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// Copyright 2016 Google Inc.  All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package uuid
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import (
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	"crypto/md5"
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	"crypto/sha1"
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	"hash"
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)
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// Well known namespace IDs and UUIDs
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var (
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	NameSpaceDNS  = Must(Parse("6ba7b810-9dad-11d1-80b4-00c04fd430c8"))
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	NameSpaceURL  = Must(Parse("6ba7b811-9dad-11d1-80b4-00c04fd430c8"))
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	NameSpaceOID  = Must(Parse("6ba7b812-9dad-11d1-80b4-00c04fd430c8"))
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	NameSpaceX500 = Must(Parse("6ba7b814-9dad-11d1-80b4-00c04fd430c8"))
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	Nil           UUID // empty UUID, all zeros
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	// The Max UUID is special form of UUID that is specified to have all 128 bits set to 1.
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	Max = UUID{
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		0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
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		0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
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	}
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)
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// NewHash returns a new UUID derived from the hash of space concatenated with
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// data generated by h.  The hash should be at least 16 byte in length.  The
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// first 16 bytes of the hash are used to form the UUID.  The version of the
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// UUID will be the lower 4 bits of version.  NewHash is used to implement
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// NewMD5 and NewSHA1.
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func NewHash(h hash.Hash, space UUID, data []byte, version int) UUID {
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	h.Reset()
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	h.Write(space[:]) //nolint:errcheck
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	h.Write(data)     //nolint:errcheck
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	s := h.Sum(nil)
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	var uuid UUID
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	copy(uuid[:], s)
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	uuid[6] = (uuid[6] & 0x0f) | uint8((version&0xf)<<4)
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	uuid[8] = (uuid[8] & 0x3f) | 0x80 // RFC 4122 variant
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	return uuid
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}
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// NewMD5 returns a new MD5 (Version 3) UUID based on the
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// supplied name space and data.  It is the same as calling:
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//
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//  NewHash(md5.New(), space, data, 3)
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func NewMD5(space UUID, data []byte) UUID {
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	return NewHash(md5.New(), space, data, 3)
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}
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// NewSHA1 returns a new SHA1 (Version 5) UUID based on the
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// supplied name space and data.  It is the same as calling:
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//
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//  NewHash(sha1.New(), space, data, 5)
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func NewSHA1(space UUID, data []byte) UUID {
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	return NewHash(sha1.New(), space, data, 5)
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}
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