Source

cheroot / cheroot / server.py

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"""The HTTP server.

For those of you wanting to understand internals of this module, here's the
basic call flow. The server's listening thread runs a very tight loop,
sticking incoming connections onto a Queue::

    server = HTTPServer(...)
    server.start()
    while True:
        tick()
        # This blocks until a request comes in:
        child = socket.accept()
        conn = HTTPConnection(child, ...)
        server.requests.put(conn)

Worker threads are kept in a pool and poll the Queue, popping off and then
handling each connection in turn. Each connection can consist of an arbitrary
number of requests and their responses, so we run a nested loop::

    while True:
        conn = server.requests.get()
        conn.communicate()
        ->  while True:
                req = HTTPRequest(...)
                req.parse_request()
                ->  # Read the Request-Line, e.g. "GET /page HTTP/1.1"
                    req.rfile.readline()
                    read_headers(req.rfile, req.inheaders)
                req.respond()
                ->  response = app(...)
                    try:
                        for chunk in response:
                            if chunk:
                                req.write(chunk)
                    finally:
                        if hasattr(response, "close"):
                            response.close()
                if req.close_connection:
                    return
"""

__all__ = ['HTTPRequest', 'HTTPConnection', 'HTTPServer',
           'SizeCheckWrapper', 'KnownLengthRFile', 'ChunkedRFile',
           'Gateway']

from cheroot._compat import bytestr, unicodestr, basestring, ntob, py3k
from cheroot._compat import HTTPDate, format_exc, unquote
from cheroot._compat import BaseHTTPRequestHandler
response_codes = BaseHTTPRequestHandler.responses.copy()

# From http://www.cherrypy.org/ticket/361
response_codes[500] = ('Internal Server Error',
                      'The server encountered an unexpected condition '
                      'which prevented it from fulfilling the request.')
response_codes[503] = ('Service Unavailable',
                      'The server is currently unable to handle the '
                      'request due to a temporary overloading or '
                      'maintenance of the server.')

LF = ntob('\n')
CRLF = ntob('\r\n')
TAB = ntob('\t')
SPACE = ntob(' ')
COLON = ntob(':')
SEMICOLON = ntob(';')
COMMA = ntob(',')
EMPTY = ntob('')
NUMBER_SIGN = ntob('#')
QUESTION_MARK = ntob('?')
ASTERISK = ntob('*')
FORWARD_SLASH = ntob('/')

import os
import re
import socket
import sys
if 'win' in sys.platform and not hasattr(socket, 'IPPROTO_IPV6'):
    socket.IPPROTO_IPV6 = 41

if py3k:
    if sys.version_info < (3,1):
        import io
    else:
        import _pyio as io
    DEFAULT_BUFFER_SIZE = io.DEFAULT_BUFFER_SIZE
else:
    DEFAULT_BUFFER_SIZE = -1

import time

from cheroot.workers import threadpool

from cheroot import errors
if py3k:
    from cheroot.py3makefile import makefile
else:
    from cheroot.py2makefile import makefile
def write(wfile, output):
    if hasattr(wfile, 'sendall'):
        wfile.sendall(output)
    else:
        wfile.write(output)

quoted_slash = re.compile(ntob("(?i)%2F"))

comma_separated_headers = [ntob(h) for h in
    ['Accept', 'Accept-Charset', 'Accept-Encoding',
     'Accept-Language', 'Accept-Ranges', 'Allow', 'Cache-Control',
     'Connection', 'Content-Encoding', 'Content-Language', 'Expect',
     'If-Match', 'If-None-Match', 'Pragma', 'Proxy-Authenticate', 'TE',
     'Trailer', 'Transfer-Encoding', 'Upgrade', 'Vary', 'Via', 'Warning',
     'WWW-Authenticate']]


import logging
if not hasattr(logging, 'statistics'): logging.statistics = {}


def read_headers(rfile, hdict=None):
    """Read headers from the given stream into the given header dict.
    
    If hdict is None, a new header dict is created. Returns the populated
    header dict.
    
    Headers which are repeated are folded together using a comma if their
    specification so dictates.
    
    This function raises ValueError when the read bytes violate the HTTP spec.
    You should probably return "400 Bad Request" if this happens.
    """
    if hdict is None:
        hdict = {}
    
    while True:
        line = rfile.readline()
        if not line:
            # No more data--illegal end of headers
            raise ValueError("Illegal end of headers.")
        
        if line == CRLF:
            # Normal end of headers
            break
        if not line.endswith(CRLF):
            raise ValueError("HTTP requires CRLF terminators")
        
        if line[0] in (SPACE, TAB):
            # It's a continuation line.
            v = line.strip()
        else:
            try:
                k, v = line.split(COLON, 1)
            except ValueError:
                raise ValueError("Illegal header line.")
            # TODO: what about TE and WWW-Authenticate?
            k = k.strip().title()
            v = v.strip()
            hname = k
        
        if k in comma_separated_headers:
            existing = hdict.get(hname)
            if existing:
                v = ntob(", ").join((existing, v))
        hdict[hname] = v
    
    return hdict


class SizeCheckWrapper(object):
    """Wraps a file-like object, raising MaxSizeExceeded if too large."""
    
    def __init__(self, rfile, maxlen):
        self.rfile = rfile
        self.maxlen = maxlen
        self.bytes_read = 0
    
    def _check_length(self):
        if self.maxlen and self.bytes_read > self.maxlen:
            raise errors.MaxSizeExceeded()
    
    def read(self, size=None):
        data = self.rfile.read(size)
        self.bytes_read += len(data)
        self._check_length()
        return data
    
    def readline(self, size=None):
        if size is not None:
            data = self.rfile.readline(size)
            self.bytes_read += len(data)
            self._check_length()
            return data
        
