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https://github.com/tinygo-org/tinygo.git
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cgo: add support for bitfields using generated getters and setters
This commit is contained in:
Ayke van Laethem
committed by
Ron Evans
Ron Evans
parent
23c8d15847
commit
1d7cc2c242
+302
-1
@@ -68,8 +68,20 @@ type typedefInfo struct {
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// elaboratedTypeInfo contains some information about an elaborated type
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// (struct, union) found in the C AST.
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type elaboratedTypeInfo struct {
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typeExpr ast.Expr
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typeExpr ast.Expr
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pos token.Pos
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bitfields []bitfieldInfo
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}
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// bitfieldInfo contains information about a single bitfield in a struct. It
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// keeps information about the start, end, and the special (renamed) base field
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// of this bitfield.
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type bitfieldInfo struct {
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field *ast.Field
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name string
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pos token.Pos
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startBit int64
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endBit int64 // may be 0 meaning "until the end of the field"
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}
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// enumInfo contains information about an enum in the C.
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@@ -581,10 +593,299 @@ func (p *cgoPackage) addElaboratedTypes() {
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}
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obj.Decl = typeSpec
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gen.Specs = append(gen.Specs, typeSpec)
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// If this struct has bitfields, create getters for them.
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for _, bitfield := range typ.bitfields {
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p.createBitfieldGetter(bitfield, typeName)
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p.createBitfieldSetter(bitfield, typeName)
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}
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}
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p.generated.Decls = append(p.generated.Decls, gen)
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}
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// createBitfieldGetter creates a bitfield getter function like the following:
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//
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// func (s *C.struct_foo) bitfield_b() byte {
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// return (s.__bitfield_1 >> 5) & 0x1
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// }
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func (p *cgoPackage) createBitfieldGetter(bitfield bitfieldInfo, typeName string) {
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// The value to return from the getter.
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// Not complete: this is just an expression to get the complete field.
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var result ast.Expr = &ast.SelectorExpr{
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X: &ast.Ident{
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NamePos: bitfield.pos,
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Name: "s",
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Obj: nil,
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},
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Sel: &ast.Ident{
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NamePos: bitfield.pos,
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Name: bitfield.field.Names[0].Name,
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},
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}
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if bitfield.startBit != 0 {
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// Shift to the right by .startBit so that fields that come before are
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// shifted off.
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result = &ast.BinaryExpr{
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X: result,
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OpPos: bitfield.pos,
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Op: token.SHR,
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Y: &ast.BasicLit{
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ValuePos: bitfield.pos,
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Kind: token.INT,
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Value: strconv.FormatInt(bitfield.startBit, 10),
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},
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}
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}
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if bitfield.endBit != 0 {
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// Mask off the high bits so that fields that come after this field are
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// masked off.
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and := (uint64(1) << uint64(bitfield.endBit-bitfield.startBit)) - 1
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result = &ast.BinaryExpr{
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X: result,
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OpPos: bitfield.pos,
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Op: token.AND,
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Y: &ast.BasicLit{
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ValuePos: bitfield.pos,
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Kind: token.INT,
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Value: "0x" + strconv.FormatUint(and, 16),
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},
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}
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}
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// Create the getter function.
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getter := &ast.FuncDecl{
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Recv: &ast.FieldList{
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Opening: bitfield.pos,
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List: []*ast.Field{
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&ast.Field{
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Names: []*ast.Ident{
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&ast.Ident{
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NamePos: bitfield.pos,
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Name: "s",
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Obj: &ast.Object{
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Kind: ast.Var,
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Name: "s",
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Decl: nil,
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},
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},
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},
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Type: &ast.StarExpr{
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Star: bitfield.pos,
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X: &ast.Ident{
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NamePos: bitfield.pos,
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Name: typeName,
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Obj: nil,
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},
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},
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},
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},
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Closing: bitfield.pos,
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},
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Name: &ast.Ident{
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NamePos: bitfield.pos,
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Name: "bitfield_" + bitfield.name,
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},
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Type: &ast.FuncType{
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Func: bitfield.pos,
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Params: &ast.FieldList{
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Opening: bitfield.pos,
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Closing: bitfield.pos,
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},
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Results: &ast.FieldList{
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List: []*ast.Field{
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&ast.Field{
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Type: bitfield.field.Type,
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},
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},
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},
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},
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Body: &ast.BlockStmt{
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Lbrace: bitfield.pos,
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List: []ast.Stmt{
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&ast.ReturnStmt{
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Return: bitfield.pos,
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Results: []ast.Expr{
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result,
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},
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},
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},
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Rbrace: bitfield.pos,
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},
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}
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p.generated.Decls = append(p.generated.Decls, getter)
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}
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// createBitfieldSetter creates a bitfield setter function like the following:
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//
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// func (s *C.struct_foo) set_bitfield_b(value byte) {
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// s.__bitfield_1 = s.__bitfield_1 ^ 0x60 | ((value & 1) << 5)
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// }
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//
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// Or the following:
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//
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// func (s *C.struct_foo) set_bitfield_c(value byte) {
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// s.__bitfield_1 = s.__bitfield_1 & 0x3f | (value << 6)
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// }
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func (p *cgoPackage) createBitfieldSetter(bitfield bitfieldInfo, typeName string) {
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// The full field with all bitfields.
