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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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