1 files changed, 245 insertions, 0 deletions
diff --git a/src/library/scala/collection/immutable/PagedSeq.scala b/src/library/scala/collection/immutable/PagedSeq.scala
new file mode 100755
index 0000000000..de034e67dd
--- /dev/null
+++ b/src/library/scala/collection/immutable/PagedSeq.scala
@@ -0,0 +1,245 @@
+/*                     __                                               *\
+**     ________ ___   / /  ___     Scala API                            **
+**    / __/ __// _ | / /  / _ |    (c) 2006-2007, LAMP/EPFL             **
+**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
+** /____/\___/_/ |_/____/_/ | |                                         **
+**                          |/                                          **
+\*                                                                      */
+
+// $Id: PagedSeq.scala 14497 2008-04-04 12:09:06Z washburn $
+
+
+package scala.collection.immutable
+
+import java.io._
+import util.matching.Regex
+
+
+/** The PagedSeq object defines a lazy implementations of
+ *  a random access sequence.
+ */
+object PagedSeq {
+  final val UndeterminedEnd = Math.MAX_INT
+
+  /** Constructs a character sequence from a character iterator */
+  def fromIterator[T](source: Iterator[T]): PagedSeq[T] =
+    new PagedSeq[T]((data: Array[T], start: Int, len: Int) => {
+      var i = 0
+      while (i < len && source.hasNext) {
+        data(start + i) = source.next
+        i += 1
+      }
+      if (i == 0) -1 else i
+    })
+
+  /** Constructs a character sequence from a character iterable */
+  def fromIterable[T](source: Iterable[T]): PagedSeq[T] =
+    fromIterator(source.elements)
+
+  /** Constructs a character sequence from a string iterator */
+  def fromStrings(source: Iterator[String]): PagedSeq[Char] = {
+    var current: String = ""
+    def more(data: Array[Char], start: Int, len: Int): Int =
+      if (current.length != 0) {
+        val cnt = current.length min len
+        current.getChars(0, cnt, data, start)
+        current = current.substring(cnt)
+        if (cnt == len) cnt
+        else (more(data, start + cnt, len - cnt) max 0) + cnt
+      } else if (source.hasNext) {
+        current = source.next
+        more(data, start, len)
+      } else -1
+    new PagedSeq(more(_: Array[Char], _: Int, _: Int))
+  }
+
+  /** Constructs a character sequence from a string iterable */
+  def fromStrings(source: Iterable[String]): PagedSeq[Char] =
+    fromStrings(source.elements)
+
+  /** Constructs a character sequence from a line iterator
+   *  Lines do not contain trailing `\n' characters; The method inserts
+   *  a line separator `\n' between any two lines in the sequence.
+   */
+  def fromLines(source: Iterator[String]): PagedSeq[Char] = {
+    var isFirst = true
+    fromStrings(source map { line =>
+      if (isFirst) line
+      else {
+        isFirst = false
+        "\n"+line
+      }
+    })
+  }
+
+  /** Constructs a character sequence from a line iterable
+   *  Lines do not contain trailing `\n' characters; The method inserts
+   *  a line separator `\n' between any two lines in the sequence.
+   */
+  def fromLines(source: Iterable[String]): PagedSeq[Char] =
+    fromLines(source.elements)
+
+  /** Constructs a character sequence from an input reader
+   */
+  def fromReader(source: Reader): PagedSeq[Char] =
+    new PagedSeq(source.read(_: Array[Char], _: Int, _: Int))
+
+  /** Constructs a character sequence from an input file
+   */
+  def fromFile(source: File): PagedSeq[Char] =
+    fromReader(new FileReader(source))
+
+  /** Constructs a character sequence from a file with given name
+   */
+  def fromFile(source: String): PagedSeq[Char] =
+    fromFile(new File(source))
+
+  /** Constructs a character sequence from a scala.io.Source value
+   */
+  def fromSource(source: io.Source) =
+    fromLines(source.getLines)
+}
+
+
+import PagedSeq._
+
+/** An implementation of lazily computed sequences, where elements are stored
+ *  in ``pages'', i.e. arrays of fixed size.
+ *
+ * @author Martin Odersky
+ */
+class PagedSeq[T] protected (more: (Array[T], Int, Int) => Int,
+                             first: Page[T], start: Int, end: Int) extends RandomAccessSeq[T] {
+
+  /**  A paged sequence is constructed from a method that produces more characters when asked.
