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keyvalue.go
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keyvalue.go
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// Copyright (c) 2017 Uber Technologies, Inc.
//
// 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 model
import (
"encoding/binary"
"encoding/hex"
"fmt"
"io"
"math"
"sort"
"strconv"
)
// ValueType describes the type of value contained in a KeyValue struct
type ValueType int
const (
// StringType indicates the value is a unicode string
StringType ValueType = iota
// BoolType indicates the value is a Boolean encoded as int64 number 0 or 1
BoolType
// Int64Type indicates the value is an int64 number
Int64Type
// Float64Type indicates the value is a float64 number stored as int64
Float64Type
// BinaryType indicates the value is binary blob stored as a byte array
BinaryType
stringTypeStr = "string"
boolTypeStr = "bool"
int64TypeStr = "int64"
float64TypeStr = "float64"
binaryTypeStr = "binary"
)
// KeyValue describes a tag or a log field that consists of a key and a typed value.
// Before accessing a value, the caller must check the type. Boolean and numeric
// values should be accessed via accessor methods Bool(), Int64(), and Float64().
//
// This struct is designed to minimize heap allocations.
type KeyValue struct {
Key string `json:"key"`
VType ValueType `json:"vType"`
VStr string `json:"vStr,omitempty"`
VNum int64 `json:"vNum,omitempty"`
VBlob []byte `json:"vBlob,omitempty"`
}
// KeyValues is a type alias that exposes convenience functions like Sort, FindByKey.
type KeyValues []KeyValue
// String creates a String-typed KeyValue
func String(key string, value string) KeyValue {
return KeyValue{Key: key, VType: StringType, VStr: value}
}
// Bool creates a Bool-typed KeyValue
func Bool(key string, value bool) KeyValue {
var val int64
if value {
val = 1
}
return KeyValue{Key: key, VType: BoolType, VNum: val}
}
// Int64 creates a Int64-typed KeyValue
func Int64(key string, value int64) KeyValue {
return KeyValue{Key: key, VType: Int64Type, VNum: value}
}
// Float64 creates a Float64-typed KeyValue
func Float64(key string, value float64) KeyValue {
return KeyValue{Key: key, VType: Float64Type, VNum: int64(math.Float64bits(value))}
}
// Binary creates a Binary-typed KeyValue
func Binary(key string, value []byte) KeyValue {
return KeyValue{Key: key, VType: BinaryType, VBlob: value}
}
// Bool returns the Boolean value stored in this KeyValue or false if it stores a different type.
// The caller must check VType before using this method.
func (kv *KeyValue) Bool() bool {
if kv.VType == BoolType {
return kv.VNum == 1
}
return false
}
// Int64 returns the Int64 value stored in this KeyValue or 0 if it stores a different type.
// The caller must check VType before using this method.
func (kv *KeyValue) Int64() int64 {
if kv.VType == Int64Type {
return kv.VNum
}
return 0
}
// Float64 returns the Float64 value stored in this KeyValue or 0 if it stores a different type.
// The caller must check VType before using this method.
func (kv *KeyValue) Float64() float64 {
if kv.VType == Float64Type {
return math.Float64frombits(uint64(kv.VNum))
}
return 0
}
// Binary returns the blob ([]byte) value stored in this KeyValue or nil if it stores a different type.
// The caller must check VType before using this method.
func (kv *KeyValue) Binary() []byte {
if kv.VType == BinaryType {
return kv.VBlob
}
return nil
}
// Value returns typed values stored in KeyValue as interface{}.
func (kv *KeyValue) Value() interface{} {
switch kv.VType {
case StringType:
return kv.VStr
case BoolType:
return kv.Bool()
case Int64Type:
return kv.Int64()
case Float64Type:
return kv.Float64()
case BinaryType:
return kv.VBlob
default:
return fmt.Errorf("unknown type %d", kv.VType)
}
}
// AsString returns a potentially lossy string representation of the value.
func (kv *KeyValue) AsString() string {
switch kv.VType {
case StringType:
return kv.VStr
case BoolType:
if kv.Bool() {
return "true"
}
return "false"
case Int64Type:
return strconv.FormatInt(kv.Int64(), 10)
case Float64Type:
return strconv.FormatFloat(kv.Float64(), 'g', 10, 64)
case BinaryType:
if len(kv.VBlob) > 256 {
return hex.EncodeToString(kv.VBlob[0:256]) + "..."
