Use more buffers (redux)

docs/release.rst

@@ -32,6 +32,12 @@ Release notes
 * Corrects handling of ``NaT`` in ``datetime64`` and ``timedelta64`` in various
   compressors (by :user:`John Kirkham <jakirkham>`; :issue:`127`, :issue:`131`).
 
+* Improvements to the compatibility layer used for normalising inputs to encode
+  and decode methods in most codecs. This removes unnecessary memory copies for
+  some codecs, and also simplifies the implementation of some codecs, improving
+  code readability and maintainability. By :user:`John Kirkham <jakirkham>` and
+  :user:`Alistair Miles <alimanfoo>`; :issue:`119`, :issue:`121`, :issue:`128`.
+
 .. _release_0.5.5:
 
 0.5.5

numcodecs/astype.py

@@ -4,7 +4,7 @@
 import numpy as np
 
 from .abc import Codec
-from .compat import buffer_copy, ndarray_from_buffer
+from .compat import ndarray_copy, ensure_ndarray
 
 
 class AsType(Codec):
@@ -49,8 +49,8 @@ def __init__(self, encode_dtype, decode_dtype):
 
     def encode(self, buf):
 
-        # view input data as 1D array
-        arr = ndarray_from_buffer(buf, self.decode_dtype)
+        # normalise input
+        arr = ensure_ndarray(buf).view(self.decode_dtype)
 
         # convert and copy
         enc = arr.astype(self.encode_dtype)
@@ -59,14 +59,14 @@ def encode(self, buf):
 
     def decode(self, buf, out=None):
 
-        # view encoded data as 1D array
-        enc = ndarray_from_buffer(buf, self.encode_dtype)
+        # normalise input
+        enc = ensure_ndarray(buf).view(self.encode_dtype)
 
         # convert and copy
         dec = enc.astype(self.decode_dtype)
 
         # handle output
-        out = buffer_copy(dec, out)
+        out = ndarray_copy(dec, out)
 
         return out