grizzled.parsing.SafeIterator.scala Maven / Gradle / Ivy

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/*
  ---------------------------------------------------------------------------
  This software is released under a BSD license, adapted from
  http://opensource.org/licenses/bsd-license.php

  Copyright © 2009-2016, Brian M. Clapper
  All rights reserved.

  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are
  met:

   * Redistributions of source code must retain the above copyright notice,
    this list of conditions and the following disclaimer.

   * Redistributions in binary form must reproduce the above copyright
    notice, this list of conditions and the following disclaimer in the
    documentation and/or other materials provided with the distribution.

   * Neither the names "clapper.org", "Grizzled Scala Library", nor the
    names of its contributors may be used to endorse or promote products
    derived from this software without specific prior written permission.

  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
  IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  ---------------------------------------------------------------------------
*/

package grizzled.parsing

/** `SafeIterator` places a simple stream on top of an iterator,
  * returning `Option`-wrapped instances from the underlying iterator.
  * When the stream is exhausted, the `Iterator` stream returns
  * `None`. Differences from a plain `Iterator` include:
  *
  * - An `SafeIterator` will not throw an exception if you try to read
  *   past the end of it. Instead, it will just keep returning `None`.
  *
  * Example of use with a string:
  *
  * {{{
  * import grizzled.parsing.SafeIterator
  *
  * val s = ...
  * val istream = new SafeIterator[Char](s.elements)
  * }}}
  *
  * @param iterator  the iterator to wrap
  */
@SuppressWarnings(Array("org.brianmckenna.wartremover.warts.Var"))
class SafeIterator[+T](private val iterator: Iterator[T]) {
  private var count = 0

  /** Alternate constructor that takes an `Iterable`.
    *
    * @param iterable the `Iterable`
    */
  def this(iterable: Iterable[T]) = this(iterable.iterator)

  /** Get the next item from the stream, advancing the cursor.
    *
    * @return an `Option` containing the next item, or `None`
    *         if the iterator is exhausted.
    */
  def next: Option[T] = {
    if (! iterator.hasNext)
      None

    else {
      count += 1
      Some(iterator.next)
    }
  }

  /** Get the count of the number of items consumed so far.
    *
    * @return the count
    */
  @deprecated("Will not be supported in future versions.", "2.4.0")
  def totalRead: Int = count
}

/** Companion object for `SafeIterator`.
  */
object SafeIterator {
  /** Create a new `SafeIterator` from an `Iterable`.
    *
    * @param iterable  the `Iterable``
    * @tparam T        the type of the `Iterable`
    *
    * @return the allocated `SafeIterator`
    */
  def apply[T](iterable: Iterable[T]): SafeIterator[T] =
    new SafeIterator(iterable)

  /** Create a new `SafeIterator` from an `Iterator`.
    *
    * @param iterator  the `Iterator``
    * @tparam T        the type of the `Iterable`
    *
    * @return the allocated `SafeIterator`
    */
  def apply[T](iterator: Iterator[T]): SafeIterator[T] =
    new SafeIterator(iterator)
}