+   *  The producer method is analogous to the read method in java.io.Reader.
+   *  It takes three parameters: an array of characters, a start index, and an end index.
+   *  It should try to fill the array between start and end indices (not including end index).
+   *  It returns the number of characters produced, or -1 if end of logical input stream was reached
+   *  before any character was read.
+   */
+  def this(more: (Array[T], Int, Int) => Int) = this(more, new Page[T](0), 0, UndeterminedEnd)
+
+  private var current: Page[T] = first
+
+  private def latest = first.latest
+
+  private def addMore() = latest.addMore(more)
+
+  private def page(absindex: Int) = {
+    if (absindex < current.start)
+      current = first
+    while (absindex >= current.end && current.next != null)
+      current = current.next
+    while (absindex >= current.end && !current.isLast) {
+      current = addMore()
+    }
+    current
+  }
+
+  /** The length of the character sequence
+   *  Note: calling this method will force sequence to be read until the end.
+   */
+  def length: Int = {
+    while (!latest.isLast) addMore()
+    (latest.end min end) - start
+  }
+
+  /** The character at position `index'.
+   */
+  def apply(index: Int) =
+    if (isDefinedAt(index)) page(index + start)(index + start)
+    else throw new IndexOutOfBoundsException(index.toString)
+
+  /** Is character sequence defined at `index'?
+   *  Unlike `length' this operation does not force reading
+   *  a lazy sequence to the end.
+   */
+  override def isDefinedAt(index: Int) =
+    index >= 0 && index < end - start && {
+      val p = page(index + start); index + start < p.end
+    }
+
+  /** the subsequence from index `start' up to and excluding
+   *  the minimum of index `end' and the length of the current sequence.
+   */
+  override def slice(_start: Int, _end: Int) = {
+    page(start)
+    val s = start + _start
+    val e = if (_end == UndeterminedEnd) _end else start + _end
+    var f = first
+    while (f.end <= s && !f.isLast) f = f.next
+    new PagedSeq(more, f, s, e)
+  }
+
+  /** the subsequence from index `start' up to the
+   *  length of the current sequence.
+   */
+  override def slice(start: Int) = slice(start, UndeterminedEnd)
+
+  /** Convert sequence to string */
+  override def toString = {
+    val buf = new StringBuilder
+    for (ch <- elements) buf append ch
+    buf.toString
+  }
+}
+
+
+/** Page containing up to PageSize characters of the input sequence.
+ */
+private class Page[T](val num: Int) {
+
+  private final val PageSize = 4096
+
+  /** The next page in the sequence */
+  var next  : Page[T] = null
+
+  /** A later page in the sequence, serves a cachae for pointing to last page */
+  var later : Page[T] = this
+
+  /** The number of characters read into this page */
+  var filled: Int = 0
+
+  /** Is this page the permamnently last one in the sequence? Only true once `more'
+   *  method has returned -1 to signal end of input. */
+  var isLast: Boolean = false
+
+  /** The character array */
+  final val data = new Array[T](PageSize)
+
+  /** The index of the first character in this page relative to the whole sequence */
+  final def start = num * PageSize
+
+  /** The index of the character following the last charcater in this page relative
+   *  to the whole sequence */
+  final def end = start + filled
+
+  /** The currently last page in the sequence; might change as more charcaters are appended */
+  final def latest: Page[T] = {
+    if (later.next != null) later = later.next.latest
+    later
+  }
+
+  /** The character at given sequence index.
+   *  That index is relative to the whole sequence, not the page. */
+  def apply(index: Int) = {
+    if (index < start || index - start >= filled) throw new IndexOutOfBoundsException(index.toString)
+    data(index - start)
+  }
+
+  /** produces more characters by calling `more' and appends them on the current page,
+   *  or fills a subsequent page if current page is full
+   *  pre: if current page is full, it is the last one in the sequence.
+   */
+  final def addMore(more: (Array[T], Int, Int) => Int): Page[T] =
+    if (filled == PageSize) {
+      next = new Page[T](num + 1)
+      next.addMore(more)
+    } else {
+      val count = more(data, filled, PageSize - filled)
+      if (count < 0) isLast = true
+      else filled += count
+      this
+    }
+}