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var field ast.Expr = &ast.SelectorExpr{
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X: &ast.Ident{
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NamePos: bitfield.pos,
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Name: "s",
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Obj: nil,
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},
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Sel: &ast.Ident{
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NamePos: bitfield.pos,
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Name: bitfield.field.Names[0].Name,
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},
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}
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// The value to insert into the field.
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var valueToInsert ast.Expr = &ast.Ident{
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NamePos: bitfield.pos,
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Name: "value",
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}
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if bitfield.endBit != 0 {
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// Make sure the value is in range with a mask.
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valueToInsert = &ast.BinaryExpr{
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X: valueToInsert,
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OpPos: bitfield.pos,
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Op: token.AND,
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Y: &ast.BasicLit{
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ValuePos: bitfield.pos,
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Kind: token.INT,
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Value: "0x" + strconv.FormatUint((uint64(1)<<uint64(bitfield.endBit-bitfield.startBit))-1, 16),
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},
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}
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// Create a mask for the AND NOT operation.
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mask := ((uint64(1) << uint64(bitfield.endBit-bitfield.startBit)) - 1) << uint64(bitfield.startBit)
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// Zero the bits in the field that will soon be inserted.
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field = &ast.BinaryExpr{
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X: field,
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OpPos: bitfield.pos,
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Op: token.AND_NOT,
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Y: &ast.BasicLit{
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ValuePos: bitfield.pos,
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Kind: token.INT,
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Value: "0x" + strconv.FormatUint(mask, 16),
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},
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}
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} else { // bitfield.endBit == 0
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// We don't know exactly how many high bits should be zeroed. So we do
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// something different: keep the low bits with a mask and OR the new
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// value with it.
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mask := (uint64(1) << uint64(bitfield.startBit)) - 1
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// Extract the lower bits.
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field = &ast.BinaryExpr{
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X: field,
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OpPos: bitfield.pos,
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Op: token.AND,
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Y: &ast.BasicLit{
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ValuePos: bitfield.pos,
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Kind: token.INT,
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Value: "0x" + strconv.FormatUint(mask, 16),
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},
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}
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}
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// Bitwise OR with the new value (after the new value has been shifted).
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field = &ast.BinaryExpr{
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X: field,
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OpPos: bitfield.pos,
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Op: token.OR,
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Y: &ast.BinaryExpr{
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X: valueToInsert,
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OpPos: bitfield.pos,
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Op: token.SHL,
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Y: &ast.BasicLit{
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ValuePos: bitfield.pos,
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Kind: token.INT,
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Value: strconv.FormatInt(bitfield.startBit, 10),
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},
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},
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}
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// Create the setter function.
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setter := &ast.FuncDecl{
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Recv: &ast.FieldList{
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Opening: bitfield.pos,
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List: []*ast.Field{
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&ast.Field{
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Names: []*ast.Ident{
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&ast.Ident{
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NamePos: bitfield.pos,
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Name: "s",
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Obj: &ast.Object{
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Kind: ast.Var,
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Name: "s",
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Decl: nil,
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},
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},
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},
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Type: &ast.StarExpr{
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Star: bitfield.pos,
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X: &ast.Ident{
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NamePos: bitfield.pos,
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Name: typeName,
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Obj: nil,
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},
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},
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},
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},
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Closing: bitfield.pos,
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},
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Name: &ast.Ident{
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NamePos: bitfield.pos,
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Name: "set_bitfield_" + bitfield.name,
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},
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Type: &ast.FuncType{
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Func: bitfield.pos,
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Params: &ast.FieldList{
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Opening: bitfield.pos,
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List: []*ast.Field{
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&ast.Field{
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Names: []*ast.Ident{
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&ast.Ident{
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NamePos: bitfield.pos,
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Name: "value",
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Obj: nil,
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},
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},
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Type: bitfield.field.Type,
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},
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},
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Closing: bitfield.pos,
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},
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},
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Body: &ast.BlockStmt{
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Lbrace: bitfield.pos,
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List: []ast.Stmt{
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&ast.AssignStmt{
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Lhs: []ast.Expr{
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&ast.SelectorExpr{
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X: &ast.Ident{
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NamePos: bitfield.pos,
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Name: "s",
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Obj: nil,
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},
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Sel: &ast.Ident{
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NamePos: bitfield.pos,
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Name: bitfield.field.Names[0].Name,
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},
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},
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},
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TokPos: bitfield.pos,
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Tok: token.ASSIGN,
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Rhs: []ast.Expr{
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field,
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},
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},
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},
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Rbrace: bitfield.pos,
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},
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}
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p.generated.Decls = append(p.generated.Decls, setter)
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}
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// addEnumTypes adds C enums to the AST. For example, the following C code:
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//
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// enum option {
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