1 files changed, 86 insertions, 0 deletions
diff --git a/nexgb/xgbgen/xml_fields.go b/nexgb/xgbgen/xml_fields.go
new file mode 100644
index 0000000..8b7b5c7
--- /dev/null
+++ b/nexgb/xgbgen/xml_fields.go
@@ -0,0 +1,86 @@
+package main
+
+import (
+	"encoding/xml"
+	"log"
+)
+
+type XMLField struct {
+	XMLName xml.Name
+
+	// For 'pad' element
+	Bytes uint `xml:"bytes,attr"`
+	Align uint16 `xml:"align,attr"`
+
+	// For 'field', 'list', 'localfield', 'exprfield' and 'switch' elements.
+	Name string `xml:"name,attr"`
+
+	// For 'field', 'list', 'localfield', and 'exprfield' elements.
+	Type string `xml:"type,attr"`
+
+	// For 'list', 'exprfield' and 'switch' elements.
+	Expr *XMLExpression `xml:",any"`
+
+	// For 'valueparm' element.
+	ValueMaskType string `xml:"value-mask-type,attr"`
+	ValueMaskName string `xml:"value-mask-name,attr"`
+	ValueListName string `xml:"value-list-name,attr"`
+
+	// For 'switch' element.
+	Bitcases []*XMLBitcase `xml:"bitcase"`
+
+	// I don't know which elements these are for. The documentation is vague.
+	// They also seem to be completely optional.
+	OptEnum    string `xml:"enum,attr"`
+	OptMask    string `xml:"mask,attr"`
+	OptAltEnum string `xml:"altenum,attr"`
+}
+
+// Bitcase represents a single expression followed by any number of fields.
+// Namely, if the switch's expression (all bitcases are inside a switch),
+// and'd with the bitcase's expression is equal to the bitcase expression,
+// then the fields should be included in its parent structure.
+// Note that since a bitcase is unique in that expressions and fields are
+// siblings, we must exhaustively search for one of them. Essentially,
+// it's the closest thing to a Union I can get to in Go without interfaces.
+// Would an '<expression>' tag have been too much to ask? :-(
+type XMLBitcase struct {
+	Fields []*XMLField `xml:",any"`
+
+	// All the different expressions.
+	// When it comes time to choose one, use the 'Expr' method.
+	ExprOp    *XMLExpression `xml:"op"`
+	ExprUnOp  *XMLExpression `xml:"unop"`
+	ExprField *XMLExpression `xml:"fieldref"`
+	ExprValue *XMLExpression `xml:"value"`
+	ExprBit   *XMLExpression `xml:"bit"`
+	ExprEnum  *XMLExpression `xml:"enumref"`
+	ExprSum   *XMLExpression `xml:"sumof"`
+	ExprPop   *XMLExpression `xml:"popcount"`
+}
+
+// Expr chooses the only non-nil Expr* field from Bitcase.
+// Panic if there is more than one non-nil expression.
+func (b *XMLBitcase) Expr() *XMLExpression {
+	choices := []*XMLExpression{
+		b.ExprOp, b.ExprUnOp, b.ExprField, b.ExprValue,
+		b.ExprBit, b.ExprEnum, b.ExprSum, b.ExprPop,
+	}
+
+	var choice *XMLExpression = nil
+	numNonNil := 0
+	for _, c := range choices {
+		if c != nil {
+			numNonNil++
+			choice = c
+		}
+	}
+
+	if choice == nil {
+		log.Panicf("No top level expression found in a bitcase.")
+	}
+	if numNonNil > 1 {
+		log.Panicf("More than one top-level expression was found in a bitcase.")
+	}
+	return choice
+}