        # User didn't specify a size ...
        # We read the line in chunks to make sure it's not a 100MB line !
        res = []
        while True:
            data = self.rfile.readline(256)
            self.bytes_read += len(data)
            self._check_length()
            res.append(data)
            # See http://www.cherrypy.org/ticket/421
            if len(data) < 256 or data[-1:] == "\n":
                return EMPTY.join(res)
    
    def readlines(self, sizehint=0):
        # Shamelessly stolen from StringIO
        total = 0
        lines = []
        line = self.readline()
        while line:
            lines.append(line)
            total += len(line)
            if 0 < sizehint <= total:
                break
            line = self.readline()
        return lines
    
    def close(self):
        self.rfile.close()
    
    def __iter__(self):
        return self
    
    def __next__(self):
        data = next(self.rfile)
        self.bytes_read += len(data)
        self._check_length()
        return data
    
    def next(self):
        data = self.rfile.next()
        self.bytes_read += len(data)
        self._check_length()
        return data


class KnownLengthRFile(object):
    """Wraps a file-like object, returning an empty string when exhausted."""
    
    def __init__(self, rfile, content_length):
        self.rfile = rfile
        self.remaining = content_length
    
    def read(self, size=None):
        if self.remaining == 0:
            return EMPTY
        if size is None:
            size = self.remaining
        else:
            size = min(size, self.remaining)
        
        data = self.rfile.read(size)
        self.remaining -= len(data)
        return data
    
    def readline(self, size=None):
        if self.remaining == 0:
            return EMPTY
        if size is None:
            size = self.remaining
        else:
            size = min(size, self.remaining)
        
        data = self.rfile.readline(size)
        self.remaining -= len(data)
        return data
    
    def readlines(self, sizehint=0):
        # Shamelessly stolen from StringIO
        total = 0
        lines = []
        line = self.readline(sizehint)
        while line:
            lines.append(line)
            total += len(line)
            if 0 < sizehint <= total:
                break
            line = self.readline(sizehint)
        return lines
    
    def close(self):
        self.rfile.close()
    
    def __iter__(self):
        return self
    
    def __next__(self):
        data = next(self.rfile)
        self.remaining -= len(data)
        return data


class ChunkedRFile(object):
    """Wraps a file-like object, returning an empty string when exhausted.
    
    This class is intended to provide a conforming wsgi.input value for
    request entities that have been encoded with the 'chunked' transfer
    encoding.
    """
    
    def __init__(self, rfile, maxlen, bufsize=8192):
        self.rfile = rfile
        self.maxlen = maxlen
        self.bytes_read = 0
        self.buffer = EMPTY
        self.bufsize = bufsize
        self.closed = False
    
    def _fetch(self):
        if self.closed:
            return
        
        line = self.rfile.readline()
        self.bytes_read += len(line)
        
        if self.maxlen and self.bytes_read > self.maxlen:
            raise errors.MaxSizeExceeded("Request Entity Too Large", self.maxlen)
        
        line = line.strip().split(SEMICOLON, 1)
        
        try:
            chunk_size = line.pop(0)
            chunk_size = int(chunk_size, 16)
        except ValueError:
            raise ValueError("Bad chunked transfer size: " + repr(chunk_size))
        
        if chunk_size <= 0:
            self.closed = True
            return
        
##            if line: chunk_extension = line[0]
        
        if self.maxlen and self.bytes_read + chunk_size > self.maxlen:
            raise IOError("Request Entity Too Large")
        
        chunk = self.rfile.read(chunk_size)
        self.bytes_read += len(chunk)
        self.buffer += chunk
        
        crlf = self.rfile.read(2)
        if crlf != CRLF:
            raise ValueError(
                 "Bad chunked transfer coding (expected '\\r\\n', "
                 "got " + repr(crlf) + ")")
    
    def read(self, size=None):
        data = EMPTY
        while True:
            if size and len(data) >= size:
                return data
            
            if not self.buffer:
                self._fetch()
                if not self.buffer:
                    # EOF
                    return data
            
            if size:
                remaining = size - len(data)
                data += self.buffer[:remaining]
                self.buffer = self.buffer[remaining:]
            else:
                data += self.buffer
                self.buffer = EMPTY

    def readline(self, size=None):
        data = EMPTY
        while True:
            if size and len(data) >= size:
                return data

            if not self.buffer:
                self._fetch()
                if not self.buffer:
                    # EOF
                    return data

            newline_pos = self.buffer.find(LF)
            if size:
                if newline_pos == -1:
                    remaining = size - len(data)
                    data += self.buffer[:remaining]
                    self.buffer = self.buffer[remaining:]
                else:
                    remaining = min(size - len(data), newline_pos + 1)
                    data += self.buffer[:remaining]
                    self.buffer = self.buffer[remaining:]
            else:
                if newline_pos == -1:
                    data += self.buffer
                    self.buffer = EMPTY
                else:
                    remaining = newline_pos + 1
                    data += self.buffer[:remaining]
                    self.buffer = self.buffer[remaining:]
    
    def readlines(self, sizehint=0):
        # Shamelessly stolen from StringIO
        total = 0
        lines = []
        line = self.readline(sizehint)
        while line:
            lines.append(line)
            total += len(line)
            if 0 < sizehint <= total:
                break
            line = self.readline(sizehint)
        return lines
    
    def read_trailer_lines(self):
        if not self.closed:
            raise ValueError(
                "Cannot read trailers until the request body has been read.")
        
        while True:
            line = self.rfile.readline()
            if not line:
                # No more data--illegal end of headers
                raise ValueError("Illegal end of headers.")
            
            self.bytes_read += len(line)
            if self.maxlen and self.bytes_read > self.maxlen:
                raise IOError("Request Entity Too Large")
            
            if line == CRLF:
                # Normal end of headers
                break
            if not line.endswith(CRLF):
                raise ValueError("HTTP requires CRLF terminators")
            
            yield line
    
    def close(self):
        self.rfile.close()
    
    def __iter__(self):
        # Shamelessly stolen from StringIO
        total = 0
        line = self.readline(sizehint)
        while line:
            yield line
            total += len(line)
            if 0 < sizehint <= total:
                break
            line = self.readline(sizehint)


class HTTPRequest(object):
    """An HTTP Request (and response).
    
