progress. still not working. this is incredibly difficult.

This commit is contained in:
Andrew Gallant (Ocelot) 2012-04-29 03:38:29 -04:00
parent 52a21b415a
commit 6bf0191fb0
10 changed files with 385 additions and 80 deletions

2
nexgb/.gitignore vendored Normal file
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@ -0,0 +1,2 @@
xgbgen
.*.swp

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@ -87,9 +87,15 @@ func newCookie(id uint16) *Cookie {
} }
} }
// Event is an interface that can contain any of the events returned by the server. // Event is an interface that can contain any of the events returned by the
// Use a type assertion switch to extract the Event structs. // server. Use a type assertion switch to extract the Event structs.
type Event interface{} type Event interface {
ImplementsEvent()
}
// newEventFuncs is a map from event numbers to functions that create
// the corresponding event.
var newEventFuncs map[int]func(buf []byte) Event
// Error contains protocol errors returned to us by the X server. // Error contains protocol errors returned to us by the X server.
type Error struct { type Error struct {
@ -100,6 +106,16 @@ type Error struct {
Id Id Id Id
} }
// Error2 is an interface that can contain any of the errors returned by
// the server. Use a type assertion switch to extract the Error structs.
type Error2 interface {
ImplementsError()
}
// newErrorFuncs is a map from error numbers to functions that create
// the corresponding error.
var newErrorFuncs map[int]func(buf []byte) Error2
func (e *Error) Error() string { func (e *Error) Error() string {
return fmt.Sprintf("Bad%s (major=%d minor=%d cookie=%d id=0x%x)", return fmt.Sprintf("Bad%s (major=%d minor=%d cookie=%d id=0x%x)",
errorNames[e.Detail], e.Major, e.Minor, e.Cookie, e.Id) errorNames[e.Detail], e.Major, e.Minor, e.Cookie, e.Id)

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@ -85,19 +85,19 @@ func (c *Conn) DefaultScreen() *ScreenInfo { return &c.Setup.Roots[c.defaultScre
// ClientMessageData holds the data from a client message, // ClientMessageData holds the data from a client message,
// duplicated in three forms because Go doesn't have unions. // duplicated in three forms because Go doesn't have unions.
type ClientMessageData struct { // type ClientMessageData struct {
Data8 [20]byte // Data8 [20]byte
Data16 [10]uint16 // Data16 [10]uint16
Data32 [5]uint32 // Data32 [5]uint32
} // }
//
func getClientMessageData(b []byte, v *ClientMessageData) int { // func getClientMessageData(b []byte, v *ClientMessageData) int {
copy(v.Data8[:], b) // copy(v.Data8[:], b)
for i := 0; i < 10; i++ { // for i := 0; i < 10; i++ {
v.Data16[i] = get16(b[i*2:]) // v.Data16[i] = get16(b[i*2:])
} // }
for i := 0; i < 5; i++ { // for i := 0; i < 5; i++ {
v.Data32[i] = get32(b[i*4:]) // v.Data32[i] = get32(b[i*4:])
} // }
return 20 // return 20
} // }

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@ -5,7 +5,6 @@ import (
"encoding/xml" "encoding/xml"
"fmt" "fmt"
"log" "log"
"strings"
) )
type Context struct { type Context struct {
@ -33,31 +32,6 @@ func (c *Context) Put(format string, v ...interface{}) {
} }
} }
// TypePrefix searches the parsed XML for a type matching 'needle'.
// It then returns the appropriate prefix to be used in source code.
// Note that the core X protocol *is* a namespace, but does not have a prefix.
// Also note that you should probably check the BaseTypeMap and TypeMap
// before calling this function.
func (c *Context) TypePrefix(needle Type) string {
// If this is xproto, quit. No prefixes needed.
if c.xml.Header == "xproto" {
return ""
}
// First check for the type in the current namespace.
if c.xml.HasType(needle) {
return strings.Title(c.xml.Header)
}
// Now check each of the imports...
for _, imp := range c.xml.Imports {
if imp.xml.Header != "xproto" && imp.xml.HasType(needle) {
return strings.Title(imp.xml.Header)
}
}
return ""
}
// Translate is the big daddy of them all. It takes in an XML byte slice // Translate is the big daddy of them all. It takes in an XML byte slice
// and writes Go code to the 'out' buffer. // and writes Go code to the 'out' buffer.
@ -76,14 +50,4 @@ func (c *Context) Translate(xmlBytes []byte) {
// It's Morphin' Time! // It's Morphin' Time!
c.xml.Morph(c) c.xml.Morph(c)
// for _, req := range c.xml.Requests {
// if req.Name != "CreateContext" && req.Name != "MakeCurrent" {
// continue
// }
// log.Println(req.Name)
// for _, field := range req.Fields {
// log.Println("\t", field.XMLName.Local, field.Type.Morph(c))
// }
// }
} }

