Simple file upload and browsing

uuid.go

@@ -0,0 +1,173 @@
+// This package provides immutable UUID structs and the functions
+// NewV3, NewV4, NewV5 and Parse() for generating versions 3, 4
+// and 5 UUIDs as specified in RFC 4122.
+//
+// Copyright (C) 2011 by Krzysztof Kowalik <chris@nu7hat.ch>
+package main
+
+import (
+	"crypto/md5"
+	"crypto/rand"
+	"crypto/sha1"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"hash"
+	"regexp"
+)
+
+// The UUID reserved variants. 
+const (
+	ReservedNCS       byte = 0x80
+	ReservedRFC4122   byte = 0x40
+	ReservedMicrosoft byte = 0x20
+	ReservedFuture    byte = 0x00
+)
+
+// The following standard UUIDs are for use with NewV3() or NewV5().
+var (
+	NamespaceDNS, _  = ParseHex("6ba7b810-9dad-11d1-80b4-00c04fd430c8")
+	NamespaceURL, _  = ParseHex("6ba7b811-9dad-11d1-80b4-00c04fd430c8")
+	NamespaceOID, _  = ParseHex("6ba7b812-9dad-11d1-80b4-00c04fd430c8")
+	NamespaceX500, _ = ParseHex("6ba7b814-9dad-11d1-80b4-00c04fd430c8")
+)
+
+// Pattern used to parse hex string representation of the UUID.
+// FIXME: do something to consider both brackets at one time,
+// current one allows to parse string with only one opening
+// or closing bracket.
+const hexPattern = "^(urn\\:uuid\\:)?\\{?([a-z0-9]{8})-([a-z0-9]{4})-" +
+	"([1-5][a-z0-9]{3})-([a-z0-9]{4})-([a-z0-9]{12})\\}?$"
+
+var re = regexp.MustCompile(hexPattern)
+
+// A UUID representation compliant with specification in
+// RFC 4122 document.
+type UUID [16]byte
+
+// ParseHex creates a UUID object from given hex string
+// representation. Function accepts UUID string in following
+// formats:
+//
+//     uuid.ParseHex("6ba7b814-9dad-11d1-80b4-00c04fd430c8")
+//     uuid.ParseHex("{6ba7b814-9dad-11d1-80b4-00c04fd430c8}")
+//     uuid.ParseHex("urn:uuid:6ba7b814-9dad-11d1-80b4-00c04fd430c8")
+//
+func ParseHex(s string) (u *UUID, err error) {
+	md := re.FindStringSubmatch(s)
+	if md == nil {
+		err = errors.New("Invalid UUID string")
+		return
+	}
+	hash := md[2] + md[3] + md[4] + md[5] + md[6]
+	b, err := hex.DecodeString(hash)
+	if err != nil {
+		return
+	}
+	u = new(UUID)
+	copy(u[:], b)
+	return
+}
+
+// Parse creates a UUID object from given bytes slice.
+func Parse(b []byte) (u *UUID, err error) {
+	if len(b) != 16 {
+		err = errors.New("Given slice is not valid UUID sequence")
+		return
+	}
+	u = new(UUID)
+	copy(u[:], b)
+	return
+}
+
+// Generate a UUID based on the MD5 hash of a namespace identifier
+// and a name.
+func NewV3(ns *UUID, name []byte) (u *UUID, err error) {
+	if ns == nil {
+		err = errors.New("Invalid namespace UUID")
+		return
+	}
+	u = new(UUID)
+	// Set all bits to MD5 hash generated from namespace and name.
+	u.setBytesFromHash(md5.New(), ns[:], name)
+	u.setVariant(ReservedRFC4122)
+	u.setVersion(3)
+	return
+}
+
+// Generate a random UUID.
+func NewV4() (u *UUID, err error) {
+	u = new(UUID)
+	// Set all bits to randomly (or pseudo-randomly) chosen values.
+	_, err = rand.Read(u[:])
+	if err != nil {
+		return
+	}
+	u.setVariant(ReservedRFC4122)
+	u.setVersion(4)
+	return
+}
+
+// Generate a UUID based on the SHA-1 hash of a namespace identifier
+// and a name.
+func NewV5(ns *UUID, name []byte) (u *UUID, err error) {
+	u = new(UUID)
+	// Set all bits to truncated SHA1 hash generated from namespace
+	// and name.
+	u.setBytesFromHash(sha1.New(), ns[:], name)
+	u.setVariant(ReservedRFC4122)
+	u.setVersion(5)
+	return
+}
+
+// Generate a MD5 hash of a namespace and a name, and copy it to the
+// UUID slice.
+func (u *UUID) setBytesFromHash(hash hash.Hash, ns, name []byte) {
+	hash.Write(ns[:])
+	hash.Write(name)
+	copy(u[:], hash.Sum([]byte{})[:16])
+}
+
+// Set the two most significant bits (bits 6 and 7) of the
+// clock_seq_hi_and_reserved to zero and one, respectively.
+func (u *UUID) setVariant(v byte) {
+	switch v {
+	case ReservedNCS:
+		u[8] = (u[8] | ReservedNCS) & 0xBF
+	case ReservedRFC4122:
+		u[8] = (u[8] | ReservedRFC4122) & 0x7F
+	case ReservedMicrosoft:
+		u[8] = (u[8] | ReservedMicrosoft) & 0x3F
+	}
+}
+
+// Variant returns the UUID Variant, which determines the internal
+// layout of the UUID. This will be one of the constants: RESERVED_NCS,
+// RFC_4122, RESERVED_MICROSOFT, RESERVED_FUTURE.
+func (u *UUID) Variant() byte {
+	if u[8]&ReservedNCS == ReservedNCS {
+		return ReservedNCS
+	} else if u[8]&ReservedRFC4122 == ReservedRFC4122 {
+		return ReservedRFC4122
+	} else if u[8]&ReservedMicrosoft == ReservedMicrosoft {
+		return ReservedMicrosoft
+	}
+	return ReservedFuture
+}
+
+// Set the four most significant bits (bits 12 through 15) of the
+// time_hi_and_version field to the 4-bit version number.
+func (u *UUID) setVersion(v byte) {
+	u[6] = (u[6] & 0xF) | (v << 4)
+}
+
+// Version returns a version number of the algorithm used to
+// generate the UUID sequence.
+func (u *UUID) Version() uint {
+	return uint(u[6] >> 4)
+}
+
+// Returns unparsed version of the generated UUID sequence.
+func (u *UUID) String() string {
+	return fmt.Sprintf("%x-%x-%x-%x-%x", u[0:4], u[4:6], u[6:8], u[8:10], u[10:])
+}