Revert "Python API: Add enum and union support."

This reverts commit a5ee900fb75201bbfceaf13c8bc57a13ed094988.

Some of the unit tests breaks. Backing out until fixed.

Change-Id: I1846fb417db44a2a772f7b59cda8bcfe6d39f8c3
Signed-off-by: Ole Troan <ot@cisco.com>

1 files changed, 891 insertions, 0 deletions

diff --git a/src/vpp-api/python/vpp_papi.py b/src/vpp-api/python/vpp_papi.py
new file mode 100644
index 00000000000..ece0e4ee52d
--- /dev/null
+++ b/src/vpp-api/python/vpp_papi.py
@@ -0,0 +1,891 @@
+#!/usr/bin/env python
+#
+# Copyright (c) 2016 Cisco and/or its affiliates.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at:
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+from __future__ import print_function
+import sys
+import os
+import logging
+import collections
+import struct
+import json
+import threading
+import fnmatch
+import weakref
+import atexit
+from cffi import FFI
+import cffi
+
+if sys.version[0] == '2':
+    import Queue as queue
+else:
+    import queue as queue
+
+ffi = FFI()
+ffi.cdef("""
+typedef void (*vac_callback_t)(unsigned char * data, int len);
+typedef void (*vac_error_callback_t)(void *, unsigned char *, int);
+int vac_connect(char * name, char * chroot_prefix, vac_callback_t cb,
+    int rx_qlen);
+int vac_disconnect(void);
+int vac_read(char **data, int *l, unsigned short timeout);
+int vac_write(char *data, int len);
+void vac_free(void * msg);
+
+int vac_get_msg_index(unsigned char * name);
+int vac_msg_table_size(void);
+int vac_msg_table_max_index(void);
+
+void vac_rx_suspend (void);
+void vac_rx_resume (void);
+void vac_set_error_handler(vac_error_callback_t);
+ """)
+
+# Barfs on failure, no need to check success.
+vpp_api = ffi.dlopen('libvppapiclient.so')
+
+
+def vpp_atexit(vpp_weakref):
+    """Clean up VPP connection on shutdown."""
+    vpp_instance = vpp_weakref()
+    if vpp_instance.connected:
+        vpp_instance.logger.debug('Cleaning up VPP on exit')
+        vpp_instance.disconnect()
+
+
+vpp_object = None
+
+
+def vpp_iterator(d):
+    if sys.version[0] == '2':
+        return d.iteritems()
+    else:
+        return d.items()
+
+
+@ffi.callback("void(unsigned char *, int)")
+def vac_callback_sync(data, len):
+    vpp_object.msg_handler_sync(ffi.buffer(data, len))
+
+
+@ffi.callback("void(unsigned char *, int)")
+def vac_callback_async(data, len):
+    vpp_object.msg_handler_async(ffi.buffer(data, len))
+
+
+@ffi.callback("void(void *, unsigned char *, int)")
+def vac_error_handler(arg, msg, msg_len):
+    vpp_object.logger.warning("VPP API client:: %s", ffi.string(msg, msg_len))
+
+
+class Empty(object):
+    pass
+
+
+class FuncWrapper(object):
+    def __init__(self, func):
+        self._func = func
+        self.__name__ = func.__name__
+
+    def __call__(self, **kwargs):
+        return self._func(**kwargs)
+
+
+class VPP():
+    """VPP interface.
+
+    This class provides the APIs to VPP.  The APIs are loaded
+    from provided .api.json files and makes functions accordingly.
+    These functions are documented in the VPP .api files, as they
+    are dynamically created.
+
+    Additionally, VPP can send callback messages; this class
+    provides a means to register a callback function to receive
+    these messages in a background thread.
+    """
+    def __init__(self, apifiles=None, testmode=False, async_thread=True,
+                 logger=None, loglevel=None,
+                 read_timeout=0):
+        """Create a VPP API object.
+
+        apifiles is a list of files containing API
+        descriptions that will be loaded - methods will be
+        dynamically created reflecting these APIs.  If not
+        provided this will load the API files from VPP's
+        default install location.
+
+        logger, if supplied, is the logging logger object to log to.
+        loglevel, if supplied, is the log level this logger is set
+        to report at (from the loglevels in the logging module).