    A single HTTP connection may consist of multiple request/response pairs.
    """
    
    server = None
    """The HTTPServer object which is receiving this request."""
    
    conn = None
    """The HTTPConnection object on which this request connected."""
    
    inheaders = {}
    """A dict of request headers."""
    
    outheaders = []
    """A list of header tuples to write in the response."""
    
    ready = False
    """When True, the request has been parsed and is ready to begin generating
    the response. When False, signals the calling Connection that the response
    should not be generated and the connection should close."""
    
    close_connection = False
    """Signals the calling Connection that the request should close. This does
    not imply an error! The client and/or server may each request that the
    connection be closed."""
    
    chunked_write = False
    """If True, output will be encoded with the "chunked" transfer-coding.
    
    This value is set automatically inside send_headers."""
    
    def __init__(self, server, conn):
        self.server= server
        self.conn = conn
        
        self.ready = False
        self.started_request = False
        self.scheme = ntob("http")
        if self.server.ssl_adapter is not None:
            self.scheme = ntob("https")
        # Use the lowest-common protocol in case read_request_line errors.
        self.response_protocol = 'HTTP/1.0'
        self.inheaders = {}
        
        self.status = ""
        self.outheaders = []
        self.sent_headers = False
        self.close_connection = self.__class__.close_connection
        self.chunked_read = False
        self.chunked_write = self.__class__.chunked_write
        self.allow_message_body = True

    def _get_status(self):
        return self._status
    def _set_status(self, value):
        if not value:
            value = ntob("200")

        if not isinstance(value, bytestr):
            value = ntob(str(value))

        parts = value.split(SPACE, 1)
        if len(parts) == 1:
            # No reason supplied.
            code, = parts
            reason = None
        else:
            code, reason = parts
            reason = reason.strip()

        try:
            code = int(code)
        except ValueError:
            raise ValueError("Illegal response status from server "
                             "(%s is non-numeric)." % repr(code))

        if code < 100 or code > 599:
            raise ValueError("Illegal response status from server "
                             "(%s is out of range)." % repr(code))

        if reason is None:
            if code not in response_codes:
                # code is unknown but not illegal
                reason = EMPTY
            else:
                reason, _ = response_codes[code]
                reason = ntob(reason)

        self._status = SPACE.join((ntob(str(code)), reason))

    status = property(_get_status, _set_status,
                      "The response code and reason in a single string.")

    def parse_request(self):
        """Parse the next HTTP request start-line and message-headers."""
        self.rfile = SizeCheckWrapper(self.conn.rfile,
                                      self.server.max_request_header_size)
        try:
            success = self.read_request_line()
        except errors.MaxSizeExceeded:
            self.simple_response("414 Request-URI Too Long",
                "The Request-URI sent with the request exceeds the maximum "
                "allowed bytes.")
            return
        else:
            if not success:
                return
        
        try:
            success = self.read_request_headers()
        except errors.MaxSizeExceeded:
            self.simple_response("413 Request Entity Too Large",
                "The headers sent with the request exceed the maximum "
                "allowed bytes.")
            return
        else:
            if not success:
                return
        
        self.ready = True
    
    def read_request_line(self):
        # HTTP/1.1 connections are persistent by default. If a client
        # requests a page, then idles (leaves the connection open),
        # then rfile.readline() will raise socket.error("timed out").
        # Note that it does this based on the value given to settimeout(),
        # and doesn't need the client to request or acknowledge the close
        # (although your TCP stack might suffer for it: cf Apache's history
        # with FIN_WAIT_2).
        request_line = self.rfile.readline()
        
        # Set started_request to True so communicate() knows to send 408
        # from here on out.
        self.started_request = True
        if not request_line:
            return False
        
        if request_line == CRLF:
            # RFC 2616 sec 4.1: "...if the server is reading the protocol
            # stream at the beginning of a message and receives a CRLF
            # first, it should ignore the CRLF."
            # But only ignore one leading line! else we enable a DoS.
            request_line = self.rfile.readline()
            if not request_line:
                return False
        
        if not request_line.endswith(CRLF):
            self.simple_response("400 Bad Request", "HTTP requires CRLF terminators")
            return False
        
        try:
            method, uri, req_protocol = request_line.strip().split(SPACE, 2)
            if py3k:
                # The [x:y] slicing is necessary for byte strings to avoid getting ord's
                rp = int(req_protocol[5:6]), int(req_protocol[7:8])
            else:
                rp = int(req_protocol[5]), int(req_protocol[7])
        except (ValueError, IndexError):
            self.simple_response("400 Bad Request", "Malformed Request-Line")
            return False
        
        self.uri = uri
        self.method = method
        
        # uri may be an abs_path (including "http://host.domain.tld");
        scheme, authority, path = self.parse_request_uri(uri)
        if NUMBER_SIGN in path:
            self.simple_response("400 Bad Request",
                                 "Illegal #fragment in Request-URI.")
            return False
        
        if scheme:
            self.scheme = scheme
        
        qs = EMPTY
        if QUESTION_MARK in path:
            path, qs = path.split(QUESTION_MARK, 1)
        
        # Unquote the path+params (e.g. "/this%20path" -> "/this path").
        # http://www.w3.org/Protocols/rfc2616/rfc2616-sec5.html#sec5.1.2
        #
        # But note that "...a URI must be separated into its components
        # before the escaped characters within those components can be
        # safely decoded." http://www.ietf.org/rfc/rfc2396.txt, sec 2.4.2
        # Therefore, "/this%2Fpath" becomes "/this%2Fpath", not "/this/path".
        try:
            atoms = [unquote(x) for x in quoted_slash.split(path)]
        except ValueError:
            ex = sys.exc_info()[1]
            self.simple_response("400 Bad Request", ex.args[0])
            return False
        path = ntob("%2F").join(atoms)
        self.path = path
        
        # Note that, like wsgiref and most other HTTP servers,
        # we "% HEX HEX"-unquote the path but not the query string.
        self.qs = qs
        
        # Compare request and server HTTP protocol versions, in case our
        # server does not support the requested protocol. Limit our output
        # to min(req, server). We want the following output:
        #     request    server     actual written   supported response
        #     protocol   protocol  response protocol    feature set
        # a     1.0        1.0           1.0                1.0
        # b     1.0        1.1           1.1                1.0
        # c     1.1        1.0           1.0                1.0
        # d     1.1        1.1           1.1                1.1
        # Notice that, in (b), the response will be "HTTP/1.1" even though
        # the client only understands 1.0. RFC 2616 10.5.6 says we should
        # only return 505 if the _major_ version is different.
        if py3k:
            # The [x:y] slicing is necessary for byte strings to avoid getting ord's
            sp = int(self.server.protocol[5:6]), int(self.server.protocol[7:8])
        else:
            sp = int(self.server.protocol[5]), int(self.server.protocol[7])
        
        if sp[0] != rp[0]:
            self.simple_response("505 HTTP Version Not Supported")
            return False

        self.request_protocol = req_protocol
        self.response_protocol = "HTTP/%s.%s" % min(rp, sp)

        return True

    def read_request_headers(self):
        """Read self.rfile into self.inheaders. Return success."""
        
