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package urn
import (
"encoding/json"
"fmt"
"strings"
)
const errInvalidURN = "invalid URN: %s"
// URN represents an Uniform Resource Name.
//
// The general form represented is:
//
// urn:<id>:<ss>
//
// Details at https://tools.ietf.org/html/rfc2141.
type URN struct {
prefix string // Static prefix. Equal to "urn" when empty.
ID string // Namespace identifier
SS string // Namespace specific string
norm string // Normalized namespace specific string
}
// Normalize turns the receiving URN into its norm version.
//
// Which means: lowercase prefix, lowercase namespace identifier, and immutate namespace specific string chars (except <hex> tokens which are lowercased).
func (u *URN) Normalize() *URN {
return &URN{
prefix: "urn",
ID: strings.ToLower(u.ID),
SS: u.norm,
}
}
// Equal checks the lexical equivalence of the current URN with another one.
func (u *URN) Equal(x *URN) bool {
return *u.Normalize() == *x.Normalize()
}
// String reassembles the URN into a valid URN string.
//
// This requires both ID and SS fields to be non-empty.
// Otherwise it returns an empty string.
//
// Default URN prefix is "urn".
func (u *URN) String() string {
var res string
if u.ID != "" && u.SS != "" {
if u.prefix == "" {
res += "urn"
}
res += u.prefix + ":" + u.ID + ":" + u.SS
}
return res
}
// Parse is responsible to create an URN instance from a byte array matching the correct URN syntax.
func Parse(u []byte) (*URN, bool) {
urn, err := NewMachine().Parse(u)
if err != nil {
return nil, false
}
return urn, true
}
// MarshalJSON marshals the URN to JSON string form (e.g. `"urn:oid:1.2.3.4"`).
func (u URN) MarshalJSON() ([]byte, error) {
return json.Marshal(u.String())
}
// MarshalJSON unmarshals a URN from JSON string form (e.g. `"urn:oid:1.2.3.4"`).
func (u *URN) UnmarshalJSON(bytes []byte) error {
var str string
if err := json.Unmarshal(bytes, &str); err != nil {
return err
}
if value, ok := Parse([]byte(str)); !ok {
return fmt.Errorf(errInvalidURN, str)
} else {
*u = *value
}
return nil
}
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