Add --rate-limit program option

youtube-dl

@@ -78,6 +78,7 @@ class FileDownloader(object):
 	format:		Video format code.
 	outtmpl:	Template for output names.
 	ignoreerrors:	Do not stop on download errors.
+	ratelimit:	Download speed limit, in bytes/sec.
 	"""
 
 	_params = None
@@ -149,6 +150,16 @@ class FileDownloader(object):
 			return int(new_min)
 		return int(rate)
 
+	@staticmethod
+	def parse_bytes(bytestr):
+		"""Parse a string indicating a byte quantity into a long integer."""
+		matchobj = re.match(r'(?i)^(\d+(?:\.\d+)?)([kMGTPEZY]?)$', bytestr)
+		if matchobj is None:
+			return None
+		number = float(matchobj.group(1))
+		multiplier = 1024.0 ** 'bkmgtpezy'.index(matchobj.group(2).lower())
+		return long(round(number * multiplier))
+
 	def set_params(self, params):
 		"""Sets parameters."""
 		if type(params) != dict:
@@ -193,6 +204,19 @@ class FileDownloader(object):
 			raise DownloadError(message)
 		return 1
 
+	def slow_down(self, start_time, byte_counter):
+		"""Sleep if the download speed is over the rate limit."""
+		rate_limit = self._params.get('ratelimit', None)
+		if rate_limit is None or byte_counter == 0:
+			return
+		now = time.time()
+		elapsed = now - start_time
+		if elapsed <= 0.0:
+			return
+		speed = float(byte_counter) / elapsed
+		if speed > rate_limit:
+			time.sleep((byte_counter - rate_limit * (now - start_time)) / rate_limit)
+
 	def report_destination(self, filename):
 		"""Report destination filename."""
 		self.to_stdout('[download] Destination: %s' % filename)
@@ -296,6 +320,9 @@ class FileDownloader(object):
 			stream.write(data_block)
 			block_size = self.best_block_size(after - before, data_block_len)
 
+			# Apply rate limit
+			self.slow_down(start, byte_counter)
+
 		self.report_finish()
 		if data_len is not None and str(byte_counter) != data_len:
 			raise ValueError('Content too short: %s/%s bytes' % (byte_counter, data_len))
@@ -575,6 +602,8 @@ if __name__ == '__main__':
 				action='store_const', dest='format', help='alias for -f 17', const='17')
 		parser.add_option('-i', '--ignore-errors',
 				action='store_true', dest='ignoreerrors', help='continue on download errors', default=False)
+		parser.add_option('-r', '--rate-limit',
+				dest='ratelimit', metavar='L', help='download rate limit (e.g. 50k or 44.6m)')
 		(opts, args) = parser.parse_args()
 
 		# Conflicting, missing and erroneous options
@@ -590,6 +619,11 @@ if __name__ == '__main__':
 			sys.exit('ERROR: using title conflicts with using literal title')
 		if opts.username is not None and opts.password is None:
 			opts.password = getpass.getpass('Type account password and press return:')
+		if opts.ratelimit is not None:
+			numeric_limit = FileDownloader.parse_bytes(opts.ratelimit)
+			if numeric_limit is None:
+				sys.exit('ERROR: invalid rate limit specified')
+			opts.ratelimit = numeric_limit
 
 		# Information extractors
 		youtube_ie = YoutubeIE()
@@ -609,6 +643,7 @@ if __name__ == '__main__':
 				or (opts.useliteral and '%(title)s-%(id)s.%(ext)s')
 				or '%(id)s.%(ext)s'),
 			'ignoreerrors': opts.ignoreerrors,
+			'ratelimit': opts.ratelimit,
 			})
 		fd.add_info_extractor(youtube_ie)
 		retcode = fd.download(args)