        # then all the http headers
        try:
            read_headers(self.rfile, self.inheaders)
        except ValueError:
            ex = sys.exc_info()[1]
            self.simple_response("400 Bad Request", ex.args[0])
            return False
        
        mrbs = self.server.max_request_body_size
        if mrbs and int(self.inheaders.get(ntob("Content-Length"), 0)) > mrbs:
            self.simple_response("413 Request Entity Too Large",
                "The entity sent with the request exceeds the maximum "
                "allowed bytes.")
            return False
        
        # Persistent connection support
        if self.response_protocol == "HTTP/1.1":
            # Both server and client are HTTP/1.1
            if self.inheaders.get(ntob("Connection"), EMPTY) == ntob("close"):
                self.close_connection = True
        else:
            # Either the server or client (or both) are HTTP/1.0
            if self.inheaders.get(ntob("Connection"), EMPTY) != ntob("Keep-Alive"):
                self.close_connection = True
        
        # Transfer-Encoding support
        te = None
        if self.response_protocol == "HTTP/1.1":
            te = self.inheaders.get(ntob("Transfer-Encoding"))
            if te:
                te = [x.strip().lower() for x in te.split(COMMA) if x.strip()]
        
        self.chunked_read = False
        
        if te:
            for enc in te:
                if enc == ntob("chunked"):
                    self.chunked_read = True
                else:
                    # Note that, even if we see "chunked", we must reject
                    # if there is an extension we don't recognize.
                    self.simple_response("501 Unimplemented")
                    self.close_connection = True
                    return False
        
        # From PEP 333:
        # "Servers and gateways that implement HTTP 1.1 must provide
        # transparent support for HTTP 1.1's "expect/continue" mechanism.
        # This may be done in any of several ways:
        #   1. Respond to requests containing an Expect: 100-continue request
        #      with an immediate "100 Continue" response, and proceed normally.
        #   2. Proceed with the request normally, but provide the application
        #      with a wsgi.input stream that will send the "100 Continue"
        #      response if/when the application first attempts to read from
        #      the input stream. The read request must then remain blocked
        #      until the client responds.
        #   3. Wait until the client decides that the server does not support
        #      expect/continue, and sends the request body on its own.
        #      (This is suboptimal, and is not recommended.)
        #
        # We used to do 3, but are now doing 1. Maybe we'll do 2 someday,
        # but it seems like it would be a big slowdown for such a rare case.
        if self.inheaders.get(ntob("Expect"), EMPTY) == ntob("100-continue"):
            # Don't use simple_response here, because it emits headers
            # we don't want. See http://www.cherrypy.org/ticket/951
            msg = ntob(self.server.protocol,'ascii') + ntob(" 100 Continue\r\n\r\n")
            try:
                write(self.conn.wfile, msg)
            except socket.error:
                x = sys.exc_info()[1]
                if x.args[0] not in errors.socket_errors_to_ignore:
                    raise
        return True
    
    def parse_request_uri(self, uri):
        """Parse a Request-URI into (scheme, authority, path).
        
        Note that Request-URI's must be one of::
            
            Request-URI    = "*" | absoluteURI | abs_path | authority
        
        Therefore, a Request-URI which starts with a double forward-slash
        cannot be a "net_path"::
        
            net_path      = "//" authority [ abs_path ]
        
        Instead, it must be interpreted as an "abs_path" with an empty first
        path segment::
        
            abs_path      = "/"  path_segments
            path_segments = segment *( "/" segment )
            segment       = *pchar *( ";" param )
            param         = *pchar
        """
        if uri == ASTERISK:
            return None, None, uri
        
        i = uri.find(ntob('://'))
        if i > 0 and QUESTION_MARK not in uri[:i]:
            # An absoluteURI.
            # If there's a scheme (and it must be http or https), then:
            # http_URL = "http:" "//" host [ ":" port ] [ abs_path [ "?" query ]]
            scheme, remainder = uri[:i].lower(), uri[i + 3:]
            authority, path = remainder.split(FORWARD_SLASH, 1)
            path = FORWARD_SLASH + path
            return scheme, authority, path
        
        if uri.startswith(FORWARD_SLASH):
            # An abs_path.
            return None, None, uri
        else:
            # An authority.
            return None, uri, None

    def respond(self):
        """Call the gateway and write its iterable output."""
        mrbs = self.server.max_request_body_size
        if self.chunked_read:
            self.rfile = ChunkedRFile(self.conn.rfile, mrbs)
        else:
            cl = int(self.inheaders.get(ntob("Content-Length"), 0))
            if mrbs and mrbs < cl:
                if not self.sent_headers:
                    self.simple_response("413 Request Entity Too Large",
                        "The entity sent with the request exceeds the maximum "
                        "allowed bytes.")
                return
            self.rfile = KnownLengthRFile(self.conn.rfile, cl)
        
        self.server.gateway(self).respond()
        
        if (self.ready and not self.sent_headers):
            self.sent_headers = True
            if not self.send_headers():
                self.close_connection = True
                return
        if self.chunked_write:
            write(self.conn.wfile, ntob("0\r\n\r\n"))
    
    def simple_response(self, status, msg=""):
        """Write a simple response back to the client."""
        status = str(status)
        buf = [ntob(self.server.protocol, "ascii") + SPACE +
               ntob(status, "ISO-8859-1") + CRLF,
               ntob("Content-Length: %s\r\n" % len(msg), "ISO-8859-1"),
               ntob("Content-Type: text/plain\r\n")]
        
