src/Pure/PIDE/yxml.scala

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/Pure/PIDE/yxml.scala	Sun Sep 04 15:21:50 2011 +0200
@@ -0,0 +1,135 @@
+/*  Title:      Pure/PIDE/yxml.scala
+    Author:     Makarius
+
+Efficient text representation of XML trees.  Suitable for direct
+inlining into plain text.
+*/
+
+package isabelle
+
+
+import scala.collection.mutable
+
+
+object YXML
+{
+  /* chunk markers */
+
+  val X = '\5'
+  val Y = '\6'
+  val X_string = X.toString
+  val Y_string = Y.toString
+
+  def detect(s: String): Boolean = s.exists(c => c == X || c == Y)
+
+
+  /* string representation */  // FIXME byte array version with pseudo-utf-8 (!?)
+
+  def string_of_body(body: XML.Body): String =
+  {
+    val s = new StringBuilder
+    def attrib(p: (String, String)) { s += Y; s ++= p._1; s += '='; s ++= p._2 }
+    def tree(t: XML.Tree): Unit =
+      t match {
+        case XML.Elem(Markup(name, atts), ts) =>
+          s += X; s += Y; s++= name; atts.foreach(attrib); s += X
+          ts.foreach(tree)
+          s += X; s += Y; s += X
+        case XML.Text(text) => s ++= text
+      }
+    body.foreach(tree)
+    s.toString
+  }
+
+  def string_of_tree(tree: XML.Tree): String = string_of_body(List(tree))
+
+
+  /* parsing */
+
+  private def err(msg: String) = error("Malformed YXML: " + msg)
+  private def err_attribute() = err("bad attribute")
+  private def err_element() = err("bad element")
+  private def err_unbalanced(name: String) =
+    if (name == "") err("unbalanced element")
+    else err("unbalanced element " + quote(name))
+
+  private def parse_attrib(source: CharSequence) = {
+    val s = source.toString
+    val i = s.indexOf('=')
+    if (i <= 0) err_attribute()
+    (s.substring(0, i), s.substring(i + 1))
+  }
+
+
+  def parse_body(source: CharSequence): XML.Body =
+  {
+    /* stack operations */
+
+    def buffer(): mutable.ListBuffer[XML.Tree] = new mutable.ListBuffer[XML.Tree]
+    var stack: List[(Markup, mutable.ListBuffer[XML.Tree])] = List((Markup.Empty, buffer()))
+
+    def add(x: XML.Tree)
+    {
+      (stack: @unchecked) match { case ((_, body) :: _) => body += x }
+    }
+
+    def push(name: String, atts: XML.Attributes)
+    {
+      if (name == "") err_element()
+      else stack = (Markup(name, atts), buffer()) :: stack
+    }
+
+    def pop()
+    {
+      (stack: @unchecked) match {
+        case ((Markup.Empty, _) :: _) => err_unbalanced("")
+        case ((markup, body) :: pending) =>
+          stack = pending
+          add(XML.Elem(markup, body.toList))
+      }
+    }
+
+
+    /* parse chunks */
+
+    for (chunk <- Library.chunks(source, X) if chunk.length != 0) {
+      if (chunk.length == 1 && chunk.charAt(0) == Y) pop()
+      else {
+        Library.chunks(chunk, Y).toList match {
+          case ch :: name :: atts if ch.length == 0 =>
+            push(name.toString, atts.map(parse_attrib))
+          case txts => for (txt <- txts) add(XML.Text(txt.toString))
+        }
+      }
+    }
+    (stack: @unchecked) match {
+      case List((Markup.Empty, body)) => body.toList
+      case (Markup(name, _), _) :: _ => err_unbalanced(name)
+    }
+  }
+
+  def parse(source: CharSequence): XML.Tree =
+    parse_body(source) match {
+      case List(result) => result
+      case Nil => XML.Text("")
+      case _ => err("multiple results")
+    }
+
+
+  /* failsafe parsing */
+
+  private def markup_malformed(source: CharSequence) =
+    XML.elem(Markup.MALFORMED, List(XML.Text(source.toString)))
+
+  def parse_body_failsafe(source: CharSequence): XML.Body =
+  {
+    try { parse_body(source) }
+    catch { case ERROR(_) => List(markup_malformed(source)) }
+  }
+
+  def parse_failsafe(source: CharSequence): XML.Tree =
+  {
+    try { parse(source) }
+    catch { case ERROR(_) => markup_malformed(source) }
+  }
+}