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@ -8,12 +8,22 @@ package main
* Imports and helper variables. * Imports and helper variables.
* Manual type and name override maps. * Manual type and name override maps.
* Constants for tweaking various morphing functions.
* Helper morphing functions. * Helper morphing functions.
* Morphing functions for each "sub-unit."
* Morphing functions for each "unit". * Morphing functions for each "unit".
* Morphing functions for collections of "units". * Morphing functions for collections of "units".
Units can be thought of as the top-level elements in an XML protocol
description file. Namely, structs, xidtypes, imports, enums, unions, etc.
Collections of units are simply "all of the UNIT in the XML file."
Sub-units can be thought of as recurring bits like struct contents (which
is used in events, replies, requests, errors, etc.) and expression
evaluation.
*/ */
import ( import (
"log"
"strings" "strings"
) )
@ -38,6 +48,24 @@ var BaseTypeMap = map[string]string{
"BOOL": "bool", "BOOL": "bool",
"float": "float64", "float": "float64",
"double": "float64", "double": "float64",
"char": "byte",
}
// BaseTypeSizes should have precisely the same keys as in BaseTypeMap,
// and the values should correspond to the size of the type in bytes.
var BaseTypeSizes = map[string]uint{
"CARD8": 1,
"CARD16": 2,
"CARD32": 4,
"INT8": 1,
"INT16": 2,
"INT32": 4,
"BYTE": 1,
"BOOL": 1,
"float": 4,
"double": 8,
"char": 1,
"Id": 4,
} }
// TypeMap is a map from types in the XML to type names that is used // TypeMap is a map from types in the XML to type names that is used
@ -54,12 +82,26 @@ var TypeMap = map[string]string{
var NameMap = map[string]string{ } var NameMap = map[string]string{ }
/******************************************************************************/ /******************************************************************************/
// Helper functions that aide in morphing repetive constructs. // Constants for changing the semantics of morphing functions.
// i.e., "structure contents", expressions, type and identifier names, etc. // These are mainly used to tweaking the writing of fields.
// Namely, reading/writing is not exactly the same across events,
// requests/replies and errors.
/******************************************************************************/
const (
FieldsEvent = iota
FieldsRequestReply
FieldsError
)
/******************************************************************************/
// Helper functions that aide in morphing repetitive constructs.
// i.e., type and identifier names, etc.
/******************************************************************************/ /******************************************************************************/
// Morph changes every TYPE (not names) into something suitable // Morph changes every TYPE (not names) into something suitable
// for your language. // for your language. It also handles adding suffixes like 'Event'
// and 'Union'. (A 'Union' suffix is used in Go because unions aren't
// supported at the language level.)
func (typ Type) Morph(c *Context) string { func (typ Type) Morph(c *Context) string {
t := string(typ) t := string(typ)
@ -87,7 +129,33 @@ func (typ Type) Morph(c *Context) string {
// Since there is no namespace, we need to look for a namespace // Since there is no namespace, we need to look for a namespace
// in the current context. // in the current context.
return c.TypePrefix(typ) + splitAndTitle(t) return typ.Prefix(c) + splitAndTitle(t)
}
// Prefix searches the parsed XML for a type matching 'typ'.
// It then returns the appropriate prefix to be used in source code.
// Note that the core X protocol *is* a namespace, but does not have a prefix.
// Also note that you should probably check the BaseTypeMap and TypeMap
// before calling this function.
func (typ Type) Prefix(c *Context) string {
// If this is xproto, quit. No prefixes needed.
if c.xml.Header == "xproto" {
return ""
}
// First check for the type in the current namespace.
if c.xml.HasType(typ) {
return strings.Title(c.xml.Header)
}
// Now check each of the imports...
for _, imp := range c.xml.Imports {
if imp.xml.Header != "xproto" && imp.xml.HasType(typ) {
return strings.Title(imp.xml.Header)
}
}
return ""
} }
// Morph changes every identifier (NOT type) into something suitable // Morph changes every identifier (NOT type) into something suitable
@ -103,6 +171,147 @@ func (name Name) Morph(c *Context) string {
return splitAndTitle(n) return splitAndTitle(n)
} }
/******************************************************************************/
// Sub-unit morphing.
// Below are functions that morph sub-units. Like collections of fields,
// expressions, etc.
// Note that collections of fields can be used in three different contexts:
// definitions, reading from the wire and writing to the wire. Thus, there
// exists 'MorphDefine', 'MorphRead', 'MorphWrite' defined on Fields.
/******************************************************************************/
func (fields Fields) MorphDefine(c *Context) {
for _, field := range fields {
field.MorphDefine(c)
}
}
func (field *Field) MorphDefine(c *Context) {
// We omit 'pad' and 'exprfield'
switch field.XMLName.Local {
case "field":
c.Putln("%s %s", field.Name.Morph(c), field.Type.Morph(c))
case "list":
c.Putln("%s []%s", field.Name.Morph(c), field.Type.Morph(c))
case "localfield":
c.Putln("%s %s", field.Name.Morph(c), field.Type.Morph(c))
case "valueparam":
c.Putln("%s %s", field.ValueMaskName.Morph(c),
field.ValueMaskType.Morph(c))
c.Putln("%s []%s", field.ValueListName.Morph(c),
field.ValueMaskType.Morph(c))
case "switch":
field.Bitcases.MorphDefine(c)
}
}
func (bitcases Bitcases) MorphDefine(c *Context) {
for _, bitcase := range bitcases {
