text: #
  # Licensed to the Apache Software Foundation (ASF) under one or more
  # contributor license agreements.  See the NOTICE file distributed with
  # this work for additional information regarding copyright ownership.
  # The ASF licenses this file to You 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.
  #
  
  """
  PySpark supports custom serializers for transferring data; this can improve
  performance.
  
  By default, PySpark uses L{PickleSerializer} to serialize objects using Python's
  C{cPickle} serializer, which can serialize nearly any Python object.
  Other serializers, like L{MarshalSerializer}, support fewer datatypes but can be
  faster.
  
  The serializer is chosen when creating L{SparkContext}:
  
  >>> from pyspark.context import SparkContext
  >>> from pyspark.serializers import MarshalSerializer
  >>> sc = SparkContext('local', 'test', serializer=MarshalSerializer())
  >>> sc.parallelize(list(range(1000))).map(lambda x: 2 * x).take(10)
  [0, 2, 4, 6, 8, 10, 12, 14, 16, 18]
  >>> sc.stop()
  
  PySpark serializes objects in batches; by default, the batch size is chosen based
  on the size of objects and is also configurable by SparkContext's C{batchSize}
  parameter:
  
  >>> sc = SparkContext('local', 'test', batchSize=2)
  >>> rdd = sc.parallelize(range(16), 4).map(lambda x: x)
  
  Behind the scenes, this creates a JavaRDD with four partitions, each of
  which contains two batches of two objects:
  
  >>> rdd.glom().collect()
  [[0, 1, 2, 3], [4, 5, 6, 7], [8, 9, 10, 11], [12, 13, 14, 15]]
  >>> int(rdd._jrdd.count())
  8
  >>> sc.stop()
  """
  
  import sys
  from itertools import chain, product
  import marshal
  import struct
  import types
  import collections
  import zlib
  import itertools
  
  if sys.version < '3':
      import cPickle as pickle
      protocol = 2
      from itertools import izip as zip, imap as map
  else:
      import pickle
      protocol = 3
      xrange = range
  
  from pyspark import cloudpickle
  
  
  __all__ = ["PickleSerializer", "MarshalSerializer", "UTF8Deserializer"]
  
  
  class SpecialLengths(object):
      END_OF_DATA_SECTION = -1
      PYTHON_EXCEPTION_THROWN = -2
      TIMING_DATA = -3
      END_OF_STREAM = -4
      NULL = -5
      START_ARROW_STREAM = -6
  
  
  class Serializer(object):
  
      def dump_stream(self, iterator, stream):
          """
          Serialize an iterator of objects to the output stream.
          """
          raise NotImplementedError
  
      def load_stream(self, stream):
          """
          Return an iterator of deserialized objects from the input stream.
          """
          raise NotImplementedError
  
      def _load_stream_without_unbatching(self, stream):
          """
          Return an iterator of deserialized batches (iterable) of objects from the input stream.
          If the serializer does not operate on batches the default implementation returns an
          iterator of single element lists.
          """
          return map(lambda x: [x], self.load_stream(stream))
  
      # Note: our notion of "equality" is that output generated by
      # equal serializers can be deserialized using the same serializer.
  
      # This default implementation handles the simple cases;
      # subclasses should override __eq__ as appropriate.
  
      def __eq__(self, other):
          return isinstance(other, self.__class__) and self.__dict__ == other.__dict__
  
      def __ne__(self, other):
          return not self.__eq__(other)
  
      def __repr__(self):
          return "%s()" % self.__class__.__name__
  
      def __hash__(self):
          return hash(str(self))
  
  
  class FramedSerializer(Serializer):
  
