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|
package yamlesque
import annotation.{switch, tailrec}
import scala.collection.mutable.ListBuffer
object YamlParser extends (Iterator[Char] => YamlValue) {
sealed trait TokenKind
object TokenKind {
case object EOF extends TokenKind
case object BAD extends TokenKind
case object DOCSTART extends TokenKind
case object DOCEND extends TokenKind
case object MAPPING extends TokenKind
case object ITEM extends TokenKind
case object IDENTIFIER extends TokenKind
case object COMMENT extends TokenKind
}
import TokenKind._
case class Token(val kind: TokenKind, value: String = "") {
var line: Int = 0
var col: Int = 0
def setPos(line: Int, col: Int): this.type = {
this.col = col
this.line = line
this
}
override def toString() = {
s"($line, $col): " + super.toString
}
}
object Chars {
final val LF = '\u000A'
final val CR = '\u000D'
final val SU = '\u001A'
@inline def isSpace(ch: Char): Boolean = ch match {
case ' ' | '\t' => true
case _ => false
}
@inline def isBlank(ch: Char): Boolean = ch match {
case ' ' | '\t' | CR | LF | SU => true
case _ => false
}
}
class Scanner(chars: Iterator[Char]) extends Iterator[Token] {
import Chars._
private var ch0: Char = 0
private var ch1: Char = 0
private var ch2: Char = 0
private var pos: Long = 0
private var line: Int = 0
private var col: Int = 0
private def skipChar(): Unit = {
val ch: Char = if (chars.hasNext) {
chars.next()
} else {
SU
}
pos += 1
col += 1
ch0 = ch1
ch1 = ch2
ch2 = ch
}
private def skipChars(n: Int): Unit = {
var i = 0
while (i < n) { skipChar(); i += 1 }
}
def init() = {
skipChars(3)
pos = 0
col = 0
line = 0
}
private var buffer = new StringBuilder()
private def putChar(): Unit = {
buffer.append(ch0)
skipChars(1)
}
private def tokenValue(): String = {
val str = buffer.result()
buffer.clear()
str
}
private var token: Token = Token(BAD, "not yet initialized")
@tailrec private def fetchToken(): Unit = {
ch0 match {
case ':' if isBlank(ch1) =>
token = Token(MAPPING).setPos(line, col)
skipChars(1)
case '-' if isBlank(ch1) =>
token = Token(ITEM).setPos(line, col)
skipChars(1)
case '-' if ch1 == '-' && ch2 == '-' =>
token = Token(DOCSTART).setPos(line, col)
skipChars(3)
case '.' if ch1 == '.' && ch2 == '.' =>
token = Token(DOCEND).setPos(line, col)
skipChars(3)
case '#' =>
val l = line
val c = col
skipChars(1)
while (ch0 != LF && ch0 != SU) {
putChar()
}
token = Token(COMMENT, tokenValue()).setPos(l, c)
buffer.clear()
case c if isSpace(c) =>
skipChars(1)
fetchToken()
case LF =>
skipChars(1)
col = 0
line += 1
fetchToken()
case CR =>
skipChars(1)
if (ch0 == LF) {
skipChars(1)
}
col = 0
line += 1
fetchToken()
case SU =>
token = Token(EOF).setPos(line, col)
skipChars(1)
case _ => fetchScalar()
}
}
private def fetchScalar(): Unit = {
def finishScalar() = token = Token(IDENTIFIER, tokenValue())
@tailrec def fetchRest(): Unit = ch0 match {
case ':' if isBlank(ch1) =>
finishScalar()
case LF =>
finishScalar()
case SU =>
finishScalar()
case c =>
putChar()
fetchRest()
}
val l = line
val c = col
fetchRest()
token.setPos(l, c)
}
override def hasNext: Boolean = true
override def next(): Token = {
fetchToken()
token
}
init()
}
def parse(tokens: Iterator[Token]): YamlValue = {
var token0 = tokens.next()
var token1 = tokens.next()
def readNext(): Unit = {
token0 = token1
token1 = tokens.next()
}
def fatal(message: String, token: Token) = {
val completeMessage =
s"parse error at line ${token.line}, column ${token.col}: $message"
throw new ParseException(completeMessage)
}
def wrongKind(found: Token, required: TokenKind*) = {
fatal(
s"token kind not allowed at this position\n" +
s" found: ${found.kind}\n" +
s" required: ${required.mkString(" or ")}\n" +
" " * found.col + found.value + "\n" +
" " * found.col + "^",
found
)
}
def nextSequence() = {
val startCol = token0.col
val items = new ListBuffer[YamlValue]
while (startCol <= token0.col && token0.kind != EOF) {
token0.kind match {
case ITEM =>
readNext()
items += nextBlock(startCol)
case _ => wrongKind(token0, ITEM)
}
}
YamlSequence(items.toVector)
}
def nextMapping() = {
val startCol = token0.col
val fields = new ListBuffer[(String, YamlValue)]
while (startCol <= token0.col && token0.kind != EOF) {
token0.kind match {
case IDENTIFIER =>
val key = token0.value
readNext()
token0.kind match {
case MAPPING =>
readNext()
val value = nextBlock(startCol)
fields += key -> value
case _ => wrongKind(token0, MAPPING)
}
case _ => wrongKind(token0, IDENTIFIER)
}
}
YamlMapping(fields.toMap)
}
def nextBlock(startCol: Int): YamlValue = {
if (token0.col < startCol) {
YamlScalar.Empty
} else {
token0.kind match {
case IDENTIFIER =>
if (token1.kind == MAPPING && token0.line == token1.line) {
nextMapping()
} else {
val y = YamlScalar(token0.value)
readNext()
y
}
case ITEM =>
nextSequence()
case EOF => YamlScalar.Empty
case _ => wrongKind(token0, IDENTIFIER, ITEM)
}
}
}
nextBlock(0)
}
def apply(data: Iterator[Char]): YamlValue = parse(new Scanner(data))
}
class ParseException(val message: String) extends Exception(message)
|