bitcase.MorphDefine(c)
}
}
func (bitcase *Bitcase) MorphDefine(c *Context) {
bitcase.Fields.MorphDefine(c)
}
func (fields Fields) MorphRead(c *Context, kind int, evNoSeq bool) {
var nextByte uint
switch kind {
case FieldsEvent:
nextByte = 1
}
for _, field := range fields {
nextByte = field.MorphRead(c, kind, nextByte)
switch kind {
case FieldsEvent:
// Skip the sequence id
if !evNoSeq && (nextByte == 2 || nextByte == 3) {
nextByte = 4
}
}
}
}
func (field *Field) MorphRead(c *Context, kind int, byt uint) uint {
consumed := uint(0)
switch field.XMLName.Local {
case "pad":
consumed = uint(field.Bytes)
case "field":
if field.Type == "ClientMessageData" {
break
}
size := field.Type.Size(c)
typ := field.Type.Morph(c)
name := field.Name.Morph(c)
_, isBase := BaseTypeMap[string(field.Type)]
c.Put("v.%s = ", name)
if !isBase {
c.Put("%s(", typ)
}
switch size {
case 1: c.Put("buf[%d]", byt)
case 2: c.Put("get16(buf[%d:])", byt)
case 4: c.Put("get32(buf[%d:])", byt)
case 8: c.Put("get64(buf[%d:])", byt)
default:
log.Fatalf("Unsupported field size '%d' for field '%s'.",
size, field)
}
if !isBase {
c.Put(")")
}
c.Putln("")
consumed = size
case "list":
c.Putln("")
}
return byt + consumed
}
func (fields Fields) MorphWrite(c *Context, kind int) {
var nextByte uint
switch kind {
case FieldsEvent:
nextByte = 1
}
for _, field := range fields {
nextByte = field.MorphWrite(c, kind, nextByte)
}
}
func (field *Field) MorphWrite(c *Context, kind int, byt uint) uint {
consumed := uint(0)
switch field.XMLName.Local {
case "pad":
consumed = uint(field.Bytes)
case "field":
size := field.Type.Size(c)
typ := field.Type.Morph(c)
name := field.Name.Morph(c)
switch size {
case 1:
c.Putln("v.%s = %s(buf[%d])", name, typ, byt)
case 2:
c.Putln("v.%s = %s(get16(buf[%d:]))", name, typ, byt)
case 4:
c.Putln("v.%s = %s(get32(buf[%d:]))", name, typ, byt)
case 8:
c.Putln("v.%s = %s(get64(buf[%d:]))", name, typ, byt)
}
consumed = size
case "list":
c.Putln("IDK")
}
return byt + consumed
}
/******************************************************************************/ /******************************************************************************/
// Per element morphing. // Per element morphing.
// Below are functions that morph a single unit. // Below are functions that morph a single unit.
@ -133,15 +342,23 @@ func (xid *Xid) Morph(c *Context) {
// TypeDef morphing. // TypeDef morphing.
func (typedef *TypeDef) Morph(c *Context) { func (typedef *TypeDef) Morph(c *Context) {
c.Putln("type %s %s", typedef.Old.Morph(c), typedef.New.Morph(c)) c.Putln("type %s %s", typedef.New.Morph(c), typedef.Old.Morph(c))
} }
// Struct morphing. // Struct morphing.
func (strct *Struct) Morph(c *Context) { func (strct *Struct) Morph(c *Context) {
c.Putln("type %s struct {", strct.Name.Morph(c))
strct.Fields.MorphDefine(c)
c.Putln("}")
c.Putln("\n")
} }
// Union morphing. // Union morphing.
func (union *Union) Morph(c *Context) { func (union *Union) Morph(c *Context) {
c.Putln("type %s struct {", union.Name.Morph(c))
union.Fields.MorphDefine(c)
c.Putln("}")
c.Putln("\n")
} }
// Request morphing. // Request morphing.
@ -150,10 +367,54 @@ func (request *Request) Morph(c *Context) {
// Event morphing. // Event morphing.
func (ev *Event) Morph(c *Context) { func (ev *Event) Morph(c *Context) {
name := ev.Name.Morph(c)
c.Putln("const %s = %d", name, ev.Number)
c.Putln("")
c.Putln("type %sEvent struct {", name)
ev.Fields.MorphDefine(c)
c.Putln("}")
c.Putln("")
c.Putln("func New%s(buf []byte) %sEvent {", name, name)
c.Putln("var v %sEvent", name)
ev.Fields.MorphRead(c, FieldsEvent, ev.NoSequence)
c.Putln("return v")
c.Putln("}")
c.Putln("")
c.Putln("func (err %sEvent) ImplementsEvent() { }", name)
c.Putln("")
c.Putln("func (ev %sEvent) Bytes() []byte {", name)
// ev.Fields.MorphWrite(c, FieldsEvent)
c.Putln("}")
c.Putln("")
c.Putln("func init() {")
c.Putln("newEventFuncs[%d] = New%s", ev.Number, name)
c.Putln("}")
c.Putln("")
} }
// EventCopy morphing. // EventCopy morphing.
func (evcopy *EventCopy) Morph(c *Context) { func (evcopy *EventCopy) Morph(c *Context) {
oldName, newName := evcopy.Ref.Morph(c), evcopy.Name.Morph(c)
c.Putln("const %s = %d", newName, evcopy.Number)
c.Putln("")
c.Putln("type %sEvent %sEvent", newName, oldName)
c.Putln("")
c.Putln("func New%s(buf []byte) %sEvent {", newName, newName)
c.Putln("return (%sEvent)(New%s(buf))", newName, oldName)
c.Putln("}")
c.Putln("")
c.Putln("func (err %sEvent) ImplementsEvent() { }", newName)
c.Putln("")
c.Putln("func (ev %sEvent) Bytes() []byte {", newName)
c.Putln("return (%sEvent)(ev).Bytes()", oldName)
c.Putln("}")
c.Putln("")
c.Putln("func init() {")
c.Putln("newEventFuncs[%d] = New%s", evcopy.Number, newName)
c.Putln("}")
c.Putln("")
} }
// Error morphing. // Error morphing.
@ -162,6 +423,26 @@ func (err *Error) Morph(c *Context) {
// ErrorCopy morphing. // ErrorCopy morphing.
func (errcopy *ErrorCopy) Morph(c *Context) { func (errcopy *ErrorCopy) Morph(c *Context) {
oldName, newName := errcopy.Ref.Morph(c), errcopy.Name.Morph(c)
c.Putln("const Bad%s = %d", newName, errcopy.Number)
c.Putln("")
c.Putln("type %sError %sError", newName, oldName)
c.Putln("")
c.Putln("func New%sError(buf []byte) %sError {", newName, newName)
c.Putln("return (%sError)(New%sError(buf))", newName, oldName)
c.Putln("}")
c.Putln("")
c.Putln("func (err %sError) ImplementsError() { }", newName)
c.Putln("")
c.Putln("func (err %sError) Bytes() []byte {", newName)
c.Putln("return (%sError)(err).Bytes()", oldName)
c.Putln("}")
c.Putln("")
c.Putln("func init() {")
c.Putln("newErrorFuncs[%d] = New%sError", errcopy.Number, newName)
c.Putln("}")
c.Putln("")
} }
/******************************************************************************/ /******************************************************************************/

