Fix Issue #21: automatic calculation of alignment padding after lists

1 files changed, 130 insertions, 0 deletions

diff --git a/nexgb/xgbgen/aligngap.go b/nexgb/xgbgen/aligngap.go
new file mode 100644
index 0000000..1e07e18
--- /dev/null
+++ b/nexgb/xgbgen/aligngap.go
@@ -0,0 +1,130 @@
+package main
+
+import (
+	"fmt"
+	"os"
+)
+
+func (p *Protocol) AddAlignGaps() {
+	for i := range p.Imports {
+		p.Imports[i].AddAlignGaps()
+	}
+	for i := range p.Types {
+		switch t := p.Types[i].(type) {
+		case *Struct:
+			t.Fields = addAlignGapsToFields(t.xmlName, t.Fields)
+		case *Event:
+			t.Fields = addAlignGapsToFields(t.xmlName, t.Fields)
+		case *Error:
+			t.Fields = addAlignGapsToFields(t.xmlName, t.Fields)
+		}
+	}
+	for i := range p.Requests {
+		p.Requests[i].Fields = addAlignGapsToFields(p.Requests[i].xmlName, p.Requests[i].Fields)
+		if p.Requests[i].Reply != nil {
+			p.Requests[i].Reply.Fields = addAlignGapsToFields(p.Requests[i].xmlName, p.Requests[i].Reply.Fields)
+		}
+	}
+}
+
+func addAlignGapsToFields(name string, fields []Field) []Field {
+	var i int
+	for i = 0; i < len(fields); i++ {
+		if _, ok := fields[i].(*ListField); ok {
+			break
+		}
+	}
+	if i >= len(fields) {
+		return fields
+	}
+
+	r := make([]Field, 0, len(fields)+2)
+	r = append(r, fields[:i]...)
+
+	r = append(r, fields[i])
+	for i = i + 1; i < len(fields); i++ {
+		switch f := fields[i].(type) {
+		case *ListField:
+			// ok, add padding
+			sz := xcbSizeOfType(f.Type)
+			switch {
+			case sz == 1:
+				// nothing
+			case sz == 2:
+				r = append(r, &PadField{0, 2})
+			case sz == 3:
+				panic(fmt.Errorf("Alignment is not a power of 2"))
+			case sz >= 4:
+				r = append(r, &PadField{0, 4})
+			}
+
+		case *LocalField:
+			// nothing
+
+		default:
+			fmt.Fprintf(os.Stderr, "Can't add alignment gaps, mix of list and non-list fields: %s\n", name)
+			return fields
+		}
+		r = append(r, fields[i])
+	}
+
+	return r
+}
+
+func xcbSizeOfField(fld Field) int {
+	switch f := fld.(type) {
+	case *PadField:
+		return int(f.Bytes)
+
+	case *SingleField:
+		return xcbSizeOfType(f.Type)
+
+	case *ListField:
+		return 0
+
+	case *ExprField:
+		return xcbSizeOfType(f.Type)
+
+	case *ValueField:
+		return xcbSizeOfType(f.MaskType)
+
+	case *SwitchField:
+		return 0
+
+	default:
+		return 0
+	}
+}
+
+func xcbSizeOfType(typ Type) int {
+	switch t := typ.(type) {
+	case *Resource:
+		return 4
+
+	case *TypeDef:
+		return t.Size().Eval()
+
+	case *Base:
+		return t.Size().Eval()
+
+	case *Struct:
+		sz := 0
+		for i := range t.Fields {
+			sz += xcbSizeOfField(t.Fields[i])
+		}
+		return sz
+
+	case *Union:
+		sz := 0
+		for i := range t.Fields {
+			csz := xcbSizeOfField(t.Fields[i])
+			if csz > sz {
+				sz = csz
+			}
+		}
+		return sz
+
+	default:
+		return 0
+	}
+}