+        """
+        global vpp_object
+        vpp_object = self
+
+        if logger is None:
+            logger = logging.getLogger(__name__)
+            if loglevel is not None:
+                logger.setLevel(loglevel)
+
+        self.logger = logger
+
+        self.messages = {}
+        self.id_names = []
+        self.id_msgdef = []
+        self.connected = False
+        self.header = struct.Struct('>HI')
+        self.apifiles = []
+        self.event_callback = None
+        self.message_queue = queue.Queue()
+        self.read_timeout = read_timeout
+        self.vpp_api = vpp_api
+        self.async_thread = async_thread
+
+        if not apifiles:
+            # Pick up API definitions from default directory
+            try:
+                apifiles = self.find_api_files()
+            except RuntimeError:
+                # In test mode we don't care that we can't find the API files
+                if testmode:
+                    apifiles = []
+                else:
+                    raise
+
+        for file in apifiles:
+            with open(file) as apidef_file:
+                api = json.load(apidef_file)
+                for t in api['types']:
+                    self.add_type(t[0], t[1:])
+
+                for m in api['messages']:
+                    self.add_message(m[0], m[1:])
+        self.apifiles = apifiles
+
+        # Basic sanity check
+        if len(self.messages) == 0 and not testmode:
+            raise ValueError(1, 'Missing JSON message definitions')
+
+        # Make sure we allow VPP to clean up the message rings.
+        atexit.register(vpp_atexit, weakref.ref(self))
+
+        # Register error handler
+        vpp_api.vac_set_error_handler(vac_error_handler)
+
+        # Support legacy CFFI
+        # from_buffer supported from 1.8.0
+        (major, minor, patch) = [int(s) for s in
+                                 cffi.__version__.split('.', 3)]
+        if major >= 1 and minor >= 8:
+            self._write = self._write_new_cffi
+        else:
+            self._write = self._write_legacy_cffi
+
+    class ContextId(object):
+        """Thread-safe provider of unique context IDs."""
+        def __init__(self):
+            self.context = 0
+            self.lock = threading.Lock()
+
+        def __call__(self):
+            """Get a new unique (or, at least, not recently used) context."""
+            with self.lock:
+                self.context += 1
+                return self.context
+    get_context = ContextId()
+
+    @classmethod
+    def find_api_dir(cls):
+        """Attempt to find the best directory in which API definition
+        files may reside. If the value VPP_API_DIR exists in the environment
+        then it is first on the search list. If we're inside a recognized
+        location in a VPP source tree (src/scripts and src/vpp-api/python)
+        then entries from there to the likely locations in build-root are
+        added. Finally the location used by system packages is added.
+
+        :returns: A single directory name, or None if no such directory
+            could be found.
+        """
+        dirs = []
+
+        if 'VPP_API_DIR' in os.environ:
+            dirs.append(os.environ['VPP_API_DIR'])
+
+        # perhaps we're in the 'src/scripts' or 'src/vpp-api/python' dir;
+        # in which case, plot a course to likely places in the src tree
+        import __main__ as main
+        if hasattr(main, '__file__'):
+            # get the path of the calling script
+            localdir = os.path.dirname(os.path.realpath(main.__file__))
+        else:
+            # use cwd if there is no calling script
+            localdir = os.getcwd()
+        localdir_s = localdir.split(os.path.sep)
+
+        def dmatch(dir):
+            """Match dir against right-hand components of the script dir"""
+            d = dir.split('/')  # param 'dir' assumes a / separator
+            length = len(d)
+            return len(localdir_s) > length and localdir_s[-length:] == d
+
+        def sdir(srcdir, variant):
+            """Build a path from srcdir to the staged API files of
+            'variant'  (typically '' or '_debug')"""
+            # Since 'core' and 'plugin' files are staged
+            # in separate directories, we target the parent dir.
+            return os.path.sep.join((
+                srcdir,
+                'build-root',
+                'install-vpp%s-native' % variant,
+                'vpp',
+                'share',
+                'vpp',
+                'api',
+            ))
+
+        srcdir = None
+        if dmatch('src/scripts'):
+            srcdir = os.path.sep.join(localdir_s[:-2])
+        elif dmatch('src/vpp-api/python'):
+            srcdir = os.path.sep.join(localdir_s[:-3])
+        elif dmatch('test'):
+            # we're apparently running tests
+            srcdir = os.path.sep.join(localdir_s[:-1])
+
+        if srcdir:
+            # we're in the source tree, try both the debug and release
+            # variants.
