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authorAndrew Gallant (Ocelot) <Andrew.Gallant@tufts.edu>2012-05-06 02:21:31 -0400
committerAndrew Gallant (Ocelot) <Andrew.Gallant@tufts.edu>2012-05-06 02:21:31 -0400
commit18b2d420b092d71313f0c05210c3038ff32483e7 (patch)
treee934f6bddd11863e82d591fb2a168d60be382f9d /nexgb/xgbgen/expression.go
parent99bc76de54729df5494faa944d4da96a8885d51e (diff)
downloadhaven-18b2d420b092d71313f0c05210c3038ff32483e7.tar.gz
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added documentation and did some slight restructuring. it's party time.
Diffstat (limited to 'nexgb/xgbgen/expression.go')
-rw-r--r--nexgb/xgbgen/expression.go41
1 files changed, 41 insertions, 0 deletions
diff --git a/nexgb/xgbgen/expression.go b/nexgb/xgbgen/expression.go
index 2350979..721ebfd 100644
--- a/nexgb/xgbgen/expression.go
+++ b/nexgb/xgbgen/expression.go
@@ -5,11 +5,32 @@ import (
"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() uint
+
+ // 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)
}
@@ -41,12 +62,17 @@ 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:
@@ -124,6 +150,8 @@ func (e *BinaryOp) Initialize(p *Protocol) {
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
@@ -158,6 +186,8 @@ 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
}
@@ -185,6 +215,8 @@ 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
}
@@ -212,6 +244,7 @@ func (e *PopCount) Initialize(p *Protocol) {
e.Expr.Initialize(p)
}
+// Value represents some constant integer.
type Value struct {
v uint
}
@@ -234,6 +267,7 @@ func (e *Value) String() string {
func (e *Value) Initialize(p *Protocol) {}
+// Bit represents some bit whose value is computed by '1 << bit'.
type Bit struct {
b uint
}
@@ -256,6 +290,8 @@ func (e *Bit) String() string {
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
}
@@ -285,6 +321,9 @@ 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
@@ -312,6 +351,8 @@ func (e *EnumRef) Initialize(p *Protocol) {
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
}