{"id":1561,"date":"2017-09-05T15:32:22","date_gmt":"2017-09-05T15:32:22","guid":{"rendered":"http:\/\/ninecrows.com\/career\/?p=1561"},"modified":"2017-09-05T15:32:22","modified_gmt":"2017-09-05T15:32:22","slug":"the-humble-guiduuid","status":"publish","type":"post","link":"https:\/\/ninecrows.com\/career\/2017\/09\/05\/the-humble-guiduuid\/","title":{"rendered":"The humble GUID\/UUID&#8230;"},"content":{"rendered":"<p><a href=\"https:\/\/en.wikipedia.org\/wiki\/Universally_unique_identifier\">Guids<\/a> come up periodically. They&#8217;re the one obvious choice when a truly unique identifier is needed but you can&#8217;t have some application specific central registry (akin to Dicom-3 identifiers).<\/p>\n<p>They look like somewhat random strings of hex digits with dash separators but there is additional structure in there.<\/p>\n<p>The originated with <a href=\"https:\/\/en.wikipedia.org\/wiki\/Distributed_Computing_Environment\">OSF-DCE<\/a> (the one unix distributed computing environment). Microsoft borrowed parts of OSF-DCE when building COM and DCOM. Guids came along for the ride in this and became part of the windows infrastructure.<\/p>\n<p>In a recent discussion, a piece of code that loaded up &#8216;fake&#8217; Guids as small integers with zero fill came up. I refreshed my memory (they&#8217;re now defined in <a href=\"https:\/\/tools.ietf.org\/html\/rfc4122\">RFC4122<\/a>) and came to the conclusion that these aren&#8217;t well formed UUIDs at all. There are a couple of short bit fields within the body of a GUID that define the version and type of the GUID. These can&#8217;t be zero unless all bits are zero (the null GUID).<\/p>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Guids come up periodically. They&#8217;re the one obvious choice when a truly unique identifier is needed but you can&#8217;t have some application specific central registry (akin to Dicom-3 identifiers). They look like somewhat random strings of hex digits with dash separators but there is additional structure in there. The originated with OSF-DCE (the one unix &hellip; <a href=\"https:\/\/ninecrows.com\/career\/2017\/09\/05\/the-humble-guiduuid\/\" class=\"more-link\">Continue reading <span class=\"screen-reader-text\">The humble GUID\/UUID&#8230;<\/span> <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","enabled":false},"version":2}},"categories":[1],"tags":[],"class_list":["post-1561","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p7F2Qc-pb","jetpack-related-posts":[],"jetpack_likes_enabled":true,"_links":{"self":[{"href":"https:\/\/ninecrows.com\/career\/wp-json\/wp\/v2\/posts\/1561"}],"collection":[{"href":"https:\/\/ninecrows.com\/career\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ninecrows.com\/career\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ninecrows.com\/career\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ninecrows.com\/career\/wp-json\/wp\/v2\/comments?post=1561"}],"version-history":[{"count":1,"href":"https:\/\/ninecrows.com\/career\/wp-json\/wp\/v2\/posts\/1561\/revisions"}],"predecessor-version":[{"id":1562,"href":"https:\/\/ninecrows.com\/career\/wp-json\/wp\/v2\/posts\/1561\/revisions\/1562"}],"wp:attachment":[{"href":"https:\/\/ninecrows.com\/career\/wp-json\/wp\/v2\/media?parent=1561"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ninecrows.com\/career\/wp-json\/wp\/v2\/categories?post=1561"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ninecrows.com\/career\/wp-json\/wp\/v2\/tags?post=1561"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}