add objectbox-c lib download script

Author: Ivan Dlugos

Makefile

@@ -32,4 +32,7 @@ clean:
 	rm -rf dist/
 	rm -rf *.egg-info
 
+get-lib:
+	python3 download-c-lib.py
+
 .PHONY: init test build benchmark

download-c-lib.py

@@ -0,0 +1,60 @@
+import urllib.request
+import tarfile
+import os
+
+version = "0.6.0"  # see objectbox/c.py required_version
+
+conan_repo = "https://dl.bintray.com/objectbox/conan/objectbox/objectbox-c"
+conan_channel = "testing"
+
+# map between ./objectbox/lib paths and hashes in the conan_repo
+# see https://github.com/objectbox/objectbox-c/blob/main/download.sh for the hashes
+out_dir = "objectbox/lib"
+file_hashes = {
+    # objectbox.h is common for all types, get it from the linux x86_64 distributable
+    "objectbox.h": "4db1be536558d833e52e862fd84d64d75c2b3656",
+
+    # linux
+    "x86_64/libobjectbox.so": "4db1be536558d833e52e862fd84d64d75c2b3656",
+    "armv7l/libobjectbox.so": "4a625f0bd5f477eacd9bd35e9c44c834d057524b",
+    "armv6l/libobjectbox.so": "d42930899c74345edc43f8b7519ec7645c13e4d8",
+
+    # mac
+    "x86_64/libobjectbox.dylib": "46f53f156846659bf39ad6675fa0ee8156e859fe",
+
+    # windows
+    "AMD64/objectbox.dll": "ca33edce272a279b24f87dc0d4cf5bbdcffbc187",
+}
+
+
+def url_for(rel_path: str) -> str:
+    return conan_repo + "/" + version + "/" + conan_channel + "/0/package/" \
+           + file_hashes[rel_path] + "/0/conan_package.tgz"
+
+
+def fullmkdir(path: str):
+    if not os.path.exists(path):
+        os.makedirs(path)
+
+
+def download(rel_path: str):
+    basename = os.path.basename(rel_path)
+    archive_dir = "include" if basename.endswith(".h") else "lib"
+    out_path = out_dir + "/" + rel_path
+
+    print("Downloading", out_path)
+    fullmkdir(os.path.dirname(out_path))
+
+    # Download the file from `url`, save it in a temporary directory and get the path to it (e.g. '/tmp/tmpb48zma')
+    tmp_file, headers = urllib.request.urlretrieve(url_for(rel_path))
+
+    # extract the file
+    archive = tarfile.open(tmp_file, mode='r:gz')
+    archived_file = archive.extractfile(archive_dir + "/" + basename)
+    with open(out_path, 'wb') as file:
+        file.writelines(archived_file.readlines())
+
+
+# execute the download for each item in the file hashes
+for key in file_hashes:
+    download(key)