arraybuffer.scala

来自「JAVA 语言的函数式编程扩展」· SCALA 代码 · 共 189 行

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2007, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

// $Id: ArrayBuffer.scala 14378 2008-03-13 11:39:05Z dragos $


package scala.collection.mutable


import Predef._

/** An implementation of the <code>Buffer</code> class using an array to
 *  represent the assembled sequence internally. Append, update and random
 *  access take constant time (amortized time). Prepends and removes are
 *  linear in the buffer size.
 *
 *  @author  Matthias Zenger
 *  @version 1.0, 15/03/2004
 */
@serializable
class ArrayBuffer[A] extends RandomAccessSeq.Mutable[A] with Buffer[A] with ResizableArray[A] {
  /** Appends a single element to this buffer and returns
   *  the identity of the buffer. It takes constant time.
   *
   *  @param elem  the element to append.
   */
  def +=(elem: A) {
    ensureSize(size0 + 1)
    array(size0) = elem
    size0 += 1
  }

  /** Appends a number of elements provided by an iterable object
   *  via its <code>elements</code> method. The identity of the
   *  buffer is returned.
   *
   *  @param iter  the iterable object.
   *  @return      the updated buffer.
   */
  override def ++=(iter: Iterable[A]) { iter copyToBuffer this }

  override def ++[B >: A](that: Iterable[B]) : ArrayBuffer[B] = {
    val buf = new ArrayBuffer[B]
    this copyToBuffer buf
    that copyToBuffer buf
    buf
  }
  
  /** Appends a number of elements in an array
   *
   *  @param src    the array
   *  @param start  the first element to append
   *  @param len    the number of elements to append           
   */
  override def ++=(src: Array[A], start: Int, len: Int) {
    ensureSize(size0 + len)
    Array.copy(src, start, array, size0, len)
    size0 += len
  }

  /** Prepends a single element to this buffer and return
   *  the identity of the buffer. It takes time linear in 
   *  the buffer size.
   *
   *  @param elem  the element to append.
   *  @return      the updated buffer.
   */
  def +:(elem: A): Buffer[A] = {
    ensureSize(size0 + 1)
    copy(0, 1, size0)
    array(0) = elem
    size0 += 1
    this
  }
   
  /** Returns the i-th element of this ArrayBuffer. It takes constant time.
   *
   *  @param i  the specified index.
   *  @return   the i-th element.
   *  @throws Predef.IndexOutOfBoundException if <code>i</code> is out of bounds.
   */
  override def apply(i: Int) = { 
    if ((i < 0) || (i >= size0))
      throw new IndexOutOfBoundsException(i.toString())
    else
      array(i)
  }

  /** Prepends a number of elements provided by an iterable object
   *  via its <code>elements</code> method. The identity of the
   *  buffer is returned.
   *
   *  @param iter  the iterable object.
   *  @return      the updated buffer.
   */
  override def ++:(iter: Iterable[A]): Buffer[A] = { insertAll(0, iter); this }
  
  /** Inserts new elements at the index <code>n</code>. Opposed to method
   *  <code>update</code>, this method will not replace an element with a
   *  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.
   *  @throws Predef.IndexOutOfBoundsException if <code>n</code> is out of bounds.
   */
  def insertAll(n: Int, iter: Iterable[A]) {
    if ((n < 0) || (n > size0))
      throw new IndexOutOfBoundsException("cannot insert element at " + n);
    val xs = iter.elements.toList
    val len = xs.length
    ensureSize(size0 + len)
    copy(n, n + len, size0 - n)
    xs.copyToArray(array, n)
    size0 += len
  }
  
  /** Replace element at index <code>n</code> with the new element
   *  <code>newelem</code>. It takes constant time.
   *
   *  @param n       the index of the element to replace.
   *  @param newelem the new element.
   *  @throws Predef.IndexOutOfBoundsException if <code>n</code> is out of bounds.
   */
  def update(n: Int, newelem: A) {
    if ((n < 0) || (n >= size0))
      throw new IndexOutOfBoundsException("cannot update element at " + n)
    else {
      val res = array(n)
      array(n) = newelem
      res
    }
  }
  
  /** Removes the element on a given index position. It takes time linear in
   *  the buffer size.
   *
   *  @param n  the index which refers to the element to delete.
   *  @return   the updated array buffer.
   *  @throws Predef.IndexOutOfBoundsException if <code>n</code> is out of bounds.
   */
  def remove(n: Int): A = {
    if ((n < 0) || (n >= size0))
      throw new IndexOutOfBoundsException("cannot remove element at " + n);
    val res = array(n)
    copy(n + 1, n, size0 - n - 1)
    size0 -= 1
    res
  }
  
  /** Clears the buffer contents.
   */
  def clear() {
    size0 = 0
  }
  
  /** Return a clone of this buffer.
   *
   *  @return an <code>ArrayBuffer</code> with the same elements.
   */
  override def clone(): Buffer[A] = {
    val res = new ArrayBuffer[A]
    res ++= this
    res
  }
  
  /** 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: ArrayBuffer[_] =>
      this.length == that.length &&
    elements.zip(that.elements).forall {
      case (thiselem, thatelem) => thiselem == thatelem
    }
    case _ =>
      false
  }

  /** Defines the prefix of the string representation.
   */
  override protected def stringPrefix: String = "ArrayBuffer"
}