Merge pull request #97 from gourlaysama/topic/move-paged-seq

Move PagedSeq from scala-library to parser-combinators

Author: gourlaysama

shared/src/main/scala/scala/util/parsing/combinator/RegexParsers.scala

@@ -13,7 +13,6 @@ package util.parsing.combinator
 import java.util.regex.Pattern
 import scala.util.matching.Regex
 import scala.util.parsing.input._
-import scala.collection.immutable.PagedSeq
 import scala.language.implicitConversions
 
 /** The ''most important'' differences between `RegexParsers` and

shared/src/main/scala/scala/util/parsing/input/PagedSeq.scala

@@ -0,0 +1,267 @@
+/*                     __                                               *\
+**     ________ ___   / /  ___     Scala API                            **
+**    / __/ __// _ | / /  / _ |    (c) 2006-2013, LAMP/EPFL             **
+**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
+** /____/\___/_/ |_/____/_/ | |                                         **
+**                          |/                                          **
+\*                                                                      */
+
+
+
+package scala
+package util.parsing.input
+
+import java.io.{File, FileReader, Reader => JReader}
+import scala.reflect.ClassTag
+
+/** The `PagedSeq` object defines a lazy implementations of
+ *  a random access sequence.
+ *
+ * Provides utility methods that return instances of `PagedSeq[Char]`.
+ * `fromIterator` and `fromIterable` provide generalised instances of `PagedSeq`
+ */
+object PagedSeq {
+  final val UndeterminedEnd = Int.MaxValue
+
+  /** Constructs a paged sequence from an iterator */
+  def fromIterator[T: ClassTag](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 paged sequence from an iterable */
+  def fromIterable[T: ClassTag](source: Iterable[T]): PagedSeq[T] =
+    fromIterator(source.iterator)
+
+  /** Constructs a paged 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 paged character sequence from a string iterable */
+  def fromStrings(source: Iterable[String]): PagedSeq[Char] =
+    fromStrings(source.iterator)
+
+  /** Constructs a paged 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) {
+        isFirst = false
+        line
+      } else "\n"+line
+    })
+  }
+
+  /** Constructs a paged 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.iterator)
+
+  /** Constructs a paged character sequence from an input reader
+   */
+  def fromReader(source: JReader): PagedSeq[Char] =
+    new PagedSeq(source.read(_: Array[Char], _: Int, _: Int))
+
+  /** Constructs a paged character sequence from an input file
+   */
+  def fromFile(source: File): PagedSeq[Char] =
+    fromReader(new FileReader(source))
+
+  /** Constructs a paged character sequence from a file with given name
+   */
+  def fromFile(source: String): PagedSeq[Char] =
+    fromFile(new File(source))
+
+  /** Constructs a paged character sequence from a scala.io.Source value
+   */
+  def fromSource(source: scala.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.
+ *
+ *  A paged sequence is constructed from a function that produces more elements when asked.
+ *  The producer function - `more`, is similar to the read method in java.io.Reader.
+ *  The `more` function takes three parameters: an array of elements, a start index, and an end index.
+ *  It should try to fill the array between start and end indices (excluding end index).
+ *  It returns the number of elements produced, or -1 if end of logical input stream was reached
+ *  before reading any element.
+ *
+ *  @tparam T     the type of the elements contained in this paged sequence, with an `ClassTag` context bound.
+ *
+ *  @author Martin Odersky
+ *  @define Coll `PagedSeq`
+ *  @define coll paged sequence
+ *  @define mayNotTerminateInf
+ *  @define willNotTerminateInf
+ */
+class PagedSeq[T: ClassTag] protected(
+  more: (Array[T], Int, Int) => Int,
+  first1: Page[T],
+  start: Int,
+  end: Int)
+extends scala.collection.AbstractSeq[T]
+   with scala.collection.IndexedSeq[T]
+{
+  def this(more: (Array[T], Int, Int) => Int) = this(more, new Page[T](0), 0, UndeterminedEnd)
+
+  private var current: Page[T] = first1
+
+  private def latest = first1.latest
+
+  private def addMore() = latest.addMore(more)
+
+  private def page(absindex: Int) = {
+    if (absindex < current.start)
+      current = first1
+    while (absindex >= current.end && current.next != null)
