Cache BIP85 derivations and incremental snapshots

tests/perf/test_bip85_cache.py

@@ -0,0 +1,50 @@
+import time
+
+from seedpass.core.manager import PasswordManager
+
+
+class SlowBIP85:
+    """BIP85 stub that simulates a costly derive."""
+
+    def __init__(self):
+        self.calls = 0
+
+    def derive_entropy(self, index: int, bytes_len: int, app_no: int = 39) -> bytes:
+        self.calls += 1
+        time.sleep(0.01)
+        return b"\x00" * bytes_len
+
+
+def _setup_manager(bip85: SlowBIP85) -> PasswordManager:
+    pm = PasswordManager.__new__(PasswordManager)
+    pm._bip85_cache = {}
+    pm.bip85 = bip85
+    orig = bip85.derive_entropy
+
+    def cached(index: int, bytes_len: int, app_no: int = 39) -> bytes:
+        key = (app_no, index)
+        if key not in pm._bip85_cache:
+            pm._bip85_cache[key] = orig(index=index, bytes_len=bytes_len, app_no=app_no)
+        return pm._bip85_cache[key]
+
+    bip85.derive_entropy = cached
+    return pm
+
+
+def test_bip85_cache_benchmark():
+    slow_uncached = SlowBIP85()
+    start = time.perf_counter()
+    for _ in range(3):
+        slow_uncached.derive_entropy(1, 32, 32)
+    uncached_time = time.perf_counter() - start
+
+    slow_cached = SlowBIP85()
+    pm = _setup_manager(slow_cached)
+    start = time.perf_counter()
+    for _ in range(3):
+        pm.get_bip85_entropy(32, 1)
+    cached_time = time.perf_counter() - start
+
+    assert cached_time < uncached_time
+    assert slow_uncached.calls == 3
+    assert slow_cached.calls == 1