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#lang scheme
(require srfi/27)
;;From Gambit Scheme Released under the LGPL
;; UUID generation
;; See: http://www.ietf.org/rfc/rfc4122.txt
;;
;; Version 4 UUID, see section 4.4
(provide make-uuid
urn)
(define random-integer-65536
(let* ((rs (make-random-source))
(ri (random-source-make-integers rs)))
(random-source-randomize! rs)
(lambda ()
(ri 65536))))
(define (make-uuid)
(define hex
'#(#\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9 #\A #\B #\C #\D #\E #\F))
(let ((n1 (random-integer-65536))
(n2 (random-integer-65536))
(n3 (random-integer-65536))
(n4 (random-integer-65536))
(n5 (random-integer-65536))
(n6 (random-integer-65536))
(n7 (random-integer-65536))
(n8 (random-integer-65536)))
(string->symbol
(string
;; time_lo
(vector-ref hex (extract-bit-field 4 12 n1))
(vector-ref hex (extract-bit-field 4 8 n1))
(vector-ref hex (extract-bit-field 4 4 n1))
(vector-ref hex (extract-bit-field 4 0 n1))
(vector-ref hex (extract-bit-field 4 12 n2))
(vector-ref hex (extract-bit-field 4 8 n2))
(vector-ref hex (extract-bit-field 4 4 n2))
(vector-ref hex (extract-bit-field 4 0 n2))
#\-
;; time_mid
(vector-ref hex (extract-bit-field 4 12 n3))
(vector-ref hex (extract-bit-field 4 8 n3))
(vector-ref hex (extract-bit-field 4 4 n3))
(vector-ref hex (extract-bit-field 4 0 n3))
#\-
;; time_hi_and_version
(vector-ref hex #b0100)
(vector-ref hex (extract-bit-field 4 8 n4))
(vector-ref hex (extract-bit-field 4 4 n4))
(vector-ref hex (extract-bit-field 4 0 n4))
#\-
;; clock_seq_hi_and_reserved
(vector-ref hex (bitwise-ior (extract-bit-field 2 12 n5) #b1000))
(vector-ref hex (extract-bit-field 4 8 n5))
;; clock_seq_low
(vector-ref hex (extract-bit-field 4 4 n5))
(vector-ref hex (extract-bit-field 4 0 n5))
#\-
;; node
(vector-ref hex (extract-bit-field 4 12 n6))
(vector-ref hex (extract-bit-field 4 8 n6))
(vector-ref hex (extract-bit-field 4 4 n6))
(vector-ref hex (extract-bit-field 4 0 n6))
(vector-ref hex (extract-bit-field 4 12 n7))
(vector-ref hex (extract-bit-field 4 8 n7))
(vector-ref hex (extract-bit-field 4 4 n7))
(vector-ref hex (extract-bit-field 4 0 n7))
(vector-ref hex (extract-bit-field 4 12 n8))
(vector-ref hex (extract-bit-field 4 8 n8))
(vector-ref hex (extract-bit-field 4 4 n8))
(vector-ref hex (extract-bit-field 4 0 n8))))))
(define (extract-bit-field size position n)
(bitwise-and (bitwise-not (arithmetic-shift -1 size))
(arithmetic-shift n (- position))))
(define (urn)
(string-append "urn:uuid:"
(symbol->string (make-uuid))))
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