pkuuid.h: first-pass + bump version to 0.4.1

1 files changed, 21 insertions, 0 deletions

diff --git a/pk.h.in b/pk.h.in
index db5a720..94129ab 100644
--- a/pk.h.in
+++ b/pk.h.in
@@ -184,6 +184,24 @@
 * `pk_tmr.e` end the end time.
 * You could then call the `pk_tmr_duration...` convenience macros as needed.
 *
+********************************************************************************
+* pkuuid.h: define PK_IMPL_UUID before including pk.h to enable ad-hoc.
+*
+* Provides a 16-byte unsigned char array struct for uuids.
+*
+* The following definitions (shown with defaults) can be overridden:
+* PK_UUID_CLOCK              CLOCK_TAI      (preferred, if available)
+* PK_UUID_CLOCK              CLOCK_REALTIME (fallback)
+*
+* The `PK_UUID_CLOCK` macro has minimal built-in fallback logic.
+* The uuidv7 specification states that the timestamp portion of the uuid must be
+*  a unix epoch, leap seconds EXCLUDED. Only `CLOCK_TAI` meets this requirement
+*  on Linux.
+*
+* Note that this currectly calls `srand()` once at startup, and calls `rand()`
+*  2 times for each uuidv7 to fill 74 bits with random data (with an XOR for the
+*  remaining 10 bits).
+*
 *******************************************************************************/
 
 #define PK_VERSION "@@PK_VERSION@@"
@@ -207,4 +225,7 @@
 # ifndef PK_IMPL_STN
 #  define PK_IMPL_STN
 # endif
+# ifndef PK_IMPL_UUID
+#  define PK_IMPL_UUID
+# endif
 #endif