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142 lines
3.3 KiB
Go
142 lines
3.3 KiB
Go
package null
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import (
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"database/sql"
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"encoding/json"
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"fmt"
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"math"
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"reflect"
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"strconv"
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)
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const (
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nullString = "null"
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)
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// Float is a nullable float64.
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// It does not consider zero values to be null.
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// It will decode to null, not zero, if null.
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type Float struct {
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sql.NullFloat64
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}
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// NewFloat creates a new Float
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func NewFloat(f float64, valid bool) Float {
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return Float{
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NullFloat64: sql.NullFloat64{
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Float64: f,
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Valid: valid,
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},
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}
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}
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// FloatFrom creates a new Float that will always be valid.
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func FloatFrom(f float64) Float {
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return NewFloat(f, true)
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}
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// FloatFromPtr creates a new Float that be null if f is nil.
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func FloatFromPtr(f *float64) Float {
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if f == nil {
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return NewFloat(0, false)
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}
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return NewFloat(*f, true)
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}
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// FloatFromString creates a new Float from string f.
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// If the string is equal to the value of nullString then the Float will be null.
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// An empty string f will return an error.
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func FloatFromString(f string, nullString string) (Float, error) {
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if f == nullString {
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return FloatFromPtr(nil), nil
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}
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fV, err := strconv.ParseFloat(f, 64)
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if err != nil {
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return Float{}, err
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}
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return FloatFrom(fV), nil
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}
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// UnmarshalJSON implements json.Unmarshaler.
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// It supports number and null input.
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// 0 will not be considered a null Float.
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// It also supports unmarshaling a sql.NullFloat64.
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func (f *Float) UnmarshalJSON(data []byte) error {
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var err error
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var v interface{}
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if err = json.Unmarshal(data, &v); err != nil {
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return err
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}
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switch x := v.(type) {
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case float64:
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f.Float64 = x
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case map[string]interface{}:
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err = json.Unmarshal(data, &f.NullFloat64)
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case nil:
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f.Valid = false
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return nil
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default:
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err = fmt.Errorf("json: cannot unmarshal %v into Go value of type null.Float", reflect.TypeOf(v).Name())
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}
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f.Valid = err == nil
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return err
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}
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// UnmarshalText implements encoding.TextUnmarshaler.
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// It will unmarshal to a null Float if the input is a blank or not an integer.
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// It will return an error if the input is not an integer, blank, or "null".
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func (f *Float) UnmarshalText(text []byte) error {
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str := string(text)
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if str == "" || str == nullString {
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f.Valid = false
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return nil
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}
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var err error
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f.Float64, err = strconv.ParseFloat(string(text), 64)
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f.Valid = err == nil
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return err
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}
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// MarshalJSON implements json.Marshaler.
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// It will encode null if this Float is null.
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func (f Float) MarshalJSON() ([]byte, error) {
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if !f.Valid || math.IsNaN(f.Float64) {
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return []byte(nullString), nil
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}
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return []byte(strconv.FormatFloat(f.Float64, 'f', -1, 64)), nil
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}
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// MarshalText implements encoding.TextMarshaler.
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// It will encode a blank string if this Float is null.
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func (f Float) MarshalText() ([]byte, error) {
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if !f.Valid {
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return []byte{}, nil
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}
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return []byte(strconv.FormatFloat(f.Float64, 'f', -1, 64)), nil
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}
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// MarshalText implements encoding.TextMarshaler.
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// It will encode a blank string if this Float is null.
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func (f Float) String() string {
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if !f.Valid {
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return nullString
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}
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return fmt.Sprintf("%1.3f", f.Float64)
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}
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// FullString returns float as string in full precision
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func (f Float) FullString() string {
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if !f.Valid {
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return nullString
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}
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return fmt.Sprintf("%f", f.Float64)
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}
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// IsZero returns true for invalid Floats, for future omitempty support (Go 1.4?)
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// A non-null Float with a 0 value will not be considered zero.
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func (f Float) IsZero() bool {
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return !f.Valid
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}
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