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|
package schema
import (
"errors"
"fmt"
"reflect"
"strconv"
)
type encoderFunc func(reflect.Value) string
// Encoder encodes values from a struct into url.Values.
type Encoder struct {
cache *cache
regenc map[reflect.Type]encoderFunc
}
// NewEncoder returns a new Encoder with defaults.
func NewEncoder() *Encoder {
return &Encoder{cache: newCache(), regenc: make(map[reflect.Type]encoderFunc)}
}
// Encode encodes a struct into map[string][]string.
//
// Intended for use with url.Values.
func (e *Encoder) Encode(src interface{}, dst map[string][]string) error {
v := reflect.ValueOf(src)
return e.encode(v, dst)
}
// RegisterEncoder registers a converter for encoding a custom type.
func (e *Encoder) RegisterEncoder(value interface{}, encoder func(reflect.Value) string) {
e.regenc[reflect.TypeOf(value)] = encoder
}
// SetAliasTag changes the tag used to locate custom field aliases.
// The default tag is "schema".
func (e *Encoder) SetAliasTag(tag string) {
e.cache.tag = tag
}
// isValidStructPointer test if input value is a valid struct pointer.
func isValidStructPointer(v reflect.Value) bool {
return v.Type().Kind() == reflect.Ptr && v.Elem().IsValid() && v.Elem().Type().Kind() == reflect.Struct
}
func isZero(v reflect.Value) bool {
switch v.Kind() {
case reflect.Func:
case reflect.Map, reflect.Slice:
return v.IsNil() || v.Len() == 0
case reflect.Array:
z := true
for i := 0; i < v.Len(); i++ {
z = z && isZero(v.Index(i))
}
return z
case reflect.Struct:
z := true
for i := 0; i < v.NumField(); i++ {
z = z && isZero(v.Field(i))
}
return z
}
// Compare other types directly:
z := reflect.Zero(v.Type())
return v.Interface() == z.Interface()
}
func (e *Encoder) encode(v reflect.Value, dst map[string][]string) error {
if v.Kind() == reflect.Ptr {
v = v.Elem()
}
if v.Kind() != reflect.Struct {
return errors.New("schema: interface must be a struct")
}
t := v.Type()
errors := MultiError{}
for i := 0; i < v.NumField(); i++ {
name, opts := fieldAlias(t.Field(i), e.cache.tag)
if name == "-" {
continue
}
// Encode struct pointer types if the field is a valid pointer and a struct.
if isValidStructPointer(v.Field(i)) {
e.encode(v.Field(i).Elem(), dst)
continue
}
encFunc := typeEncoder(v.Field(i).Type(), e.regenc)
// Encode non-slice types and custom implementations immediately.
if encFunc != nil {
value := encFunc(v.Field(i))
if opts.Contains("omitempty") && isZero(v.Field(i)) {
continue
}
dst[name] = append(dst[name], value)
continue
}
if v.Field(i).Type().Kind() == reflect.Struct {
e.encode(v.Field(i), dst)
continue
}
if v.Field(i).Type().Kind() == reflect.Slice {
encFunc = typeEncoder(v.Field(i).Type().Elem(), e.regenc)
}
if encFunc == nil {
errors[v.Field(i).Type().String()] = fmt.Errorf("schema: encoder not found for %v", v.Field(i))
continue
}
// Encode a slice.
if v.Field(i).Len() == 0 && opts.Contains("omitempty") {
continue
}
dst[name] = []string{}
for j := 0; j < v.Field(i).Len(); j++ {
dst[name] = append(dst[name], encFunc(v.Field(i).Index(j)))
}
}
if len(errors) > 0 {
return errors
}
return nil
}
func typeEncoder(t reflect.Type, reg map[reflect.Type]encoderFunc) encoderFunc {
if f, ok := reg[t]; ok {
return f
}
switch t.Kind() {
case reflect.Bool:
return encodeBool
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
return encodeInt
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
return encodeUint
case reflect.Float32:
return encodeFloat32
case reflect.Float64:
return encodeFloat64
case reflect.Ptr:
f := typeEncoder(t.Elem(), reg)
return func(v reflect.Value) string {
if v.IsNil() {
return "null"
}
return f(v.Elem())
}
case reflect.String:
return encodeString
default:
return nil
}
}
func encodeBool(v reflect.Value) string {
return strconv.FormatBool(v.Bool())
}
func encodeInt(v reflect.Value) string {
return strconv.FormatInt(int64(v.Int()), 10)
}
func encodeUint(v reflect.Value) string {
return strconv.FormatUint(uint64(v.Uint()), 10)
}
func encodeFloat(v reflect.Value, bits int) string {
return strconv.FormatFloat(v.Float(), 'f', 6, bits)
}
func encodeFloat32(v reflect.Value) string {
return encodeFloat(v, 32)
}
func encodeFloat64(v reflect.Value) string {
return encodeFloat(v, 64)
}
func encodeString(v reflect.Value) string {
return v.String()
}
|
