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arikawa/utils/json/json.go
2022-11-03 02:30:25 -07:00

105 lines
2.8 KiB
Go

// Package json allows for different implementations of JSON serializing, as
// well as extra optional types needed.
package json
import (
"encoding/json"
"io"
"reflect"
"unsafe"
)
type Driver interface {
Marshal(v interface{}) ([]byte, error)
Unmarshal(data []byte, v interface{}) error
DecodeStream(r io.Reader, v interface{}) error
EncodeStream(w io.Writer, v interface{}) error
}
type DefaultDriver struct{}
func (d DefaultDriver) Marshal(v interface{}) ([]byte, error) {
return json.Marshal(v)
}
func (d DefaultDriver) Unmarshal(data []byte, v interface{}) error {
return json.Unmarshal(data, v)
}
func (d DefaultDriver) DecodeStream(r io.Reader, v interface{}) error {
return json.NewDecoder(r).Decode(v)
}
func (d DefaultDriver) EncodeStream(w io.Writer, v interface{}) error {
return json.NewEncoder(w).Encode(v)
}
// Default is the default JSON driver, which uses encoding/json.
var Default Driver = DefaultDriver{}
// Marshal uses the default driver.
func Marshal(v interface{}) ([]byte, error) {
return Default.Marshal(v)
}
// Unmarshal uses the default driver.
func Unmarshal(data []byte, v interface{}) error {
return Default.Unmarshal(data, v)
}
// DecodeStream uses the default driver.
func DecodeStream(r io.Reader, v interface{}) error {
return Default.DecodeStream(r, v)
}
// EncodeStream uses the default driver.
func EncodeStream(w io.Writer, v interface{}) error {
return Default.EncodeStream(w, v)
}
// PartialUnmarshal partially unmarshals the JSON in b onto v. Fields that
// cannot be unmarshaled will be left as their zero values. Fields that can be
// marshaled will be unmarshaled and its name will be added to the returned
// slice.
//
// Only use this for the most cursed of JSONs, such as ones coming from Discord.
// Try not to use this as much as possible.
func PartialUnmarshal(b []byte, v interface{}) []error {
var errs []error
dstv := reflect.Indirect(reflect.ValueOf(v))
dstt := dstv.Type()
// ptrVal will be used by reflect to store our temporary object. This allows
// us to free up n heap allocations just for one pointer.
var ptrVal struct {
_ *struct{}
}
dstfields := dstt.NumField()
for i := 0; i < dstfields; i++ {
dstfield := dstt.Field(i)
// Create us a custom struct with this one field, except its type is a
// pointer type. We prefer to do this over parsing JSON's tags.
fake := reflect.NewAt(reflect.StructOf([]reflect.StructField{
{
Name: dstfield.Name,
Type: reflect.PtrTo(dstfield.Type),
Tag: dstfield.Tag,
},
}), unsafe.Pointer(&ptrVal))
// We can use this pointer to set the value of the field.
fake.Elem().Field(0).Set(dstv.Field(i).Addr())
// Unmarshal into this struct.
if err := json.Unmarshal(b, fake.Interface()); err != nil {
errs = append(errs, err)
}
}
return errs
}