursor.head
cursor = cursor.tail
}
}
/** Returns the length of this buffer.
*/
def length: int = start.length
private def noElem(n: int): All =
error("element " + n + " does not exist in buffer")
/** Returns the <code>n</code>th element of this list. This method
* yields an error if the element does not exist.
*/
def apply(n: Int): A = try {
start(n)
} catch {
case ex: Error => noElem(n)
}
/** Replace element at index <code>n</code> with the new element
* <code>newelem</code>.
*
* @param n the index of the element to replace.
* @param x the new element.
*/
def update(n: Int, x: A): unit = try {
if (exported) copy()
if (n == 0) {
val newElem = new scala.:: (x, start.tail);
if (last eq start) last = newElem
start = newElem
} else {
var cursor = start;
var i = 1;
while (i < n) {
cursor = cursor.tail
i = i + 1
}
val newElem = new scala.:: (x, cursor.tail.tail)
if (last eq cursor.tail) last = newElem
cursor.asInstanceOf[scala.::[A]].tl = newElem
}
} catch {
case ex: Error => noElem(n)
}
/** Inserts new elements at the index <code>n</code>. Opposed to method
* <code>update</code>, this method will not replace an element with a new
* one. Instead, it will insert a new element at index <code>n</code>.
*
* @param n the index where a new element will be inserted.
* @param iter the iterable object providing all elements to insert.
*/
def insertAll(n: Int, iter: Iterable[A]): unit = try {
if (exported) copy()
var elems = iter.elements.toList.reverse
if (n == 0) {
while (!elems.isEmpty) {
val newElem = new scala.:: (elems.head, start);
if (start.isEmpty) last = newElem
start = newElem
elems = elems.tail
}
} else {
var cursor = start
var i = 1
while (i < n) {
cursor = cursor.tail
i = i + 1
}
while (!elems.isEmpty) {
val newElem = new scala.:: (elems.head, cursor.tail);
if (cursor.tail.isEmpty) last = newElem
cursor.asInstanceOf[scala.::[A]].tl = newElem
elems = elems.tail
}
}
} catch {
case ex: Error => noElem(n)
}
/** Removes the element on a given index position.
*
* @param n the index which refers to the element to delete.
* @return n the element that was formerly at posiition `n'
* @pre an element exists at position `n'
*/
def remove(n: Int): A = try {
if (exported) copy()
var old = start.head;
if (n == 0) {
start = start.tail
} else {
var cursor = start
var i = 1
while (i < n) {
cursor = cursor.tail
i = i + 1
}
old = cursor.tail.head
if (last eq cursor.tail) last = cursor.asInstanceOf[scala.::[A]]
cursor.asInstanceOf[scala.::[A]].tl = cursor.tail.tail
}
old
} catch {
case ex: Error => noElem(n)
}
/** Returns an iterator over all elements of this list.
* Note: the iterator can be affected by insertions, updates and deletions
* that are performed afterwards on the buffer. To get iterator an over the current
* buffer snapshot, use toList.elements
*/
override def elements = new Iterator[A] {
var cursor: List[A] = null
def hasNext: Boolean = !start.isEmpty && cursor != last
def next: A =
if (!hasNext) {
error("next on empty Iterator")
} else {
if (cursor == null) cursor = start else cursor = cursor.tail
cursor.head
}
}
/** Return a clone of this buffer.
*
* @return a <code>ListBuffer</code> with the same elements.
*/
override def clone(): Buffer[A] = (new ListBuffer[A]) ++ this
/** Checks if two buffers are structurally identical.
*
* @return true, iff both buffers contain the same sequence of elements.
*/
override def equals(obj: Any): Boolean = obj match {
case that: ListBuffer[A] =>
(this.length == that.length &&
elements.zip(that.elements).forall {
case Pair(thiselem, thatelem) => thiselem == thatelem
})
case _ => false
}
/** Defines the prefix of the string representation.
*/
override protected def stringPrefix: String = "ListBuffer"
}
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