haven/nexgb/xgbgen/expression.go

383 lines
8.1 KiB
Go

package main
import (
"fmt"
"log"
)
// Expression represents all the different forms of expressions possible in
// side an XML protocol description file. It's also received a few custom
// addendums to make applying special functions (like padding) easier.
type Expression interface {
// Concrete determines whether this particular expression can be computed
// to some constant value inside xgbgen. (The alternative is that the
// expression can only be computed with values at run time of the
// generated code.)
Concrete() bool
// Eval evaluates a concrete expression. It is an error to call Eval
// on any expression that is not concrete (or contains any sub-expression
// that is not concrete).
Eval() int
// Reduce attempts to evaluate any concrete sub-expressions.
// i.e., (1 + 2 * (5 + 1 + someSizeOfStruct) reduces to
// (3 * (6 + someSizeOfStruct)).
// 'prefix' is used preprended to any field reference name.
Reduce(prefix string) string
// String is an alias for Reduce("")
String() string
// Initialize makes sure all names in this expression and any subexpressions
// have been translated to Go source names.
Initialize(p *Protocol)
}
// Function is a custom expression not found in the XML. It's simply used
// to apply a function named in 'Name' to the Expr expression.
type Function struct {
Name string
Expr Expression
}
func (e *Function) Concrete() bool {
return false
}
func (e *Function) Eval() int {
log.Fatalf("Cannot evaluate a 'Function'. It is not concrete.")
panic("unreachable")
}
func (e *Function) Reduce(prefix string) string {
return fmt.Sprintf("%s(%s)", e.Name, e.Expr.Reduce(prefix))
}
func (e *Function) String() string {
return e.Reduce("")
}
func (e *Function) Initialize(p *Protocol) {
e.Expr.Initialize(p)
}
// BinaryOp is an expression that performs some operation (defined in the XML
// file) with Expr1 and Expr2 as operands.
type BinaryOp struct {
Op string
Expr1 Expression
Expr2 Expression
}
// newBinaryOp constructs a new binary expression when both expr1 and expr2
// are not nil. If one or both are nil, then the non-nil expression is
// returned unchanged or nil is returned.
func newBinaryOp(op string, expr1, expr2 Expression) Expression {
switch {
case expr1 != nil && expr2 != nil:
return &BinaryOp{
Op: op,
Expr1: expr1,
Expr2: expr2,
}
case expr1 != nil && expr2 == nil:
return expr1
case expr1 == nil && expr2 != nil:
return expr2
case expr1 == nil && expr2 == nil:
return nil
}
panic("unreachable")
}
func (e *BinaryOp) Concrete() bool {
return e.Expr1.Concrete() && e.Expr2.Concrete()
}
func (e *BinaryOp) Eval() int {
switch e.Op {
case "+":
return e.Expr1.Eval() + e.Expr2.Eval()
case "-":
return e.Expr1.Eval() - e.Expr2.Eval()
case "*":
return e.Expr1.Eval() * e.Expr2.Eval()
case "/":
return e.Expr1.Eval() / e.Expr2.Eval()
case "&":
return e.Expr1.Eval() & e.Expr2.Eval()
case "<<":
return int(uint(e.Expr1.Eval()) << uint(e.Expr2.Eval()))
}
log.Fatalf("Invalid binary operator '%s' for expression.", e.Op)
panic("unreachable")
}
func (e *BinaryOp) Reduce(prefix string) string {
if e.Concrete() {
return fmt.Sprintf("%d", e.Eval())
}
// An incredibly dirty hack to make sure any time we perform an operation
// on a field, we're dealing with ints...
expr1, expr2 := e.Expr1, e.Expr2
switch expr1.(type) {
case *FieldRef:
expr1 = &Function{
Name: "int",
Expr: expr1,
}
}
switch expr2.(type) {
case *FieldRef:
expr2 = &Function{
Name: "int",
Expr: expr2,
}
}
return fmt.Sprintf("(%s %s %s)",
expr1.Reduce(prefix), e.Op, expr2.Reduce(prefix))
}
func (e *BinaryOp) String() string {
return e.Reduce("")
}
func (e *BinaryOp) Initialize(p *Protocol) {
e.Expr1.Initialize(p)
e.Expr2.Initialize(p)
}
// UnaryOp is the same as BinaryOp, except it's a unary operator with only
// one sub-expression.
type UnaryOp struct {
Op string
Expr Expression
}
func (e *UnaryOp) Concrete() bool {
return e.Expr.Concrete()
}
func (e *UnaryOp) Eval() int {
switch e.Op {
case "~":
return ^e.Expr.Eval()
}
log.Fatalf("Invalid unary operator '%s' for expression.", e.Op)
panic("unreachable")
}
func (e *UnaryOp) Reduce(prefix string) string {
if e.Concrete() {
return fmt.Sprintf("%d", e.Eval())
}
return fmt.Sprintf("(%s (%s))", e.Op, e.Expr.Reduce(prefix))
}
func (e *UnaryOp) String() string {
return e.Reduce("")
}
func (e *UnaryOp) Initialize(p *Protocol) {
e.Expr.Initialize(p)
}
// Padding represents the application of the 'pad' function to some
// sub-expression.