+            dirs.append(sdir(srcdir, '_debug'))
+            dirs.append(sdir(srcdir, ''))
+
+        # Test for staged copies of the scripts
+        # For these, since we explicitly know if we're running a debug versus
+        # release variant, target only the relevant directory
+        if dmatch('build-root/install-vpp_debug-native/vpp/bin'):
+            srcdir = os.path.sep.join(localdir_s[:-4])
+            dirs.append(sdir(srcdir, '_debug'))
+        if dmatch('build-root/install-vpp-native/vpp/bin'):
+            srcdir = os.path.sep.join(localdir_s[:-4])
+            dirs.append(sdir(srcdir, ''))
+
+        # finally, try the location system packages typically install into
+        dirs.append(os.path.sep.join(('', 'usr', 'share', 'vpp', 'api')))
+
+        # check the directories for existance; first one wins
+        for dir in dirs:
+            if os.path.isdir(dir):
+                return dir
+
+        return None
+
+    @classmethod
+    def find_api_files(cls, api_dir=None, patterns='*'):
+        """Find API definition files from the given directory tree with the
+        given pattern. If no directory is given then find_api_dir() is used
+        to locate one. If no pattern is given then all definition files found
+        in the directory tree are used.
+
+        :param api_dir: A directory tree in which to locate API definition
+            files; subdirectories are descended into.
+            If this is None then find_api_dir() is called to discover it.
+        :param patterns: A list of patterns to use in each visited directory
+            when looking for files.
+            This can be a list/tuple object or a comma-separated string of
+            patterns. Each value in the list will have leading/trialing
+            whitespace stripped.
+            The pattern specifies the first part of the filename, '.api.json'
+            is appended.
+            The results are de-duplicated, thus overlapping patterns are fine.
+            If this is None it defaults to '*' meaning "all API files".
+        :returns: A list of file paths for the API files found.
+        """
+        if api_dir is None:
+            api_dir = cls.find_api_dir()
+            if api_dir is None:
+                raise RuntimeError("api_dir cannot be located")
+
+        if isinstance(patterns, list) or isinstance(patterns, tuple):
+            patterns = [p.strip() + '.api.json' for p in patterns]
+        else:
+            patterns = [p.strip() + '.api.json' for p in patterns.split(",")]
+
+        api_files = []
+        for root, dirnames, files in os.walk(api_dir):
+            # iterate all given patterns and de-dup the result
+            files = set(sum([fnmatch.filter(files, p) for p in patterns], []))
+            for filename in files:
+                api_files.append(os.path.join(root, filename))
+
+        return api_files
+
+    def status(self):
+        """Debug function: report current VPP API status to stdout."""
+        print('Connected') if self.connected else print('Not Connected')
+        print('Read API definitions from', ', '.join(self.apifiles))
+
+    def __struct(self, t, n=None, e=-1, vl=None):
+        """Create a packing structure for a message."""
+        base_types = {'u8': 'B',
+                      'u16': 'H',
+                      'u32': 'I',
+                      'i32': 'i',
+                      'u64': 'Q',
+                      'f64': 'd', }
+
+        if t in base_types:
+            if not vl:
+                if e > 0 and t == 'u8':
+                    # Fixed byte array
+                    s = struct.Struct('>' + str(e) + 's')
+                    return s.size, s
+                if e > 0:
+                    # Fixed array of base type
+                    s = struct.Struct('>' + base_types[t])
+                    return s.size, [e, s]
+                elif e == 0:
+                    # Old style variable array
+                    s = struct.Struct('>' + base_types[t])
+                    return s.size, [-1, s]
+            else:
+                # Variable length array
+                if t == 'u8':
+                    s = struct.Struct('>s')
+                    return s.size, [vl, s]
+                else:
+                    s = struct.Struct('>' + base_types[t])
+                return s.size, [vl, s]
+
+            s = struct.Struct('>' + base_types[t])
+            return s.size, s
+
+        if t in self.messages:
+            size = self.messages[t]['sizes'][0]
+
+            # Return a list in case of array
+            if e > 0 and not vl:
+                return size, [e, lambda self, encode, buf, offset, args: (
+                    self.__struct_type(encode, self.messages[t], buf, offset,
+                                       args))]
+            if vl:
+                return size, [vl, lambda self, encode, buf, offset, args: (
+                    self.__struct_type(encode, self.messages[t], buf, offset,
+                                       args))]
+            elif e == 0:
+                # Old style VLA
+                raise NotImplementedError(1,
+                                          'No support for compound types ' + t)
+            return size, lambda self, encode, buf, offset, args: (
+                self.__struct_type(encode, self.messages[t], buf, offset, args)
+            )
+
+        raise ValueError(1, 'Invalid message type: ' + t)
+
+    def __struct_type(self, encode, msgdef, buf, offset, kwargs):
+        """Get a message packer or unpacker."""
