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