Shrink core.Value (#256)

* shrink the value type

went down from 40 bytes to 24

* add missing license blurb

* stringify value type

* print string value types in stdout exporter

* make Value function take a pointer receiver

api/core/key.go

@@ -1,5 +1,21 @@
+// Copyright 2019, OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 package core
 
+//go:generate stringer -type=ValueType
+
 import (
 	"fmt"
 	"unsafe"
@@ -15,20 +31,10 @@ type KeyValue struct {
 type ValueType int
 
 type Value struct {
-	Type    ValueType
-	Bool    bool
-	Int64   int64
-	Uint64  uint64
-	Float64 float64
-	String  string
-
-	// Note: this type could be made smaller by using a
-	// core.Number to represent four of these fields, e.g.,
-	// struct {
-	//   Type   ValueType
-	//   String string
-	//   Number Number
-	// }
+	vtype    ValueType
+	numeric  uint64
+	stringly string
+	// TODO Lazy value type?
 }
 
 const (
@@ -43,116 +49,217 @@ const (
 	STRING
 )
 
+func Bool(v bool) Value {
+	return Value{
+		vtype:   BOOL,
+		numeric: boolToRaw(v),
+	}
+}
+
+func Int64(v int64) Value {
+	return Value{
+		vtype:   INT64,
+		numeric: int64ToRaw(v),
+	}
+}
+
+func Uint64(v uint64) Value {
+	return Value{
+		vtype:   UINT64,
+		numeric: uint64ToRaw(v),
+	}
+}
+
+func Float64(v float64) Value {
+	return Value{
+		vtype:   FLOAT64,
+		numeric: float64ToRaw(v),
+	}
+}
+
+func Int32(v int32) Value {
+	return Value{
+		vtype:   INT32,
+		numeric: int32ToRaw(v),
+	}
+}
+
+func Uint32(v uint32) Value {
+	return Value{
+		vtype:   UINT32,
+		numeric: uint32ToRaw(v),
+	}
+}
+
+func Float32(v float32) Value {
+	return Value{
+		vtype:   FLOAT32,
+		numeric: float32ToRaw(v),
+	}
+}
+
+func String(v string) Value {
+	return Value{
+		vtype:    STRING,
+		stringly: v,
+	}
+}
+
+func Int(v int) Value {
+	if unsafe.Sizeof(v) == 4 {
+		return Int32(int32(v))
+	}
+	return Int64(int64(v))
+}
+
+func Uint(v uint) Value {
+	if unsafe.Sizeof(v) == 4 {
+		return Uint32(uint32(v))
+	}
+	return Uint64(uint64(v))
+}
+
 func (k Key) Bool(v bool) KeyValue {
 	return KeyValue{
-		Key: k,
-		Value: Value{
-			Type: BOOL,
-			Bool: v,
-		},
+		Key:   k,
+		Value: Bool(v),
 	}
 }
 
 func (k Key) Int64(v int64) KeyValue {
 	return KeyValue{
-		Key: k,
-		Value: Value{
-			Type:  INT64,
-			Int64: v,
-		},
+		Key:   k,
+		Value: Int64(v),
 	}
 }
 
 func (k Key) Uint64(v uint64) KeyValue {
 	return KeyValue{
-		Key: k,
-		Value: Value{
-			Type:   UINT64,
-			Uint64: v,
-		},
+		Key:   k,
+		Value: Uint64(v),
 	}
 }
 
 func (k Key) Float64(v float64) KeyValue {
 	return KeyValue{
-		Key: k,
-		Value: Value{
-			Type:    FLOAT64,
-			Float64: v,
-		},
+		Key:   k,
+		Value: Float64(v),
 	}
 }
 
 func (k Key) Int32(v int32) KeyValue {
 	return KeyValue{
-		Key: k,
-		Value: Value{
-			Type:  INT32,
-			Int64: int64(v),
-		},
+		Key:   k,
+		Value: Int32(v),
 	}
 }
 
 func (k Key) Uint32(v uint32) KeyValue {
 	return KeyValue{
-		Key: k,
-		Value: Value{
-			Type:   UINT32,
-			Uint64: uint64(v),
-		},
+		Key:   k,
+		Value: Uint32(v),
 	}
 }
 
 func (k Key) Float32(v float32) KeyValue {
 	return KeyValue{
-		Key: k,
-		Value: Value{
-			Type:    FLOAT32,
-			Float64: float64(v),
-		},
+		Key:   k,
+		Value: Float32(v),
 	}
 }
 
 func (k Key) String(v string) KeyValue {
 	return KeyValue{
-		Key: k,
-		Value: Value{
-			Type:   STRING,
-			String: v,
-		},
+		Key:   k,
+		Value: String(v),
 	}
 }
 
 func (k Key) Int(v int) KeyValue {
-	if unsafe.Sizeof(v) == 4 {
-		return k.Int32(int32(v))
+	return KeyValue{
+		Key:   k,
+		Value: Int(v),
 	}
-	return k.Int64(int64(v))
 }
 
 func (k Key) Uint(v uint) KeyValue {
-	if unsafe.Sizeof(v) == 4 {
-		return k.Uint32(uint32(v))
+	return KeyValue{
+		Key:   k,
+		Value: Uint(v),
 	}
-	return k.Uint64(uint64(v))
 }
 
 func (k Key) Defined() bool {
 	return len(k) != 0
 }
 
-func (v Value) Emit() string {
-	switch v.Type {
-	case BOOL:
-		return fmt.Sprint(v.Bool)
-	case INT32, INT64:
-		return fmt.Sprint(v.Int64)
-	case UINT32, UINT64:
-		return fmt.Sprint(v.Uint64)
-	case FLOAT32, FLOAT64:
-		return fmt.Sprint(v.Float64)
-	case STRING:
-		return v.String
-	}
-	return "unknown"
+func (v *Value) Type() ValueType {
+	return v.vtype
+}
+
+func (v *Value) AsBool() bool {
+	return rawToBool(v.numeric)
+}
+
+func (v *Value) AsInt32() int32 {
+	return rawToInt32(v.numeric)
+}
+
+func (v *Value) AsInt64() int64 {
+	return rawToInt64(v.numeric)
+}
+
+func (v *Value) AsUint32() uint32 {
+	return rawToUint32(v.numeric)
+}
+
+func (v *Value) AsUint64() uint64 {
+	return rawToUint64(v.numeric)
+}
+
+func (v *Value) AsFloat32() float32 {
+	return rawToFloat32(v.numeric)
+}
+
+func (v *Value) AsFloat64() float64 {
+	return rawToFloat64(v.numeric)
+}
+
+func (v *Value) AsString() string {
+	return v.stringly
+}
+
+type unknownValueType struct{}
+
+func (v *Value) AsInterface() interface{} {
+	switch v.Type() {
+	case BOOL:
+		return v.AsBool()
+	case INT32:
+		return v.AsInt32()
+	case INT64:
+		return v.AsInt64()
+	case UINT32:
+		return v.AsUint32()
+	case UINT64:
+		return v.AsUint64()
+	case FLOAT32:
+		return v.AsFloat32()
+	case FLOAT64:
+		return v.AsFloat64()
+	case STRING:
+		return v.stringly
+	}
+	return unknownValueType{}
+}
+
+func (v *Value) Emit() string {
+	if v.Type() == STRING {
+		return v.stringly
+	}
+	i := v.AsInterface()
+	if _, ok := i.(unknownValueType); ok {
+		return "unknown"
+	}
+	return fmt.Sprint(i)
 }