Add collation version support to querylocale(3).

Provide a way to ask for an opaque version string for a locale_t, so
that potential changes in sort order can be detected.  Similar to
ICU's ucol_getVersion() and Windows' GetNLSVersionEx(), this API is
intended to allow databases to detect when text order-based indexes
might need to be rebuilt.

The CLDR version is extracted from CLDR source data by the Makefile
under tools/tools/locale, written into the machine-generated Makefile
under shared/colldef, passed to localedef -V, and then written into
LC_COLLATE file headers.  The initial version is 34.0.
tools/tools/locale was recently updated to pull down 35.0, but the
output hasn't been committed under share/colldef yet, so that will
provide the first observable change when it happens.  Other versioning
schemes are possible in future, because the format is unspecified.

Reviewed by:	bapt, 0mp, kib, yuripv (albeit a long time ago)
Differential Revision:	https://reviews.freebsd.org/D17166

1 files changed, 26 insertions, 6 deletions

diff --git a/lib/libc/locale/querylocale.3 b/lib/libc/locale/querylocale.3
index d1bb688ed907..ecafee49a712 100644
--- a/lib/libc/locale/querylocale.3
+++ b/lib/libc/locale/querylocale.3
@@ -27,12 +27,12 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd May 3, 2013
+.Dd November 8, 2020
 .Dt QUERYLOCALE 3
 .Os
 .Sh NAME
 .Nm querylocale
-.Nd Look up the locale name for a specified category
+.Nd Look up the locale name or version for a specified category
 .Sh LIBRARY
 .Lb libc
 .Sh SYNOPSIS
@@ -40,11 +40,22 @@
 .Ft const char *
 .Fn querylocale "int mask" "locale_t locale"
 .Sh DESCRIPTION
-Returns the name of the locale for the category specified by
+Returns the name or version of the locale for the category specified by
 .Fa mask .
-This possible values for the mask are the same as those in
-.Xr newlocale 3 .
-If more than one bit in the mask is set, the returned value is undefined.
+The possible values for the mask are the same as those in
+.Xr newlocale 3 ,
+when requesting the locale name.
+Specify the bitwise OR of
+.Fa LC_VERSION_MASK
+and another mask value to request a version string.
+Version strings can be compared to detect changes to the locale's definition.
+The structure of the version string is unspecified.
+Currently, version information is only available for
+.Fa LC_COLLATE_MASK ,
+and an empty string is returned for other categories.
+If more than one bit in the mask is set, not counting
+.Fa LC_VERSION_MASK ,
+the returned value is undefined.
 .Sh SEE ALSO
 .Xr duplocale 3 ,
 .Xr freelocale 3 ,
@@ -52,3 +63,12 @@ If more than one bit in the mask is set, the returned value is undefined.
 .Xr newlocale 3 ,
 .Xr uselocale 3 ,
 .Xr xlocale 3
+.Sh HISTORY
+The
+.Fn querylocale
+function first appeared in
+.Fx 9.1 ,
+and is based on the function of the same name in Darwin.
+.Fa LC_VERSION_MASK
+first appeared in
+.Fx 13.0 .