httpd.py

#!/usr/bin/env python
#
# Copyright (c) 2011 The Native Client Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
#

"""A tiny web server.

This is intended to be used for testing.
"""

import BaseHTTPServer
import logging
import os
import SimpleHTTPServer
import SocketServer
import sys
import urlparse
import shutil

# Using 'localhost' means that we only accept connections
# via the loop back interface.
SERVER_PORT = 5103
SERVER_HOST = ''

# We only run from the examples directory (the one that contains scons-out), so
# that not too much is exposed via this HTTP server.  Everything in the
# directory is served, so there should never be anything potentially sensitive
# in the serving directory, especially if the machine might be a
# multi-user machine and not all users are trusted.  We only serve via
# the loopback interface.

SAFE_DIR_COMPONENTS = ['web']
SAFE_DIR_SUFFIX = os.path.join(*SAFE_DIR_COMPONENTS)

def SanityCheckDirectory():
  if os.getcwd().endswith(SAFE_DIR_SUFFIX):
    return
  logging.error('httpd.py should only be run from the %s', SAFE_DIR_SUFFIX)
  logging.error('directory for testing purposes.')
  logging.error('We are currently in %s', os.getcwd())
  sys.exit(1)


# An HTTP server that will quit when |is_running| is set to False.  We also use
# SocketServer.ThreadingMixIn in order to handle requests asynchronously for
# faster responses.
class QuittableHTTPServer(SocketServer.ThreadingMixIn,
                          BaseHTTPServer.HTTPServer):
  pass


# "Safely" split a string at |sep| into a [key, value] pair.  If |sep| does not
# exist in |str|, then the entire |str| is the key and the value is set to an
# empty string.
def KeyValuePair(str, sep='='):
  if sep in str:
    return str.split(sep)
  else:
    return [str, '']


# A small handler that looks for '?quit=1' query in the path and shuts itself
# down if it finds that parameter.
class QuittableHTTPHandler(SimpleHTTPServer.SimpleHTTPRequestHandler):
  def do_OPTIONS(self):
    self.send_response(200, 'OK');
    self.send_header('Access-Control-Allow-Methods', 'GET, OPTIONS, HEAD');
    self.send_header('Access-Control-Allow-Headers', 'target');
    self.end_headers()

  def do_GET(self):
    (_, _, _, query, _) = urlparse.urlsplit(self.path)
    url_params = dict([KeyValuePair(key_value)
                      for key_value in query.split('&')])
    if 'quit' in url_params and '1' in url_params['quit']:
      self.send_response(200, 'OK')
      self.send_header('Content-type', 'text/html')
      self.send_header('Content-length', '0')
      self.end_headers()
      self.server.shutdown()
      return

    headers = str(self.headers)
    begin = headers.find('Range: ')
    if begin != -1:
      end = headers.find('\n', begin)
      if end != -1:
        line = headers[begin:end]
        ind = line.find('=')
        byte_range = line[ind+1:].split('-')
        byte_begin = int(byte_range[0])
        byte_end = int(byte_range[1])
        length = byte_end-byte_begin+1
        f = self.send_partial(byte_begin, length)
        if f:
          curr_pos = f.tell()
          shutil.copyfileobj(f, self.wfile, length)
          f.seek(-byte_begin, os.SEEK_CUR)
          f.close()
          return

    SimpleHTTPServer.SimpleHTTPRequestHandler.do_GET(self)

  def end_headers(self):
    self.send_header("Access-Control-Allow-Origin", "*")
    SimpleHTTPServer.SimpleHTTPRequestHandler.end_headers(self)

  def send_partial(self, offset, length):
    """
    The following code is lifed from SimpleHTTPServer.send_head()
    The only change is that a 206 response is sent instead of 200.
    """

    path = self.translate_path(self.path)
    f = None
    if os.path.isdir(path):
      if not self.path.endswith('/'):
        # redirect browser - doing basically what apache does
        self.send_response(301)
        self.send_header("Location", self.path + "/")
        self.end_headers()
        return None
      for index in "index.html", "index.htm":
        index = os.path.join(path, index)
        if os.path.exists(index):
          path = index
          break
      else:
        return self.list_directory(path)
    ctype = self.guess_type(path)
    try:
      # Always read in binary mode. Opening files in text mode may cause
      # newline translations, making the actual size of the content
      # transmitted *less* than the content-length!
      f = open(path, 'rb')
      #f.seek(offset)
    except IOError:
      self.send_error(404, "File not found")
      return None
    fs = os.fstat(f.fileno())
    if (offset + length > fs[6] or length < 0):
      self.send_error(416, 'Request range not satisfiable')
      return None
    self.send_response(206, 'Partial content')
    f.seek(offset, os.SEEK_CUR)
    self.send_header("Content-Range", str(offset) + '-' + str(length+offset-1))
    self.send_header("Content-Length", str(length))
    self.send_header("Content-type", ctype)
    self.send_header("Last-Modified", self.date_time_string(fs.st_mtime))
    self.end_headers()
    return f


def Run(server_address,
        server_class=QuittableHTTPServer,
        handler_class=QuittableHTTPHandler):
  httpd = server_class(server_address, handler_class)
  logging.info("Starting local server on port %d", server_address[1])
  logging.info("To shut down send http://localhost:%d?quit=1",
               server_address[1])
  httpd.serve_forever()
  logging.info("Shutting down local server on port %d", server_address[1])


if __name__ == '__main__':
  logging.getLogger().setLevel(logging.INFO)
  os.chdir('web')
  SanityCheckDirectory()
  if len(sys.argv) > 1:
    Run((SERVER_HOST, int(sys.argv[1])))
  else:
    Run((SERVER_HOST, SERVER_PORT))
  sys.exit(0)