Utilities to bridge native types and functions into

interpreter values.  Also, print nil values properly.

R=rsc
APPROVED=rsc
DELTA=173  (173 added, 0 deleted, 0 changed)
OCL=33837
CL=33973

usr/austin/eval/bridge.go

+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package eval
+
+import (
+	"log";
+	"go/token";
+	"reflect";
+)
+
+/*
+ * Type bridging
+ */
+
+var (
+	evalTypes   = make(map[reflect.Type] Type);
+	nativeTypes = make(map[Type] reflect.Type);
+)
+
+// TypeFromNative converts a regular Go type into a the corresponding
+// interpreter Type.
+func TypeFromNative(t reflect.Type) Type {
+	if et, ok := evalTypes[t]; ok {
+		return et;
+	}
+
+	var nt *NamedType;
+	if t.Name() != "" {
+		name := t.PkgPath() + "·" + t.Name();
+		nt = &NamedType{token.Position{}, name, nil, true, make(map[string] Method)};
+		evalTypes[t] = nt;
+	}
+
+	var et Type;
+	switch t := t.(type) {
+	case *reflect.BoolType:
+		et = BoolType;
+	case *reflect.Float32Type:
+		et = Float32Type;
+	case *reflect.Float64Type:
+		et = Float64Type;
+	case *reflect.FloatType:
+		et = FloatType;
+	case *reflect.Int16Type:
+		et = Int16Type;
+	case *reflect.Int32Type:
+		et = Int32Type;
+	case *reflect.Int64Type:
+		et = Int64Type;
+	case *reflect.Int8Type:
+		et = Int8Type;
+	case *reflect.IntType:
+		et = IntType;
+	case *reflect.StringType:
+		et = StringType;
+	case *reflect.Uint16Type:
+		et = Uint16Type;
+	case *reflect.Uint32Type:
+		et = Uint32Type;
+	case *reflect.Uint64Type:
+		et = Uint64Type;
+	case *reflect.Uint8Type:
+		et = Uint8Type;
+	case *reflect.UintType:
+		et = UintType;
+	case *reflect.UintptrType:
+		et = UintptrType;
+
+	case *reflect.ArrayType:
+		et = NewArrayType(int64(t.Len()), TypeFromNative(t.Elem()));
+	case *reflect.ChanType:
+		log.Crashf("%T not implemented", t);
+	case *reflect.FuncType:
+		nin := t.NumIn();
+		// Variadic functions have DotDotDotType at the end
+		varidic := false;
+		if nin > 0 {
+			if _, ok := t.In(nin - 1).(*reflect.DotDotDotType); ok {
+				varidic = true;
+				nin--;
+			}
+		}
+		in := make([]Type, nin);
+		for i := range in {
+			in[i] = TypeFromNative(t.In(i));
+		}
+		out := make([]Type, t.NumOut());
+		for i := range out {
+			out[i] = TypeFromNative(t.Out(i));
+		}
+		et = NewFuncType(in, varidic, out);
+	case *reflect.InterfaceType:
+		log.Crashf("%T not implemented", t);
+	case *reflect.MapType:
+		log.Crashf("%T not implemented", t);
+	case *reflect.PtrType:
+		et = NewPtrType(TypeFromNative(t.Elem()));
+	case *reflect.SliceType:
+		et = NewSliceType(TypeFromNative(t.Elem()));
+	case *reflect.StructType:
+		n := t.NumField();
+		fields := make([]StructField, n);
+		for i := 0; i < n; i++ {
+			sf := t.Field(i);
+			// TODO(austin) What to do about private fields?
+			fields[i].Name = sf.Name;
+			fields[i].Type = TypeFromNative(sf.Type);
+			fields[i].Anonymous = sf.Anonymous;
+		}
+		et = NewStructType(fields);
+	case *reflect.UnsafePointerType:
+		log.Crashf("%T not implemented", t);
+	default:
+		log.Crashf("unexpected reflect.Type: %T", t);
+	}
+
+	if nt != nil {
+		nt.def = et;
+		et = nt;
+	}
+
+	nativeTypes[et] = t;
+	evalTypes[t] = et;
+
+	return et;
+}
+
+// TypeOfNative returns the interpreter Type of a regular Go value.
+func TypeOfNative(v interface {}) Type {
+	return TypeFromNative(reflect.Typeof(v));
+}
+
+/*
+ * Function bridging
+ */
+
+type nativeFunc struct {
+	fn func([]Value, []Value);
+	in, out int;
+}
+
+func (f *nativeFunc) NewFrame() *Frame {
+	vars := make([]Value, f.in + f.out);
+	return &Frame{nil, vars};
+}
+
+func (f *nativeFunc) Call(fr *Frame) {
+	f.fn(fr.Vars[0:f.in], fr.Vars[f.in:f.in+f.out]);
+}
+
+// FuncFromNative creates an interpreter function from a native
+// function that takes its in and out arguments as slices of
+// interpreter Value's.  While somewhat inconvenient, this avoids
+// value marshalling.
+func FuncFromNative(fn func([]Value, []Value), t *FuncType) FuncValue {
+	return &funcV{&nativeFunc{fn, len(t.In), len(t.Out)}};
+}
+
+// FuncFromNativeTyped is like FuncFromNative, but constructs the
+// function type from a function pointer using reflection.  Typically,
+// the type will be given as a nil pointer to a function with the
+// desired signature.
+func FuncFromNativeTyped(fn func([]Value, []Value), t interface{}) (*FuncType, FuncValue) {
+	ft := TypeOfNative(t).(*FuncType);
+	return ft, FuncFromNative(fn, ft);
+}

usr/austin/eval/value.go

@@ -433,6 +433,9 @@ type ptrV struct {
 }
 
 func (v *ptrV) String() string {
+	if v.target == nil {
+		return "<nil>";
+	}
 	return "&" + v.target.String();
 }
 
@@ -482,6 +485,9 @@ type sliceV struct {
 }
 
 func (v *sliceV) String() string {
+	if v.Base == nil {
+		return "<nil>";
+	}
 	res := "{";
 	for i := int64(0); i < v.Len; i++ {
 		if i > 0 {
@@ -513,6 +519,9 @@ type mapV struct {
 }
 
 func (v *mapV) String() string {
+	if v.target == nil {
+		return "<nil>";
+	}
 	res := "map[";
 	i := 0;
 	v.target.Iter(func(key interface{}, val Value) bool {