site/vendor/gopkg.in/segmentio/analytics-go.v3/json.go

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2018-08-22 03:17:59 +00:00
package analytics
import (
"reflect"
"strings"
)
// Imitate what what the JSON package would do when serializing a struct value,
// the only difference is we we don't serialize zero-value struct fields as well.
// Note that this function doesn't recursively convert structures to maps, only
// the value passed as argument is transformed.
func structToMap(v reflect.Value, m map[string]interface{}) map[string]interface{} {
t := v.Type()
n := t.NumField()
if m == nil {
m = make(map[string]interface{}, n)
}
for i := 0; i != n; i++ {
field := t.Field(i)
value := v.Field(i)
name, omitempty := parseJsonTag(field.Tag.Get("json"), field.Name)
if name != "-" && !(omitempty && isZeroValue(value)) {
m[name] = value.Interface()
}
}
return m
}
// Parses a JSON tag the way the json package would do it, returing the expected
// name of the field once serialized and if empty values should be omitted.
func parseJsonTag(tag string, defName string) (name string, omitempty bool) {
args := strings.Split(tag, ",")
if len(args) == 0 || len(args[0]) == 0 {
name = defName
} else {
name = args[0]
}
if len(args) > 1 && args[1] == "omitempty" {
omitempty = true
}
return
}
// Checks if the value given as argument is a zero-value, it is based on the
// isEmptyValue function in https://golang.org/src/encoding/json/encode.go
// but also checks struct types recursively.
func isZeroValue(v reflect.Value) bool {
switch v.Kind() {
case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
return v.Len() == 0
case reflect.Bool:
return !v.Bool()
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
return v.Int() == 0
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
return v.Uint() == 0
case reflect.Float32, reflect.Float64:
return v.Float() == 0
case reflect.Interface, reflect.Ptr:
return v.IsNil()
case reflect.Struct:
for i, n := 0, v.NumField(); i != n; i++ {
if !isZeroValue(v.Field(i)) {
return false
}
}
return true
case reflect.Invalid:
return true
}
return false
}