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236 lines
6.1 KiB
Go
236 lines
6.1 KiB
Go
// Package guid provides a GUID type. The backing structure for a GUID is
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// identical to that used by the golang.org/x/sys/windows GUID type.
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// There are two main binary encodings used for a GUID, the big-endian encoding,
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// and the Windows (mixed-endian) encoding. See here for details:
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// https://en.wikipedia.org/wiki/Universally_unique_identifier#Encoding
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package guid
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import (
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"crypto/rand"
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"crypto/sha1"
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"encoding"
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"encoding/binary"
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"fmt"
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"strconv"
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"golang.org/x/sys/windows"
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)
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// Variant specifies which GUID variant (or "type") of the GUID. It determines
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// how the entirety of the rest of the GUID is interpreted.
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type Variant uint8
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// The variants specified by RFC 4122.
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const (
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// VariantUnknown specifies a GUID variant which does not conform to one of
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// the variant encodings specified in RFC 4122.
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VariantUnknown Variant = iota
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VariantNCS
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VariantRFC4122
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VariantMicrosoft
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VariantFuture
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)
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// Version specifies how the bits in the GUID were generated. For instance, a
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// version 4 GUID is randomly generated, and a version 5 is generated from the
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// hash of an input string.
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type Version uint8
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var _ = (encoding.TextMarshaler)(GUID{})
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var _ = (encoding.TextUnmarshaler)(&GUID{})
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// GUID represents a GUID/UUID. It has the same structure as
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// golang.org/x/sys/windows.GUID so that it can be used with functions expecting
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// that type. It is defined as its own type so that stringification and
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// marshaling can be supported. The representation matches that used by native
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// Windows code.
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type GUID windows.GUID
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// NewV4 returns a new version 4 (pseudorandom) GUID, as defined by RFC 4122.
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func NewV4() (GUID, error) {
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var b [16]byte
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if _, err := rand.Read(b[:]); err != nil {
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return GUID{}, err
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}
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g := FromArray(b)
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g.setVersion(4) // Version 4 means randomly generated.
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g.setVariant(VariantRFC4122)
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return g, nil
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}
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// NewV5 returns a new version 5 (generated from a string via SHA-1 hashing)
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// GUID, as defined by RFC 4122. The RFC is unclear on the encoding of the name,
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// and the sample code treats it as a series of bytes, so we do the same here.
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//
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// Some implementations, such as those found on Windows, treat the name as a
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// big-endian UTF16 stream of bytes. If that is desired, the string can be
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// encoded as such before being passed to this function.
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func NewV5(namespace GUID, name []byte) (GUID, error) {
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b := sha1.New()
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namespaceBytes := namespace.ToArray()
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b.Write(namespaceBytes[:])
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b.Write(name)
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a := [16]byte{}
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copy(a[:], b.Sum(nil))
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g := FromArray(a)
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g.setVersion(5) // Version 5 means generated from a string.
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g.setVariant(VariantRFC4122)
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return g, nil
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}
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func fromArray(b [16]byte, order binary.ByteOrder) GUID {
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var g GUID
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g.Data1 = order.Uint32(b[0:4])
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g.Data2 = order.Uint16(b[4:6])
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g.Data3 = order.Uint16(b[6:8])
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copy(g.Data4[:], b[8:16])
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return g
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}
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func (g GUID) toArray(order binary.ByteOrder) [16]byte {
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b := [16]byte{}
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order.PutUint32(b[0:4], g.Data1)
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order.PutUint16(b[4:6], g.Data2)
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order.PutUint16(b[6:8], g.Data3)
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copy(b[8:16], g.Data4[:])
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return b
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}
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// FromArray constructs a GUID from a big-endian encoding array of 16 bytes.
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func FromArray(b [16]byte) GUID {
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return fromArray(b, binary.BigEndian)
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}
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// ToArray returns an array of 16 bytes representing the GUID in big-endian
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// encoding.