}
return hex.EncodeToString(kv.VBlob)
default:
return fmt.Sprintf("unknown type %d", kv.VType)
}
}
// Equal compares KeyValue object with another KeyValue.
func (kv *KeyValue) Equal(other *KeyValue) bool {
if kv.Key != other.Key {
return false
}
if kv.VType != other.VType {
return false
}
switch kv.VType {
case StringType:
return kv.VStr == other.VStr
case BoolType, Int64Type:
return kv.VNum == other.VNum
case Float64Type:
return kv.Float64() == other.Float64()
case BinaryType:
l1, l2 := len(kv.VBlob), len(other.VBlob)
if l1 != l2 {
return false
}
for i := 0; i < l1; i++ {
if kv.VBlob[i] != other.VBlob[i] {
return false
}
}
return true
default:
return false
}
}
// IsLess compares KeyValue object with another KeyValue.
// The order is based first on the keys, then on type, and finally on the value.
func (kv *KeyValue) IsLess(two *KeyValue) bool {
if kv.Key != two.Key {
return kv.Key < two.Key
}
if kv.VType != two.VType {
return kv.VType < two.VType
}
switch kv.VType {
case StringType:
return kv.VStr < two.VStr
case BoolType, Int64Type:
return kv.VNum < two.VNum
case Float64Type:
return kv.Float64() < two.Float64()
case BinaryType:
l1, l2 := len(kv.VBlob), len(two.VBlob)
minLen := l1
if l2 < minLen {
minLen = l2
}
for i := 0; i < minLen; i++ {
if d := int(kv.VBlob[i]) - int(two.VBlob[i]); d != 0 {
return d < 0
}
}
if l1 == l2 {
return false
}
return l1 < l2
default:
return false
}
}
func (kvs KeyValues) Len() int { return len(kvs) }
func (kvs KeyValues) Swap(i, j int) { kvs[i], kvs[j] = kvs[j], kvs[i] }
func (kvs KeyValues) Less(i, j int) bool {
return kvs[i].IsLess(&kvs[j])
}
// Sort does in-place sorting of KeyValues, then by value type, then by value.
func (kvs KeyValues) Sort() {
sort.Sort(kvs)
}
// FindByKey scans the list of key-values searching for the first one with the given key.
// Returns found tag and a boolean flag indicating if the search was successful.
func (kvs KeyValues) FindByKey(key string) (KeyValue, bool) {
for _, kv := range kvs {
if kv.Key == key {
return kv, true
}
}
return KeyValue{}, false
}
// Equal compares KyValues with another list. Both lists must be already sorted.
func (kvs KeyValues) Equal(other KeyValues) bool {
l1, l2 := len(kvs), len(other)
if l1 != l2 {
return false
}
for i := 0; i < l1; i++ {
if !kvs[i].Equal(&other[i]) {
return false
}
}
return true
}
// Hash implements Hash from Hashable.
func (kvs KeyValues) Hash(w io.Writer) error {
for i := range kvs {
if err := kvs[i].Hash(w); err != nil {
return err
}
}
return nil
}
func (p ValueType) String() string {
switch p {
case StringType:
return stringTypeStr
case BoolType:
return boolTypeStr
case Int64Type:
return int64TypeStr
case Float64Type:
return float64TypeStr
case BinaryType:
return binaryTypeStr
}
return "<invalid>"
}
// ValueTypeFromString converts a string into ValueType enum.
func ValueTypeFromString(s string) (ValueType, error) {
switch s {
case stringTypeStr:
return StringType, nil
case boolTypeStr:
return BoolType, nil
case int64TypeStr:
return Int64Type, nil
case float64TypeStr:
return Float64Type, nil
case binaryTypeStr:
return BinaryType, nil
}
return ValueType(0), fmt.Errorf("not a valid ValueType string %s", s)
}
// MarshalText allows ValueType to serialize itself in JSON as a string.
func (p ValueType) MarshalText() ([]byte, error) {
return []byte(p.String()), nil
}
// UnmarshalText allows ValueType to deserialize itself from a JSON string.
func (p *ValueType) UnmarshalText(text []byte) error {
q, err := ValueTypeFromString(string(text))
if err != nil {
return err
}
*p = q
return nil
}
// Hash implements Hash from Hashable.
func (kv KeyValue) Hash(w io.Writer) error {
if _, err := w.Write([]byte(kv.Key)); err != nil {
return err
}
if err := binary.Write(w, binary.BigEndian, uint16(kv.VType)); err != nil {
return err
}
var err error
switch kv.VType {
case StringType:
_, err = w.Write([]byte(kv.VStr))
case BoolType, Int64Type, Float64Type:
err = binary.Write(w, binary.BigEndian, kv.VNum)
case BinaryType:
_, err = w.Write(kv.VBlob)
default:
err = fmt.Errorf("unknown type %d", kv.VType)
}
return err
}