[fragment,aria2c] Generalize and refactor some code

2 files changed, 30 insertions, 42 deletions

diff --git a/yt_dlp/downloader/external.py b/yt_dlp/downloader/external.py
index a0d346c12..025eb38cb 100644
--- a/yt_dlp/downloader/external.py
+++ b/yt_dlp/downloader/external.py
@@ -6,7 +6,7 @@ import subprocess
 import sys
 import time
 
-from .common import FileDownloader
+from .fragment import FragmentFD
 from ..aes import aes_cbc_decrypt_bytes
 from ..compat import (
     compat_setenv,
@@ -30,7 +30,7 @@ from ..utils import (
 )
 
 
-class ExternalFD(FileDownloader):
+class ExternalFD(FragmentFD):
     SUPPORTED_PROTOCOLS = ('http', 'https', 'ftp', 'ftps')
     can_download_to_stdout = False
 
@@ -142,6 +142,7 @@ class ExternalFD(FileDownloader):
                     self.report_error('Giving up after %s fragment retries' % fragment_retries)
                     return -1
 
+            decrypt_fragment = self.decrypter(info_dict)
             dest, _ = sanitize_open(tmpfilename, 'wb')
             for frag_index, fragment in enumerate(info_dict['fragments']):
                 fragment_filename = '%s-Frag%d' % (tmpfilename, frag_index)
@@ -153,21 +154,7 @@ class ExternalFD(FileDownloader):
                         continue
                     self.report_error('Unable to open fragment %d' % frag_index)
                     return -1
-                decrypt_info = fragment.get('decrypt_info')
-                if decrypt_info:
-                    if decrypt_info['METHOD'] == 'AES-128':
-                        iv = decrypt_info.get('IV') or compat_struct_pack('>8xq', fragment['media_sequence'])
-                        decrypt_info['KEY'] = decrypt_info.get('KEY') or self.ydl.urlopen(
-                            self._prepare_url(info_dict, info_dict.get('_decryption_key_url') or decrypt_info['URI'])).read()
-                        encrypted_data = src.read()
-                        decrypted_data = aes_cbc_decrypt_bytes(encrypted_data, decrypt_info['KEY'], iv)
-                        dest.write(decrypted_data)
-                    else:
-                        fragment_data = src.read()
-                        dest.write(fragment_data)
-                else:
-                    fragment_data = src.read()
-                    dest.write(fragment_data)
+                dest.write(decrypt_fragment(fragment, src.read()))
                 src.close()
                 if not self.params.get('keep_fragments', False):
                     os.remove(encodeFilename(fragment_filename))
@@ -181,10 +168,6 @@ class ExternalFD(FileDownloader):
                 self.to_stderr(stderr.decode('utf-8', 'replace'))
         return p.returncode
 
-    def _prepare_url(self, info_dict, url):
-        headers = info_dict.get('http_headers')
-        return sanitized_Request(url, None, headers) if headers else url
-
 
 class CurlFD(ExternalFD):
     AVAILABLE_OPT = '-V'
@@ -518,7 +501,7 @@ class AVconvFD(FFmpegFD):
 _BY_NAME = dict(
     (klass.get_basename(), klass)
     for name, klass in globals().items()
-    if name.endswith('FD') and name != 'ExternalFD'
+    if name.endswith('FD') and name not in ('ExternalFD', 'FragmentFD')
 )
 
 
diff --git a/yt_dlp/downloader/fragment.py b/yt_dlp/downloader/fragment.py
index 10ab90ba6..ebdef27db 100644
--- a/yt_dlp/downloader/fragment.py
+++ b/yt_dlp/downloader/fragment.py
@@ -324,6 +324,29 @@ class FragmentFD(FileDownloader):
             'fragment_index': 0,
         })
 
+    def decrypter(self, info_dict):
+        _key_cache = {}
+
+        def _get_key(url):
+            if url not in _key_cache:
+                _key_cache[url] = self.ydl.urlopen(self._prepare_url(info_dict, url)).read()
+            return _key_cache[url]
+
+        def decrypt_fragment(fragment, frag_content):
+            decrypt_info = fragment.get('decrypt_info')
+            if not decrypt_info or decrypt_info['METHOD'] != 'AES-128':
+                return frag_content
+            iv = decrypt_info.get('IV') or compat_struct_pack('>8xq', fragment['media_sequence'])
+            decrypt_info['KEY'] = decrypt_info.get('KEY') or _get_key(info_dict.get('_decryption_key_url') or decrypt_info['URI'])
+            # Don't decrypt the content in tests since the data is explicitly truncated and it's not to a valid block
+            # size (see https://github.com/ytdl-org/youtube-dl/pull/27660). Tests only care that the correct data downloaded,
+            # not what it decrypts to.
+            if self.params.get('test', False):
+                return frag_content
+            return aes_cbc_decrypt_bytes(frag_content, decrypt_info['KEY'], iv)
+
+        return decrypt_fragment
+
     def download_and_append_fragments(self, ctx, fragments, info_dict, *, pack_func=None, finish_func=None):
         fragment_retries = self.params.get('fragment_retries', 0)
         is_fatal = (lambda idx: idx == 0) if self.params.get('skip_unavailable_fragments', True) else (lambda _: True)
@@ -369,26 +392,6 @@ class FragmentFD(FileDownloader):
                 return False, frag_index
             return frag_content, frag_index
 
-        _key_cache = {}
-
-        def _get_key(url):
-            if url not in _key_cache:
-                _key_cache[url] = self.ydl.urlopen(self._prepare_url(info_dict, url)).read()
-            return _key_cache[url]
-
-        def decrypt_fragment(fragment, frag_content):
-            decrypt_info = fragment.get('decrypt_info')
-            if not decrypt_info or decrypt_info['METHOD'] != 'AES-128':
-                return frag_content
-            iv = decrypt_info.get('IV') or compat_struct_pack('>8xq', fragment['media_sequence'])
-            decrypt_info['KEY'] = decrypt_info.get('KEY') or _get_key(info_dict.get('_decryption_key_url') or decrypt_info['URI'])
-            # Don't decrypt the content in tests since the data is explicitly truncated and it's not to a valid block
-            # size (see https://github.com/ytdl-org/youtube-dl/pull/27660). Tests only care that the correct data downloaded,
-            # not what it decrypts to.
-            if self.params.get('test', False):
-                return frag_content
-            return aes_cbc_decrypt_bytes(frag_content, decrypt_info['KEY'], iv)
-
         def append_fragment(frag_content, frag_index, ctx):
             if not frag_content:
                 if not is_fatal(frag_index - 1):
@@ -402,6 +405,8 @@ class FragmentFD(FileDownloader):
             self._append_fragment(ctx, pack_func(frag_content, frag_index))
             return True
 
+        decrypt_fragment = self.decrypter(info_dict)
+
         max_workers = self.params.get('concurrent_fragment_downloads', 1)
         if can_threaded_download and max_workers > 1: