Scala example source code file (Path.scala)

This example Scala source code file (Path.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

boolean, directory, file, iterator, jfile, list, option, path, reflection, securityexception, string, utilities

The Path.scala Scala example source code

/* NSC -- new Scala compiler
 * Copyright 2005-2013 LAMP/EPFL
 * @author Paul Phillips
 */

package scala
package reflect
package io

import java.io.{
  FileInputStream, FileOutputStream, BufferedReader, BufferedWriter, InputStreamReader, OutputStreamWriter,
  BufferedInputStream, BufferedOutputStream, RandomAccessFile, File => JFile }
import java.net.{ URI, URL }
import scala.util.Random.alphanumeric
import scala.language.implicitConversions
import scala.reflect.internal.util.Statistics

/** An abstraction for filesystem paths.  The differences between
 *  Path, File, and Directory are primarily to communicate intent.
 *  Since the filesystem can change at any time, there is no way to
 *  reliably associate Files only with files and so on.  Any Path
 *  can be converted to a File or Directory (and thus gain access to
 *  the additional entity specific methods) by calling toFile or
 *  toDirectory, which has no effect on the filesystem.
 *
 *  Also available are createFile and createDirectory, which attempt
 *  to create the path in question.
 *
 *  @author  Paul Phillips
 *  @since   2.8
 *
 *  ''Note:  This library is considered experimental and should not be used unless you know what you are doing.''
 */
object Path {
  def isExtensionJarOrZip(jfile: JFile): Boolean = isExtensionJarOrZip(jfile.getName)
  def isExtensionJarOrZip(name: String): Boolean = {
    val ext = extension(name)
    ext == "jar" || ext == "zip"
  }
  def extension(name: String): String = {
    var i = name.length - 1
    while (i >= 0 && name.charAt(i) != '.')
      i -= 1

    if (i < 0) ""
    else name.substring(i + 1).toLowerCase
  }

  // not certain these won't be problematic, but looks good so far
  implicit def string2path(s: String): Path = apply(s)
  implicit def jfile2path(jfile: JFile): Path = apply(jfile)

  def onlyDirs(xs: Iterator[Path]): Iterator[Directory] = xs filter (_.isDirectory) map (_.toDirectory)
  def onlyDirs(xs: List[Path]): List[Directory] = xs filter (_.isDirectory) map (_.toDirectory)
  def onlyFiles(xs: Iterator[Path]): Iterator[File] = xs filter (_.isFile) map (_.toFile)

  def roots: List[Path] = java.io.File.listRoots().toList map Path.apply

  def apply(path: String): Path = apply(new JFile(path))
  def apply(jfile: JFile): Path = try {
    def isFile = {
      if (Statistics.canEnable) Statistics.incCounter(IOStats.fileIsFileCount)
      jfile.isFile
    }

    def isDirectory = {
      if (Statistics.canEnable) Statistics.incCounter(IOStats.fileIsDirectoryCount)
      jfile.isDirectory
    }

    if (isFile) new File(jfile)
    else if (isDirectory) new Directory(jfile)
    else new Path(jfile)
  } catch { case ex: SecurityException => new Path(jfile) }

  /** Avoiding any shell/path issues by only using alphanumerics. */
  private[io] def randomPrefix = alphanumeric take 6 mkString ""
  private[io] def fail(msg: String) = throw FileOperationException(msg)
}
import Path._

/** The Path constructor is private so we can enforce some
 *  semantics regarding how a Path might relate to the world.
 *
 *  ''Note:  This library is considered experimental and should not be used unless you know what you are doing.''
 */
class Path private[io] (val jfile: JFile) {
  val separator = java.io.File.separatorChar
  val separatorStr = java.io.File.separator

  // conversions
  def toFile: File = new File(jfile)
  def toDirectory: Directory = new Directory(jfile)
  def toAbsolute: Path = if (isAbsolute) this else Path(jfile.getAbsolutePath())
  def toCanonical: Path = Path(jfile.getCanonicalPath())
  def toURI: URI = jfile.toURI()
  def toURL: URL = toURI.toURL()

  /** If this path is absolute, returns it: otherwise, returns an absolute
   *  path made up of root / this.
   */
  def toAbsoluteWithRoot(root: Path) = if (isAbsolute) this else root.toAbsolute / this

  /** Creates a new Path with the specified path appended.  Assumes
   *  the type of the new component implies the type of the result.
   */
  def /(child: Path): Path = if (isEmpty) child else new Path(new JFile(jfile, child.path))
  def /(child: Directory): Directory = /(child: Path).toDirectory
  def /(child: File): File = /(child: Path).toFile

  /** If this path is a container, recursively iterate over its contents.
   *  The supplied condition is a filter which is applied to each element,
   *  with that branch of the tree being closed off if it is true.  So for
   *  example if the condition is true for some subdirectory, nothing
   *  under that directory will be in the Iterator; but otherwise each
   *  file and subdirectory underneath it will appear.
   */
  def walkFilter(cond: Path => Boolean): Iterator[Path] =
    if (isFile) toFile walkFilter cond
    else if (isDirectory) toDirectory walkFilter cond
    else Iterator.empty

