d-v-b · Sep 27, 2026 · Sep 27, 2026 · Sep 27, 2026 · Sep 27, 2026
diff --git a/.github/workflows/ci-i386.yml b/.github/workflows/ci-i386.yml
@@ -18,7 +18,6 @@ jobs:
       - name: Checkout source
         uses: actions/checkout@v6
         with:
-          submodules: recursive
           fetch-depth: 0 # required for version resolution
 
       - name: Setup Alpine Linux environment

diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
@@ -24,7 +24,6 @@ jobs:
       - name: Checkout source
         uses: actions/checkout@v6
         with:
-          submodules: recursive
           fetch-depth: 0 # required for version resolution
 
       - name: Set up Python
@@ -75,7 +74,6 @@ jobs:
       - name: Checkout source
         uses: actions/checkout@v6
         with:
-          submodules: recursive
           fetch-depth: 0
 
       - name: Set up Python
@@ -125,7 +123,6 @@ jobs:
       - name: Checkout source
         uses: actions/checkout@v6
         with:
-          submodules: recursive
           fetch-depth: 0 # required for version resolution
 
       - name: Set up Python

diff --git a/.github/workflows/wheel.yaml b/.github/workflows/wheel.yaml
@@ -32,7 +32,6 @@ jobs:
     steps:
       - uses: actions/checkout@v6
         with:
-          submodules: true
           fetch-depth: 0  # required for version resolution for nightly wheels
 
       - uses: pypa/cibuildwheel@v3.4.1
@@ -48,7 +47,6 @@ jobs:
     steps:
       - uses: actions/checkout@v6
         with:
-          submodules: true
           fetch-depth: 0
 
       - uses: actions/setup-python@v6

diff --git a/.gitignore b/.gitignore
@@ -99,4 +99,8 @@ ENV/
 .pixi/*
 *.egg-info
 pixi.lock
-uv.lock
+uv.lock
+# meson subprojects: only wraps and our overlays are tracked
+/subprojects/*
+!/subprojects/*.wrap
+!/subprojects/packagefiles/
diff --git a/.gitmodules b/.gitmodules
diff --git a/.readthedocs.yaml b/.readthedocs.yaml
@@ -1,8 +1,5 @@
 version: 2
 
-submodules:
-  include: all
-
 build:
   os: ubuntu-24.04
   tools:

diff --git a/LICENSES/BITSHUFFLE.txt b/LICENSES/BITSHUFFLE.txt
@@ -0,0 +1,21 @@
+Bitshuffle - Filter for improving compression of typed binary data.
+
+Copyright (c) 2014 Kiyoshi Masui (kiyo@physics.ubc.ca)
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
diff --git a/LICENSES/BLOSC.txt b/LICENSES/BLOSC.txt
@@ -0,0 +1,31 @@
+BSD License
+
+For Blosc - A blocking, shuffling and lossless compression library
+
+Copyright (c) 2009-2018 Francesc Alted <francesc@blosc.org>
+Copyright (c) 2019-present Blosc Development Team <blosc@blosc.org>
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+ * Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+
+ * Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+ * Neither the name Francesc Alted nor the names of its contributors may be used
+   to endorse or promote products derived from this software without specific
+   prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/LICENSES/FASTLZ.txt b/LICENSES/FASTLZ.txt
@@ -0,0 +1,20 @@
+FastLZ - Byte-aligned LZ77 compression library
+Copyright (C) 2005-2020 Ariya Hidayat <ariya.hidayat@gmail.com>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
diff --git a/LICENSES/LZ4.txt b/LICENSES/LZ4.txt
@@ -0,0 +1,24 @@
+LZ4 Library
+Copyright (c) 2011-2020, Yann Collet
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+* Redistributions of source code must retain the above copyright notice, this
+  list of conditions and the following disclaimer.
+
+* Redistributions in binary form must reproduce the above copyright notice, this
+  list of conditions and the following disclaimer in the documentation and/or
+  other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/LICENSES/ZLIB.txt b/LICENSES/ZLIB.txt
@@ -0,0 +1,22 @@
+Copyright notice:
+
+ (C) 1995-2026 Jean-loup Gailly and Mark Adler
+
+  This software is provided 'as-is', without any express or implied
+  warranty.  In no event will the authors be held liable for any damages
+  arising from the use of this software.
+
+  Permission is granted to anyone to use this software for any purpose,
+  including commercial applications, and to alter it and redistribute it
+  freely, subject to the following restrictions:
+
+  1. The origin of this software must not be misrepresented; you must not
+     claim that you wrote the original software. If you use this software
+     in a product, an acknowledgment in the product documentation would be
+     appreciated but is not required.
+  2. Altered source versions must be plainly marked as such, and must not be
+     misrepresented as being the original software.
+  3. This notice may not be removed or altered from any source distribution.
+
+  Jean-loup Gailly        Mark Adler
+  jloup@gzip.org          madler@alumni.caltech.edu
diff --git a/LICENSES/ZSTD.txt b/LICENSES/ZSTD.txt
@@ -0,0 +1,30 @@
+BSD License
+
+For Zstandard software
+
+Copyright (c) Meta Platforms, Inc. and affiliates. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+ * Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+
+ * Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+ * Neither the name Facebook, nor Meta, nor the names of its contributors may
+   be used to endorse or promote products derived from this software without
+   specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/c-blosc b/c-blosc
diff --git a/docs/contributing.md b/docs/contributing.md
@@ -62,13 +62,13 @@ You will need your own fork to work on the code. Go to the link above and hit
 the "Fork" button. Then clone your fork to your local machine:
 
 ```
-$ git clone --recursive git@github.com:your-user-name/numcodecs.git  # with ssh
+$ git clone git@github.com:your-user-name/numcodecs.git  # with ssh
 ```
 
 or:
 
 ```
-$ git clone --recursive https://github.com/your-user-name/numcodecs.git  # with https
+$ git clone https://github.com/your-user-name/numcodecs.git  # with https
 ```
 
