cc-backend/schema/float.go
2022-01-27 09:29:53 +01:00

106 lines
2.5 KiB
Go

package schema
import (
"errors"
"io"
"math"
"strconv"
)
// A custom float type is used so that (Un)MarshalJSON and
// (Un)MarshalGQL can be overloaded and NaN/null can be used.
// The default behaviour of putting every nullable value behind
// a pointer has a bigger overhead.
type Float float64
var NaN Float = Float(math.NaN())
var nullAsBytes []byte = []byte("null")
func (f Float) IsNaN() bool {
return math.IsNaN(float64(f))
}
// NaN will be serialized to `null`.
func (f Float) MarshalJSON() ([]byte, error) {
if f.IsNaN() {
return nullAsBytes, nil
}
return strconv.AppendFloat(make([]byte, 0, 10), float64(f), 'f', 2, 64), nil
}
// `null` will be unserialized to NaN.
func (f *Float) UnmarshalJSON(input []byte) error {
s := string(input)
if s == "null" {
*f = NaN
return nil
}
val, err := strconv.ParseFloat(s, 64)
if err != nil {
return err
}
*f = Float(val)
return nil
}
// UnmarshalGQL implements the graphql.Unmarshaler interface.
func (f *Float) UnmarshalGQL(v interface{}) error {
f64, ok := v.(float64)
if !ok {
return errors.New("invalid Float scalar")
}
*f = Float(f64)
return nil
}
// MarshalGQL implements the graphql.Marshaler interface.
// NaN will be serialized to `null`.
func (f Float) MarshalGQL(w io.Writer) {
if f.IsNaN() {
w.Write(nullAsBytes)
} else {
w.Write(strconv.AppendFloat(make([]byte, 0, 10), float64(f), 'f', 2, 64))
}
}
// Only used via REST-API, not via GraphQL.
// This uses a lot less allocations per series,
// but it turns out that the performance increase
// from using this is not that big.
func (s *Series) MarshalJSON() ([]byte, error) {
buf := make([]byte, 0, 512+len(s.Data)*8)
buf = append(buf, `{"hostname":"`...)
buf = append(buf, s.Hostname...)
buf = append(buf, '"')
if s.Id != nil {
buf = append(buf, `,"id":`...)
buf = strconv.AppendInt(buf, int64(*s.Id), 10)
}
if s.Statistics != nil {
buf = append(buf, `,"statistics":{"min":`...)
buf = strconv.AppendFloat(buf, s.Statistics.Min, 'f', 2, 64)
buf = append(buf, `,"avg":`...)
buf = strconv.AppendFloat(buf, s.Statistics.Avg, 'f', 2, 64)
buf = append(buf, `,"max":`...)
buf = strconv.AppendFloat(buf, s.Statistics.Max, 'f', 2, 64)
buf = append(buf, '}')
}
buf = append(buf, `,"data":[`...)
for i := 0; i < len(s.Data); i++ {
if i != 0 {
buf = append(buf, ',')
}
if s.Data[i].IsNaN() {
buf = append(buf, `null`...)
} else {
buf = strconv.AppendFloat(buf, float64(s.Data[i]), 'f', 2, 32)
}
}
buf = append(buf, ']', '}')
return buf, nil
}