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package main
// Union types
func (u *Union) Define(c *Context) {
c.Putln("// %s is a represention of the %s union type.",
u.SrcName(), 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("// %s%sNew(%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)
}
func (u *Union) New(c *Context) {
for _, field := range u.Fields {
c.Putln("// %s%sNew constructs a new %s union type with the %s field.",
u.SrcName(), field.SrcName(), u.SrcName(), field.SrcName())
c.Putln("func %s%sNew(%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, "v.")
c.Putln("")
}
c.Putln("return v")
c.Putln("}")
c.Putln("")
}
}
func (u *Union) Read(c *Context) {
c.Putln("// %sRead reads a byte slice into a %s value.",
u.SrcName(), u.SrcName())
c.Putln("func %sRead(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, "v.")
c.Putln("")
}
c.Putln("return %s", u.Size())
c.Putln("}")
c.Putln("")
}
func (u *Union) ReadList(c *Context) {
c.Putln("// %sReadList reads a byte slice into a list of %s values.",
u.SrcName(), u.SrcName())
c.Putln("func %sReadList(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 += %sRead(buf[b:], &dest[i])", u.SrcName())
c.Putln("}")
c.Putln("return xgb.Pad(b)")
c.Putln("}")
c.Putln("")
}
// 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("// Bytes writes a %s value to a byte slice.", 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, "v.")
c.Putln("return buf")
c.Putln("}")
c.Putln("")
}
func (u *Union) WriteList(c *Context) {
c.Putln("// %sListBytes writes a list of %s values to a byte slice.",
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:], unionBytes)")
c.Putln("b += xgb.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("// %sListSize computes the size (bytes) of a list of %s values.",
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("")
}
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