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@rhcarvalho
Created September 3, 2020 10:12
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Smart timestamps in Go: decode/encode JSON from Unix timestamp numbers or RFC3339 strings
// https://play.golang.org/p/wSZvxQbT3KY
package main
import (
"encoding/json"
"fmt"
"os"
"strconv"
"text/tabwriter"
"time"
)
// Timestamp is like time.Time, but knows how to unmarshal from JSON Unix timestamp numbers or RFC3339 strings, and
// marshal back into the same JSON representation.
type Timestamp struct {
time.Time
rfc3339 bool
}
func (t Timestamp) MarshalJSON() ([]byte, error) {
if t.rfc3339 {
return t.Time.MarshalJSON()
}
return t.formatUnix()
}
func (t *Timestamp) UnmarshalJSON(data []byte) error {
err := t.Time.UnmarshalJSON(data)
if err != nil {
return t.parseUnix(data)
}
t.rfc3339 = true
return nil
}
func (t Timestamp) formatUnix() ([]byte, error) {
sec := float64(t.Time.UnixNano()) * float64(time.Nanosecond) / float64(time.Second)
return strconv.AppendFloat(nil, sec, 'f', -1, 64), nil
}
func (t *Timestamp) parseUnix(data []byte) error {
f, err := strconv.ParseFloat(string(data), 64)
if err != nil {
return err
}
t.Time = time.Unix(0, int64(f*float64(time.Second/time.Nanosecond)))
return nil
}
func main() {
t := Timestamp{Time: time.Now()}
fmt.Println("Now:", t.Format(time.RFC3339Nano), "==", t.Unix())
w := tabwriter.NewWriter(os.Stdout, 0, 0, 1, ' ', tabwriter.Debug)
defer w.Flush()
fmt.Fprintf(w, "%s\t%s\t%s\t%s\n", "INPUT", "PARSED TIME", "INPUT in RFC3339", "ROUNDTRIP TO JSON")
for _, s := range []string{
`1257894000`,
`1257894000.45221`,
`"2009-11-10T23:00:00Z"`,
`"2009-11-10T23:00:00.45221Z"`,
} {
err := json.Unmarshal([]byte(s), &t)
if err != nil {
panic(err)
}
j, err := t.MarshalJSON()
if err != nil {
panic(err)
}
fmt.Fprintf(w, "%s\t%s\t%t\t%s\n", s, t.Format(time.RFC3339Nano), t.rfc3339, j)
}
}
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