1 files changed, 103 insertions, 0 deletions
diff --git a/src/guuid.go b/src/guuid.go
new file mode 100644
index 0000000..9e3e2ba
--- /dev/null
+++ b/src/guuid.go
@@ -0,0 +1,103 @@
+package guuid
+
+import (
+	"crypto/rand"
+	"encoding/hex"
+	"errors"
+	"io"
+	"strings"
+)
+
+
+
+const (
+	uuidByteCount     = 16
+	uuidDashCount     = 4
+	uuidEncodedLength = (uuidByteCount * 2) + uuidDashCount
+)
+
+
+var (
+	dashIndexes = []int { 8, 13, 18, 23 }
+	emptyUUID   = UUID {}
+)
+
+var (
+	BadLengthError       = errors.New("guuid: str isn't of the correct length")
+	BadDashCountError    = errors.New("guuid: Bad count of dashes in string")
+	BadDashPositionError = errors.New("guuid: Bad char in string")
+)
+
+
+
+type UUID [uuidByteCount]byte
+
+
+
+func NewFrom(r io.Reader) (UUID, error) {
+	var uuid UUID
+	_, err := io.ReadFull(r, uuid[:])
+	if err != nil {
+		return emptyUUID, err
+	}
+	uuid[6] = (uuid[6] & 0x0f) | 0x40 // v4
+	uuid[8] = (uuid[8] & 0x3f) | 0x80 // variant 10
+	return uuid, nil
+}
+
+func New() UUID {
+	uuid, err := NewFrom(rand.Reader)
+	if err != nil {
+		panic(err)
+	}
+	return uuid
+}
+
+func (uuid UUID) String() string {
+	dst := [uuidEncodedLength]byte {
+		0, 0, 0, 0,
+		0, 0, 0, 0,
+		'-',
+		0, 0, 0, 0,
+		'-',
+		0, 0, 0, 0,
+		'-',
+		0, 0, 0, 0,
+		'-',
+		0, 0, 0, 0,
+		0, 0, 0, 0,
+		0, 0, 0, 0,
+	}
+
+	hex.Encode(dst[ 0:8],  uuid[0:4])
+	hex.Encode(dst[ 9:13], uuid[4:6])
+	hex.Encode(dst[14:18], uuid[6:8])
+	hex.Encode(dst[19:23], uuid[8:10])
+	hex.Encode(dst[24:36], uuid[10:])
+
+	return string(dst[:])
+}
+
+func FromString(str string) (UUID, error) {
+	if len(str) != uuidEncodedLength {
+		return emptyUUID, BadLengthError
+	}
+
+	if strings.Count(str, "-") != uuidDashCount {
+		return emptyUUID, BadDashCountError
+	}
+
+	for _, idx := range dashIndexes {
+		if str[idx] != '-' {
+			return emptyUUID, BadDashPositionError
+		}
+	}
+
+	hexstr := strings.Join(strings.Split(str, "-"), "")
+	data, err := hex.DecodeString(hexstr)
+	if err != nil {
+		return emptyUUID, err
+	}
+
+	return [uuidByteCount]byte(data), nil
+}