type Padding struct {
Expr Expression
}
func (e *Padding) Concrete() bool {
return e.Expr.Concrete()
}
func (e *Padding) Eval() int {
return pad(e.Expr.Eval())
}
func (e *Padding) Reduce(prefix string) string {
if e.Concrete() {
return fmt.Sprintf("%d", e.Eval())
}
return fmt.Sprintf("xgb.Pad(%s)", e.Expr.Reduce(prefix))
}
func (e *Padding) String() string {
return e.Reduce("")
}
func (e *Padding) Initialize(p *Protocol) {
e.Expr.Initialize(p)
}
// PopCount represents the application of the 'PopCount' function to
// some sub-expression.
type PopCount struct {
Expr Expression
}
func (e *PopCount) Concrete() bool {
return e.Expr.Concrete()
}
func (e *PopCount) Eval() int {
return int(popCount(uint(e.Expr.Eval())))
}
func (e *PopCount) Reduce(prefix string) string {
if e.Concrete() {
return fmt.Sprintf("%d", e.Eval())
}
return fmt.Sprintf("xgb.PopCount(%s)", e.Expr.Reduce(prefix))
}
func (e *PopCount) String() string {
return e.Reduce("")
}
func (e *PopCount) Initialize(p *Protocol) {
e.Expr.Initialize(p)
}
// Value represents some constant integer.
type Value struct {
v int
}
func (e *Value) Concrete() bool {
return true
}
func (e *Value) Eval() int {
return e.v
}
func (e *Value) Reduce(prefix string) string {
return fmt.Sprintf("%d", e.v)
}
func (e *Value) String() string {
return e.Reduce("")
}
func (e *Value) Initialize(p *Protocol) {}
// Bit represents some bit whose value is computed by '1 << bit'.
type Bit struct {
b int
}
func (e *Bit) Concrete() bool {
return true
}
func (e *Bit) Eval() int {
return int(1 << uint(e.b))
}
func (e *Bit) Reduce(prefix string) string {
return fmt.Sprintf("%d", e.Eval())
}
func (e *Bit) String() string {
return e.Reduce("")
}
func (e *Bit) Initialize(p *Protocol) {}
// FieldRef represents a reference to some variable in the generated code
// with name Name.
type FieldRef struct {
Name string
}
func (e *FieldRef) Concrete() bool {
return false
}
func (e *FieldRef) Eval() int {
log.Fatalf("Cannot evaluate a 'FieldRef'. It is not concrete.")
panic("unreachable")
}
func (e *FieldRef) Reduce(prefix string) string {
val := e.Name
if len(prefix) > 0 {
val = fmt.Sprintf("%s%s", prefix, val)
}
return val
}
func (e *FieldRef) String() string {
return e.Reduce("")
}
func (e *FieldRef) Initialize(p *Protocol) {
e.Name = SrcName(p, e.Name)
}
// EnumRef represents a reference to some enumeration field.
// EnumKind is the "group" an EnumItem is the name of the specific enumeration
// value inside that group.
type EnumRef struct {
EnumKind Type
EnumItem string
}
func (e *EnumRef) Concrete() bool {
return false
}
func (e *EnumRef) Eval() int {
log.Fatalf("Cannot evaluate an 'EnumRef'. It is not concrete.")
panic("unreachable")
}
func (e *EnumRef) Reduce(prefix string) string {
return fmt.Sprintf("%s%s", e.EnumKind, e.EnumItem)
}
func (e *EnumRef) String() string {
return e.Reduce("")
}
func (e *EnumRef) Initialize(p *Protocol) {
e.EnumKind = e.EnumKind.(*Translation).RealType(p)
e.EnumItem = SrcName(p, e.EnumItem)
}
// SumOf represents a summation of the variable in the generated code named by
// Name. It is not currently used. (It's XKB voodoo.)
type SumOf struct {
Name string
}
func (e *SumOf) Concrete() bool {
return false
}
func (e *SumOf) Eval() int {
log.Fatalf("Cannot evaluate a 'SumOf'. It is not concrete.")
panic("unreachable")
}
func (e *SumOf) Reduce(prefix string) string {
if len(prefix) > 0 {
return fmt.Sprintf("sum(%s%s)", prefix, e.Name)
}
return fmt.Sprintf("sum(%s)", e.Name)
}
func (e *SumOf) String() string {
return e.Reduce("")
}
func (e *SumOf) Initialize(p *Protocol) {
e.Name = SrcName(p, e.Name)
}