Some initial experimentation with SCPD reading.

v2alpha/description/xmlscpd/xmlscpd.go

@@ -0,0 +1,161 @@
+// Package xmlscpd contains the XML data structures used in SCPD (Service Control Protocol Description).
+//
+// Described in section 2.5 of
+// https://openconnectivity.org/upnp-specs/UPnP-arch-DeviceArchitecture-v2.0-20200417.pdf.
+package xmlscpd
+
+import (
+	"bytes"
+	"encoding/xml"
+	"fmt"
+	"strings"
+)
+
+func cleanWhitespace(s *string) {
+	*s = strings.TrimSpace(*s)
+}
+
+// SCPD is the top level XML service description.
+type SCPD struct {
+	XMLName        xml.Name         `xml:"scpd"`
+	ConfigId       string           `xml:"configId,attr"`
+	SpecVersion    SpecVersion      `xml:"specVersion"`
+	Actions        []*Action        `xml:"actionList>action"`
+	StateVariables []*StateVariable `xml:"serviceStateTable>stateVariable"`
+}
+
+// Clean removes stray whitespace in the structure.
+//
+// It's common for stray whitespace to be present in SCPD documents, this method removes them
+// in-place.
+func (scpd *SCPD) Clean() {
+	cleanWhitespace(&scpd.ConfigId)
+	for i := range scpd.Actions {
+		scpd.Actions[i].Clean()
+	}
+	for i := range scpd.StateVariables {
+		scpd.StateVariables[i].Clean()
+	}
+}
+
+// SpecVersion is part of a SCPD document, describes the version of the
+// specification that the data adheres to.
+type SpecVersion struct {
+	Major int32 `xml:"major"`
+	Minor int32 `xml:"minor"`
+}
+
+// Action XML description data.
+type Action struct {
+	Name      string      `xml:"name"`
+	Arguments []*Argument `xml:"argumentList>argument"`
+}
+
+// Clean removes stray whitespace in the structure.
+func (action *Action) Clean() {
+	cleanWhitespace(&action.Name)
+	for i := range action.Arguments {
+		action.Arguments[i].Clean()
+	}
+}
+
+// Argument XML data.
+type Argument struct {
+	Name                 string `xml:"name"`
+	Direction            string `xml:"direction"`            // in|out
+	RelatedStateVariable string `xml:"relatedStateVariable"` // ?
+	Retval               string `xml:"retval"`               // ?
+}
+
+// Clean removes stray whitespace in the structure.
+func (arg *Argument) Clean() {
+	cleanWhitespace(&arg.Name)
+	cleanWhitespace(&arg.Direction)
+	cleanWhitespace(&arg.RelatedStateVariable)
+	cleanWhitespace(&arg.Retval)
+}
+
+// StateVariable XML data.
+type StateVariable struct {
+	Optional          PresenceBool
+	Name              string             `xml:"name"`
+	SendEvents        string             `xml:"sendEvents,attr"` // yes|no
+	Multicast         string             `xml:"multicast,attr"`  // yes|no
+	DataType          DataType           `xml:"dataType"`
+	DefaultValue      string             `xml:"defaultValue"`
+	AllowedValueRange *AllowedValueRange `xml:"allowedValueRange"`
+	AllowedValues     []string           `xml:"allowedValueList>allowedValue"`
+}
+
+// Clean removes stray whitespace in the structure.
+func (v *StateVariable) Clean() {
+	cleanWhitespace(&v.Name)
+	cleanWhitespace(&v.SendEvents)
+	cleanWhitespace(&v.Multicast)
+	v.DataType.Clean()
+	cleanWhitespace(&v.DefaultValue)
+	if v.AllowedValueRange != nil {
+		v.AllowedValueRange.Clean()
+	}
+	for i := range v.AllowedValues {
+		cleanWhitespace(&v.AllowedValues[i])
+	}
+}
+
+// AllowedValueRange XML data.
+type AllowedValueRange struct {
+	Minimum string `xml:"minimum"`
+	Maximum string `xml:"maximum"`
+	Step    string `xml:"step"`
+}
+
+// Clean removes stray whitespace in the structure.
+func (r *AllowedValueRange) Clean() {
+	cleanWhitespace(&r.Minimum)
+	cleanWhitespace(&r.Maximum)
+	cleanWhitespace(&r.Step)
+}
+
+// DataType XML data.
+type DataType struct {
+	Name string `xml:",chardata"`
+	Type string `xml:"type,attr"`
+}
+
+// Clean removes stray whitespace in the structure.
+func (dt *DataType) Clean() {
+	cleanWhitespace(&dt.Name)
+	cleanWhitespace(&dt.Type)
+}
+
+// PresenceBool represents an empty XML element that is true if present.
+//
+// Is an error if it contains any attributes or contents.
+type PresenceBool bool
+
+func (pb *PresenceBool) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
+	*pb = true
+	if len(start.Attr) > 0 {
+		return fmt.Errorf("unexpected attributes on element %s:%s",
+			start.Name.Space, start.Name.Local)
+	}
+	for {
+		tok, err := d.Token()
+		if err != nil {
+			return err
+		}
+		switch tok := tok.(type) {
+		case xml.CharData:
+			if len(bytes.TrimSpace([]byte(tok))) > 0 {
+				return fmt.Errorf("unexpected char data on element %s:%s",
+					start.Name.Space, start.Name.Local)
+			}
+		case xml.EndElement:
+			return nil
+		case xml.Comment:
+		default:
+			return fmt.Errorf("unexpected %T token on element %s:%s",
+				tok, start.Name.Space, start.Name.Local)
+		}
+	}
+}