258 lines
7.5 KiB
Go
258 lines
7.5 KiB
Go
// Copyright (C) 2013-2018 by Maxim Bublis <b@codemonkey.ru>
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//
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// Permission is hereby granted, free of charge, to any person obtaining
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// a copy of this software and associated documentation files (the
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// "Software"), to deal in the Software without restriction, including
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// without limitation the rights to use, copy, modify, merge, publish,
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// distribute, sublicense, and/or sell copies of the Software, and to
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// permit persons to whom the Software is furnished to do so, subject to
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// the following conditions:
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//
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// The above copyright notice and this permission notice shall be
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// included in all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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// Package uuid provides implementations of the Universally Unique Identifier
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// (UUID), as specified in RFC-4122,
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//
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// RFC-4122[1] provides the specification for versions 1, 3, 4, and 5.
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//
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// DCE 1.1[2] provides the specification for version 2, but version 2 support
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// was removed from this package in v4 due to some concerns with the
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// specification itself. Reading the spec, it seems that it would result in
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// generating UUIDs that aren't very unique. In having read the spec it seemed
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// that our implementation did not meet the spec. It also seems to be at-odds
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// with RFC 4122, meaning we would need quite a bit of special code to support
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// it. Lastly, there were no Version 2 implementations that we could find to
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// ensure we were understanding the specification correctly.
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//
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// [1] https://tools.ietf.org/html/rfc4122
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// [2] http://pubs.opengroup.org/onlinepubs/9696989899/chap5.htm#tagcjh_08_02_01_01
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package uuid
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import (
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"encoding/binary"
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"encoding/hex"
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"fmt"
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"io"
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"strings"
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"time"
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)
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// Size of a UUID in bytes.
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const Size = 16
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// UUID is an array type to represent the value of a UUID, as defined in RFC-4122.
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type UUID [Size]byte
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// UUID versions.
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const (
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_ byte = iota
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V1 // Version 1 (date-time and MAC address)
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_ // Version 2 (date-time and MAC address, DCE security version) [removed]
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V3 // Version 3 (namespace name-based)
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V4 // Version 4 (random)
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V5 // Version 5 (namespace name-based)
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)
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// UUID layout variants.
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const (
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VariantNCS byte = iota
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VariantRFC4122
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VariantMicrosoft
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VariantFuture
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)
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// UUID DCE domains.
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const (
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DomainPerson = iota
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DomainGroup
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DomainOrg
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)
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// Timestamp is the count of 100-nanosecond intervals since 00:00:00.00,
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// 15 October 1582 within a V1 UUID. This type has no meaning for other
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// UUID versions since they don't have an embedded timestamp.
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type Timestamp uint64
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const _100nsPerSecond = 10000000
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// Time returns the UTC time.Time representation of a Timestamp
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func (t Timestamp) Time() (time.Time, error) {
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secs := uint64(t) / _100nsPerSecond
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nsecs := 100 * (uint64(t) % _100nsPerSecond)
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return time.Unix(int64(secs)-(epochStart/_100nsPerSecond), int64(nsecs)), nil
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}
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// TimestampFromV1 returns the Timestamp embedded within a V1 UUID.
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// Returns an error if the UUID is any version other than 1.
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func TimestampFromV1(u UUID) (Timestamp, error) {
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if u.Version() != 1 {
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err := fmt.Errorf("uuid: %s is version %d, not version 1", u, u.Version())
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return 0, err
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}
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low := binary.BigEndian.Uint32(u[0:4])
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mid := binary.BigEndian.Uint16(u[4:6])
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hi := binary.BigEndian.Uint16(u[6:8]) & 0xfff
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return Timestamp(uint64(low) + (uint64(mid) << 32) + (uint64(hi) << 48)), nil
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}
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// String parse helpers.
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var (
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urnPrefix = []byte("urn:uuid:")
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byteGroups = []int{8, 4, 4, 4, 12}
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)
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// Nil is the nil UUID, as specified in RFC-4122, that has all 128 bits set to
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// zero.
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var Nil = UUID{}
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// Predefined namespace UUIDs.
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var (
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NamespaceDNS = Must(FromString("6ba7b810-9dad-11d1-80b4-00c04fd430c8"))
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NamespaceURL = Must(FromString("6ba7b811-9dad-11d1-80b4-00c04fd430c8"))
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NamespaceOID = Must(FromString("6ba7b812-9dad-11d1-80b4-00c04fd430c8"))
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NamespaceX500 = Must(FromString("6ba7b814-9dad-11d1-80b4-00c04fd430c8"))
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)
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// Version returns the algorithm version used to generate the UUID.
