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package com.github.jodersky.mavlink
import scala.language.postfixOps
import scala.xml.Node
import scala.util.Try
import trees._
/**
* Provides means to parse a MAVLink dialect definition into a
* scala object representation.
*/
object Parser {
def fatal(error: String, node: Node) = throw new ParseError("Parse error at " + node + ": " + error)
def warn(warning: String, node: Node) = Console.err.println("Warning " + node + ": " + warning)
def parseDialect(node: Node): Dialect = parse(node) match {
case p: Dialect => p
case _ => fatal("expected mavlink protocol definition", node)
}
def parse(node: Node): Tree = node match {
case <field>{_*}</field> =>
val description = node.text
val name = (node \ "@name").map(_.text).headOption getOrElse fatal("no name defined for field", node)
val enum = (node \ "@enum").map(_.text).headOption
val (tpe, native) = (node \ "@type") map (_.text) headOption match {
case Some(t) => (parseType(t, node), t)
case None => fatal("no field type specified", node)
}
Field(tpe, native, name, enum, description)
case <entry>{_*}</entry> =>
val value = (node \ "@value").map(_.text).headOption map { str =>
Try { Integer.parseInt(str) } getOrElse fatal("value must be an integer", node)
} getOrElse fatal("no value defined", node)
val name = (node \ "@name").map(_.text).headOption getOrElse fatal("no name defined for enum entry", node)
val description = (node \ "description").text
EnumEntry(value, name, description)
case <enum>{_*}</enum> =>
val name = (node \ "@name").map(_.text).headOption getOrElse fatal("no name defined for enum", node)
val entries = (node \ "entry").toSet map { n: Node =>
parse(n) match {
case e: EnumEntry => e
case _ => fatal("illegal definition in enum, only entries are allowed", n)
}
}
Enum(name, entries)
case <message>{_*}</message> =>
val id = (node \ "@id").map(_.text).headOption map { str =>
val id = Try { Integer.parseInt(str) } getOrElse fatal("id must be an integer", node)
if (id < 0 || id > 255) warn("message id is not in the range [0-255]", node)
id.toByte
} getOrElse fatal("no id defined", node)
val name = (node \ "@name").map(_.text).headOption getOrElse fatal("no name defined for message", node)
val description = (node \ "description").text
val fields = (node \ "field") map { n: Node =>
parse(n) match {
case e: Field => e
case _ => fatal("illegal definition in message, only fields are allowed", n)
}
}
Message(id, name, description, fields)
case <mavlink>{_*}</mavlink> =>
val version = (node \ "version").text
val enums = (node \ "enums" \ "_").toSet map { n: Node =>
parse(n) match {
case e: Enum => e
case _ => fatal("illegal definition in enums, only enum declarations are allowed", n)
}
}
val messages = (node \ "messages" \ "_").toSet map { n: Node =>
parse(n) match {
case e: Message => e
case e => fatal("illegal definition in messages, only message declarations are allowed", n)
}
}
Dialect(version, enums, messages)
case x => fatal("unknown", x)
}
val ArrayPattern = """(.*)\[(\d+)\]""".r
def parseType(typeStr: String, node: Node): Type = typeStr match {
case "int8_t" => IntType(1, true)
case "int16_t" => IntType(2, true)
case "int32_t" => IntType(4, true)
case "int64_t" => IntType(8, true)
case "uint8_t" => IntType(1, false)
case "uint16_t" => IntType(2, false)
case "uint32_t" => IntType(4, false)
case "uint64_t" => IntType(8, false)
case "float" => FloatType(4)
case "double" => FloatType(8)
case "char" => IntType(1, true)
case ArrayPattern("char", l) => StringType(l.toInt)
case ArrayPattern(u, l) => ArrayType(parseType(u, node), l.toInt)
case unknown => fatal("unknown field type " + unknown, node)
}
}
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