Ensure encode returns a ndarray

Standardize the output of the `encode` function a bit by ensuring it
returns an `ndarray`. This is done without copying as it only takes a
view onto the data. Has the advantage of leveraging objects under the
hood that might not appear as nice like objects' internal buffers
without impacting the user or unnecessarily copying the data to `bytes`.
Also makes it a bit easier to work with the output as users can do
anything they would normally want to with `ndarray`s.

Author: jakirkham

numcodecs/blosc.pyx

@@ -16,7 +16,7 @@ from cpython.bytes cimport PyBytes_FromStringAndSize, PyBytes_AS_STRING
 
 from .compat_ext cimport Buffer
 from .compat_ext import Buffer
-from .compat import PY2, text_type, ensure_contiguous_ndarray
+from .compat import PY2, text_type, ensure_ndarray, ensure_contiguous_ndarray
 from .abc import Codec
 
 
@@ -488,7 +488,8 @@ class Blosc(Codec):
 
     def encode(self, buf):
         buf = ensure_contiguous_ndarray(buf, self.max_buffer_size)
-        return compress(buf, self._cname_bytes, self.clevel, self.shuffle, self.blocksize)
+        out = compress(buf, self._cname_bytes, self.clevel, self.shuffle, self.blocksize)
+        return  ensure_ndarray(out)
 
     def decode(self, buf, out=None):
         buf = ensure_contiguous_ndarray(buf, self.max_buffer_size)

numcodecs/bz2.py

@@ -4,7 +4,7 @@
 
 
 from numcodecs.abc import Codec
-from numcodecs.compat import ndarray_copy, ensure_contiguous_ndarray
+from numcodecs.compat import ndarray_copy, ensure_ndarray, ensure_contiguous_ndarray
 
 
 class BZ2(Codec):
@@ -28,7 +28,7 @@ def encode(self, buf):
         buf = ensure_contiguous_ndarray(buf)
 
         # do compression
-        return _bz2.compress(buf, self.level)
+        return ensure_ndarray(_bz2.compress(buf, self.level))
 
     # noinspection PyMethodMayBeStatic
     def decode(self, buf, out=None):

numcodecs/gzip.py

@@ -5,7 +5,7 @@
 
 
 from .abc import Codec
-from .compat import ndarray_copy, ensure_contiguous_ndarray, PY2
+from .compat import ndarray_copy, ensure_ndarray, ensure_contiguous_ndarray, PY2
 
 
 class GZip(Codec):
@@ -38,9 +38,13 @@ def encode(self, buf):
                             mode='wb',
                             compresslevel=self.level) as compressor:
             compressor.write(buf)
-        compressed = compressed.getvalue()
 
-        return compressed
+        try:
+            compressed = compressed.getbuffer()
+        except AttributeError:  # pragma: py3 no cover
+            compressed = compressed.getvalue()
+
+        return ensure_ndarray(compressed)
 
     # noinspection PyMethodMayBeStatic
     def decode(self, buf, out=None):

numcodecs/lz4.pyx

@@ -13,7 +13,7 @@ from cpython.bytes cimport PyBytes_FromStringAndSize, PyBytes_AS_STRING
 
 from .compat_ext cimport Buffer
 from .compat_ext import Buffer
-from .compat import PY2, ensure_contiguous_ndarray
+from .compat import PY2, ensure_ndarray, ensure_contiguous_ndarray
 from .abc import Codec
 
 
@@ -219,7 +219,7 @@ class LZ4(Codec):
 
     def encode(self, buf):
         buf = ensure_contiguous_ndarray(buf, self.max_buffer_size)
-        return compress(buf, self.acceleration)
+        return ensure_ndarray(compress(buf, self.acceleration))
 
     def decode(self, buf, out=None):
         buf = ensure_contiguous_ndarray(buf, self.max_buffer_size)

numcodecs/lzma.py

@@ -15,7 +15,7 @@
 if _lzma:
 
     from .abc import Codec
-    from .compat import ndarray_copy, ensure_contiguous_ndarray
+    from .compat import ndarray_copy, ensure_ndarray, ensure_contiguous_ndarray
 
     # noinspection PyShadowingBuiltins
     class LZMA(Codec):
@@ -51,8 +51,8 @@ def encode(self, buf):
             buf = ensure_contiguous_ndarray(buf)
 
             # do compression
-            return _lzma.compress(buf, format=self.format, check=self.check,
-                                  preset=self.preset, filters=self.filters)
+            return ensure_ndarray(_lzma.compress(buf, format=self.format, check=self.check,
+                                                 preset=self.preset, filters=self.filters))
 
         def decode(self, buf, out=None):
 

numcodecs/vlen.pyx

@@ -13,7 +13,7 @@ import numpy as np
 from .abc import Codec
 from .compat_ext cimport Buffer
 from .compat_ext import Buffer
-from .compat import ensure_contiguous_ndarray
+from .compat import ensure_ndarray, ensure_contiguous_ndarray
 from cpython cimport (PyBytes_GET_SIZE, PyBytes_AS_STRING, PyBytes_Check,
                       PyBytes_FromStringAndSize, PyUnicode_AsUTF8String)
 from cpython.buffer cimport PyBUF_ANY_CONTIGUOUS
@@ -130,7 +130,7 @@ class VLenUTF8(Codec):
             memcpy(data, encv, l)
             data += l
 
-        return out
+        return ensure_ndarray(out)
 
     @cython.wraparound(False)
     @cython.boundscheck(False)

numcodecs/zlib.py

@@ -4,7 +4,7 @@
 
 
 from .abc import Codec
-from .compat import ndarray_copy, ensure_contiguous_ndarray
+from .compat import ndarray_copy, ensure_ndarray, ensure_contiguous_ndarray
 
 
 class Zlib(Codec):
@@ -28,7 +28,7 @@ def encode(self, buf):
         buf = ensure_contiguous_ndarray(buf)
 
         # do compression
-        return _zlib.compress(buf, self.level)
+        return ensure_ndarray(_zlib.compress(buf, self.level))
 
     # noinspection PyMethodMayBeStatic
     def decode(self, buf, out=None):

numcodecs/zstd.pyx

@@ -13,7 +13,7 @@ from cpython.bytes cimport PyBytes_FromStringAndSize, PyBytes_AS_STRING
 
 from .compat_ext cimport Buffer
 from .compat_ext import Buffer
-from .compat import ensure_contiguous_ndarray
+from .compat import ensure_ndarray, ensure_contiguous_ndarray
 from .abc import Codec
 
 
@@ -214,7 +214,7 @@ class Zstd(Codec):
 
     def encode(self, buf):
         buf = ensure_contiguous_ndarray(buf)
-        return compress(buf, self.level)
+        return ensure_ndarray(compress(buf, self.level))
 
     def decode(self, buf, out=None):
         buf = ensure_contiguous_ndarray(buf)