+      current = current.next
+    while (absindex >= current.end && !current.isLast) {
+      current = addMore()
+    }
+    current
+  }
+
+  /** The length of the paged sequence
+   *  @note Calling this method will force the entire sequence to be read.
+   */
+  def length: Int = {
+    while (!latest.isLast && latest.end < end) addMore()
+    (latest.end min end) - start
+  }
+
+  /** The element at position `index`.
+   */
+  def apply(index: Int) =
+    if (isDefinedAt(index)) page(index + start)(index + start)
+    else throw new IndexOutOfBoundsException(index.toString)
+
+  /** Predicate method to check if an element is defined
+   *  at position `index` of the current sequence.
+   *  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 absidx = index + start
+      absidx >= 0 && absidx < page(absidx).end
+    }
+
+   /** The subsequence from index `start` up to `end -1` if `end`
+   *   is lesser than the length of the current sequence and up to
+   *   length of the sequence otherwise. This is limited up to the length
+   *   of the current sequence if `end` is larger than its length.
+   */
+  override def slice(_start: Int, _end: Int): PagedSeq[T] = {
+    page(start)
+    val s = start + _start
+    val e = if (_end == UndeterminedEnd) _end else start + _end
+    var f = first1
+    while (f.end <= s && !f.isLast) {
+      if (f.next eq null) f = f.addMore(more)
+      else f = f.next
+    }
+    // Warning -- not refining `more` means that slices can freely request and obtain
+    // data outside of their slice.  This is part of the design of PagedSeq
+    // (to read pages!) but can be surprising.
+    new PagedSeq(more, f, s, e)
+  }
+
+  /** The subsequence from index `start` up to
+   *  the length of the current sequence.
+   */
+  def slice(start: Int): PagedSeq[T] = slice(start, UndeterminedEnd)
+
+  /** Convert sequence to string */
+  override def toString = {
+    val buf = new StringBuilder
+    for (ch <- PagedSeq.this.iterator) buf append ch
+    buf.toString
+  }
+}
+
+
+/** Page containing up to PageSize characters of the input sequence.
+ */
+private class Page[T: ClassTag](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 cache for pointing to last page */
+  var later : Page[T] = this
+
+  /** The number of elements read into this page */
+  var filled: Int = 0
+
+  /** Set true if the current page is the last in the sequence or if
+  *   the `more` function returned -1 signalling end of input. */
+  var isLast: Boolean = false
+
+  /** The element array */
+  final val data = new Array[T](PageSize)
+
+  /** The index of the first element in this page relative to the whole sequence */
+  final def start = num * PageSize
+
+  /** The index of the element following the last element in this page relative
+   *  to the whole sequence */
+  final def end = start + filled
+
+  /** The last page as currently present in the sequence; This can change as more
+   *  elements get appended to the sequence.  */
+  final def latest: Page[T] = {
+    if (later.next != null) later = later.next.latest
+    later
+  }
+
+  /** The element at the 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 elements by calling `more` and adds them on the current page,
+   *  or fills a subsequent page if current page is full.
+   *  @note 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
+    }
+}

shared/src/main/scala/scala/util/parsing/input/PagedSeqReader.scala

@@ -10,8 +10,6 @@
 package scala
 package util.parsing.input
 
-import scala.collection.immutable.PagedSeq
-
 /** An object encapsulating basic character constants.
  *
  * @author Martin Odersky

shared/src/main/scala/scala/util/parsing/input/StreamReader.scala

@@ -10,7 +10,6 @@ package scala
 package util.parsing.input
 
 import java.io.BufferedReader
-import scala.collection.immutable.PagedSeq
 
 /** An object to create a `StreamReader` from a `java.io.Reader`.
  *

shared/src/test/scala/scala/util/parsing/combinator/gh45.scala

@@ -1,7 +1,6 @@
 package scala.util.parsing.combinator
 
 import scala.util.parsing.input._
-import scala.collection.immutable.PagedSeq
 
 import org.junit.Test
 import org.junit.Assert.assertTrue

shared/src/test/scala/scala/util/parsing/combinator/t8879.scala

@@ -1,5 +1,4 @@
 import scala.util.parsing.input._
-import scala.collection.immutable.PagedSeq
 
 import org.junit.Test
 import org.junit.Assert.fail