        if status[:3] in ("413", "414"):
            # Request Entity Too Large / Request-URI Too Long
            self.close_connection = True
            if self.response_protocol == 'HTTP/1.1':
                # This will not be true for 414, since read_request_line
                # usually raises 414 before reading the whole line, and we
                # therefore cannot know the proper response_protocol.
                buf.append(ntob("Connection: close\r\n"))
            else:
                # HTTP/1.0 had no 413/414 status nor Connection header.
                # Emit 400 instead and trust the message body is enough.
                status = "400 Bad Request"
        
        buf.append(CRLF)
        if msg:
            if isinstance(msg, unicodestr):
                msg = msg.encode("ISO-8859-1")
            buf.append(msg)
        
        try:
            write(self.conn.wfile, EMPTY.join(buf))
        except socket.error:
            x = sys.exc_info()[1]
            if x.args[0] not in errors.socket_errors_to_ignore:
                raise
    
    def write(self, chunk):
        """Write unbuffered data to the client."""
        if self.chunked_write and chunk:
            buf = [ntob(hex(len(chunk)), 'ASCII')[2:], CRLF, chunk, CRLF]
            write(self.conn.wfile, EMPTY.join(buf))
        else:
            write(self.conn.wfile, chunk)
    
    def send_headers(self):
        """Assert, process, and send the HTTP response message-headers.
        
        You must set self.status, and self.outheaders before calling this.
        """
        hkeys = [key.lower() for key, value in self.outheaders]
        try:
            status = int(self.status[:3])
        except ValueError:
            self.simple_response("500 Illegal Status",
                "Illegal response status from server ('%s' is non-numeric)." %
                self.status)
            return
        
        if status == 413:
            # Request Entity Too Large. Close conn to avoid garbage.
            self.close_connection = True

        # "All 1xx (informational), 204 (no content),
        # and 304 (not modified) responses MUST NOT
        # include a message-body." So no point chunking.
        if status < 200 or status in (204, 205, 304):
            self.outheaders = [(k, v) for k, v in self.outheaders
                               if k.lower() != ntob('content-length')]
            self.allow_message_body = False
        elif ntob("content-length") not in hkeys:
            if (self.response_protocol == 'HTTP/1.1'
                and self.method != ntob('HEAD')):
                # Use the chunked transfer-coding
                self.chunked_write = True
                self.outheaders.append((ntob("Transfer-Encoding"), ntob("chunked")))
            else:
                # Closing the conn is the only way to determine len.
                self.close_connection = True
        
        if ntob("connection") not in hkeys:
            if self.response_protocol == 'HTTP/1.1':
                # Both server and client are HTTP/1.1 or better
                if self.close_connection:
                    self.outheaders.append((ntob("Connection"), ntob("close")))
            else:
                # Server and/or client are HTTP/1.0
                if not self.close_connection:
                    self.outheaders.append((ntob("Connection"), ntob("Keep-Alive")))
        
        if (not self.close_connection) and (not self.chunked_read):
            # Read any remaining request body data on the socket.
            # "If an origin server receives a request that does not include an
            # Expect request-header field with the "100-continue" expectation,
            # the request includes a request body, and the server responds
            # with a final status code before reading the entire request body
            # from the transport connection, then the server SHOULD NOT close
            # the transport connection until it has read the entire request,
            # or until the client closes the connection. Otherwise, the client
            # might not reliably receive the response message. However, this
            # requirement is not be construed as preventing a server from
            # defending itself against denial-of-service attacks, or from
            # badly broken client implementations."
            remaining = getattr(self.rfile, 'remaining', 0)
            if remaining > 0:
                self.rfile.read(remaining)
        
        if ntob("date") not in hkeys:
            self.outheaders.append((ntob("Date"), HTTPDate()))
        
        if ntob("server") not in hkeys:
            self.outheaders.append(
                (ntob("Server"), ntob(self.server.server_name)))
        
        buf = [ntob(self.server.protocol, 'ascii') + SPACE + self.status + CRLF]
        for k, v in self.outheaders:
            buf.append(k + COLON + SPACE + v + CRLF)
        buf.append(CRLF)
        write(self.conn.wfile, EMPTY.join(buf))


class HTTPConnection(object):
    """An HTTP connection (active socket).
    
    server: the Server object which received this connection.
    socket: the raw socket object (usually TCP) for this connection.
    makefile: a class for reading from the socket.
    """
    
    remote_addr = None
    remote_port = None
    ssl_env = None
    rbufsize = DEFAULT_BUFFER_SIZE
    wbufsize = DEFAULT_BUFFER_SIZE
    RequestHandlerClass = HTTPRequest
    
    def __init__(self, server, sock, makefile=makefile):
        self.server = server
        self.socket = sock
        self.rfile = makefile(sock, "rb", self.rbufsize)
        self.wfile = makefile(sock, "wb", self.wbufsize)
        self.requests_seen = 0
    
    def communicate(self):
        """Read each request and respond appropriately."""
        request_seen = False
        try:
            while True:
                # (re)set req to None so that if something goes wrong in
                # the RequestHandlerClass constructor, the error doesn't
                # get written to the previous request.
                req = None
                req = self.RequestHandlerClass(self.server, self)
                
