add support for group metadata

Author: alimanfoo

zarr/meta.py

@@ -10,11 +10,14 @@
 from zarr.errors import MetadataError
 
 
-def decode_metadata(b):
+ZARR_FORMAT = 2
+
+
+def decode_array_metadata(b):
     s = text_type(b, 'ascii')
     meta = json.loads(s)
     zarr_format = meta.get('zarr_format', None)
-    if zarr_format != 1:
+    if zarr_format != ZARR_FORMAT:
         raise MetadataError('unsupported zarr format: %s' % zarr_format)
     try:
         meta = dict(
@@ -33,9 +36,9 @@ def decode_metadata(b):
         return meta
 
 
-def encode_metadata(meta):
+def encode_array_metadata(meta):
     meta = dict(
-        zarr_format=1,
+        zarr_format=ZARR_FORMAT,
         shape=meta['shape'],
         chunks=meta['chunks'],
         dtype=encode_dtype(meta['dtype']),
@@ -72,3 +75,28 @@ def _decode_dtype_descr(d):
 def decode_dtype(d):
     d = _decode_dtype_descr(d)
     return np.dtype(d)
+
+
+def decode_group_metadata(b):
+    s = text_type(b, 'ascii')
+    meta = json.loads(s)
+    zarr_format = meta.get('zarr_format', None)
+    if zarr_format != ZARR_FORMAT:
+        raise MetadataError('unsupported zarr format: %s' % zarr_format)
+    try:
+        meta = dict(
+            zarr_format=meta['zarr_format'],
+        )
+    except Exception as e:
+        raise MetadataError('error decoding metadata: %s' % e)
+    else:
+        return meta
+
+
+def encode_group_metadata(meta=None):
+    meta = dict(
+        zarr_format=ZARR_FORMAT,
+    )
+    s = json.dumps(meta, indent=4, sort_keys=True, ensure_ascii=True)
+    b = s.encode('ascii')
+    return b