+        if encode:
+            return self.__struct_type_encode(msgdef, buf, offset, kwargs)
+        else:
+            return self.__struct_type_decode(msgdef, buf, offset)
+
+    def __struct_type_encode(self, msgdef, buf, offset, kwargs):
+        off = offset
+        size = 0
+
+        for k in kwargs:
+            if k not in msgdef['args']:
+                raise ValueError(1, 'Non existing argument [' + k + ']' +
+                                    ' used in call to: ' +
+                                 self.id_names[kwargs['_vl_msg_id']] + '()')
+
+        for k, v in vpp_iterator(msgdef['args']):
+            off += size
+            if k in kwargs:
+                if type(v) is list:
+                    if callable(v[1]):
+                        e = kwargs[v[0]] if v[0] in kwargs else v[0]
+                        if e != len(kwargs[k]):
+                            raise (ValueError(1,
+                                              'Input list length mismatch: '
+                                              '%s (%s != %s)' %
+                                              (k, e, len(kwargs[k]))))
+                        size = 0
+                        for i in range(e):
+                            size += v[1](self, True, buf, off + size,
+                                         kwargs[k][i])
+                    else:
+                        if v[0] in kwargs:
+                            kwargslen = kwargs[v[0]]
+                            if kwargslen != len(kwargs[k]):
+                                raise ValueError(1,
+                                                 'Input list length mismatch:'
+                                                 ' %s (%s != %s)' %
+                                                 (k, kwargslen,
+                                                  len(kwargs[k])))
+                        else:
+                            kwargslen = len(kwargs[k])
+                        if v[1].size == 1:
+                            buf[off:off + kwargslen] = bytearray(kwargs[k])
+                            size = kwargslen
+                        else:
+                            size = 0
+                            for i in kwargs[k]:
+                                v[1].pack_into(buf, off + size, i)
+                                size += v[1].size
+                else:
+                    if callable(v):
+                        size = v(self, True, buf, off, kwargs[k])
+                    else:
+                        if type(kwargs[k]) is str and v.size < len(kwargs[k]):
+                            raise ValueError(1,
+                                             'Input list length mismatch: '
+                                             '%s (%s < %s)' %
+                                             (k, v.size, len(kwargs[k])))
+                        v.pack_into(buf, off, kwargs[k])
+                        size = v.size
+            else:
+                size = v.size if not type(v) is list else 0
+
+        return off + size - offset
+
+    def __getitem__(self, name):
+        if name in self.messages:
+            return self.messages[name]
+        return None
+
+    def get_size(self, sizes, kwargs):
+        total_size = sizes[0]
+        for e in sizes[1]:
+            if e in kwargs and type(kwargs[e]) is list:
+                total_size += len(kwargs[e]) * sizes[1][e]
+        return total_size
+
+    def encode(self, msgdef, kwargs):
+        # Make suitably large buffer
+        size = self.get_size(msgdef['sizes'], kwargs)
+        buf = bytearray(size)
+        offset = 0
+        size = self.__struct_type(True, msgdef, buf, offset, kwargs)
+        return buf[:offset + size]
+
+    def decode(self, msgdef, buf):
+        return self.__struct_type(False, msgdef, buf, 0, None)[1]
+
+    def __struct_type_decode(self, msgdef, buf, offset):
+        res = []
+        off = offset
+        size = 0
+        for k, v in vpp_iterator(msgdef['args']):
+            off += size
+            if type(v) is list:
+                lst = []
+                if callable(v[1]):  # compound type
+                    size = 0
+                    if v[0] in msgdef['args']:  # vla
+                        e = res[v[2]]
+                    else:  # fixed array
+                        e = v[0]
+                    res.append(lst)
+                    for i in range(e):
+                        (s, l) = v[1](self, False, buf, off + size, None)
+                        lst.append(l)
+                        size += s
+                    continue
+                if v[1].size == 1:
+                    if type(v[0]) is int:
+                        size = len(buf) - off
+                    else:
+                        size = res[v[2]]
+                    res.append(buf[off:off + size])
+                else:
+                    e = v[0] if type(v[0]) is int else res[v[2]]
+                    if e == -1:
+                        e = (len(buf) - off) / v[1].size
+                    lst = []