                # This order of operations should guarantee correct pipelining.
                req.parse_request()
                if self.server.stats['Enabled']:
                    self.requests_seen += 1
                if not req.ready:
                    # Something went wrong in the parsing (and the server has
                    # probably already made a simple_response). Return and
                    # let the conn close.
                    return
                
                request_seen = True
                req.respond()
                if req.close_connection:
                    return
        except socket.error:
            e = sys.exc_info()[1]
            errnum = e.args[0]
            # sadly SSL sockets return a different (longer) time out string
            if errnum == 'timed out' or errnum == 'The read operation timed out':
                # Don't error if we're between requests; only error
                # if 1) no request has been started at all, or 2) we're
                # in the middle of a request.
                # See http://www.cherrypy.org/ticket/853
                if (not request_seen) or (req and req.started_request):
                    # Don't bother writing the 408 if the response
                    # has already started being written.
                    if req and not req.sent_headers:
                        try:
                            req.simple_response("408 Request Timeout")
                        except errors.FatalSSLAlert:
                            # Close the connection.
                            return
            elif errnum not in errors.socket_errors_to_ignore:
                self.server.error_log("socket.error %s" % repr(errnum),
                                      level=logging.WARNING, traceback=True)
                if req and not req.sent_headers:
                    try:
                        req.simple_response("500 Internal Server Error")
                    except errors.FatalSSLAlert:
                        # Close the connection.
                        return
            return
        except (KeyboardInterrupt, SystemExit):
            raise
        except errors.FatalSSLAlert:
            # Close the connection.
            return
        except errors.NoSSLError:
            if req and not req.sent_headers:
                # Unwrap our wfile
                self.wfile = makefile(self.socket._sock, "wb", self.wbufsize)
                req.simple_response("400 Bad Request",
                    "The client sent a plain HTTP request, but "
                    "this server only speaks HTTPS on this port.")
                self.linger = True
        except Exception:
            e = sys.exc_info()[1]
            self.server.error_log(repr(e), level=logging.ERROR, traceback=True)
            if req and not req.sent_headers:
                try:
                    req.simple_response("500 Internal Server Error")
                except errors.FatalSSLAlert:
                    # Close the connection.
                    return
    
    linger = False
    
    def close(self):
        """Close the socket underlying this connection."""
        self.rfile.close()
        
        if not self.linger:
            # Python's socket module does NOT call close on the kernel socket
            # when you call socket.close(). We do so manually here because we
            # want this server to send a FIN TCP segment immediately. Note this
            # must be called *before* calling socket.close(), because the latter
            # drops its reference to the kernel socket.
            # Python 3 *probably* fixed this with socket._real_close; hard to tell.
            if not py3k:
                if hasattr(self.socket, '_sock'):
                    self.socket._sock.close()
            self.socket.close()
        else:
            # On the other hand, sometimes we want to hang around for a bit
            # to make sure the client has a chance to read our entire
            # response. Skipping the close() calls here delays the FIN
            # packet until the socket object is garbage-collected later.
            # Someday, perhaps, we'll do the full lingering_close that
            # Apache does, but not today.
            pass


try:
    import fcntl
except ImportError:
    try:
        from ctypes import windll, WinError
    except ImportError:
        def prevent_socket_inheritance(sock):
            """Dummy function, since neither fcntl nor ctypes are available."""
            pass
    else:
        def prevent_socket_inheritance(sock):
            """Mark the given socket fd as non-inheritable (Windows)."""
            if not windll.kernel32.SetHandleInformation(sock.fileno(), 1, 0):
                raise WinError()
else:
    def prevent_socket_inheritance(sock):
        """Mark the given socket fd as non-inheritable (POSIX)."""
        fd = sock.fileno()
        old_flags = fcntl.fcntl(fd, fcntl.F_GETFD)
        fcntl.fcntl(fd, fcntl.F_SETFD, old_flags | fcntl.FD_CLOEXEC)


class HTTPServer(object):
    """An HTTP server."""
    
    _bind_addr = "127.0.0.1"
    _interrupt = None
    
    gateway = None
    """A Gateway instance."""
    
    minthreads = None
    """The minimum number of worker threads to create (default 10)."""
    
    maxthreads = None
    """The maximum number of worker threads to create (default -1 = no limit)."""
    
    server_name = None
    """The name of the server; defaults to socket.gethostname()."""
    
    protocol = "HTTP/1.1"
    """The version string to write in the Status-Line of all HTTP responses.
    
    For example, "HTTP/1.1" is the default. This also limits the supported
    features used in the response."""
    
    request_queue_size = 5
    """The 'backlog' arg to socket.listen(); max queued connections (default 5)."""
    
    shutdown_timeout = 5
    """The total time, in seconds, to wait for worker threads to cleanly exit."""
    
    timeout = 10
    """The timeout in seconds for accepted connections (default 10)."""
    
    version = "Cheroot/3.3.0alpha"
    """A version string for the HTTPServer."""
    
    software = None
    """The value to set for the SERVER_SOFTWARE entry in the environ.
    
    If None, this defaults to ``'%s Server' % self.version``."""
    
    ready = False
    """An internal flag which marks whether the socket is accepting connections."""
    
    max_request_header_size = 0
    """The maximum size, in bytes, for request headers, or 0 for no limit."""
    
    max_request_body_size = 0
    """The maximum size, in bytes, for request bodies, or 0 for no limit."""
    
    nodelay = True
    """If True (the default since 3.1), sets the TCP_NODELAY socket option."""
    
    ConnectionClass = HTTPConnection
    """The class to use for handling HTTP connections."""
    
    ssl_adapter = None
    """An instance of SSLAdapter (or a subclass).
    
    You must have the corresponding SSL driver library installed."""
    
    def __init__(self, bind_addr, gateway, minthreads=10, maxthreads=-1,
                 server_name=None, protocol='HTTP/1.1', ssl_adapter=None):
        self.bind_addr = bind_addr
        self.gateway = gateway
        
        self.requests = threadpool.ThreadPool(
            self, min=minthreads or 1, max=maxthreads)
        
        if not server_name:
            server_name = socket.gethostname()
        self.server_name = server_name
        self.protocol = protocol
        self.ssl_adapter = ssl_adapter

        self.clear_stats()
    
    def clear_stats(self):
        self._start_time = None
        self._run_time = 0
        self.stats = {
            'Enabled': False,
            'Bind Address': lambda s: repr(self.bind_addr),
            'Run time': lambda s: (not s['Enabled']) and -1 or self.runtime(),
            'Accepts': 0,
            'Accepts/sec': lambda s: s['Accepts'] / self.runtime(),
            'Queue': lambda s: getattr(self.requests, "qsize", None),
            'Threads': lambda s: len(getattr(self.requests, "_threads", [])),
            'Threads Idle': lambda s: getattr(self.requests, "idle", None),
            'Socket Errors': 0,
            'Requests': lambda s: (not s['Enabled']) and -1 or sum([w['Requests'](w) for w
                                       in s['Worker Threads'].values()], 0),
            'Bytes Read': lambda s: (not s['Enabled']) and -1 or sum([w['Bytes Read'](w) for w
                                         in s['Worker Threads'].values()], 0),
            'Bytes Written': lambda s: (not s['Enabled']) and -1 or sum([w['Bytes Written'](w) for w
                                            in s['Worker Threads'].values()], 0),
            'Work Time': lambda s: (not s['Enabled']) and -1 or sum([w['Work Time'](w) for w
                                         in s['Worker Threads'].values()], 0),
            'Read Throughput': lambda s: (not s['Enabled']) and -1 or sum(
                [w['Bytes Read'](w) / (w['Work Time'](w) or 1e-6)
                 for w in s['Worker Threads'].values()], 0),
            'Write Throughput': lambda s: (not s['Enabled']) and -1 or sum(
                [w['Bytes Written'](w) / (w['Work Time'](w) or 1e-6)
                 for w in s['Worker Threads'].values()], 0),
            'Worker Threads': {},
            }
        logging.statistics["Cheroot HTTPServer %d" % id(self)] = self.stats
    
    def runtime(self):
        if self._start_time is None:
            return self._run_time
        else:
            return self._run_time + (time.time() - self._start_time)
    
    def __str__(self):
        return "%s.%s(%r)" % (self.__module__, self.__class__.__name__,
                              self.bind_addr)
    
    def _get_bind_addr(self):
        return self._bind_addr
    def _set_bind_addr(self, value):
        if isinstance(value, tuple) and value[0] in ('', None):
            # Despite the socket module docs, using '' does not
            # allow AI_PASSIVE to work. Passing None instead
            # returns '0.0.0.0' like we want. In other words:
            #     host    AI_PASSIVE     result
            #      ''         Y         192.168.x.y
            #      ''         N         192.168.x.y
            #     None        Y         0.0.0.0
            #     None        N         127.0.0.1
            # But since you can get the same effect with an explicit
            # '0.0.0.0', we deny both the empty string and None as values.
            raise ValueError("Host values of '' or None are not allowed. "
                             "Use '0.0.0.0' (IPv4) or '::' (IPv6) instead "
                             "to listen on all active interfaces.")
        self._bind_addr = value
    bind_addr = property(_get_bind_addr, _set_bind_addr,
        doc="""The interface on which to listen for connections.
        
        For TCP sockets, a (host, port) tuple. Host values may be any IPv4
        or IPv6 address, or any valid hostname. The string 'localhost' is a
        synonym for '127.0.0.1' (or '::1', if your hosts file prefers IPv6).
        The string '0.0.0.0' is a special IPv4 entry meaning "any active
        interface" (INADDR_ANY), and '::' is the similar IN6ADDR_ANY for
        IPv6. The empty string or None are not allowed.
        
        For UNIX sockets, supply the filename as a string.""")

    def safe_start(self):
        """Run the server forever, and stop it cleanly on exit."""
        try:
            self.start()
        except (KeyboardInterrupt, IOError):
            # The time.sleep call might raise
            # "IOError: [Errno 4] Interrupted function call" on KBInt.
            self.error_log('Keyboard Interrupt: shutting down')
            self.stop()
            raise
        except SystemExit:
            self.error_log('SystemExit raised: shutting down')
            self.stop()
            raise

    def start(self):
        """Run the server forever."""
        # Don't trap KeyboardInterrupt or SystemExit here; let the caller do
        # that, and it can then decide to call self.stop() or not (and when).
        # See self.safe_start() if you'd rather do it automatically.
        self._interrupt = None
        
        if self.software is None:
            self.software = "%s Server" % self.version

        # Select the appropriate socket
        if isinstance(self.bind_addr, basestring):
            # AF_UNIX socket
            
            # So we can reuse the socket...
            try: os.unlink(self.bind_addr)
            except: pass
            
            # So everyone can access the socket...
            try: os.chmod(self.bind_addr, 511) # 0777
            except: pass
            
            info = [(socket.AF_UNIX, socket.SOCK_STREAM, 0, "", self.bind_addr)]
        else:
            # AF_INET or AF_INET6 socket
            # Get the correct address family for our host (allows IPv6 addresses)
            host, port = self.bind_addr
            try:
                info = socket.getaddrinfo(host, port, socket.AF_UNSPEC,
                                          socket.SOCK_STREAM, 0, socket.AI_PASSIVE)
            except socket.gaierror:
                if ':' in self.bind_addr[0]:
                    info = [(socket.AF_INET6, socket.SOCK_STREAM,
                             0, "", self.bind_addr + (0, 0))]
                else:
                    info = [(socket.AF_INET, socket.SOCK_STREAM,
                             0, "", self.bind_addr)]
        
        self.socket = None
        msg = "No socket could be created"
        for res in info:
            af, socktype, proto, canonname, sa = res
            try:
                self.bind(af, socktype, proto)
            except socket.error:
                if self.socket:
                    self.socket.close()
                self.socket = None
                continue
            break
        if not self.socket:
            raise socket.error(msg)
        
        # Timeout so KeyboardInterrupt can be caught on Win32
        self.socket.settimeout(1)
        self.socket.listen(self.request_queue_size)
        
        # Create worker threads
        self.requests.start()
        
        self.ready = True
        self._start_time = time.time()
        while self.ready:
            try:
                self.tick()
            except (KeyboardInterrupt, SystemExit):
                raise
            except:
                self.error_log("Error in HTTPServer.tick", level=logging.ERROR,
                               traceback=True)
            
            if self.interrupt:
                while self.interrupt is True:
                    # Wait for self.stop() to complete. See _set_interrupt.
                    time.sleep(0.1)
                if self.interrupt:
                    raise self.interrupt

    def error_log(self, msg="", level=20, traceback=False):
        # Override this in subclasses as desired
        sys.stderr.write(msg + '\n')
        sys.stderr.flush()
        if traceback:
            tblines = format_exc()
            sys.stderr.write(tblines)
            sys.stderr.flush()

    def bind(self, family, type, proto=0):
        """Create (or recreate) the actual socket object."""
        self.socket = socket.socket(family, type, proto)
        prevent_socket_inheritance(self.socket)
        self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        if self.nodelay and not isinstance(self.bind_addr, str):
            self.socket.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
        
        if self.ssl_adapter is not None:
            self.socket = self.ssl_adapter.bind(self.socket)
        
        # If listening on the IPV6 any address ('::' = IN6ADDR_ANY),
        # activate dual-stack. See http://www.cherrypy.org/ticket/871.
        if (hasattr(socket, 'AF_INET6') and family == socket.AF_INET6
            and self.bind_addr[0] in ('::', '::0', '::0.0.0.0')):
            try:
                self.socket.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_V6ONLY, 0)
            except (AttributeError, socket.error):
                # Apparently, the socket option is not available in
                # this machine's TCP stack
                pass
        
        self.socket.bind(self.bind_addr)
    
    def tick(self):
        """Accept a new connection and put it on the Queue."""
        try:
            try:
                s, addr = self.socket.accept()
            except AttributeError:
                # Our socket got shut down (set to None) in self.stop()
                return
            if self.stats['Enabled']:
                self.stats['Accepts'] += 1
            if not self.ready:
                return
            
            prevent_socket_inheritance(s)
            if hasattr(s, 'settimeout'):
                s.settimeout(self.timeout)
            
            mf = makefile
            ssl_env = {}
            # if ssl cert and key are set, we try to be a secure HTTP server
            if self.ssl_adapter is not None:
                try:
                    s, ssl_env = self.ssl_adapter.wrap(s)
                except errors.NoSSLError:
                    msg = ("The client sent a plain HTTP request, but "
                           "this server only speaks HTTPS on this port.")
                    self.error_log(msg)

                    buf = ["%s 400 Bad Request\r\n" % self.protocol,
                           "Content-Length: %s\r\n" % len(msg),
                           "Content-Type: text/plain\r\n\r\n",
                           msg]

                    wfile = mf(s, "wb", DEFAULT_BUFFER_SIZE)
                    try:
                        write(wfile, ntob("".join(buf)))
                    except socket.error:
                        x = sys.exc_info()[1]
                        if x.args[0] not in errors.socket_errors_to_ignore:
                            raise
                    return
                if not s:
                    return
                mf = self.ssl_adapter.makefile
                # Re-apply our timeout since we may have a new socket object
                if hasattr(s, 'settimeout'):
                    s.settimeout(self.timeout)
            
            conn = self.ConnectionClass(self, s, mf)
            
            if not isinstance(self.bind_addr, basestring):
                # optional values
                # Until we do DNS lookups, omit REMOTE_HOST
                if addr is None: # sometimes this can happen
                    # figure out if AF_INET or AF_INET6.
                    if len(s.getsockname()) == 2:
                        # AF_INET
                        addr = ('0.0.0.0', 0)
                    else:
                        # AF_INET6
                        addr = ('::', 0)
                conn.remote_addr = addr[0]
                conn.remote_port = addr[1]
            
            conn.ssl_env = ssl_env
            
            self.requests.put(conn)
        except socket.timeout:
            # The only reason for the timeout in start() is so we can
            # notice keyboard interrupts on Win32, which don't interrupt
            # accept() by default
            return
        except socket.error:
            x = sys.exc_info()[1]
            if self.stats['Enabled']:
                self.stats['Socket Errors'] += 1
            if x.args[0] in errors.socket_error_eintr:
                # I *think* this is right. EINTR should occur when a signal
                # is received during the accept() call; all docs say retry
                # the call, and I *think* I'm reading it right that Python
                # will then go ahead and poll for and handle the signal
                # elsewhere. See http://www.cherrypy.org/ticket/707.
                return
            if x.args[0] in errors.socket_errors_nonblocking:
                # Just try again. See http://www.cherrypy.org/ticket/479.
                return
            if x.args[0] in errors.socket_errors_to_ignore:
                # Our socket was closed.
                # See http://www.cherrypy.org/ticket/686.
                return
            raise
    
    def _get_interrupt(self):
        return self._interrupt
    def _set_interrupt(self, interrupt):
        self._interrupt = True
        self.stop()
        self._interrupt = interrupt
    interrupt = property(_get_interrupt, _set_interrupt,
                         doc="Set this to an Exception instance to "
                             "interrupt the server.")
    
    def stop(self):
        """Gracefully shutdown a server that is serving forever."""
        self.ready = False
        if self._start_time is not None:
            self._run_time += (time.time() - self._start_time)
        self._start_time = None
        
        sock = getattr(self, "socket", None)
        if sock:
            if not isinstance(self.bind_addr, basestring):
                # Touch our own socket to make accept() return immediately.
                try:
                    host, port = sock.getsockname()[:2]
                except socket.error:
                    x = sys.exc_info()[1]
                    if x.args[0] not in errors.socket_errors_to_ignore:
                        # Changed to use error code and not message
                        # See http://www.cherrypy.org/ticket/860.
                        raise
                else:
                    # Note that we're explicitly NOT using AI_PASSIVE,
                    # here, because we want an actual IP to touch.
                    # localhost won't work if we've bound to a public IP,
                    # but it will if we bound to '0.0.0.0' (INADDR_ANY).
                    for res in socket.getaddrinfo(host, port, socket.AF_UNSPEC,
                                                  socket.SOCK_STREAM):
                        af, socktype, proto, canonname, sa = res
                        s = None
                        try:
                            s = socket.socket(af, socktype, proto)
                            # See http://groups.google.com/group/cherrypy-users/
                            #        browse_frm/thread/bbfe5eb39c904fe0
                            s.settimeout(1.0)
                            s.connect((host, port))
                            s.close()
                        except socket.error:
                            if s:
                                s.close()
            if hasattr(sock, "close"):
                sock.close()
            self.socket = None
        
        self.requests.stop(self.shutdown_timeout)


class Gateway(object):
    """A base class to interface HTTPServer with other systems, such as WSGI."""
    
    def __init__(self, req):
        self.req = req
    
    def respond(self):
        """Process the current request. Must be overridden in a subclass."""
        raise NotImplemented
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