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Check-in Number:
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5394 | |
| Date: |
2006-May-10 11:07:33 (local)
2006-May-10 09:07:33 (UTC) |
| User: | rse |
| Branch: | |
| Comment: |
Added an "OVERVIEW" file which tries to give the "big picture"
about UUIDs and allows to survice during the nasty UUID bit fiddling. |
| Tickets: |
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| Inspections: |
|
| Files: |
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ossp-pkg/uuid/ChangeLog 1.113 -> 1.114
--- ChangeLog 2006/05/10 08:53:11 1.113
+++ ChangeLog 2006/05/10 09:07:33 1.114
@@ -13,6 +13,10 @@
Changes between 1.4.2 and 1.4.3 (13-Mar-2006 to XX-May-2006)
+ o Added an "OVERVIEW" file which tries to give the "big picture"
+ about UUIDs and allows to survice during the nasty UUID bit fiddling.
+ [Ralf S. Engelschall]
+
o Replaced "clock_seq_and_reserved" with
"clock_seq_high_and_reserved" in uuid.pod to already reflect the
description in the forthcoming RFC.
|
|
ossp-pkg/uuid/OVERVIEW -> 1.1
*** /dev/null Tue Apr 30 19:00:39 2024
--- - Tue Apr 30 19:01:22 2024
***************
*** 0 ****
--- 1,81 ----
+
+ _ ___ ____ ____ ____ _ _
+ |_|_ _ / _ \/ ___/ ___|| _ \ _ _ _ _(_) __| |
+ _|_||_| | | | \___ \___ \| |_) | | | | | | | | |/ _` |
+ |_||_|_| | |_| |___) |__) | __/ | |_| | |_| | | (_| |
+ |_|_|_| \___/|____/____/|_| \__,_|\__,_|_|\__,_|
+
+ OSSP uuid - Universally Unique Identifier
+
+ OVERVIEW
+
+ A UUID consists of 128 bits (16-octets) which are split into 6
+ octet-bounded unsigned integer fields ("time_low", "time_mid",
+ "time_hi_and_version", "clk_seq_hi_res", "clk_seq_low" and "node") and
+ where two fields are multiplexed with a fixed size 4-bit "version" and
+ a variable sized 2-3 bit "variant" field.
+
+ The UUID octets are counted from left to right 15 to 0 and the bits
+ in each octet are counted from left to right 7 to 0 (most significant
+ bit first, least significant bit last). The unsigned integer fields
+ formed out of multiple octets are stored in "network byte order" (most
+ significant octet first, least significant octet last). A UUID is
+ stored and transmitted from left to right, i.e., in "network byte
+ order" with the most significant octet first and the least significant
+ octet last.
+
+ Illustration 1:
+ (single octet array, less compact, more annotations)
+
+
+ Bits: [4] [2-3]
+ Field: version variant
+ MSO -->| |<-- -->| |<-- LSO
+ \ | | | | /
+ Octet: 15 14 13 12 11 10 | |9 8 | | 7 6 5 4 3 2 1 0
+ +------++------++------++------++------++------++------++------++------++------++------++------++------++------++------++------+
+ UUID: | || || || || || |#### || |##: || || || || || || || |
+ +------++------++------++------++------++------++------++------++------++------++------++------++------++------++------++------+
+ Bit: 76543210765432107654321076543210765432107654321076543210765432107654321076543210765432107654321076543210765432107654321076543210
+ /| || || || || || |\
+ MSB | || || || || || | LSB
+ |<---------------------------->||<------------>||<------------>||<---->||<---->||<-------------------------------------------->|
+ time_hi clk_seq clk_seq
+ Field: time_low time_mid _and_version _hi_res _low node
+ Bits: [32] [16] [16] [5-6] [8] [48]
+
+
+ Illustration 2:
+ (two octet arrays, more compact, less annotations)
+
+ [4]
+ version
+ -->| |<--
+ | |
+ | | [16]
+ [32] [16] | |time_hi
+ time_low time_mid | _and_version
+ |<---------------------------->||<------------>||<------------>|
+ | MSO || || | |
+ | / || || | |
+ | 15 14 13 12 || 11 10 || |9 8 |
+ 7654321076543210765432107654321076543210765432107654321076543210
+ /+------++------++------++------++------++------++------++------+~
+ MSB | || || || || || |#### || | ...
+ +------++------++------++------++------++------++------++------+~
+ ~+------++------++------++------++------++------++------++------+
+ ... ##: || || || || || || || | LSB
+ ~+------++------++------++------++------++------++------++------+/
+ 7654321076543210765432107654321076543210765432107654321076543210
+ | | 7 || 6 || 5 4 3 2 1 0 |
+ | | || || / |
+ | | || || LSO |
+ |<---->||<---->||<-------------------------------------------->|
+ |clk_seq clk_seq node
+ |_hi_res _low [48]
+ |[5-6] [8]
+ | |
+ -->| |<--
+ variant
+ [2-3]
+
|
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