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func (g GUID) ToArray() [16]byte {
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return g.toArray(binary.BigEndian)
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}
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// FromWindowsArray constructs a GUID from a Windows encoding array of bytes.
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func FromWindowsArray(b [16]byte) GUID {
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return fromArray(b, binary.LittleEndian)
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}
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// ToWindowsArray returns an array of 16 bytes representing the GUID in Windows
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// encoding.
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func (g GUID) ToWindowsArray() [16]byte {
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return g.toArray(binary.LittleEndian)
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}
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func (g GUID) String() string {
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return fmt.Sprintf(
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"%08x-%04x-%04x-%04x-%012x",
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g.Data1,
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g.Data2,
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g.Data3,
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g.Data4[:2],
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g.Data4[2:])
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}
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// FromString parses a string containing a GUID and returns the GUID. The only
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// format currently supported is the `xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx`
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// format.
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func FromString(s string) (GUID, error) {
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if len(s) != 36 {
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return GUID{}, fmt.Errorf("invalid GUID %q", s)
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}
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if s[8] != '-' || s[13] != '-' || s[18] != '-' || s[23] != '-' {
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return GUID{}, fmt.Errorf("invalid GUID %q", s)
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}
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var g GUID
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data1, err := strconv.ParseUint(s[0:8], 16, 32)
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if err != nil {
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return GUID{}, fmt.Errorf("invalid GUID %q", s)
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}
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g.Data1 = uint32(data1)
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data2, err := strconv.ParseUint(s[9:13], 16, 16)
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if err != nil {
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return GUID{}, fmt.Errorf("invalid GUID %q", s)
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}
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g.Data2 = uint16(data2)
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data3, err := strconv.ParseUint(s[14:18], 16, 16)
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if err != nil {
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return GUID{}, fmt.Errorf("invalid GUID %q", s)
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}
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g.Data3 = uint16(data3)
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for i, x := range []int{19, 21, 24, 26, 28, 30, 32, 34} {
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v, err := strconv.ParseUint(s[x:x+2], 16, 8)
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if err != nil {
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return GUID{}, fmt.Errorf("invalid GUID %q", s)
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}
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g.Data4[i] = uint8(v)
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}
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return g, nil
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}
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func (g *GUID) setVariant(v Variant) {
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d := g.Data4[0]
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switch v {
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case VariantNCS:
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d = (d & 0x7f)
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case VariantRFC4122:
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d = (d & 0x3f) | 0x80
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case VariantMicrosoft:
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d = (d & 0x1f) | 0xc0
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case VariantFuture:
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d = (d & 0x0f) | 0xe0
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case VariantUnknown:
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fallthrough
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default:
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panic(fmt.Sprintf("invalid variant: %d", v))
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}
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g.Data4[0] = d
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}
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// Variant returns the GUID variant, as defined in RFC 4122.
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func (g GUID) Variant() Variant {
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b := g.Data4[0]
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if b&0x80 == 0 {
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return VariantNCS
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} else if b&0xc0 == 0x80 {
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return VariantRFC4122
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} else if b&0xe0 == 0xc0 {
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return VariantMicrosoft
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} else if b&0xe0 == 0xe0 {
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return VariantFuture
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}
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return VariantUnknown
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}
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func (g *GUID) setVersion(v Version) {
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g.Data3 = (g.Data3 & 0x0fff) | (uint16(v) << 12)
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}
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// Version returns the GUID version, as defined in RFC 4122.
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func (g GUID) Version() Version {
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return Version((g.Data3 & 0xF000) >> 12)
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}
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// MarshalText returns the textual representation of the GUID.
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func (g GUID) MarshalText() ([]byte, error) {
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return []byte(g.String()), nil
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}
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// UnmarshalText takes the textual representation of a GUID, and unmarhals it
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// into this GUID.
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func (g *GUID) UnmarshalText(text []byte) error {
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g2, err := FromString(string(text))
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if err != nil {
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return err
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}
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*g = g2
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return nil
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}
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