Move download.py functions to FetcherInterface

Make download_file and download_bytes functions part of
the FetcherInterface class. Remove download.py module.

Signed-off-by: Teodora Sechkova <[email protected]>

tuf/ngclient/fetcher.py

@@ -6,7 +6,15 @@
 
 # Imports
 import abc
-from typing import Iterator
+import logging
+import tempfile
+from contextlib import contextmanager
+from typing import IO, Iterator
+from urllib import parse
+
+from tuf import exceptions
+
+logger = logging.getLogger(__name__)
 
 
 # Classes
@@ -40,3 +48,51 @@ def fetch(self, url: str, required_length: int) -> Iterator[bytes]:
             A bytes iterator
         """
         raise NotImplementedError  # pragma: no cover
+
+    @contextmanager
+    def download_file(self, url: str, required_length: int) -> Iterator[IO]:
+        """Opens a connection to 'url' and downloads the content
+        up to 'required_length'.
+
+        Args:
+          url: a URL string that represents the location of the file.
+          required_length: an integer value representing the length of
+              the file or an upper boundary.
+
+        Raises:
+          DownloadLengthMismatchError: a mismatch of observed vs expected
+              lengths while downloading the file.
+
+        Yields:
+          A file object that points to the contents of 'url'.
+        """
+        # 'url.replace('\\', '/')' is needed for compatibility with
+        # Windows-based systems, because they might use back-slashes in place
+        # of forward-slashes. This converts it to the common format.
+        # unquote() replaces %xx escapes in a url with their single-character
+        # equivalent. A back-slash may beencoded as %5c in the url, which
+        # should also be replaced with a forward slash.
+        url = parse.unquote(url).replace("\\", "/")
+        logger.debug("Downloading: %s", url)
+
+        number_of_bytes_received = 0
+
+        with tempfile.TemporaryFile() as temp_file:
+            chunks = self.fetch(url, required_length)
+            for chunk in chunks:
+                temp_file.write(chunk)
+                number_of_bytes_received += len(chunk)
+            if number_of_bytes_received > required_length:
+                raise exceptions.DownloadLengthMismatchError(
+                    required_length, number_of_bytes_received
+                )
+            temp_file.seek(0)
+            yield temp_file
+
+    def download_bytes(self, url: str, required_length: int) -> bytes:
+        """Download bytes from given url
+
+        Returns the downloaded bytes, otherwise like download_file()
+        """
+        with self.download_file(url, required_length) as dl_file:
+            return dl_file.read()

tuf/ngclient/updater.py

@@ -15,11 +15,7 @@
 from securesystemslib import util as sslib_util
 
 from tuf import exceptions
-from tuf.ngclient._internal import (
-    download,
-    requests_fetcher,
-    trusted_metadata_set,
-)
+from tuf.ngclient._internal import requests_fetcher, trusted_metadata_set
 from tuf.ngclient.fetcher import FetcherInterface
 
 # Globals
@@ -35,7 +31,7 @@
 
 class Updater:
     """
-    An implemetation of the TUF client workflow.
+    An implementation of the TUF client workflow.
     Provides a public API for integration in client applications.
     """
 
@@ -207,8 +203,8 @@ def download_target(
 
         full_url = parse.urljoin(target_base_url, targetinfo["filepath"])
 
-        with download.download_file(
-            full_url, targetinfo["fileinfo"].length, self._fetcher
+        with self._fetcher.download_file(
+            full_url, targetinfo["fileinfo"].length
         ) as target_file:
             _check_file_length(target_file, targetinfo["fileinfo"].length)
             _check_hashes_obj(target_file, targetinfo["fileinfo"].hashes)
@@ -227,7 +223,7 @@ def _download_metadata(
         else:
             filename = f"{version}.{rolename}.json"
         url = parse.urljoin(self._metadata_base_url, filename)
-        return download.download_bytes(url, length, self._fetcher)
+        return self._fetcher.download_bytes(url, length)
 
     def _load_local_metadata(self, rolename: str) -> bytes:
         with open(os.path.join(self._dir, f"{rolename}.json"), "rb") as f: