util/convert.go

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// Package util ...
//
// Description : 任意类型之间的相互转换
//
// Author : go_developer@163.com<白茶清欢>
//
// Date : 2021-02-23 10:23 下午
package util
/*
Desc : 在处理一些参数的时候可能需要将参数转换为各种类型这里实现一个通用的转换函数实现各种类型之间的相互转换
当然如果源数据格式和目标数据类型不一致是会返回错误的例如将字符串一二三转换为数值类型则会报错而将字符串123转换为数值类型则OK
这段代码实际抄自go自带的database/sql只是源代码作为内部函数无法在外面调用可以单独把需要的功能拎出来使用
代码中有一个Scaner接口可以自行实现然后通过"convertAssign()"函数作为dst参数传入
Author : zhangdeman001@ke.com<白茶清欢>
*/
import (
"errors"
"fmt"
"reflect"
"strconv"
"time"
)
// RawBytes is a byte slice that holds a reference to memory owned by
// the database itself. After a Scan into a RawBytes, the slice is only
// valid until the next call to Next, Scan, or Close.
type RawBytes []byte
var errNilPtr = errors.New("destination pointer is nil") // embedded in descriptive error
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// ConvertAssign ...
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// convertAssign copies to dest the value in src, converting it if possible.
// An error is returned if the copy would result in loss of information.
// dest should be a pointer type.
func ConvertAssign(dest, src interface{}) error {
// Common cases, without reflect.
switch s := src.(type) {
case string:
switch d := dest.(type) {
case *string:
if d == nil {
return errNilPtr
}
*d = s
return nil
case *[]byte:
if d == nil {
return errNilPtr
}
*d = []byte(s)
return nil
case *RawBytes:
if d == nil {
return errNilPtr
}
*d = append((*d)[:0], s...)
return nil
}
case []byte:
switch d := dest.(type) {
case *string:
if d == nil {
return errNilPtr
}
*d = string(s)
return nil
case *interface{}:
if d == nil {
return errNilPtr
}
*d = cloneBytes(s)
return nil
case *[]byte:
if d == nil {
return errNilPtr
}
*d = cloneBytes(s)
return nil
case *RawBytes:
if d == nil {
return errNilPtr
}
*d = s
return nil
}
case time.Time:
switch d := dest.(type) {
case *time.Time:
*d = s
return nil
case *string:
*d = s.Format(time.RFC3339Nano)
return nil
case *[]byte:
if d == nil {
return errNilPtr
}
*d = []byte(s.Format(time.RFC3339Nano))
return nil
case *RawBytes:
if d == nil {
return errNilPtr
}
*d = s.AppendFormat((*d)[:0], time.RFC3339Nano)
return nil
}
case nil:
switch d := dest.(type) {
case *interface{}:
if d == nil {
return errNilPtr
}
*d = nil
return nil
case *[]byte:
if d == nil {
return errNilPtr
}
*d = nil
return nil
case *RawBytes:
if d == nil {
return errNilPtr
}
*d = nil
return nil
}
}
var sv reflect.Value
switch d := dest.(type) {
case *string:
sv = reflect.ValueOf(src)
switch sv.Kind() {
case reflect.Bool,
reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
reflect.Float32, reflect.Float64:
*d = asString(src)
return nil
}
case *[]byte:
sv = reflect.ValueOf(src)
if b, ok := asBytes(nil, sv); ok {
*d = b
return nil
}
case *RawBytes:
sv = reflect.ValueOf(src)
if b, ok := asBytes([]byte(*d)[:0], sv); ok {
*d = RawBytes(b)
return nil
}
case *bool:
bv, err := Bool.ConvertValue(src)
if err == nil {
*d = bv.(bool)
}
return err
case *interface{}:
*d = src
return nil
}
if scanner, ok := dest.(Scanner); ok {
return scanner.Scan(src)
}
dpv := reflect.ValueOf(dest)
if dpv.Kind() != reflect.Ptr {
return errors.New("destination not a pointer")
}
if dpv.IsNil() {
return errNilPtr
}
if !sv.IsValid() {
sv = reflect.ValueOf(src)
}
dv := reflect.Indirect(dpv)
if sv.IsValid() && sv.Type().AssignableTo(dv.Type()) {
switch b := src.(type) {
case []byte:
dv.Set(reflect.ValueOf(cloneBytes(b)))
default:
dv.Set(sv)
}
return nil
}
if dv.Kind() == sv.Kind() && sv.Type().ConvertibleTo(dv.Type()) {
dv.Set(sv.Convert(dv.Type()))
return nil
}
// The following conversions use a string value as an intermediate representation
// to convert between various numeric types.
//
// This also allows scanning into user defined types such as "type Int int64".
// For symmetry, also check for string destination types.
switch dv.Kind() {
case reflect.Ptr:
if src == nil {
dv.Set(reflect.Zero(dv.Type()))
return nil
}
dv.Set(reflect.New(dv.Type().Elem()))
return ConvertAssign(dv.Interface(), src)
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
s := asString(src)
i64, err := strconv.ParseInt(s, 10, dv.Type().Bits())
if err != nil {
err = strconvErr(err)
return fmt.Errorf("converting driver.Value type %T (%q) to a %s: %v", src, s, dv.Kind(), err)
}
dv.SetInt(i64)
return nil
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
s := asString(src)
u64, err := strconv.ParseUint(s, 10, dv.Type().Bits())
if err != nil {
err = strconvErr(err)
return fmt.Errorf("converting driver.Value type %T (%q) to a %s: %v", src, s, dv.Kind(), err)
}
dv.SetUint(u64)
return nil
case reflect.Float32, reflect.Float64:
s := asString(src)
f64, err := strconv.ParseFloat(s, dv.Type().Bits())
if err != nil {
err = strconvErr(err)
return fmt.Errorf("converting driver.Value type %T (%q) to a %s: %v", src, s, dv.Kind(), err)
}
dv.SetFloat(f64)
return nil
case reflect.String:
switch v := src.(type) {
case string:
dv.SetString(v)
return nil
case []byte:
dv.SetString(string(v))
return nil
}
}
return fmt.Errorf("unsupported Scan, storing driver.Value type %T into type %T", src, dest)
}
func strconvErr(err error) error {
if ne, ok := err.(*strconv.NumError); ok {
return ne.Err
}
return err
}
func cloneBytes(b []byte) []byte {
if b == nil {
return nil
}
c := make([]byte, len(b))
copy(c, b)
return c
}
func ToString(src interface{}) string {
return asString(src)
}
func asString(src interface{}) string {
switch v := src.(type) {
case string:
return v
case []byte:
return string(v)
}
rv := reflect.ValueOf(src)
switch rv.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
return strconv.FormatInt(rv.Int(), 10)
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
return strconv.FormatUint(rv.Uint(), 10)
case reflect.Float64:
return strconv.FormatFloat(rv.Float(), 'g', -1, 64)
case reflect.Float32:
return strconv.FormatFloat(rv.Float(), 'g', -1, 32)
case reflect.Bool:
return strconv.FormatBool(rv.Bool())
}
return fmt.Sprintf("%v", src)
}
func asBytes(buf []byte, rv reflect.Value) (b []byte, ok bool) {
switch rv.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
return strconv.AppendInt(buf, rv.Int(), 10), true
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
return strconv.AppendUint(buf, rv.Uint(), 10), true
case reflect.Float32:
return strconv.AppendFloat(buf, rv.Float(), 'g', -1, 32), true
case reflect.Float64:
return strconv.AppendFloat(buf, rv.Float(), 'g', -1, 64), true
case reflect.Bool:
return strconv.AppendBool(buf, rv.Bool()), true
case reflect.String:
s := rv.String()
return append(buf, s...), true
}
return
}
// Value is a value that drivers must be able to handle.
// It is either nil, a type handled by a database driver's NamedValueChecker
// interface, or an instance of one of these types:
//
// int64
// float64
// bool
// []byte
// string
// time.Time
type Value interface{}
type boolType struct{}
var Bool boolType
func (boolType) String() string { return "Bool" }
func (boolType) ConvertValue(src interface{}) (Value, error) {
switch s := src.(type) {
case bool:
return s, nil
case string:
b, err := strconv.ParseBool(s)
if err != nil {
return nil, fmt.Errorf("sql/driver: couldn't convert %q into type bool", s)
}
return b, nil
case []byte:
b, err := strconv.ParseBool(string(s))
if err != nil {
return nil, fmt.Errorf("sql/driver: couldn't convert %q into type bool", s)
}
return b, nil
}
sv := reflect.ValueOf(src)
switch sv.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
iv := sv.Int()
if iv == 1 || iv == 0 {
return iv == 1, nil
}
return nil, fmt.Errorf("sql/driver: couldn't convert %d into type bool", iv)
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
uv := sv.Uint()
if uv == 1 || uv == 0 {
return uv == 1, nil
}
return nil, fmt.Errorf("sql/driver: couldn't convert %d into type bool", uv)
}
return nil, fmt.Errorf("sql/driver: couldn't convert %v (%T) into type bool", src, src)
}
type Scanner interface {
// Scan assigns a value from a database driver.
//
// The src value will be of one of the following types:
//
// int64
// float64
// bool
// []byte
// string
// time.Time
// nil - for NULL values
//
// An error should be returned if the value cannot be stored
// without loss of information.
//
// Reference types such as []byte are only valid until the next call to Scan
// and should not be retained. Their underlying memory is owned by the driver.
// If retention is necessary, copy their values before the next call to Scan.
Scan(src interface{}) error
}