wheat-cache/pkg/structure/value.go

package structure

import (
	"bytes"
	"encoding/binary"
	"gitee.com/timedb/wheatCache/pkg/errorx"
	"math"
	"strconv"
)

// Value 提供一个基础的 动态类型

type Value struct {
	val    []byte
	length int
	onType DynamicType
}

func NewValue() *Value {
	return &Value{
		val:    make([]byte, defaultLen),
		length: 0,
		onType: DynamicNull,
	}
}

func (v *Value) GetLength() int {
	return len(v.val)
}

func (v *Value) GetDynamicType() DynamicType {
	return v.onType
}

func (v *Value) SetString(str string) {
	v.onType = DynamicString
	if len(v.val) >= len(str) {
		copy(v.val, str)
		v.length = len(str)
		return
	}

	// 超过 cap
	if len(str) > cap(v.val) {
		v.val = make([]byte, len(str))
		copy(v.val, str)
		v.length = len(str)
		return
	}

	// 在 cap 以内
	copy(v.val, str[:v.length])
	v.val = append(v.val, str[v.length:]...)
}

func (v *Value) ToString() string {
	return string(v.val[:v.length])
}

// SetInt 使用高位存储
func (v *Value) SetInt(i int64) {
	byteBuf := bytes.NewBuffer([]byte{})
	binary.Write(byteBuf, binary.BigEndian, i)
	v.val = byteBuf.Bytes()
	v.length = len(v.val)
	v.onType = DynamicInt
}

func (v *Value) ToInt() (reI int64, err error) {
	if v.onType != DynamicInt {
		return 0, errorx.New("can only be resolved from dynamic int")
	}

	byteBuff := bytes.NewBuffer(v.val)
	err = binary.Read(byteBuff, binary.BigEndian, &reI)
	if err != nil {
		return 0, err
	}

	return reI, nil
}

func (v *Value) SetFloat64(f float64) {
	bits := math.Float64bits(f)
	v.length = 8
	binary.LittleEndian.PutUint64(v.val[:v.length], bits)
	v.onType = DynamicFloat
}

func (v *Value) ToFloat64() (float64, error) {
	if v.onType != DynamicFloat {
		return 0, errorx.New("can only be resolved from dynamic float")
	}

	bits := binary.LittleEndian.Uint64(v.val[:v.length])
	return math.Float64frombits(bits), nil
}

// InferValue 通过字符串来自动推导类型，性能较低
func (v *Value) InferValue(str string) {
	rInt, err := strconv.Atoi(str)
	if err == nil {
		v.SetInt(int64(rInt))
		return
	}

	rf, err := strconv.ParseFloat(str, 64)
	if err == nil {
		v.SetFloat64(rf)
		return
	}

	v.SetString(str)
}

// ChangeValueLength 根据类型推断 change 的大小
func (v *Value) ChangeValueLength(f func()) int64 {
	startLen := v.GetLength()
	f()
	return int64(v.GetLength() - startLen)
}