Add UnzipZarr processor & Update registry (#47)

pop_tools/data_registry.txt

@@ -10,3 +10,4 @@ g.e20.G.TL319_t13.control.001_hfreq.nc 439eb1abf14737341ead088bfd9a3c1b795dc1f79
 g.e20.G.TL319_t13.control.001_hfreq-coarsen.nc 145659813daf1a607d0857c10699c721693333e39aeb270e116103185b7236ae
 Pac_POP0.1_JRA_IAF_1993-12-6-test.nc fc9c649428c1e62108fad00644805130f58e4063e0219ed677a357c077886f8e
 Pac_grid_pbc_1301x305x62.tx01_62l.2013-07-13.nc 9ead77ee8b1e352c9b0316664b3bfe9b84e322ca785bfd9a024da54a2b6dc60e
+comp-grid.tx9.1v3.20170718.zarr.zip 2c1cd41c1c803c0565bc6120268aac728757207963386b727f00b822b81155da

pop_tools/datasets.py

@@ -3,6 +3,7 @@
 """
 
 import os
+from pathlib import Path
 
 import pkg_resources
 import pooch
@@ -12,5 +13,44 @@
     version_dev='master',
     base_url='ftp://ftp.cgd.ucar.edu/archive/aletheia-data/cesm-data/ocn/',
 )
-
 DATASETS.load_registry(pkg_resources.resource_stream('pop_tools', 'data_registry.txt'))
+
+
+class UnzipZarr(pooch.processors.Unzip):
+    """
+    Processor that unpacks a zarr store zip archive and
+    returns the zarr store path.
+    """
+
+    def __call__(self, fname, action, pooch):
+        """
+        Extract all files from the given archive.
+        Parameters
+        ----------
+        fname : str
+            Full path of the zipped file in local storage.
+        action : str
+            Indicates what action was taken by :meth:`pooch.Pooch.fetch`:
+            * ``"download"``: File didn't exist locally and was downloaded
+            * ``"update"``: Local file was outdated and was re-download
+            * ``"fetch"``: File exists and is updated so it wasn't downloaded
+        pooch : :class:`pooch.Pooch`
+            The instance of :class:`pooch.Pooch` that is calling this.
+        Returns
+        -------
+        zarr_store : str
+            A full path to a zarr store in the extracted archive.
+        """
+        extract_dir = fname + self.suffix
+        if action in ('update', 'download') or not os.path.exists(extract_dir):
+            # Make sure that the folder with the extracted files exists
+            if not os.path.exists(extract_dir):
+                os.makedirs(extract_dir)
+            self._extract_file(fname, extract_dir)
+        # Get a list of all file names (including subdirectories) in our folder
+        # of unzipped files.
+        fnames = [
+            os.path.join(path, fname) for path, _, files in os.walk(extract_dir) for fname in files
+        ]
+        # Return the path of the zarr store
+        return Path(sorted(fnames)[0]).parent.as_posix()