Add zstd codec

docs/v3/codecs/zstd/v1.0.rst

@@ -0,0 +1,109 @@
+==========================
+ Zstd codec (version 1.0)
+==========================
+
+  **Editor's draft 26 July 2019**
+
+Specification URI:
+    https://zarr-specs.readthedocs.io/en/latest/v3/codecs/zstd/v1.0.html
+Corresponding ZEP:
+    `ZEP 1 — Zarr specification version 3 <https://zarr.dev/zeps/draft/ZEP0001.html>`_
+Issue tracking:
+    `GitHub issues <https://github.com/zarr-developers/zarr-specs/labels/codec>`_
+Suggest an edit for this spec:
+    `GitHub editor <https://github.com/zarr-developers/zarr-specs/blob/main/docs/v3/codecs/zstd/v1.0.rst>`_
+
+Copyright 2020 `Zarr core development team
+<https://github.com/orgs/zarr-developers/teams/core-devs>`_. This work
+is licensed under a `Creative Commons Attribution 3.0 Unported License
+<https://creativecommons.org/licenses/by/3.0/>`_.
+
+----
+
+
+Abstract
+========
+
+Defines a ``bytes -> bytes`` codec that applies zstd compression.
+
+
+Status of this document
+=======================
+
+.. warning::
+    This document is a draft for review and subject to changes.
+    It will become final when the `Zarr Enhancement Proposal (ZEP) 1 <https://zarr.dev/zeps/draft/ZEP0001.html>`_
+    is approved via the `ZEP process <https://zarr.dev/zeps/active/ZEP0000.html>`_.
+
+
+Document conventions
+====================
+
+Conformance requirements are expressed with a combination of
+descriptive assertions and [RFC2119]_ terminology. The key words
+"MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD",
+"SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in the normative
+parts of this document are to be interpreted as described in
+[RFC2119]_. However, for readability, these words do not appear in all
+uppercase letters in this specification.
+
+All of the text of this specification is normative except sections
+explicitly marked as non-normative, examples, and notes. Examples in
+this specification are introduced with the words "for example".
+
+
+Codec name
+==========
+
+The value of the ``name`` member in the codec object MUST be ``zstd``.
+
+
+Configuration parameters
+========================
+
+level:
+    An integer from -131072 to 22 which controls the speed and level
+    of compression (has no impact on decoding).  A value of 0 indicates to use
+    the default compression level.  Otherwise, a higher level is expected to
+    achieve a higher compression ratio at the cost of lower speed.
+
+checksum:
+    A boolean that indicates whether to store a checksum when writing that will
+    be verified when reading.
+
+For example, the array metadata below specifies that the compressor is the Zstd
+codec configured with a compression level of 1 and with the checksum stored::
+
+    {
+        "codecs": [{
+            "name": "zstd",
+            "configuration": {
+                "level": 1,
+                "checksum": true
+            }
+        }],
+    }
+
+
+Format and algorithm
+====================
+
+This is a ``bytes -> bytes`` codec.
+
+Encoded data should conform to the Zstandard file format [RFC8878]_.
+
+References
+==========
+
+.. [RFC2119] S. Bradner. Key words for use in RFCs to Indicate
+   Requirement Levels. March 1997. Best Current Practice. URL:
+   https://tools.ietf.org/html/rfc2119
+
+.. [RFC8878] Y. Collet. Zstandard Compression and the
+   'application/zstd' Media Type. Februrary 2021. Informational. URL:
+   https://tools.ietf.org/html/rfc8878
+
+Change log
+==========
+
+No changes yet.