      """
      Serializer that writes objects as a stream of (length, data) pairs,
      where C{length} is a 32-bit integer and data is C{length} bytes.
      """
  
      def __init__(self):
          # On Python 2.6, we can't write bytearrays to streams, so we need to convert them
          # to strings first. Check if the version number is that old.
          self._only_write_strings = sys.version_info[0:2] <= (2, 6)
  
      def dump_stream(self, iterator, stream):
          for obj in iterator:
              self._write_with_length(obj, stream)
  
      def load_stream(self, stream):
          while True:
              try:
                  yield self._read_with_length(stream)
              except EOFError:
                  return
  
      def _write_with_length(self, obj, stream):
          serialized = self.dumps(obj)
          if serialized is None:
              raise ValueError("serialized value should not be None")
          if len(serialized) > (1 << 31):
              raise ValueError("can not serialize object larger than 2G")
          write_int(len(serialized), stream)
          if self._only_write_strings:
              stream.write(str(serialized))
          else:
              stream.write(serialized)
  
      def _read_with_length(self, stream):
          length = read_int(stream)
          if length == SpecialLengths.END_OF_DATA_SECTION:
              raise EOFError
          elif length == SpecialLengths.NULL:
              return None
          obj = stream.read(length)
          if len(obj) < length:
              raise EOFError
          return self.loads(obj)
  
      def dumps(self, obj):
          """
          Serialize an object into a byte array.
          When batching is used, this will be called with an array of objects.
          """
          raise NotImplementedError
  
      def loads(self, obj):
          """
          Deserialize an object from a byte array.
          """
          raise NotImplementedError
  
  
  class ArrowSerializer(FramedSerializer):
      """
      Serializes bytes as Arrow data with the Arrow file format.
      """
  
      def dumps(self, batch):
          import pyarrow as pa
          import io
          sink = io.BytesIO()
          writer = pa.RecordBatchFileWriter(sink, batch.schema)
          writer.write_batch(batch)
          writer.close()
          return sink.getvalue()
  
      def loads(self, obj):
          import pyarrow as pa
          reader = pa.RecordBatchFileReader(pa.BufferReader(obj))
          return reader.read_all()
  
      def __repr__(self):
          return "ArrowSerializer"
  
  
  def _create_batch(series, timezone):
      """
      Create an Arrow record batch from the given pandas.Series or list of Series, with optional type.
  
      :param series: A single pandas.Series, list of Series, or list of (series, arrow_type)
      :param timezone: A timezone to respect when handling timestamp values
      :return: Arrow RecordBatch
      """
      import decimal
      from distutils.version import LooseVersion
      import pyarrow as pa
      from pyspark.sql.types import _check_series_convert_timestamps_internal
      # Make input conform to [(series1, type1), (series2, type2), ...]
      if not isinstance(series, (list, tuple)) or \
              (len(series) == 2 and isinstance(series[1], pa.DataType)):
          series = [series]
      series = ((s, None) if not isinstance(s, (list, tuple)) else s for s in series)
  
      def create_array(s, t):
          mask = s.isnull()
          # Ensure timestamp series are in expected form for Spark internal representation
          # TODO: maybe don't need None check anymore as of Arrow 0.9.1
          if t is not None and pa.types.is_timestamp(t):
              s = _check_series_convert_timestamps_internal(s.fillna(0), timezone)
              # TODO: need cast after Arrow conversion, ns values cause error with pandas 0.19.2
              return pa.Array.from_pandas(s, mask=mask).cast(t, safe=False)
          elif t is not None and pa.types.is_string(t) and sys.version < '3':
              # TODO: need decode before converting to Arrow in Python 2
              # TODO: don't need as of Arrow 0.9.1
              return pa.Array.from_pandas(s.apply(
                  lambda v: v.decode("utf-8") if isinstance(v, str) else v), mask=mask, type=t)
          elif t is not None and pa.types.is_decimal(t) and \
                  LooseVersion("0.9.0") <= LooseVersion(pa.__version__) < LooseVersion("0.10.0"):
              # TODO: see ARROW-2432. Remove when the minimum PyArrow version becomes 0.10.0.
              return pa.Array.from_pandas(s.apply(
                  lambda v: decimal.Decimal('NaN') if v is None else v), mask=mask, type=t)
          return pa.Array.from_pandas(s, mask=mask, type=t)
  
