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// Copyright 2016 Luke Shumaker
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package sd_id128 reads, generates, and processes 128-bit ID values.
//
// These 128-bit IDs are a generalization of DCE UUIDs (of which
// Microsoft GUIDs are one implementation), but use a simpler string
// format. This package imposes no structure on the used IDs, unlike
// UUIDs, but are fully compatible with those types of IDs.
//
// DCE UUID: https://tools.ietf.org/html/rfc4122
//
// Microsoft GUID: https://msdn.microsoft.com/en-us/library/windows/desktop/aa373931(v=vs.85).aspx
//
// The UUID string representation is a (zero-padded) 32-digit
// hexadecimal number with a hyphen after the 8th, 12th, 16th, and
// 20th digits (for a total length of 36 glyphs). This package
// supports this format, but the primary ("plain") string
// representation is simply a (zero-padded) 32-digit hexadecimal
// number.
//
// For example:
//
// Plain: 6ba7b8109dad11d180b400c04fd430c8
// UUID : 6ba7b810-9dad-11d1-80b4-00c04fd430c8
//
// Several restrictions are imposed on the structure of UUIDs. Most
// notably, the most significant 1-3 bits of the 8th octet specify the
// UUID type ("variant"); unless dealing with legacy UUIDs, the most
// significant 2 bits of the octet will be "10", specifying a RFC 4122
// type UUID. Assuming RFC 4122 type, the most significant 4 bits of
// the 6th octet then specify the sub-type ("version"), which could
// impose complicated requirements on the rest of the UUID.
//
// This package doesn't really care about all of these UUID structure
// requirements. Nothing in this package ever inspects an ID's
// structure. However, because it is anticipated that the IDs
// generated by this package might be used in a context where a UUID
// is required, many of the functions that emit an ID ensure that the
// ID emitted is structured to be a valid UUID.
package sd_id128
import (
"errors"
)
var (
ErrInvalid = errors.New("Invalid ID")
ErrNone = errors.New("No Invocation ID set")
)
type ID128 [16]byte
// String formats the ID as a plain zero-padded 32-digit hexadecimal
// number.
func (id ID128) String() string {
var s [32]byte
for n := range id {
s[n*2] = hexchar(id[n] >> 4)
s[n*2+1] = hexchar(id[n] & 0xF)
}
return string(s[:])
}
// UUID formats the ID as a UUID string.
func (id ID128) UUID() string {
var s [36]byte
k := 0
for n := range id {
switch n {
case 4, 6, 8, 10:
s[k] = '-'
k++
}
s[k] = hexchar(id[n] >> 4)
k++
s[k] = hexchar(id[n] & 0xF)
k++
}
return string(s[:])
}
// Parse parses a 128-bit ID represented either in the plain string
// format, or in the UUID string format.
//
// If you need to validate that the string is in one format or the
// other, then you should use the ParsePlain or ParseUUID functions.
//
// If the input string does not match either of these formats, then
// ErrInvalid is returned.
func Parse(s string) (ID128, error) {
ret := ID128{}
isGuid := false
i := 0
n := 0
for n < 16 {
if s[i] == '-' {
if i == 8 {
isGuid = true
} else if i == 13 || i == 18 || i == 23 {
if !isGuid {
return ID128{}, ErrInvalid
}
} else {
return ID128{}, ErrInvalid
}
i++
} else {
if i+2 >= len(s) {
return ID128{}, ErrInvalid
}
a, err := unhexchar(s[i])
i++
if err != nil {
return ID128{}, err
}
b, err := unhexchar(s[i])
i++
if err != nil {
return ID128{}, err
}
ret[n] = (a << 4) | b
n++
}
}
if !((i == 36 && isGuid) || (i == 32 && !isGuid)) {
return ID128{}, ErrInvalid
}
if i != len(s) {
return ID128{}, ErrInvalid
}
return ret, nil
}
// ParsePlain parses a 128-bit ID represented in the plain string
// format.
//
// If you would like more flexibility, and would like to be accept
// either the plain string format or the UUID string format, then you
// should use the Parse function.
//
// If the input string is not a 32-digit hexadecimal number, then
// ErrInvalid is returned.
func ParsePlain(s string) (ID128, error) {
if len(s) != 32 {
return ID128{}, ErrInvalid
}
return Parse(s)
}
// ParsePlain parses a 128-bit ID represented in the UUID string
// format.
//
// If you would like more flexibility, and would like to be accept
// either the plain string format or the UUID string format, then you
// should use the Parse function.
//
// If the input string is not a 36-character UUID string, then
// ErrInvalid is returned. This function does not validate the
// variant or version bit fields, nor does it validate any structure
// implied by them.
func ParseUUID(s string) (ID128, error) {
if len(s) != 36 {
return ID128{}, ErrInvalid
}
return Parse(s)
}
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