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@ -55,6 +55,7 @@ func main() {
cmdGofmt := exec.Command("gofmt") cmdGofmt := exec.Command("gofmt")
cmdGofmt.Stdin = c.out cmdGofmt.Stdin = c.out
cmdGofmt.Stdout = os.Stdout cmdGofmt.Stdout = os.Stdout
cmdGofmt.Stderr = os.Stderr
err = cmdGofmt.Run() err = cmdGofmt.Run()
if err != nil { if err != nil {
log.Fatal(err) log.Fatal(err)

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@ -21,6 +21,11 @@ func popCount(mask uint) uint {
return n return n
} }
// pad makes sure 'n' aligns on 4 bytes.
func pad(n int) int {
return (n + 3) & ^3
}
// splitAndTitle takes a string, splits it by underscores, capitalizes the // splitAndTitle takes a string, splits it by underscores, capitalizes the
// first letter of each chunk, and smushes'em back together. // first letter of each chunk, and smushes'em back together.
func splitAndTitle(s string) string { func splitAndTitle(s string) string {
@ -29,9 +34,9 @@ func splitAndTitle(s string) string {
return strings.Title(strings.ToLower(s)) return strings.Title(strings.ToLower(s))
} }
// If the string has no underscores, leave it be. // If the string has no underscores, capitalize it and leave it be.
if i := strings.Index(s, "_"); i == -1 { if i := strings.Index(s, "_"); i == -1 {
return s return strings.Title(s)
} }
// Now split the name at underscores, capitalize the first // Now split the name at underscores, capitalize the first

