feat(crypt): Add cryptography submodule

Author: Eta0

tensorizer/_crypt/__init__.py

@@ -0,0 +1,39 @@
+"""
+Internal cryptographic library for tensorizer.
+These functions are only meant to be used by tensorizer itself,
+and are not guaranteed to have a stable interface across versions.
+"""
+
+__all__ = (
+    "available",
+    "ChunkedEncryption",
+    "CryptographyError",
+    "crypto_pwhash_SALTBYTES",
+    "pwhash",
+    "random_bytes",
+)
+
+from ._exceptions import CryptographyError
+
+try:
+    from ._encryption import (
+        ChunkedEncryption,
+        SequentialEncryption,
+        crypto_pwhash_SALTBYTES,
+        pwhash,
+        random_bytes,
+    )
+
+    available: bool = True
+
+
+except (OSError, AttributeError):
+    available: bool = False
+
+    def __getattr__(name):
+        if name in __all__:
+            raise RuntimeError(
+                "Encryption module was not initialized,"
+                " make sure a recent version of libsodium is installed"
+            )
+        raise AttributeError(f"module {__name__!r} has no attribute {name!r}")