chore(tools): device-QA DataStore config injector for the proxy app

tools/mk_datastore.py

@@ -0,0 +1,38 @@
+#!/usr/bin/env python3
+"""Build a Preferences-DataStore protobuf for the vojo proxy app from a ProxyState
+JSON on stdin; emit it base64-encoded on stdout (pipe through `base64 -d` via run-as).
+
+Wire layout (androidx.datastore.preferences):
+  PreferenceMap.preferences = field 1 (map) -> entry{ key=field1 string, value=field2 Value }
+  Value.string              = field 5
+"""
+import sys
+import base64
+
+
+def varint(n):
+    out = bytearray()
+    while True:
+        b = n & 0x7F
+        n >>= 7
+        if n:
+            out.append(b | 0x80)
+        else:
+            out.append(b)
+            return bytes(out)
+
+
+def ld(field, data):  # length-delimited field: tag=(field<<3)|2
+    return bytes([(field << 3) | 2]) + varint(len(data)) + data
+
+
+def main():
+    state_json = sys.stdin.read().strip().encode("utf-8")
+    value_msg = ld(5, state_json)                       # Value.string
+    entry = ld(1, b"state") + ld(2, value_msg)          # entry: key + Value
+    pref_map = ld(1, entry)                             # PreferenceMap.preferences
+    sys.stdout.write(base64.b64encode(pref_map).decode())
+
+
+if __name__ == "__main__":
+    main()