some caching work

hashchecking needs to be checked to see if it's still OK
timestamp checking should involved the timestamps from inside the region
file, not of the region file itself.

chunk.py

@@ -129,7 +129,6 @@ fluid_blocks = set([8,9,10,11])
 nospawn_blocks = set([20,44])
 
 def find_oldimage(chunkXY, cached, cave):
-# TODO update this
     blockid = "%d.%d" % chunkXY
 
     # Get the name of the existing image.
@@ -145,7 +144,14 @@ def find_oldimage(chunkXY, cached, cave):
          logging.debug("Found cached image {0}".format(oldimg))
     return oldimg, oldimg_path
 
-def check_cache(chunkfile, oldimg):
+def check_cache(world, chunkXY, oldimg):
+    """Returns True is oldimg is OK to use (i.e. not stale)"""
+# TODO read to the region file and get the timestamp??
+# TODO currently, just use the mtime on the region file
+# TODO (which will cause a single chunk update to invalidate everything in the region
+
+    chunkfile = os.path.join(world.worlddir, "region", "r.%d.%d.mcr" % (chunkXY[0]%64, chunkXY[1]%64))
+    #logging.debug("checking cache  %s against %s", chunkfile, oldimg[1])
     try:
         if oldimg[1] and os.path.getmtime(chunkfile) <= os.path.getmtime(oldimg[1]):
             return True
@@ -504,6 +510,7 @@ class ChunkRenderer(object):
                 # hashes match.
                 # Before we return it, update its mtime so the next round
                 # doesn't have to check the hash
+                # TODO fix up hash checking
                 os.utime(dest_path, None)
                 logging.debug("Using cached image")
                 return dest_path