  /** Equivalent to walkFilter(_ => false).
   */
  def walk: Iterator[Path] = walkFilter(_ => true)

  // identity
  def name: String = jfile.getName()
  def path: String = jfile.getPath()
  def normalize: Path = Path(jfile.getAbsolutePath())

  def resolve(other: Path) = if (other.isAbsolute || isEmpty) other else /(other)
  def relativize(other: Path) = {
    assert(isAbsolute == other.isAbsolute, "Paths not of same type: "+this+", "+other)

    def createRelativePath(baseSegs: List[String], otherSegs: List[String]) : String = {
      (baseSegs, otherSegs) match {
        case (b :: bs, o :: os) if b == o => createRelativePath(bs, os)
        case (bs, os) => ((".."+separator)*bs.length)+os.mkString(separatorStr)
      }
    }

    Path(createRelativePath(segments, other.segments))
  }

  def segments: List[String] = (path split separator).toList filterNot (_.length == 0)

  /**
   * @return The path of the parent directory, or root if path is already root
   */
  def parent: Directory = path match {
    case "" | "." => Directory("..")
    case _        =>
      // the only solution <-- a comment which could have used elaboration
      if (segments.nonEmpty && segments.last == "..")
        (path / "..").toDirectory
      else jfile.getParent match {
        case null =>
          if (isAbsolute) toDirectory // it should be a root. BTW, don't need to worry about relative pathed root
          else Directory(".")         // a dir under pwd
        case x    =>
          Directory(x)
      }
  }
  def parents: List[Directory] = {
    val p = parent
    if (p isSame this) Nil else p :: p.parents
  }
  // if name ends with an extension (e.g. "foo.jpg") returns the extension ("jpg"), otherwise ""
  def extension: String = {
    var i = name.length - 1
    while (i >= 0 && name.charAt(i) != '.')
      i -= 1

    if (i < 0) ""
    else name.substring(i + 1)
  }
  // compares against extensions in a CASE INSENSITIVE way.
  def hasExtension(ext: String, exts: String*) = {
    val lower = extension.toLowerCase
    ext.toLowerCase == lower || exts.exists(_.toLowerCase == lower)
  }
  // returns the filename without the extension.
  def stripExtension: String = name stripSuffix ("." + extension)
  // returns the Path with the extension.
  def addExtension(ext: String): Path = Path(path + "." + ext)
  // changes the existing extension out for a new one, or adds it
  // if the current path has none.
  def changeExtension(ext: String): Path = (
    if (extension == "") addExtension(ext)
    else Path(path.stripSuffix(extension) + ext)
  )

  // conditionally execute
  def ifFile[T](f: File => T): Option[T] = if (isFile) Some(f(toFile)) else None
  def ifDirectory[T](f: Directory => T): Option[T] = if (isDirectory) Some(f(toDirectory)) else None

  // Boolean tests
  def canRead = jfile.canRead()
  def canWrite = jfile.canWrite()
  def exists = {
    if (Statistics.canEnable) Statistics.incCounter(IOStats.fileExistsCount)
    try jfile.exists() catch { case ex: SecurityException => false }
  }

  def isFile = {
    if (Statistics.canEnable) Statistics.incCounter(IOStats.fileIsFileCount)
    try jfile.isFile() catch { case ex: SecurityException => false }
  }
  def isDirectory = {
    if (Statistics.canEnable) Statistics.incCounter(IOStats.fileIsDirectoryCount)
    try jfile.isDirectory() catch { case ex: SecurityException => jfile.getPath == "." }
  }
  def isAbsolute = jfile.isAbsolute()
  def isEmpty = path.length == 0

  // Information
  def lastModified = jfile.lastModified()
  def length = jfile.length()

  // Boolean path comparisons
  def endsWith(other: Path) = segments endsWith other.segments
  def isSame(other: Path) = toCanonical == other.toCanonical
  def isFresher(other: Path) = lastModified > other.lastModified

  // creations
  def createDirectory(force: Boolean = true, failIfExists: Boolean = false): Directory = {
    val res = if (force) jfile.mkdirs() else jfile.mkdir()
    if (!res && failIfExists && exists) fail("Directory '%s' already exists." format name)
    else if (isDirectory) toDirectory
    else new Directory(jfile)
  }
  def createFile(failIfExists: Boolean = false): File = {
    val res = jfile.createNewFile()
    if (!res && failIfExists && exists) fail("File '%s' already exists." format name)
    else if (isFile) toFile
    else new File(jfile)
  }

  // deletions
  def delete() = jfile.delete()

  /** Deletes the path recursively. Returns false on failure.
   *  Use with caution!
   */
  def deleteRecursively(): Boolean = deleteRecursively(jfile)
  private def deleteRecursively(f: JFile): Boolean = {
    if (f.isDirectory) f.listFiles match {
      case null =>
      case xs   => xs foreach deleteRecursively
    }
    f.delete()
  }

  def truncate() =
    isFile && {
      val raf = new RandomAccessFile(jfile, "rw")
      raf setLength 0
      raf.close()
      length == 0
    }

  override def toString() = path
  override def equals(other: Any) = other match {
    case x: Path  => path == x.path
    case _        => false
  }
  override def hashCode() = path.hashCode()
}