emacs里的uuid生成函数

Table of Contents

uuid这种不依赖中心化生成的唯一ID，在emacs里的两种实现。

自己构建

(defun generate-uuid ()
  (let ((random-bytes (make-vector 16 0)))
    (dotimes (i 16)
      (aset random-bytes i (random 256)))
    (aset random-bytes 6 (logior (logand (aref random-bytes 6) 15) 64)) ; Version 4
    (aset random-bytes 8 (logior (logand (aref random-bytes 8) 63) 128)) ; Variant 10
    (format "%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x"
            (aref random-bytes 0) (aref random-bytes 1) (aref random-bytes 2) (aref random-bytes 3)
            (aref random-bytes 4) (aref random-bytes 5) (aref random-bytes 6) (aref random-bytes 7)
            (aref random-bytes 8) (aref random-bytes 9) (aref random-bytes 10) (aref random-bytes 11)
            (aref random-bytes 12) (aref random-bytes 13) (aref random-bytes 14) (aref random-bytes 15))))

生成一个 16 字节的初始向量，所有元素初始为 0，然后生成16字节的随机字节。 

(let ((random-bytes (make-vector 16 0)))

(dotimes (i 16)
  (aset random-bytes i (random 256)))

设置第7字节的版本位和第9字节的变体位。 

(aset random-bytes 6 (logior (logand (aref random-bytes 6) 15) 64))
(aset random-bytes 8 (logior (logand (aref random-bytes 8) 63) 128))

最后就是格式化输出，组成xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx这种标准格式。 

(format "%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x"
  (aref random-bytes 0)  (aref random-bytes 1)  (aref random-bytes 2)  (aref random-bytes 3)
  (aref random-bytes 4)  (aref random-bytes 5)
  (aref random-bytes 6)  (aref random-bytes 7)
  (aref random-bytes 8)  (aref random-bytes 9)
  (aref random-bytes 10) (aref random-bytes 11) (aref random-bytes 12) (aref random-bytes 13)
  (aref random-bytes 14) (aref random-bytes 15)))

这种实现符合UUID v4的标准，不过自带的random可能不够安全，你也可以通过外部的随机数生成器来进行扩展。

自带的方式

(require 'org-id)
(let ((uuid (org-id-uuid)))
  )

org自带有一个org-id-uuid函数会返回uuid。

用途

我用来构建给org文件，生成一组标题、日期和ID的模板。 

(define-skeleton note-template
  "Insert a template for org notes with title, date, and UUID"
  "title:"
  > "#+TITLE: " (file-name-base buffer-file-name) "\n"
  > "#+DATE: " (current-time-string) "\n"
  > "#+ID: " (org-uuid-uuid) "\n"
  > "" \n
  > "" \n
  )