      arrs = [create_array(s, t) for s, t in series]
      return pa.RecordBatch.from_arrays(arrs, ["_%d" % i for i in xrange(len(arrs))])
  
  
  class ArrowStreamPandasSerializer(Serializer):
      """
      Serializes Pandas.Series as Arrow data with Arrow streaming format.
      """
  
      def __init__(self, timezone):
          super(ArrowStreamPandasSerializer, self).__init__()
          self._timezone = timezone
  
      def dump_stream(self, iterator, stream):
          """
          Make ArrowRecordBatches from Pandas Series and serialize. Input is a single series or
          a list of series accompanied by an optional pyarrow type to coerce the data to.
          """
          import pyarrow as pa
          writer = None
          try:
              for series in iterator:
                  batch = _create_batch(series, self._timezone)
                  if writer is None:
                      write_int(SpecialLengths.START_ARROW_STREAM, stream)
                      writer = pa.RecordBatchStreamWriter(stream, batch.schema)
                  writer.write_batch(batch)
          finally:
              if writer is not None:
                  writer.close()
  
      def load_stream(self, stream):
          """
          Deserialize ArrowRecordBatches to an Arrow table and return as a list of pandas.Series.
          """
          from pyspark.sql.types import from_arrow_schema, _check_dataframe_convert_date, \
              _check_dataframe_localize_timestamps
          import pyarrow as pa
          reader = pa.open_stream(stream)
          schema = from_arrow_schema(reader.schema)
          for batch in reader:
              pdf = batch.to_pandas()
              pdf = _check_dataframe_convert_date(pdf, schema)
              pdf = _check_dataframe_localize_timestamps(pdf, self._timezone)
              yield [c for _, c in pdf.iteritems()]
  
      def __repr__(self):
          return "ArrowStreamPandasSerializer"
  
  
  class BatchedSerializer(Serializer):
  
      """
      Serializes a stream of objects in batches by calling its wrapped
      Serializer with streams of objects.
      """
  
      UNLIMITED_BATCH_SIZE = -1
      UNKNOWN_BATCH_SIZE = 0
  
      def __init__(self, serializer, batchSize=UNLIMITED_BATCH_SIZE):
          self.serializer = serializer
          self.batchSize = batchSize
  
      def _batched(self, iterator):
          if self.batchSize == self.UNLIMITED_BATCH_SIZE:
              yield list(iterator)
          elif hasattr(iterator, "__len__") and hasattr(iterator, "__getslice__"):
              n = len(iterator)
              for i in xrange(0, n, self.batchSize):
                  yield iterator[i: i + self.batchSize]
          else:
              items = []
              count = 0
              for item in iterator:
                  items.append(item)
                  count += 1
                  if count == self.batchSize:
                      yield items
                      items = []
                      count = 0
              if items:
                  yield items
  
      def dump_stream(self, iterator, stream):
          self.serializer.dump_stream(self._batched(iterator), stream)
  
      def load_stream(self, stream):
          return chain.from_iterable(self._load_stream_without_unbatching(stream))
  
      def _load_stream_without_unbatching(self, stream):
          return self.serializer.load_stream(stream)
  
      def __repr__(self):
          return "BatchedSerializer(%s, %d)" % (str(self.serializer), self.batchSize)
  
  
  class FlattenedValuesSerializer(BatchedSerializer):
  
      """
      Serializes a stream of list of pairs, split the list of values
      which contain more than a certain number of objects to make them
      have similar sizes.
      """
      def __init__(self, serializer, batchSize=10):
          BatchedSerializer.__init__(self, serializer, batchSize)
  
      def _batched(self, iterator):
          n = self.batchSize
          for key, values in iterator:
              for i in range(0, len(values), n):
                  yield key, values[i:i + n]
  
      def load_stream(self, stream):
          return self.serializer.load_stream(stream)
  
      def __repr__(self):
          return "FlattenedValuesSerializer(%s, %d)" % (self.serializer, self.batchSize)
  
