[PATCH] Add support for TZ names with <> in tzset

Howdy all,

Attached is a patch which extends the tzset() function to support a format
for "unnamed" TZ environment timezones which use "<+/-nn>" as the timezone
name instead of an alphabetic name.  These are supported in glibc and are
present in several major TZ databases that we use on the ESP8266 Arduino
core.  For example, 

> #define TZ_Africa_Casablanca	  "<+01>-1"

The existing tzset sscanf format string breaks at the first "+", assuming
it's the
beginning of the offset.  This patch special-cases names beginning with "<"
to
circumvent the issue.

Signed-off-by: Earle F. Philhower, III   <[email protected]>

---
 newlib/libc/time/tzset_r.c | 46 ++++++++++++++++++++++++++++++--------
 1 file changed, 37 insertions(+), 9 deletions(-)

diff --git a/newlib/libc/time/tzset_r.c b/newlib/libc/time/tzset_r.c
index 9e0cf834b..5b8b692ee 100644
--- a/newlib/libc/time/tzset_r.c
+++ b/newlib/libc/time/tzset_r.c
@@ -45,8 +45,19 @@ _tzset_unlocked_r (struct _reent *reent_ptr)
   if (*tzenv == ':')
     ++tzenv;

-  if (sscanf (tzenv, "%10[^0-9,+-]%n", __tzname_std, &n) <= 0)
-    return;
+  if (tzenv[0] == '<')
+    {
+      /* This is of the form "<[+-]nn>" so needs a different parsing */
+      if (sscanf (tzenv, "%9[^>]>%n", __tzname_std, &n) <= 0)
+        return;
+      /* Include the final > */
+      strcat (__tzname_std, ">");
+    }
+  else
+    {
+      if (sscanf (tzenv, "%10[^0-9,+-]%n", __tzname_std, &n) <= 0)
+        return;
+    }

   tzenv += n;

@@ -69,15 +80,32 @@ _tzset_unlocked_r (struct _reent *reent_ptr)
   _tzname[0] = __tzname_std;
   tzenv += n;

-  if (sscanf (tzenv, "%10[^0-9,+-]%n", __tzname_dst, &n) <= 0)
-    { /* No dst */
-      _tzname[1] = _tzname[0];
-      _timezone = tz->__tzrule[0].offset;
-      _daylight = 0;
-      return;
+  if (tzenv[0] == '<')
+    {
+      /* This is of the form "<[+-]nn>" so needs a different parsing */
+      if (sscanf (tzenv, "%9[^>]>%n", __tzname_dst, &n) <= 0)
+        { /* No dst */
+          _tzname[1] = _tzname[0];
+          _timezone = tz->__tzrule[0].offset;
+          _daylight = 0;
+          return;
+        }
+      /* Include the final > */
+      strcat (__tzname_dst, ">");
+      _tzname[1] = __tzname_dst;
     }
   else
-    _tzname[1] = __tzname_dst;
+    {
+      if (sscanf (tzenv, "%10[^0-9,+-]%n", __tzname_dst, &n) <= 0)
+        { /* No dst */
+          _tzname[1] = _tzname[0];
+          _timezone = tz->__tzrule[0].offset;
+          _daylight = 0;
+          return;
+        }
+      else
+        _tzname[1] = __tzname_dst;
+    }

   tzenv += n;

--
2.17.1