terom@166: 
terom@166: import pypngtile
terom@166: 
terom@166: import os.path
terom@166: import threading
terom@166: 
terom@166: class Error (Exception):
terom@166:     pass
terom@166: 
terom@166: class NotFound (KeyError):
terom@166:     pass
terom@166: 
terom@166: class InvalidImage (Exception):
terom@166:     pass
terom@166: 
terom@166: class UncachedImage (Exception):
terom@166:     pass
terom@166: 
terom@166: class PNGTileStore (object):
terom@166:     """
terom@166:         Access pypngtile.Image's on a filesystem.
terom@166:         
terom@166:         Intended to be threadsafe for open()
terom@166:     """
terom@166: 
terom@166:     IMAGE_TYPES = (
terom@166:         'png',
terom@166:     )
terom@166: 
terom@166:     def __init__ (self, image_root):
terom@166:         if not os.path.isdir(image_root) :
terom@166:             raise Error("Given image_root does not exist: {image_root}".format(image_root=image_root))
terom@166: 
terom@166:         self.image_root = os.path.abspath(image_root)
terom@166:         
terom@166:         # cache opened Images
terom@166:         self.images = { }
terom@166:         self.images_lock = threading.Lock()
terom@166: 
terom@166:     def lookup (self, url):
terom@166:         """
terom@166:             Lookup image by request path.
terom@166: 
terom@166:             Returns name, path, type. For dirs, type will be None.
terom@166: 
terom@166:             Raises Error, NotFound, InvalidImage
terom@166: 
terom@166:             Threadless.
terom@166:         """
terom@166: 
terom@166:         if not os.path.isdir(self.image_root):
terom@166:             raise Error("Server image_root has gone missing")
terom@166:     
terom@166:         # path to image
terom@166:         name = url.lstrip('/')
terom@166:         
terom@166:         # build absolute path
terom@166:         path = os.path.abspath(os.path.join(self.image_root, name))
terom@166: 
terom@166:         # ensure the path points inside the data root
terom@166:         if not path.startswith(self.image_root):
terom@166:             raise NotFound(name)
terom@166:         
terom@166:         if not os.path.exists(path):
terom@166:             raise NotFound(name)
terom@166:         
terom@166:         # determine time
terom@166:         if os.path.isdir(path):
terom@166:             return name, path, None
terom@166:         else:
terom@166:             basename, type = path.rsplit('.', 1)
terom@166: 
terom@166:             if type not in self.IMAGE_TYPES:
terom@166:                 raise InvalidImage(name)
terom@166:  
terom@166:             return name, path, type
terom@166: 
terom@166:     def list (self, url):
terom@166:         """
terom@166:             Yield a series of valid sub-names for the given directory:
terom@166:                 foo.type
terom@166:                 foo/
terom@166:             
terom@166:             The yielded items should be sorted before use.
terom@166:         """
terom@166: 
terom@166:         name, root, type = self.lookup(url)
terom@166: 
terom@166:         if type:
terom@166:             raise InvalidImage(name)
terom@166: 
terom@166:         for name in os.listdir(root):
terom@166:             path = os.path.join(root, name)
terom@166: 
terom@166:             # skip dotfiles
terom@166:             if name.startswith('.'):
terom@166:                 continue
terom@166:             
terom@166:             # show dirs
terom@166:             if os.path.isdir(path):
terom@166:                 if not os.access(path, os.R_OK):
terom@166:                     # skip inaccessible dirs
terom@166:                     continue
terom@166: 
terom@166:                 yield name + '/'
terom@166: 
terom@166:             # examine ext
terom@166:             if '.' in name:
terom@166:                 name_base, name_type = name.rsplit('.', 1)
terom@166:             else:
terom@166:                 name_base = name
terom@166:                 name_type = None
terom@166: 
terom@166:             # show .png files with a .cache file
terom@166:             if name_type in self.IMAGE_TYPES and os.path.exists(os.path.join(root, name_base + '.cache')):
terom@166:                 yield name
terom@166: 
terom@166:     def open (self, url):
terom@166:         """
terom@166:             Return Image object for given URL.
terom@166: 
terom@166:             Raises UncachedImage, pypngtile.Error
terom@166: 
terom@166:             Threadsafe.
terom@166:         """
terom@166: 
terom@166:         name, path, type = self.lookup(url)
terom@166: 
terom@166:         if not type:
terom@166:             raise InvalidImage(name)
terom@166: 
terom@166:         # get Image object
terom@166:         with self.images_lock:
terom@166:             image = self.images.get(path)
terom@166: 
terom@166:         if not image:
terom@166:             # open
terom@166:             image = pypngtile.Image(path)
terom@166: 
terom@166:             # check
terom@166:             if image.status() not in (pypngtile.CACHE_FRESH, pypngtile.CACHE_STALE):
terom@166:                 raise UncachedImage(name)
terom@166: 
terom@166:             # load
terom@166:             image.open()
terom@166: 
terom@166:             # cache
terom@166:             with self.images_lock:
terom@166:                 # we don't really care if some other thread raced us on the same Image and opened it up concurrently...
terom@166:                 # this is just a cache
terom@166:                 self.images[path] = image
terom@166:         
terom@166:         return image, name