1 files changed, 132 insertions, 2 deletions
diff --git a/nexgb/xgbgen/go_union.go b/nexgb/xgbgen/go_union.go
index 5721c49..3b7365d 100644
--- a/nexgb/xgbgen/go_union.go
+++ b/nexgb/xgbgen/go_union.go
@@ -3,13 +3,143 @@ package main
 // Union types
 func (u *Union) Define(c *Context) {
 	c.Putln("// Union definition %s", u.SrcName())
+	c.Putln("// Note that to *create* a Union, you should *never* create")
+	c.Putln("// this struct directly (unless you know what you're doing).")
+	c.Putln("// Instead use one of the following constructors for '%s':",
+		u.SrcName())
+	for _, field := range u.Fields {
+		c.Putln("//     New%s%s(%s %s) %s", u.SrcName(), field.SrcName(),
+			field.SrcName(), field.SrcType(), u.SrcName())
+	}
+
+	c.Putln("type %s struct {", u.SrcName())
+	for _, field := range u.Fields {
+		field.Define(c)
+	}
+	c.Putln("}")
+	c.Putln("")
+
+	// Write functions for each field that create instances of this
+	// union using the corresponding field.
+	u.New(c)
+
+	// Write function that reads bytes and produces this union.
+	u.Read(c)
+
+	// Write function that reads bytes and produces a list of this union.
+	u.ReadList(c)
+
+	// Write function that writes bytes given this union.
+	u.Write(c)
+
+	// Write function that writes a list of this union.
+	u.WriteList(c)
+
+	// Write function that computes the size of a list of these unions.
+	u.WriteListSize(c)
 }
 
-func (u *Union) Read(c *Context, prefix string) {
+func (u *Union) New(c *Context) {
+	for _, field := range u.Fields {
+		c.Putln("// Union constructor for %s for field %s.",
+			u.SrcName(), field.SrcName())
+		c.Putln("func New%s%s(%s %s) %s {",
+			u.SrcName(), field.SrcName(), field.SrcName(),
+			field.SrcType(), u.SrcName())
+		c.Putln("var b int")
+		c.Putln("buf := make([]byte, %s)", u.Size())
+		c.Putln("")
+		field.Write(c)
+		c.Putln("")
+		c.Putln("// Create the Union type")
+		c.Putln("v := %s{}", u.SrcName())
+		c.Putln("")
+		c.Putln("// Now copy buf into all fields")
+		c.Putln("")
+		for _, field2 := range u.Fields {
+			c.Putln("b = 0 // always read the same bytes")
+			field2.Read(c)
+			c.Putln("")
+		}
+		c.Putln("return v")
+		c.Putln("}")
+		c.Putln("")
+	}
+}
+
+func (u *Union) Read(c *Context) {
 	c.Putln("// Union read %s", u.SrcName())
+	c.Putln("func Read%s(buf []byte, v *%s) int {", u.SrcName(), u.SrcName())
+	c.Putln("var b int")
+	c.Putln("")
+	for _, field := range u.Fields {
+		c.Putln("b = 0 // re-read the same bytes")
+		field.Read(c)
+		c.Putln("")
+	}
+	c.Putln("return %s", u.Size())
+	c.Putln("}")
+	c.Putln("")
+}
+
+func (u *Union) ReadList(c *Context) {
+	c.Putln("// Union list read %s", u.SrcName())
+	c.Putln("func Read%sList(buf []byte, dest []%s) int {",
+		u.SrcName(), u.SrcName())
+	c.Putln("b := 0")
+	c.Putln("for i := 0; i < len(dest); i++ {")
+	c.Putln("dest[i] = %s{}", u.SrcName())
+	c.Putln("b += Read%s(buf[b:], &dest[i])", u.SrcName())
+	c.Putln("}")
+	c.Putln("return pad(b)")
+	c.Putln("}")
+	c.Putln("")
 }
 
-func (u *Union) Write(c *Context, prefix string) {
+// This is a bit tricky since writing from a Union implies that only
+// the data inside ONE of the elements is actually written.
+// However, we only currently support unions where every field has the
+// *same* *fixed* size. Thus, we make sure to always read bytes into
+// every field which allows us to simply pick the first field and write it.
+func (u *Union) Write(c *Context) {
 	c.Putln("// Union write %s", u.SrcName())
+	c.Putln("// Each field in a union must contain the same data.")
+	c.Putln("// So simply pick the first field and write that to the wire.")
+	c.Putln("func (v %s) Bytes() []byte {", u.SrcName())
+	c.Putln("buf := make([]byte, %s)", u.Size().Reduce("v.", ""))
+	c.Putln("b := 0")
+	c.Putln("")
+	u.Fields[0].Write(c)
+	c.Putln("return buf")
+	c.Putln("}")
+	c.Putln("")
+}
+
+func (u *Union) WriteList(c *Context) {
+	c.Putln("// Union list write %s", u.SrcName())
+	c.Putln("func %sListBytes(buf []byte, list []%s) int {",
+		u.SrcName(), u.SrcName())
+	c.Putln("b := 0")
+	c.Putln("var unionBytes []byte")
+	c.Putln("for _, item := range list {")
+	c.Putln("unionBytes = item.Bytes()")
+	c.Putln("copy(buf[b:], len(unionBytes))")
+	c.Putln("b += pad(len(unionBytes))")
+	c.Putln("}")
+	c.Putln("return b")
+	c.Putln("}")
+	c.Putln("")
+}
+
+func (u *Union) WriteListSize(c *Context) {
+	c.Putln("// Union list size %s", u.SrcName())
+	c.Putln("func %sListSize(list []%s) int {", u.SrcName(), u.SrcName())
+	c.Putln("size := 0")
+	c.Putln("for _, item := range list {")
+	c.Putln("size += %s", u.Size().Reduce("item.", ""))
+	c.Putln("}")
+	c.Putln("return size")
+	c.Putln("}")
+	c.Putln("")
 }