Fix tzdata update tools for 'backzone'.

To maintain the status quo, we need to pull in backzone file. This file
can't be built on its own, so the easiest fix is to give zic(1) all the
files at once.

We also now have a situation where we have links to links, so we need to
dereference them until we find actual data.

Bug: 18330681

(cherry picked from commit 2c2463bd30)

Change-Id: I654b80518a7144038d8b3ea7223f49e2b1d2ad13

libc/tools/zoneinfo/ZoneCompactor.java

@@ -132,9 +132,15 @@ public class ZoneCompactor {
         throw new RuntimeException("zone filename too long: " + zoneName.length());
       }
 
+      // Follow the chain of links to work out where the real data for this zone lives.
+      String actualZoneName = zoneName;
+      while (links.get(actualZoneName) != null) {
+        actualZoneName = links.get(actualZoneName);
+      }
+
       f.write(toAscii(new byte[MAXNAME], zoneName));
-      f.writeInt(offsets.get(zoneName));
+      f.writeInt(offsets.get(actualZoneName));
-      f.writeInt(lengths.get(zoneName));
+      f.writeInt(lengths.get(actualZoneName));
       f.writeInt(0); // Used to be raw GMT offset. No longer used.
     }
 

libc/tools/zoneinfo/update-tzdata.py

@@ -13,8 +13,11 @@ import sys
 import tarfile
 import tempfile
 
-regions = ['africa', 'antarctica', 'asia', 'australasia', 'backward',
+regions = ['africa', 'antarctica', 'asia', 'australasia',
-           'etcetera', 'europe', 'northamerica', 'southamerica']
+           'etcetera', 'europe', 'northamerica', 'southamerica',
+           # These two deliberately come last so they override what came
+           # before (and each other).
+           'backward', 'backzone' ]
 
 def CheckDirExists(dir, dirname):
   if not os.path.isdir(dir):
@@ -49,16 +52,16 @@ def WriteSetupFile():
       fields = line.split()
       if fields:
         if fields[0] == 'Link':
-          links.append('%s %s %s\n' % (fields[0], fields[1], fields[2]))
+          links.append('%s %s %s' % (fields[0], fields[1], fields[2]))
           zones.append(fields[2])
         elif fields[0] == 'Zone':
           zones.append(fields[1])
   zones.sort()
 
   setup = open('setup', 'w')
-  for link in links:
+  for link in sorted(set(links)):
-    setup.write(link)
+    setup.write('%s\n' % link)
-  for zone in zones:
+  for zone in sorted(set(zones)):
     setup.write('%s\n' % zone)
   setup.close()
 
@@ -165,9 +168,10 @@ def BuildBionicToolsAndData(data_filename):
 
   print 'Calling zic(1)...'
   os.mkdir('data')
-  for region in regions:
+  zic_inputs = [ 'extracted/%s' % x for x in regions ]
-    if region != 'backward':
+  zic_cmd = ['zic', '-d', 'data' ]
-      subprocess.check_call(['zic', '-d', 'data', 'extracted/%s' % region])
+  zic_cmd.extend(zic_inputs)
+  subprocess.check_call(zic_cmd)
 
   WriteSetupFile()