+                    res.append(lst)
+                    size = 0
+                    for i in range(e):
+                        lst.append(v[1].unpack_from(buf, off + size)[0])
+                        size += v[1].size
+            else:
+                if callable(v):
+                    size = 0
+                    (s, l) = v(self, False, buf, off, None)
+                    res.append(l)
+                    size += s
+                else:
+                    res.append(v.unpack_from(buf, off)[0])
+                    size = v.size
+
+        return off + size - offset, msgdef['return_tuple']._make(res)
+
+    def ret_tup(self, name):
+        if name in self.messages and 'return_tuple' in self.messages[name]:
+            return self.messages[name]['return_tuple']
+        return None
+
+    def duplicate_check_ok(self, name, msgdef):
+        crc = None
+        for c in msgdef:
+            if type(c) is dict and 'crc' in c:
+                crc = c['crc']
+                break
+        if crc:
+            # We can get duplicates because of imports
+            if crc == self.messages[name]['crc']:
+                return True
+        return False
+
+    def add_message(self, name, msgdef, typeonly=False):
+        if name in self.messages:
+            if typeonly:
+                if self.duplicate_check_ok(name, msgdef):
+                    return
+            raise ValueError('Duplicate message name: ' + name)
+
+        args = collections.OrderedDict()
+        argtypes = collections.OrderedDict()
+        fields = []
+        msg = {}
+        total_size = 0
+        sizes = {}
+        for i, f in enumerate(msgdef):
+            if type(f) is dict and 'crc' in f:
+                msg['crc'] = f['crc']
+                continue
+            field_type = f[0]
+            field_name = f[1]
+            if len(f) == 3 and f[2] == 0 and i != len(msgdef) - 2:
+                raise ValueError('Variable Length Array must be last: ' + name)
+            size, s = self.__struct(*f)
+            args[field_name] = s
+            if type(s) == list and type(s[0]) == int and \
+               type(s[1]) == struct.Struct:
+                if s[0] < 0:
+                    sizes[field_name] = size
+                else:
+                    sizes[field_name] = size
+                    total_size += s[0] * size
+            else:
+                sizes[field_name] = size
+                total_size += size
+
+            argtypes[field_name] = field_type
+            if len(f) == 4:  # Find offset to # elements field
+                idx = list(args.keys()).index(f[3]) - i
+                args[field_name].append(idx)
+            fields.append(field_name)
+        msg['return_tuple'] = collections.namedtuple(name, fields,
+                                                     rename=True)
+        self.messages[name] = msg
+        self.messages[name]['args'] = args
+        self.messages[name]['argtypes'] = argtypes
+        self.messages[name]['typeonly'] = typeonly
+        self.messages[name]['sizes'] = [total_size, sizes]
+        return self.messages[name]
+
+    def add_type(self, name, typedef):
+        return self.add_message('vl_api_' + name + '_t', typedef,
+                                typeonly=True)
+
+    def make_function(self, name, i, msgdef, multipart, async):
+        if (async):
+            def f(**kwargs):
+                return self._call_vpp_async(i, msgdef, **kwargs)
+        else:
+            def f(**kwargs):
+                return self._call_vpp(i, msgdef, multipart, **kwargs)
+        args = self.messages[name]['args']
+        argtypes = self.messages[name]['argtypes']
+        f.__name__ = str(name)
+        f.__doc__ = ", ".join(["%s %s" %
+                               (argtypes[k], k) for k in args.keys()])
+        return f
+
+    @property
+    def api(self):
+        if not hasattr(self, "_api"):
+            raise Exception("Not connected, api definitions not available")
+        return self._api
+
+    def _register_functions(self, async=False):
+        self.id_names = [None] * (self.vpp_dictionary_maxid + 1)
+        self.id_msgdef = [None] * (self.vpp_dictionary_maxid + 1)
+        self._api = Empty()
+        for name, msgdef in vpp_iterator(self.messages):
+            if self.messages[name]['typeonly']:
+                continue
+            crc = self.messages[name]['crc']
+            n = name + '_' + crc[2:]
+            i = vpp_api.vac_get_msg_index(n.encode())
+            if i > 0:
+                self.id_msgdef[i] = msgdef
+                self.id_names[i] = name
+                multipart = True if name.find('_dump') > 0 else False
+                f = self.make_function(name, i, msgdef, multipart, async)
+                setattr(self._api, name, FuncWrapper(f))
+            else:
+                self.logger.debug(
+                    'No such message type or failed CRC checksum: %s', n)
+
+    def _write_new_cffi(self, buf):
+        """Send a binary-packed message to VPP."""
