view mercurial/hgweb/server.py @ 47965:f9e6f2bb721d

rhg: Don’t compare ambiguous files one byte at a time

Even though the use of `BufReader` reduces the number of syscalls to read
the file from disk, `.bytes()` yields a separate `Result` for every byte.
Creating those results and dispatching on them is most likely costly.

Instead, this commit opts for simplicity by reading the entire file into memory
and comparing a single pair of byte strings. Note that memory already needs to
contain the entire previous contents of the file, as read from the filelog.
So with an extremely large file this doubles memory use but does not make it
grow by orders of magnitude.

At first I wrote code that still avoids reading the entire file into memory
and compares one buffer at a time with `BufReader`. Find this code below for
posterity. However its correctness is subtle. I ended up preferring the
simplicity of the obviously-correct single comparison.

```rust
let mut reader = BufReader::new(fobj);
let mut expected = &contents_in_p1[..];
loop {
    let buf = reader.fill_buf().when_reading_file(&fs_path)?;
    if buf.is_empty() {
        // Found EOF
        return Ok(expected.is_empty());
    } else if let Some(rest) = expected.drop_prefix(buf) {
        // What we read so far matches the expected content, continue reading
        let buf_len = buf.len();
        reader.consume(buf_len);
        expected = rest
    } else {
        // Found different content
        return Ok(false);
    }
}
```

Differential Revision: https://phab.mercurial-scm.org/D11412

# hgweb/server.py - The standalone hg web server.
#
# Copyright 21 May 2005 - (c) 2005 Jake Edge <[e-mail]>
# Copyright 2005-2007 Olivia Mackall <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from __future__ import absolute_import

import errno
import importlib
import os
import socket
import sys
import traceback
import wsgiref.validate

from ..i18n import _
from ..pycompat import (
    getattr,
    open,
)

from .. import (
    encoding,
    error,
    pycompat,
    util,
)
from ..utils import (
    urlutil,
)

httpservermod = util.httpserver
socketserver = util.socketserver
urlerr = util.urlerr
urlreq = util.urlreq

from . import common


def _splitURI(uri):
    """Return path and query that has been split from uri

    Just like CGI environment, the path is unquoted, the query is
    not.
    """
    if '?' in uri:
        path, query = uri.split('?', 1)
    else:
        path, query = uri, r''
    return urlreq.unquote(path), query


class _error_logger(object):
    def __init__(self, handler):
        self.handler = handler

    def flush(self):
        pass

    def write(self, str):
        self.writelines(str.split(b'\n'))

    def writelines(self, seq):
        for msg in seq:
            self.handler.log_error("HG error:  %s", encoding.strfromlocal(msg))


class _httprequesthandler(httpservermod.basehttprequesthandler):

    url_scheme = b'http'

    @staticmethod
    def preparehttpserver(httpserver, ui):
        """Prepare .socket of new HTTPServer instance"""

    def __init__(self, *args, **kargs):
        self.protocol_version = r'HTTP/1.1'
        httpservermod.basehttprequesthandler.__init__(self, *args, **kargs)

    def _log_any(self, fp, format, *args):
        fp.write(
            pycompat.sysbytes(
                r"%s - - [%s] %s"
                % (
                    self.client_address[0],
                    self.log_date_time_string(),
                    format % args,
                )
            )
            + b'\n'
        )
        fp.flush()

    def log_error(self, format, *args):
        self._log_any(self.server.errorlog, format, *args)

    def log_message(self, format, *args):
        self._log_any(self.server.accesslog, format, *args)

    def log_request(self, code='-', size='-'):
        xheaders = []
        if util.safehasattr(self, b'headers'):
            xheaders = [
                h for h in self.headers.items() if h[0].startswith('x-')
            ]
        self.log_message(
            '"%s" %s %s%s',
            self.requestline,
            str(code),
            str(size),
            ''.join([' %s:%s' % h for h in sorted(xheaders)]),
        )

    def do_write(self):
        try:
            self.do_hgweb()
        except socket.error as inst:
            if inst.errno != errno.EPIPE:
                raise

    def do_POST(self):
        try:
            self.do_write()
        except Exception as e:
            # I/O below could raise another exception. So log the original
            # exception first to ensure it is recorded.
            if not (
                isinstance(e, (OSError, socket.error))
                and e.errno == errno.ECONNRESET
            ):
                tb = "".join(traceback.format_exception(*sys.exc_info()))
                # We need a native-string newline to poke in the log
                # message, because we won't get a newline when using an
                # r-string. This is the easy way out.
                newline = chr(10)
                self.log_error(
                    r"Exception happened during processing "
                    "request '%s':%s%s",
                    self.path,
                    newline,
                    tb,
                )

            self._start_response("500 Internal Server Error", [])
            self._write(b"Internal Server Error")
            self._done()

    def do_PUT(self):
        self.do_POST()

    def do_GET(self):
        self.do_POST()

    def do_hgweb(self):
        self.sent_headers = False
        path, query = _splitURI(self.path)

        # Ensure the slicing of path below is valid
        if path != self.server.prefix and not path.startswith(
            self.server.prefix + b'/'
        ):
            self._start_response(pycompat.strurl(common.statusmessage(404)), [])
            if self.command == 'POST':
                # Paranoia: tell the client we're going to close the
                # socket so they don't try and reuse a socket that
                # might have a POST body waiting to confuse us. We do
                # this by directly munging self.saved_headers because
                # self._start_response ignores Connection headers.
                self.saved_headers = [('Connection', 'Close')]
            self._write(b"Not Found")
            self._done()
            return

        env = {}
        env['GATEWAY_INTERFACE'] = 'CGI/1.1'
        env['REQUEST_METHOD'] = self.command
        env['SERVER_NAME'] = self.server.server_name
        env['SERVER_PORT'] = str(self.server.server_port)
        env['REQUEST_URI'] = self.path
        env['SCRIPT_NAME'] = pycompat.sysstr(self.server.prefix)
        env['PATH_INFO'] = pycompat.sysstr(path[len(self.server.prefix) :])
        env['REMOTE_HOST'] = self.client_address[0]
        env['REMOTE_ADDR'] = self.client_address[0]
        env['QUERY_STRING'] = query or ''

        if pycompat.ispy3:
            if self.headers.get_content_type() is None:
                env['CONTENT_TYPE'] = self.headers.get_default_type()
            else:
                env['CONTENT_TYPE'] = self.headers.get_content_type()
            length = self.headers.get('content-length')
        else:
            if self.headers.typeheader is None:
                env['CONTENT_TYPE'] = self.headers.type
            else:
                env['CONTENT_TYPE'] = self.headers.typeheader
            length = self.headers.getheader('content-length')
        if length:
            env['CONTENT_LENGTH'] = length
        for header in [
            h
            for h in self.headers.keys()
            if h.lower() not in ('content-type', 'content-length')
        ]:
            hkey = 'HTTP_' + header.replace('-', '_').upper()
            hval = self.headers.get(header)
            hval = hval.replace('\n', '').strip()
            if hval:
                env[hkey] = hval
        env['SERVER_PROTOCOL'] = self.request_version
        env['wsgi.version'] = (1, 0)
        env['wsgi.url_scheme'] = pycompat.sysstr(self.url_scheme)
        if env.get('HTTP_EXPECT', b'').lower() == b'100-continue':
            self.rfile = common.continuereader(self.rfile, self.wfile.write)

        env['wsgi.input'] = self.rfile
        env['wsgi.errors'] = _error_logger(self)
        env['wsgi.multithread'] = isinstance(
            self.server, socketserver.ThreadingMixIn
        )
        if util.safehasattr(socketserver, b'ForkingMixIn'):
            env['wsgi.multiprocess'] = isinstance(
                self.server, socketserver.ForkingMixIn
            )
        else:
            env['wsgi.multiprocess'] = False

        env['wsgi.run_once'] = 0

        wsgiref.validate.check_environ(env)

        self.saved_status = None
        self.saved_headers = []
        self.length = None
        self._chunked = None
        for chunk in self.server.application(env, self._start_response):
            self._write(chunk)
        if not self.sent_headers:
            self.send_headers()
        self._done()

    def send_headers(self):
        if not self.saved_status:
            raise AssertionError(
                b"Sending headers before start_response() called"
            )
        saved_status = self.saved_status.split(None, 1)
        saved_status[0] = int(saved_status[0])
        self.send_response(*saved_status)
        self.length = None
        self._chunked = False
        for h in self.saved_headers:
            self.send_header(*h)
            if h[0].lower() == 'content-length':
                self.length = int(h[1])
        if self.length is None and saved_status[0] != common.HTTP_NOT_MODIFIED:
            self._chunked = (
                not self.close_connection and self.request_version == 'HTTP/1.1'
            )
            if self._chunked:
                self.send_header('Transfer-Encoding', 'chunked')
            else:
                self.send_header('Connection', 'close')
        self.end_headers()
        self.sent_headers = True

    def _start_response(self, http_status, headers, exc_info=None):
        assert isinstance(http_status, str)
        code, msg = http_status.split(None, 1)
        code = int(code)
        self.saved_status = http_status
        bad_headers = ('connection', 'transfer-encoding')
        self.saved_headers = [
            h for h in headers if h[0].lower() not in bad_headers
        ]
        return self._write

    def _write(self, data):
        if not self.saved_status:
            raise AssertionError(b"data written before start_response() called")
        elif not self.sent_headers:
            self.send_headers()
        if self.length is not None:
            if len(data) > self.length:
                raise AssertionError(
                    b"Content-length header sent, but more "
                    b"bytes than specified are being written."
                )
            self.length = self.length - len(data)
        elif self._chunked and data:
            data = b'%x\r\n%s\r\n' % (len(data), data)
        self.wfile.write(data)
        self.wfile.flush()

    def _done(self):
        if self._chunked:
            self.wfile.write(b'0\r\n\r\n')
            self.wfile.flush()

    def version_string(self):
        if self.server.serverheader:
            return encoding.strfromlocal(self.server.serverheader)
        return httpservermod.basehttprequesthandler.version_string(self)


class _httprequesthandlerssl(_httprequesthandler):
    """HTTPS handler based on Python's ssl module"""

    url_scheme = b'https'

    @staticmethod
    def preparehttpserver(httpserver, ui):
        try:
            from .. import sslutil

            sslutil.wrapserversocket
        except ImportError:
            raise error.Abort(_(b"SSL support is unavailable"))

        certfile = ui.config(b'web', b'certificate')

        # These config options are currently only meant for testing. Use
        # at your own risk.
        cafile = ui.config(b'devel', b'servercafile')
        reqcert = ui.configbool(b'devel', b'serverrequirecert')

        httpserver.socket = sslutil.wrapserversocket(
            httpserver.socket,
            ui,
            certfile=certfile,
            cafile=cafile,
            requireclientcert=reqcert,
        )

    def setup(self):
        self.connection = self.request
        self.rfile = self.request.makefile("rb", self.rbufsize)
        self.wfile = self.request.makefile("wb", self.wbufsize)


try:
    import threading

    threading.active_count()  # silence pyflakes and bypass demandimport
    _mixin = socketserver.ThreadingMixIn
except ImportError:
    if util.safehasattr(os, b"fork"):
        _mixin = socketserver.ForkingMixIn
    else:

        class _mixin(object):
            pass


def openlog(opt, default):
    if opt and opt != b'-':
        return open(opt, b'ab')
    return default


class MercurialHTTPServer(_mixin, httpservermod.httpserver, object):

    # SO_REUSEADDR has broken semantics on windows
    if pycompat.iswindows:
        allow_reuse_address = 0

    def __init__(self, ui, app, addr, handler, **kwargs):
        httpservermod.httpserver.__init__(self, addr, handler, **kwargs)
        self.daemon_threads = True
        self.application = app

        handler.preparehttpserver(self, ui)

        prefix = ui.config(b'web', b'prefix')
        if prefix:
            prefix = b'/' + prefix.strip(b'/')
        self.prefix = prefix

        alog = openlog(ui.config(b'web', b'accesslog'), ui.fout)
        elog = openlog(ui.config(b'web', b'errorlog'), ui.ferr)
        self.accesslog = alog
        self.errorlog = elog

        self.addr, self.port = self.socket.getsockname()[0:2]
        self.fqaddr = self.server_name

        self.serverheader = ui.config(b'web', b'server-header')


class IPv6HTTPServer(MercurialHTTPServer):
    address_family = getattr(socket, 'AF_INET6', None)

    def __init__(self, *args, **kwargs):
        if self.address_family is None:
            raise error.RepoError(_(b'IPv6 is not available on this system'))
        super(IPv6HTTPServer, self).__init__(*args, **kwargs)


def create_server(ui, app):

    if ui.config(b'web', b'certificate'):
        handler = _httprequesthandlerssl
    else:
        handler = _httprequesthandler

    if ui.configbool(b'web', b'ipv6'):
        cls = IPv6HTTPServer
    else:
        cls = MercurialHTTPServer

    # ugly hack due to python issue5853 (for threaded use)
    try:
        import mimetypes

        mimetypes.init()
    except UnicodeDecodeError:
        # Python 2.x's mimetypes module attempts to decode strings
        # from Windows' ANSI APIs as ascii (fail), then re-encode them
        # as ascii (clown fail), because the default Python Unicode
        # codec is hardcoded as ascii.

        sys.argv  # unwrap demand-loader so that reload() works
        # resurrect sys.setdefaultencoding()
        try:
            importlib.reload(sys)
        except AttributeError:
            reload(sys)
        oldenc = sys.getdefaultencoding()
        sys.setdefaultencoding(b"latin1")  # or any full 8-bit encoding
        mimetypes.init()
        sys.setdefaultencoding(oldenc)

    address = ui.config(b'web', b'address')
    port = urlutil.getport(ui.config(b'web', b'port'))
    try:
        return cls(ui, app, (address, port), handler)
    except socket.error as inst:
        raise error.Abort(
            _(b"cannot start server at '%s:%d': %s")
            % (address, port, encoding.strtolocal(inst.args[1]))
        )