  
  class AutoBatchedSerializer(BatchedSerializer):
      """
      Choose the size of batch automatically based on the size of object
      """
  
      def __init__(self, serializer, bestSize=1 << 16):
          BatchedSerializer.__init__(self, serializer, self.UNKNOWN_BATCH_SIZE)
          self.bestSize = bestSize
  
      def dump_stream(self, iterator, stream):
          batch, best = 1, self.bestSize
          iterator = iter(iterator)
          while True:
              vs = list(itertools.islice(iterator, batch))
              if not vs:
                  break
  
              bytes = self.serializer.dumps(vs)
              write_int(len(bytes), stream)
              stream.write(bytes)
  
              size = len(bytes)
              if size < best:
                  batch *= 2
              elif size > best * 10 and batch > 1:
                  batch //= 2
  
      def __repr__(self):
          return "AutoBatchedSerializer(%s)" % self.serializer
  
  
  class CartesianDeserializer(Serializer):
  
      """
      Deserializes the JavaRDD cartesian() of two PythonRDDs.
      Due to pyspark batching we cannot simply use the result of the Java RDD cartesian,
      we additionally need to do the cartesian within each pair of batches.
      """
  
      def __init__(self, key_ser, val_ser):
          self.key_ser = key_ser
          self.val_ser = val_ser
  
      def _load_stream_without_unbatching(self, stream):
          key_batch_stream = self.key_ser._load_stream_without_unbatching(stream)
          val_batch_stream = self.val_ser._load_stream_without_unbatching(stream)
          for (key_batch, val_batch) in zip(key_batch_stream, val_batch_stream):
              # for correctness with repeated cartesian/zip this must be returned as one batch
              yield product(key_batch, val_batch)
  
      def load_stream(self, stream):
          return chain.from_iterable(self._load_stream_without_unbatching(stream))
  
      def __repr__(self):
          return "CartesianDeserializer(%s, %s)" % \
                 (str(self.key_ser), str(self.val_ser))
  
  
  class PairDeserializer(Serializer):
  
      """
      Deserializes the JavaRDD zip() of two PythonRDDs.
      Due to pyspark batching we cannot simply use the result of the Java RDD zip,
      we additionally need to do the zip within each pair of batches.
      """
  
      def __init__(self, key_ser, val_ser):
          self.key_ser = key_ser
          self.val_ser = val_ser
  
      def _load_stream_without_unbatching(self, stream):
          key_batch_stream = self.key_ser._load_stream_without_unbatching(stream)
          val_batch_stream = self.val_ser._load_stream_without_unbatching(stream)
          for (key_batch, val_batch) in zip(key_batch_stream, val_batch_stream):
              # For double-zipped RDDs, the batches can be iterators from other PairDeserializer,
              # instead of lists. We need to convert them to lists if needed.
              key_batch = key_batch if hasattr(key_batch, '__len__') else list(key_batch)
              val_batch = val_batch if hasattr(val_batch, '__len__') else list(val_batch)
              if len(key_batch) != len(val_batch):
                  raise ValueError("Can not deserialize PairRDD with different number of items"
                                   " in batches: (%d, %d)" % (len(key_batch), len(val_batch)))
              # for correctness with repeated cartesian/zip this must be returned as one batch
              yield zip(key_batch, val_batch)
  
      def load_stream(self, stream):
          return chain.from_iterable(self._load_stream_without_unbatching(stream))
  
      def __repr__(self):
          return "PairDeserializer(%s, %s)" % (str(self.key_ser), str(self.val_ser))
  
  
  class NoOpSerializer(FramedSerializer):
  
      def loads(self, obj):
          return obj
  
      def dumps(self, obj):
          return obj
  
  
  # Hack namedtuple, make it picklable
  
  __cls = {}
  
  
  def _restore(name, fields, value):
      """ Restore an object of namedtuple"""
      k = (name, fields)
      cls = __cls.get(k)
      if cls is None:
          cls = collections.namedtuple(name, fields)
          __cls[k] = cls
      return cls(*value)
  
