/* Title: Pure/General/yxml.scala
Author: Makarius
Efficient text representation of XML trees.
*/
package isabelle
object YXML
{
/* chunk markers */
private val X = '\5'
private val Y = '\6'
private val X_string = X.toString
private val Y_string = Y.toString
/* iterate over chunks (resembles space_explode in ML) */
private def chunks(sep: Char, source: CharSequence) = new Iterator[CharSequence]
{
private val end = source.length
private var state = if (end == 0) None else get_chunk(-1)
private def get_chunk(i: Int) =
{
if (i < end) {
var j = i; do j += 1 while (j < end && source.charAt(j) != sep)
Some((source.subSequence(i + 1, j), j))
}
else None
}
def hasNext() = state.isDefined
def next() = state match {
case Some((s, i)) => { state = get_chunk(i); s }
case None => throw new NoSuchElementException("next on empty iterator")
}
}
/* decoding pseudo UTF-8 */
private class Decode_Chars(decode: String => String,
buffer: Array[Byte], start: Int, end: Int) extends CharSequence
{
def length: Int = end - start
def charAt(i: Int): Char = (buffer(start + i).asInstanceOf[Int] & 0xFF).asInstanceOf[Char]
def subSequence(i: Int, j: Int): CharSequence =
new Decode_Chars(decode, buffer, start + i, start + j)
// toString with adhoc decoding: abuse of CharSequence interface
override def toString: String = decode(Library.decode_permissive_utf8(this))
}
def decode_chars(decode: String => String,
buffer: Array[Byte], start: Int, end: Int): CharSequence =
{
require(0 <= start && start <= end && end <= buffer.length)
new Decode_Chars(decode, buffer, start, end)
}
/* 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 \"" + name + "\"")
private def parse_attrib(source: CharSequence) = {
val s = source.toString
val i = s.indexOf('=')
if (i <= 0) err_attribute()
(s.substring(0, i).intern, s.substring(i + 1))
}
def parse_body(source: CharSequence): List[XML.Tree] =
{
/* stack operations */
var stack: List[((String, XML.Attributes), List[XML.Tree])] = null
def add(x: XML.Tree) = (stack: @unchecked) match {
case ((elem, body) :: pending) => stack = (elem, x :: body) :: pending
}
def push(name: String, atts: XML.Attributes) =
if (name == "") err_element()
else stack = ((name, atts), Nil) :: stack
def pop() = (stack: @unchecked) match {
case ((("", _), _) :: _) => err_unbalanced("")
case (((name, atts), body) :: pending) =>
stack = pending; add(XML.Elem(name, atts, body.reverse))
}
/* parse chunks */
stack = List((("", Nil), Nil))
for (chunk <- chunks(X, source) if chunk.length != 0) {
if (chunk.length == 1 && chunk.charAt(0) == Y) pop()
else {
chunks(Y, chunk).toList match {
case ch :: name :: atts if ch.length == 0 =>
push(name.toString.intern, atts.map(parse_attrib))
case txts => for (txt <- txts) add(XML.Text(txt.toString))
}
}
}
stack match {
case List((("", _), result)) => result.reverse
case ((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_failsafe(source: CharSequence) =
XML.Elem (Markup.MALFORMED, Nil,
List(XML.Text(source.toString.replace(X_string, "\\<^X>").replace(Y_string, "\\<^Y>"))))
def parse_body_failsafe(source: CharSequence): List[XML.Tree] =
{
try { parse_body(source) }
catch { case _: RuntimeException => List(markup_failsafe(source)) }
}
def parse_failsafe(source: CharSequence): XML.Tree =
{
try { parse(source) }
catch { case _: RuntimeException => markup_failsafe(source) }
}
}