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