  
  def _hack_namedtuple(cls):
      """ Make class generated by namedtuple picklable """
      name = cls.__name__
      fields = cls._fields
  
      def __reduce__(self):
          return (_restore, (name, fields, tuple(self)))
      cls.__reduce__ = __reduce__
      cls._is_namedtuple_ = True
      return cls
  
  
  def _hijack_namedtuple():
      """ Hack namedtuple() to make it picklable """
      # hijack only one time
      if hasattr(collections.namedtuple, "__hijack"):
          return
  
      global _old_namedtuple  # or it will put in closure
      global _old_namedtuple_kwdefaults  # or it will put in closure too
  
      def _copy_func(f):
          return types.FunctionType(f.__code__, f.__globals__, f.__name__,
                                    f.__defaults__, f.__closure__)
  
      def _kwdefaults(f):
          # __kwdefaults__ contains the default values of keyword-only arguments which are
          # introduced from Python 3. The possible cases for __kwdefaults__ in namedtuple
          # are as below:
          #
          # - Does not exist in Python 2.
          # - Returns None in <= Python 3.5.x.
          # - Returns a dictionary containing the default values to the keys from Python 3.6.x
          #    (See https://bugs.python.org/issue25628).
          kargs = getattr(f, "__kwdefaults__", None)
          if kargs is None:
              return {}
          else:
              return kargs
  
      _old_namedtuple = _copy_func(collections.namedtuple)
      _old_namedtuple_kwdefaults = _kwdefaults(collections.namedtuple)
  
      def namedtuple(*args, **kwargs):
          for k, v in _old_namedtuple_kwdefaults.items():
              kwargs[k] = kwargs.get(k, v)
          cls = _old_namedtuple(*args, **kwargs)
          return _hack_namedtuple(cls)
  
      # replace namedtuple with the new one
      collections.namedtuple.__globals__["_old_namedtuple_kwdefaults"] = _old_namedtuple_kwdefaults
      collections.namedtuple.__globals__["_old_namedtuple"] = _old_namedtuple
      collections.namedtuple.__globals__["_hack_namedtuple"] = _hack_namedtuple
      collections.namedtuple.__code__ = namedtuple.__code__
      collections.namedtuple.__hijack = 1
  
      # hack the cls already generated by namedtuple.
      # Those created in other modules can be pickled as normal,
      # so only hack those in __main__ module
      for n, o in sys.modules["__main__"].__dict__.items():
          if (type(o) is type and o.__base__ is tuple
                  and hasattr(o, "_fields")
                  and "__reduce__" not in o.__dict__):
              _hack_namedtuple(o)  # hack inplace
  
  
  _hijack_namedtuple()
  
  
  class PickleSerializer(FramedSerializer):
  
      """
      Serializes objects using Python's pickle serializer:
  
          http://docs.python.org/2/library/pickle.html
  
      This serializer supports nearly any Python object, but may
      not be as fast as more specialized serializers.
      """
  
      def dumps(self, obj):
          return pickle.dumps(obj, protocol)
  
      if sys.version >= '3':
          def loads(self, obj, encoding="bytes"):
              return pickle.loads(obj, encoding=encoding)
      else:
          def loads(self, obj, encoding=None):
              return pickle.loads(obj)
  
  
  class CloudPickleSerializer(PickleSerializer):
  
      def dumps(self, obj):
          return cloudpickle.dumps(obj, 2)
  
  
  class MarshalSerializer(FramedSerializer):
  
      """
      Serializes objects using Python's Marshal serializer:
  
          http://docs.python.org/2/library/marshal.html
  
      This serializer is faster than PickleSerializer but supports fewer datatypes.
      """
  
      def dumps(self, obj):
          return marshal.dumps(obj)
  
      def loads(self, obj):
          return marshal.loads(obj)
  
  
  class AutoSerializer(FramedSerializer):
  