Binary file not shown.

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@ -71,16 +71,16 @@ func (x *XML) Morph(c *Context) {
x.Requests.Morph(c) x.Requests.Morph(c)
c.Putln("") c.Putln("")
x.Events.Morph(c)
c.Putln("")
x.Errors.Morph(c) x.Errors.Morph(c)
c.Putln("") c.Putln("")
x.EventCopies.Morph(c) x.ErrorCopies.Morph(c)
c.Putln("") c.Putln("")
x.ErrorCopies.Morph(c) x.Events.Morph(c)
c.Putln("")
x.EventCopies.Morph(c)
c.Putln("") c.Putln("")
} }
@ -166,6 +166,38 @@ type Name string
type Type string type Type string
// Size is a nifty function that takes any type and digs until it finds
// its underlying base type. At which point, the size can be determined.
func (typ Type) Size(c *Context) uint {
// If this is a base type, we're done.
if size, ok := BaseTypeSizes[string(typ)]; ok {
return size
}
// If it's a resource, we're also done.
if c.xml.IsResource(typ) {
return BaseTypeSizes["Id"]
}
// It's not, so that implies there is *some* typedef declaring it
// in terms of another type. Just follow that chain until we get to
// a base type. We also need to check imported stuff.
for _, typedef := range c.xml.TypeDefs {
if typ == typedef.New {
return typedef.Old.Size(c)
}
}
for _, imp := range c.xml.Imports {
for _, typedef := range imp.xml.TypeDefs {
if typ == typedef.New {
return typedef.Old.Size(c)
}
}
}
log.Panicf("Could not find base size of type '%s'.", typ)
panic("unreachable")
}
type Imports []*Import type Imports []*Import
func (imports Imports) Eval() { func (imports Imports) Eval() {
@ -239,7 +271,7 @@ type EventCopies []*EventCopy
type EventCopy struct { type EventCopy struct {
Name Type `xml:"name,attr"` Name Type `xml:"name,attr"`
Number string `xml:"number,attr"` Number int `xml:"number,attr"`
Ref Type `xml:"ref,attr"` Ref Type `xml:"ref,attr"`
} }
@ -247,7 +279,7 @@ type ErrorCopies []*ErrorCopy
type ErrorCopy struct { type ErrorCopy struct {
Name Type `xml:"name,attr"` Name Type `xml:"name,attr"`
Number string `xml:"number,attr"` Number int `xml:"number,attr"`
Ref Type `xml:"ref,attr"` Ref Type `xml:"ref,attr"`
} }
@ -255,14 +287,14 @@ type Structs []*Struct
type Struct struct { type Struct struct {
Name Type `xml:"name,attr"` Name Type `xml:"name,attr"`
Fields []*Field `xml:",any"` Fields Fields `xml:",any"`
} }
type Unions []*Union type Unions []*Union
type Union struct { type Union struct {
Name Type `xml:"name,attr"` Name Type `xml:"name,attr"`
Fields []*Field `xml:",any"` Fields Fields `xml:",any"`
} }
type Requests []*Request type Requests []*Request
@ -271,12 +303,12 @@ type Request struct {
Name Type `xml:"name,attr"` Name Type `xml:"name,attr"`
Opcode int `xml:"opcode,attr"` Opcode int `xml:"opcode,attr"`
Combine bool `xml:"combine-adjacent,attr"` Combine bool `xml:"combine-adjacent,attr"`
Fields []*Field `xml:",any"` Fields Fields `xml:",any"`
Reply *Reply `xml:"reply"` Reply *Reply `xml:"reply"`
} }
type Reply struct { type Reply struct {
Fields []*Field `xml:",any"` Fields Fields `xml:",any"`
} }
type Events []*Event type Events []*Event
@ -285,7 +317,7 @@ type Event struct {
Name Type `xml:"name,attr"` Name Type `xml:"name,attr"`
Number int `xml:"number,attr"` Number int `xml:"number,attr"`
NoSequence bool `xml:"no-sequence-number,true"` NoSequence bool `xml:"no-sequence-number,true"`
Fields []*Field `xml:",any"` Fields Fields `xml:",any"`
} }
type Errors []*Error type Errors []*Error
@ -293,6 +325,6 @@ type Errors []*Error
type Error struct { type Error struct {
Name Type `xml:"name,attr"` Name Type `xml:"name,attr"`
Number int `xml:"number,attr"` Number int `xml:"number,attr"`
Fields []*Field `xml:",any"` Fields Fields `xml:",any"`
} }