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func (u UUID) Version() byte {
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return u[6] >> 4
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}
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// Variant returns the UUID layout variant.
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func (u UUID) Variant() byte {
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switch {
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case (u[8] >> 7) == 0x00:
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return VariantNCS
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case (u[8] >> 6) == 0x02:
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return VariantRFC4122
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case (u[8] >> 5) == 0x06:
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return VariantMicrosoft
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case (u[8] >> 5) == 0x07:
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fallthrough
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default:
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return VariantFuture
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}
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}
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// Bytes returns a byte slice representation of the UUID.
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func (u UUID) Bytes() []byte {
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return u[:]
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}
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// String returns a canonical RFC-4122 string representation of the UUID:
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// xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx.
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func (u UUID) String() string {
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buf := make([]byte, 36)
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hex.Encode(buf[0:8], u[0:4])
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buf[8] = '-'
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hex.Encode(buf[9:13], u[4:6])
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buf[13] = '-'
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hex.Encode(buf[14:18], u[6:8])
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buf[18] = '-'
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hex.Encode(buf[19:23], u[8:10])
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buf[23] = '-'
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hex.Encode(buf[24:], u[10:])
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return string(buf)
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}
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// Format implements fmt.Formatter for UUID values.
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//
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// The behavior is as follows:
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// The 'x' and 'X' verbs output only the hex digits of the UUID, using a-f for 'x' and A-F for 'X'.
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// The 'v', '+v', 's' and 'q' verbs return the canonical RFC-4122 string representation.
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// The 'S' verb returns the RFC-4122 format, but with capital hex digits.
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// The '#v' verb returns the "Go syntax" representation, which is a 16 byte array initializer.
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// All other verbs not handled directly by the fmt package (like '%p') are unsupported and will return
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// "%!verb(uuid.UUID=value)" as recommended by the fmt package.
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func (u UUID) Format(f fmt.State, c rune) {
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switch c {
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case 'x', 'X':
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s := hex.EncodeToString(u.Bytes())
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if c == 'X' {
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s = strings.Map(toCapitalHexDigits, s)
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}
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_, _ = io.WriteString(f, s)
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case 'v':
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var s string
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if f.Flag('#') {
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s = fmt.Sprintf("%#v", [Size]byte(u))
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} else {
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s = u.String()
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}
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_, _ = io.WriteString(f, s)
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case 's', 'S':
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s := u.String()
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if c == 'S' {
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s = strings.Map(toCapitalHexDigits, s)
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}
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_, _ = io.WriteString(f, s)
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case 'q':
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_, _ = io.WriteString(f, `"`+u.String()+`"`)
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default:
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// invalid/unsupported format verb
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fmt.Fprintf(f, "%%!%c(uuid.UUID=%s)", c, u.String())
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}
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}
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func toCapitalHexDigits(ch rune) rune {
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// convert a-f hex digits to A-F
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switch ch {
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case 'a':
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return 'A'
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case 'b':
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return 'B'
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case 'c':
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return 'C'
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case 'd':
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return 'D'
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case 'e':
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return 'E'
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case 'f':
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return 'F'
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default:
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return ch
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}
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}
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// SetVersion sets the version bits.
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func (u *UUID) SetVersion(v byte) {
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u[6] = (u[6] & 0x0f) | (v << 4)
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}
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// SetVariant sets the variant bits.
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func (u *UUID) SetVariant(v byte) {
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switch v {
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case VariantNCS:
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u[8] = (u[8]&(0xff>>1) | (0x00 << 7))
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case VariantRFC4122:
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u[8] = (u[8]&(0xff>>2) | (0x02 << 6))
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case VariantMicrosoft:
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u[8] = (u[8]&(0xff>>3) | (0x06 << 5))
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case VariantFuture:
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fallthrough
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default:
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u[8] = (u[8]&(0xff>>3) | (0x07 << 5))
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}
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}
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// Must is a helper that wraps a call to a function returning (UUID, error)
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// and panics if the error is non-nil. It is intended for use in variable
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// initializations such as
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// var packageUUID = uuid.Must(uuid.FromString("123e4567-e89b-12d3-a456-426655440000"))
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func Must(u UUID, err error) UUID {
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if err != nil {
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panic(err)
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}
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return u
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}
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