diff options
Diffstat (limited to 'nexgb/xgbgen/expression.go')
| -rw-r--r-- | nexgb/xgbgen/expression.go | 41 |
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 } |