gobs part 1: types.

not ready to be part of the standard build yet; this is just a checkpoint.

R=rsc
DELTA=361  (361 added, 0 deleted, 0 changed)
OCL=30782
CL=30785

src/pkg/gob/type.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 gob
+
+import (
+	"fmt";
+	"os";
+	"reflect";
+	"sync";
+)
+
+var id	uint32	// incremented for each new type we build
+var typeLock	sync.Mutex	// set while building a type
+
+type Type interface {
+	id()	uint32;
+	setId(id uint32);
+	String()	string;
+	safeString(seen map[uint32] bool)	string;
+}
+var types = make(map[reflect.Type] Type)
+
+// Common elements of all types.
+type commonType struct {
+	name	string;
+	_id	uint32;
+}
+
+func (t *commonType) id() uint32 {
+	return t._id
+}
+
+func (t *commonType) setId(id uint32) {
+	t._id = id
+}
+
+func (t *commonType) String() string {
+	return t.name
+}
+
+func (t *commonType) safeString(seen map[uint32] bool) string {
+	return t.name
+}
+
+func (t *commonType) Name() string {
+	return t.name
+}
+
+// Basic type identifiers, predefined.
+var tBool Type
+var tInt Type
+var tUint Type
+var tFloat32 Type
+var tFloat64 Type
+var tString Type
+
+// Array type
+type arrayType struct {
+	commonType;
+	Elem	Type;
+	Len	int;
+}
+
+func newArrayType(name string, elem Type, length int) *arrayType {
+	a := &arrayType{ commonType{ name: name }, elem, length };
+	return a;
+}
+
+func (a *arrayType) safeString(seen map[uint32] bool) string {
+	if _, ok := seen[a._id]; ok {
+		return a.name
+	}
+	seen[a._id] = true;
+	return fmt.Sprintf("[%d]%s", a.Len, a.Elem.safeString(seen));
+}
+
+func (a *arrayType) String() string {
+	return a.safeString(make(map[uint32] bool))
+}
+
+// Slice type
+type sliceType struct {
+	commonType;
+	Elem	Type;
+}
+
+func newSliceType(name string, elem Type) *sliceType {
+	s := &sliceType{ commonType{ name: name }, elem };
+	return s;
+}
+
+func (s *sliceType) safeString(seen map[uint32] bool) string {
+	if _, ok := seen[s._id]; ok {
+		return s.name
+	}
+	seen[s._id] = true;
+	return fmt.Sprintf("[]%s", s.Elem.safeString(seen));
+}
+
+func (s *sliceType) String() string {
+	return s.safeString(make(map[uint32] bool))
+}
+
+// Struct type
+type fieldType struct {
+	name	string;
+	typ	Type;
+}
+
+type structType struct {
+	commonType;
+	field	[]*fieldType;
+}
+
+func (s *structType) safeString(seen map[uint32] bool) string {
+	if _, ok := seen[s._id]; ok {
+		return s.name
+	}
+	seen[s._id] = true;
+	str := "struct { ";
+	for _, f := range s.field {
+		str += fmt.Sprintf("%s %s; ", f.name, f.typ.safeString(seen));
+	}
+	str += "}";
+	return str;
+}
+
+func (s *structType) String() string {
+	return s.safeString(make(map[uint32] bool))
+}
+
+func newStructType(name string) *structType {
+	s := &structType{ commonType{ name: name }, nil };
+	return s;
+}
+
+// Construction
+func newType(name string, rt reflect.Type) Type
+
+func newTypeObject(name string, rt reflect.Type) Type {
+	switch rt.Kind() {
+	// All basic types are easy: they are predefined.
+	case reflect.BoolKind:
+		return tBool
+	case reflect.IntKind, reflect.Int32Kind, reflect.Int64Kind:
+		return tInt
+	case reflect.UintKind, reflect.Uint32Kind, reflect.Uint64Kind:
+		return tUint
+	case reflect.FloatKind, reflect.Float32Kind:
+		return tFloat32
+	case reflect.Float64Kind:
+		return tFloat64
+	case reflect.StringKind:
+		return tString
+	case reflect.ArrayKind:
+		// TODO(r): worth a special case for array of bytes?
+		at := rt.(reflect.ArrayType);
+		if at.IsSlice() {
+			return newSliceType(name, newType("", at.Elem()));
+		} else {
+			return newArrayType(name, newType("", at.Elem()), at.Len());
+		}
+	case reflect.StructKind:
+		// Install the struct type itself before the fields so recursive
+		// structures can be constructed safely.
+		strType := newStructType(name);
+		types[rt] = strType;
+		st := rt.(reflect.StructType);
+		field := make([]*fieldType, st.Len());
+		for i := 0; i < st.Len(); i++ {
+			name, typ, tag, offset := st.Field(i);
+			field[i] =  &fieldType{ name, newType("", typ) };
+		}
+		strType.field = field;
+		return strType;
+	default:
+		panicln("gob NewTypeObject can't handle type", rt.String());	// TODO(r): panic?
+	}
+	return nil
+}
+
+func newType(name string, rt reflect.Type) Type {
+	// Flatten the data structure by collapsing out pointers
+	for rt.Kind() == reflect.PtrKind {
+		rt = rt.(reflect.PtrType).Sub();
+	}
+	typ, present := types[rt];
+	if present {
+		return typ
+	}
+	typ = newTypeObject(name, rt);
+	id++;
+	typ.setId(id);
+	types[rt] = typ;
+	return typ
+}
+
+// GetType returns the Gob type describing the interface value.
+func GetType(name string, e interface{}) Type {
+	rt := reflect.Typeof(e);
+	// Set lock; all code running under here is synchronized.
+	typeLock.Lock();
+	t := newType(name, rt);
+	typeLock.Unlock();
+	return t;
+}
+
+// used for building the basic types; called only from init()
+func bootstrapType(name string, e interface{}) Type {
+	rt := reflect.Typeof(e);
+	_, present := types[rt];
+	if present {
+		panicln("bootstrap type already present:", name);
+	}
+	typ := &commonType{ name: name };
+	id++;
+	typ.setId(id);
+	types[rt] = typ;
+	return typ
+}
+
+func init() {
+	tBool= bootstrapType("bool", false);
+	tInt = bootstrapType("int", int(0));
+	tUint = bootstrapType("uint", uint(0));
+	tFloat32 = bootstrapType("float32", float32(0));
+	tFloat64 = bootstrapType("float64", float64(0));
+	tString= bootstrapType("string", "");
+}

