Move write_xattr to utils.py

There are some other places that use xattr functions. It's better to
move it to a common place so that others can use it.

youtube_dl/utils.py

@@ -42,6 +42,7 @@ from .compat import (
     compat_html_entities_html5,
     compat_http_client,
     compat_kwargs,
+    compat_os_name,
     compat_parse_qs,
     compat_shlex_quote,
     compat_socket_create_connection,
@@ -775,6 +776,25 @@ class ContentTooShortError(Exception):
         self.expected = expected
 
 
+class XAttrMetadataError(Exception):
+    def __init__(self, code=None, msg='Unknown error'):
+        super(XAttrMetadataError, self).__init__(msg)
+        self.code = code
+
+        # Parsing code and msg
+        if (self.code in (errno.ENOSPC, errno.EDQUOT) or
+                'No space left' in self.msg or 'Disk quota excedded' in self.msg):
+            self.reason = 'NO_SPACE'
+        elif self.code == errno.E2BIG or 'Argument list too long' in self.msg:
+            self.reason = 'VALUE_TOO_LONG'
+        else:
+            self.reason = 'NOT_SUPPORTED'
+
+
+class XAttrUnavailableError(Exception):
+    pass
+
+
 def _create_http_connection(ydl_handler, http_class, is_https, *args, **kwargs):
     # Working around python 2 bug (see http://bugs.python.org/issue17849) by limiting
     # expected HTTP responses to meet HTTP/1.0 or later (see also
@@ -3131,3 +3151,82 @@ def decode_png(png_data):
             current_row.append(color)
 
     return width, height, pixels
+
+
+def write_xattr(path, key, value):
+    # This mess below finds the best xattr tool for the job
+    try:
+        # try the pyxattr module...
+        import xattr
+
+        # Unicode arguments are not supported in python-pyxattr until
+        # version 0.5.0
+        # See https://github.com/rg3/youtube-dl/issues/5498
+        pyxattr_required_version = '0.5.0'
+        if version_tuple(xattr.__version__) < version_tuple(pyxattr_required_version):
+            # TODO: fallback to CLI tools
+            raise XAttrUnavailableError(
+                'python-pyxattr is detected but is too old. '
+                'youtube-dl requires %s or above while your version is %s. '
+                'Falling back to other xattr implementations' % (
+                    pyxattr_required_version, xattr.__version__))
+
+        try:
+            xattr.set(path, key, value)
+        except EnvironmentError as e:
+            raise XAttrMetadataError(e.errno, e.strerror)
+
+    except ImportError:
+        if compat_os_name == 'nt':
+            # Write xattrs to NTFS Alternate Data Streams:
+            # http://en.wikipedia.org/wiki/NTFS#Alternate_data_streams_.28ADS.29
+            assert ':' not in key
+            assert os.path.exists(path)
+
+            ads_fn = path + ':' + key
+            try:
+                with open(ads_fn, 'wb') as f:
+                    f.write(value)
+            except EnvironmentError as e:
+                raise XAttrMetadataError(e.errno, e.strerror)
+        else:
+            user_has_setfattr = check_executable('setfattr', ['--version'])
+            user_has_xattr = check_executable('xattr', ['-h'])
+
+            if user_has_setfattr or user_has_xattr:
+
+                value = value.decode('utf-8')
+                if user_has_setfattr:
+                    executable = 'setfattr'
+                    opts = ['-n', key, '-v', value]
+                elif user_has_xattr:
+                    executable = 'xattr'
+                    opts = ['-w', key, value]
+
+                cmd = ([encodeFilename(executable, True)] +
+                       [encodeArgument(o) for o in opts] +
+                       [encodeFilename(path, True)])
+
+                try:
+                    p = subprocess.Popen(
+                        cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE)
+                except EnvironmentError as e:
+                    raise XAttrMetadataError(e.errno, e.strerror)
+                stdout, stderr = p.communicate()
+                stderr = stderr.decode('utf-8', 'replace')
+                if p.returncode != 0:
+                    raise XAttrMetadataError(p.returncode, stderr)
+
+            else:
+                # On Unix, and can't find pyxattr, setfattr, or xattr.
+                if sys.platform.startswith('linux'):
+                    raise XAttrUnavailableError(
+                        "Couldn't find a tool to set the xattrs. "
+                        "Install either the python 'pyxattr' or 'xattr' "
+                        "modules, or the GNU 'attr' package "
+                        "(which contains the 'setfattr' tool).")
+                else:
+                    raise XAttrUnavailableError(
+                        "Couldn't find a tool to set the xattrs. "
+                        "Install either the python 'xattr' module, "
+                        "or the 'xattr' binary.")