+        if not self.connected:
+            raise IOError(1, 'Not connected')
+        return vpp_api.vac_write(ffi.from_buffer(buf), len(buf))
+
+    def _write_legacy_cffi(self, buf):
+        """Send a binary-packed message to VPP."""
+        if not self.connected:
+            raise IOError(1, 'Not connected')
+        return vpp_api.vac_write(bytes(buf), len(buf))
+
+    def _read(self):
+        if not self.connected:
+            raise IOError(1, 'Not connected')
+        mem = ffi.new("char **")
+        size = ffi.new("int *")
+        rv = vpp_api.vac_read(mem, size, self.read_timeout)
+        if rv:
+            raise IOError(rv, 'vac_read failed')
+        msg = bytes(ffi.buffer(mem[0], size[0]))
+        vpp_api.vac_free(mem[0])
+        return msg
+
+    def connect_internal(self, name, msg_handler, chroot_prefix, rx_qlen,
+                         async):
+        pfx = chroot_prefix.encode() if chroot_prefix else ffi.NULL
+        rv = vpp_api.vac_connect(name.encode(), pfx, msg_handler, rx_qlen)
+        if rv != 0:
+            raise IOError(2, 'Connect failed')
+        self.connected = True
+
+        self.vpp_dictionary_maxid = vpp_api.vac_msg_table_max_index()
+        self._register_functions(async=async)
+
+        # Initialise control ping
+        crc = self.messages['control_ping']['crc']
+        self.control_ping_index = vpp_api.vac_get_msg_index(
+            ('control_ping' + '_' + crc[2:]).encode())
+        self.control_ping_msgdef = self.messages['control_ping']
+        if self.async_thread:
+            self.event_thread = threading.Thread(
+                target=self.thread_msg_handler)
+            self.event_thread.daemon = True
+            self.event_thread.start()
+        return rv
+
+    def connect(self, name, chroot_prefix=None, async=False, rx_qlen=32):
+        """Attach to VPP.
+
+        name - the name of the client.
+        chroot_prefix - if VPP is chroot'ed, the prefix of the jail
+        async - if true, messages are sent without waiting for a reply
+        rx_qlen - the length of the VPP message receive queue between
+        client and server.
+        """
+        msg_handler = vac_callback_sync if not async else vac_callback_async
+        return self.connect_internal(name, msg_handler, chroot_prefix, rx_qlen,
+                                     async)
+
+    def connect_sync(self, name, chroot_prefix=None, rx_qlen=32):
+        """Attach to VPP in synchronous mode. Application must poll for events.
+
+        name - the name of the client.
+        chroot_prefix - if VPP is chroot'ed, the prefix of the jail
+        rx_qlen - the length of the VPP message receive queue between
+        client and server.
+        """
+
+        return self.connect_internal(name, ffi.NULL, chroot_prefix, rx_qlen,
+                                     async=False)
+
+    def disconnect(self):
+        """Detach from VPP."""
+        rv = vpp_api.vac_disconnect()
+        self.connected = False
+        self.message_queue.put("terminate event thread")
+        return rv
+
+    def msg_handler_sync(self, msg):
+        """Process an incoming message from VPP in sync mode.
+
+        The message may be a reply or it may be an async notification.