View File

@ -23,6 +23,8 @@ import (
"strings" "strings"
) )
type Fields []*Field
type Field struct { type Field struct {
XMLName xml.Name XMLName xml.Name
@ -30,7 +32,7 @@ type Field struct {
Bytes int `xml:"bytes,attr"` Bytes int `xml:"bytes,attr"`
// For 'field', 'list', 'localfield', 'exprfield' and 'switch' elements. // For 'field', 'list', 'localfield', 'exprfield' and 'switch' elements.
Name string `xml:"name,attr"` Name Name `xml:"name,attr"`
// For 'field', 'list', 'localfield', and 'exprfield' elements. // For 'field', 'list', 'localfield', and 'exprfield' elements.
Type Type `xml:"type,attr"` Type Type `xml:"type,attr"`
@ -40,11 +42,11 @@ type Field struct {
// For 'valueparm' element. // For 'valueparm' element.
ValueMaskType Type `xml:"value-mask-type,attr"` ValueMaskType Type `xml:"value-mask-type,attr"`
ValueMaskName string `xml:"value-mask-name,attr"` ValueMaskName Name `xml:"value-mask-name,attr"`
ValueListName string `xml:"value-list-name,attr"` ValueListName Name `xml:"value-list-name,attr"`
// For 'switch' element. // For 'switch' element.
Bitcases []*Bitcase `xml:"bitcase"` Bitcases Bitcases `xml:"bitcase"`
// I don't know which elements these are for. The documentation is vague. // I don't know which elements these are for. The documentation is vague.
// They also seem to be completely optional. // They also seem to be completely optional.
@ -86,6 +88,8 @@ func (f *Field) String() string {
panic("unreachable") panic("unreachable")
} }
type Bitcases []*Bitcase
// Bitcase represents a single expression followed by any number of fields. // Bitcase represents a single expression followed by any number of fields.
// Namely, if the switch's expression (all bitcases are inside a switch), // 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, // and'd with the bitcase's expression is equal to the bitcase expression,
@ -95,7 +99,7 @@ func (f *Field) String() string {
// it's the closest thing to a Union I can get to in Go without interfaces. // 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? :-( // Would an '<expression>' tag have been too much to ask? :-(
type Bitcase struct { type Bitcase struct {
Fields []*Field `xml:",any"` Fields Fields `xml:",any"`
// All the different expressions. // All the different expressions.
// When it comes time to choose one, use the 'Expr' method. // When it comes time to choose one, use the 'Expr' method.