 Then `cd` into the clone and add the `upstream` remote:
@@ -78,12 +78,11 @@ $ cd numcodecs
 $ git remote add upstream https://github.com/zarr-developers/numcodecs.git
 ```
 
-Note the ``--recursive`` flag is required to clone the ``c-blosc`` git submodule. If you
-forgot it, you can initialize it later with:
-
-```
-$ git submodule update --init --recursive
-```
+The C libraries numcodecs links against (c-blosc, zstd, lz4, zlib) are not stored in the
+repository. They are pinned in `subprojects/*.wrap` and downloaded by meson the first time
+you build, so the first build needs network access. To fetch them ahead of time, run
+`meson subprojects download`. Numcodecs-specific build files and patches for c-blosc live in
+`subprojects/packagefiles/c-blosc/`.
 
 ### Creating a development environment
 

diff --git a/docs/index.md b/docs/index.md
@@ -58,14 +58,11 @@ To work with Numcodecs source code in development, see the
 development environment with venv or uv.
 
 ```
-$ git clone --recursive https://github.com/zarr-developers/numcodecs.git
+$ git clone https://github.com/zarr-developers/numcodecs.git
 $ cd numcodecs
 $ pip install -e .[test,msgpack,zfpy]
 ```
 
-Note: if you prefer to use the GitHub CLI `gh` you will need to append `-- --recurse-submodules`
-to the clone command to everything works properly.
-
 To verify that Numcodecs has been fully installed (including the Blosc
 extension) run the test suite:
 

diff --git a/docs/release.md b/docs/release.md
@@ -14,6 +14,30 @@
 
 ## Unreleased
 
+### Enhancements
+
+* Blosc byte-shuffle and unshuffle now use NEON SIMD on aarch64 (Apple Silicon, AWS
+  Graviton, etc). c-blosc 1.x only ships SSE2/AVX2 kernels, so on ARM it previously fell
+  back to a scalar loop that dominated Blosc runtime. The NEON kernels are taken from
+  c-blosc2 and produce byte-identical output. On an Apple M5, decoding 1 MiB lz4+shuffle
+  chunks is ~5-6x faster and encoding ~2x faster. Controlled by the new `neon` meson
+  option (default `auto`).
+  By {user}`Davis Bennett <d-v-b>`.
+
+### Maintenance
+
+* **Replace the c-blosc git submodule with meson wrap subprojects.** zstd, lz4 and zlib
+  now come from [WrapDB](https://mesonbuild.com/Wrapdb-projects.html) and are pinned
+  independently of c-blosc (zstd 1.5.6 -> 1.5.7, zlib 1.3.1 -> 1.3.2). c-blosc is pinned
+  in `subprojects/c-blosc.wrap` to a trimmed source tarball generated by
+  `tools/make_c_blosc_tarball.py`, with its meson build and numcodecs patches in
+  `subprojects/packagefiles/c-blosc/`. Cloning no longer needs `--recursive`; the first
+  build downloads the sources, and the sdist includes them so it still builds offline.
+  Building from source now also requires a C++ compiler (zstd's meson build declares
+  C++). The `system_*` meson options are unchanged. License texts for the bundled
+  libraries, including the previously missing zstd license, are in `LICENSES/`.
+  By {user}`Davis Bennett <d-v-b>`.
+
 (release_0.17.0)=
 
 * Allow building against a system Zlib. Note, this is only required if blosc is still

diff --git a/meson.options b/meson.options
@@ -10,3 +10,5 @@ option('sse2', type: 'feature', value: 'auto',
        description: 'Enable SSE2 SIMD optimizations')
 option('avx2', type: 'feature', value: 'auto',
        description: 'Enable AVX2 SIMD optimizations')
+option('neon', type: 'feature', value: 'auto',
+       description: 'Enable NEON SIMD shuffle on aarch64')
diff --git a/pyproject.toml b/pyproject.toml
@@ -36,8 +36,7 @@ maintainers = [
 license = "MIT"
 license-files = [
     "LICENSE.txt",
-    "c-blosc/LICENSE.txt",
-    "c-blosc/LICENSES/*",
+    "LICENSES/*",
 ]
 
 [project.urls]
@@ -238,6 +237,13 @@ warn_redundant_casts = true
 warn_unused_ignores = true
 warn_unused_configs = true
 
+[tool.meson-python.args]
+# C libraries are built as static subprojects and linked into the extension
+# modules; don't install their headers, static libraries or pkg-config files.
+install = ["--skip-subprojects"]
+# Ship the subproject sources in the sdist so it builds without network access.
+dist = ["--include-subprojects"]
+
 [tool.uv]
 # meson-python editable installs require build deps (ninja, meson) at runtime for
 # auto-rebuild on import. Skip build isolation so the venv's ninja is used.