+        """
+        r = self.decode_incoming_msg(msg)
+        if r is None:
+            return
+
+        # If we have a context, then use the context to find any
+        # request waiting for a reply
+        context = 0
+        if hasattr(r, 'context') and r.context > 0:
+            context = r.context
+
+        if context == 0:
+            # No context -> async notification that we feed to the callback
+            self.message_queue.put_nowait(r)
+        else:
+            raise IOError(2, 'RPC reply message received in event handler')
+
+    def decode_incoming_msg(self, msg):
+        if not msg:
+            self.logger.warning('vpp_api.read failed')
+            return
+
+        i, ci = self.header.unpack_from(msg, 0)
+        if self.id_names[i] == 'rx_thread_exit':
+            return
+
+        #
+        # Decode message and returns a tuple.
+        #
+        msgdef = self.id_msgdef[i]
+        if not msgdef:
+            raise IOError(2, 'Reply message undefined')
+
+        r = self.decode(msgdef, msg)
+
+        return r
+
+    def msg_handler_async(self, msg):
+        """Process a message from VPP in async mode.
+
+        In async mode, all messages are returned to the callback.
+        """
+        r = self.decode_incoming_msg(msg)
+        if r is None:
+            return
+
+        msgname = type(r).__name__
+
+        if self.event_callback:
+            self.event_callback(msgname, r)
+
+    def _control_ping(self, context):
+        """Send a ping command."""
+        self._call_vpp_async(self.control_ping_index,
+                             self.control_ping_msgdef,
+                             context=context)
+
+    def _call_vpp(self, i, msgdef, multipart, **kwargs):
+        """Given a message, send the message and await a reply.
+
+        msgdef - the message packing definition
+        i - the message type index
+        multipart - True if the message returns multiple
+        messages in return.
+        context - context number - chosen at random if not
+        supplied.
+        The remainder of the kwargs are the arguments to the API call.
+
+        The return value is the message or message array containing
+        the response.  It will raise an IOError exception if there was
+        no response within the timeout window.
+        """
+
+        if 'context' not in kwargs:
+            context = self.get_context()
+            kwargs['context'] = context
+        else:
+            context = kwargs['context']
+        kwargs['_vl_msg_id'] = i
+        b = self.encode(msgdef, kwargs)
+
+        vpp_api.vac_rx_suspend()
+        self._write(b)
+
+        if multipart:
+            # Send a ping after the request - we use its response
+            # to detect that we have seen all results.
+            self._control_ping(context)
+
+        # Block until we get a reply.
+        rl = []
+        while (True):
+            msg = self._read()
+            if not msg:
+                raise IOError(2, 'VPP API client: read failed')
+
+            r = self.decode_incoming_msg(msg)
+            msgname = type(r).__name__
+            if context not in r or r.context == 0 or context != r.context:
+                self.message_queue.put_nowait(r)
+                continue
+
+            if not multipart:
+                rl = r
+                break
+            if msgname == 'control_ping_reply':
+                break
+
+            rl.append(r)
+
+        vpp_api.vac_rx_resume()
+
+        return rl
+
+    def _call_vpp_async(self, i, msgdef, **kwargs):
+        """Given a message, send the message and await a reply.
+
+        msgdef - the message packing definition
+        i - the message type index
+        context - context number - chosen at random if not
+        supplied.
+        The remainder of the kwargs are the arguments to the API call.
+        """
+        if 'context' not in kwargs:
+            context = self.get_context()
+            kwargs['context'] = context
+        else:
+            context = kwargs['context']
+        kwargs['_vl_msg_id'] = i
+        b = self.encode(msgdef, kwargs)
+
+        self._write(b)
+
+    def register_event_callback(self, callback):
+        """Register a callback for async messages.
+
+        This will be called for async notifications in sync mode,
+        and all messages in async mode.  In sync mode, replies to
+        requests will not come here.
+
+        callback is a fn(msg_type_name, msg_type) that will be
+        called when a message comes in.  While this function is
+        executing, note that (a) you are in a background thread and
+        may wish to use threading.Lock to protect your datastructures,
+        and (b) message processing from VPP will stop (so if you take
+        a long while about it you may provoke reply timeouts or cause
+        VPP to fill the RX buffer).  Passing None will disable the
+        callback.
+        """
+        self.event_callback = callback
+
+    def thread_msg_handler(self):
+        """Python thread calling the user registerd message handler.
+
+        This is to emulate the old style event callback scheme. Modern
+        clients should provide their own thread to poll the event
+        queue.
+        """
+        while True:
+            r = self.message_queue.get()
+            if r == "terminate event thread":
+                break
+            msgname = type(r).__name__
+            if self.event_callback:
+                self.event_callback(msgname, r)
+
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4