src/pkg/gob/type_test.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 gob
+
+import (
+"fmt";
+	"gob";
+	"os";
+	"testing";
+)
+
+func checkType(ti Type, expected string, t *testing.T) {
+	if ti.String() != expected {
+		t.Errorf("checkType: expected %q got %s", expected, ti.String())
+	}
+	if ti.id() == 0 {
+		t.Errorf("id for %q is zero", expected)
+	}
+}
+
+type typeT struct {
+	typ	Type;
+	str	string;
+}
+var basicTypes = []typeT {
+	typeT { tBool, "bool" },
+	typeT { tInt, "int" },
+	typeT { tUint, "uint" },
+	typeT { tFloat32, "float32" },
+	typeT { tFloat64, "float64" },
+	typeT { tString, "string" },
+}
+
+// Sanity checks
+func TestBasic(t *testing.T) {
+	for _, tt := range basicTypes {
+		if tt.typ.String() != tt.str {
+			t.Errorf("checkType: expected %q got %s", tt.str, tt.typ.String())
+		}
+		if tt.typ.id() == 0 {
+			t.Errorf("id for %q is zero", tt.str)
+		}
+	}
+}
+
+// Reregister some basic types to check registration is idempotent.
+func TestReregistration(t *testing.T) {
+	newtyp := GetType("int", 0);
+	if newtyp != tInt {
+		t.Errorf("reregistration of %s got new type", newtyp.String())
+	}
+	newtyp = GetType("uint", uint(0));
+	if newtyp != tUint {
+		t.Errorf("reregistration of %s got new type", newtyp.String())
+	}
+	newtyp = GetType("string", "hello");
+	if newtyp != tString {
+		t.Errorf("reregistration of %s got new type", newtyp.String())
+	}
+}
+
+func TestArrayType(t *testing.T) {
+	var a3 [3]int;
+	a3int := GetType("foo", a3);
+	var newa3 [3]int;
+	newa3int := GetType("bar", a3);
+	if a3int != newa3int {
+		t.Errorf("second registration of [3]int creates new type");
+	}
+	var a4 [4]int;
+	a4int := GetType("goo", a4);
+	if a3int == a4int {
+		t.Errorf("registration of [3]int creates same type as [4]int");
+	}
+	var b3 [3]bool;
+	a3bool := GetType("", b3);
+	if a3int == a3bool {
+		t.Errorf("registration of [3]bool creates same type as [3]int");
+	}
+	str := a3bool.String();
+	expected := "[3]bool";
+	if str != expected {
+		t.Errorf("array printed as %q; expected %q", str, expected);
+	}
+}
+
+func TestSliceType(t *testing.T) {
+	var s []int;
+	sint := GetType("slice", s);
+	var news []int;
+	newsint := GetType("slice1", news);
+	if sint != newsint {
+		t.Errorf("second registration of []int creates new type");
+	}
+	var b []bool;
+	sbool := GetType("", b);
+	if sbool == sint {
+		t.Errorf("registration of []bool creates same type as []int");
+	}
+	str := sbool.String();
+	expected := "[]bool";
+	if str != expected {
+		t.Errorf("slice printed as %q; expected %q", str, expected);
+	}
+}
+
+type Bar struct {
+	x string
+}
+
+// This structure has pointers and refers to itself, making it a good test case.
+type Foo struct {
+	a int;
+	b int32;	// will become int
+	c string;
+	d *float;	// will become float32
+	e ****float64;	// will become float64
+	f *Bar;
+	g *Foo;	// will not explode
+}
+
+func TestStructType(t *testing.T) {
+	sstruct := GetType("Foo", Foo{});
+	str := sstruct.String();
+	// If we can print it correctly, we built it correctly.
+	expected := "struct { a int; b int; c string; d float32; e float64; f struct { x string; }; g Foo; }";
+	if str != expected {
+		t.Errorf("struct printed as %q; expected %q", str, expected);
+	}
+}