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