      """
      Choose marshal or pickle as serialization protocol automatically
      """
  
      def __init__(self):
          FramedSerializer.__init__(self)
          self._type = None
  
      def dumps(self, obj):
          if self._type is not None:
              return b'P' + pickle.dumps(obj, -1)
          try:
              return b'M' + marshal.dumps(obj)
          except Exception:
              self._type = b'P'
              return b'P' + pickle.dumps(obj, -1)
  
      def loads(self, obj):
          _type = obj[0]
          if _type == b'M':
              return marshal.loads(obj[1:])
          elif _type == b'P':
              return pickle.loads(obj[1:])
          else:
              raise ValueError("invalid serialization type: %s" % _type)
  
  
  class CompressedSerializer(FramedSerializer):
      """
      Compress the serialized data
      """
      def __init__(self, serializer):
          FramedSerializer.__init__(self)
          assert isinstance(serializer, FramedSerializer), "serializer must be a FramedSerializer"
          self.serializer = serializer
  
      def dumps(self, obj):
          return zlib.compress(self.serializer.dumps(obj), 1)
  
      def loads(self, obj):
          return self.serializer.loads(zlib.decompress(obj))
  
      def __repr__(self):
          return "CompressedSerializer(%s)" % self.serializer
  
  
  class UTF8Deserializer(Serializer):
  
      """
      Deserializes streams written by String.getBytes.
      """
  
      def __init__(self, use_unicode=True):
          self.use_unicode = use_unicode
  
      def loads(self, stream):
          length = read_int(stream)
          if length == SpecialLengths.END_OF_DATA_SECTION:
              raise EOFError
          elif length == SpecialLengths.NULL:
              return None
          s = stream.read(length)
          return s.decode("utf-8") if self.use_unicode else s
  
      def load_stream(self, stream):
          try:
              while True:
                  yield self.loads(stream)
          except struct.error:
              return
          except EOFError:
              return
  
      def __repr__(self):
          return "UTF8Deserializer(%s)" % self.use_unicode
  
  
  def read_long(stream):
      length = stream.read(8)
      if not length:
          raise EOFError
      return struct.unpack("!q", length)[0]
  
  
  def write_long(value, stream):
      stream.write(struct.pack("!q", value))
  
  
  def pack_long(value):
      return struct.pack("!q", value)
  
  
  def read_int(stream):
      length = stream.read(4)
      if not length:
          raise EOFError
      return struct.unpack("!i", length)[0]
  
  
  def write_int(value, stream):
      stream.write(struct.pack("!i", value))
  
  
  def read_bool(stream):
      length = stream.read(1)
      if not length:
          raise EOFError
      return struct.unpack("!?", length)[0]
  
  
  def write_with_length(obj, stream):
      write_int(len(obj), stream)
      stream.write(obj)
  
  
  class ChunkedStream(object):
  
      """
      This file-like object takes a stream of data, of unknown length, and breaks it into fixed
      length frames.  The intended use case is serializing large data and sending it immediately over
      a socket -- we do not want to buffer the entire data before sending it, but the receiving end
      needs to know whether or not there is more data coming.
  
      It works by buffering the incoming data in some fixed-size chunks.  If the buffer is full, it
      first sends the buffer size, then the data.  This repeats as long as there is more data to send.
      When this is closed, it sends the length of whatever data is in the buffer, then that data, and
      finally a "length" of -1 to indicate the stream has completed.
      """
  
      def __init__(self, wrapped, buffer_size):
          self.buffer_size = buffer_size
          self.buffer = bytearray(buffer_size)
          self.current_pos = 0
          self.wrapped = wrapped
  
      def write(self, bytes):
          byte_pos = 0
          byte_remaining = len(bytes)
          while byte_remaining > 0:
              new_pos = byte_remaining + self.current_pos
              if new_pos < self.buffer_size:
                  # just put it in our buffer
                  self.buffer[self.current_pos:new_pos] = bytes[byte_pos:]
                  self.current_pos = new_pos
                  byte_remaining = 0
              else:
                  # fill the buffer, send the length then the contents, and start filling again
                  space_left = self.buffer_size - self.current_pos
                  new_byte_pos = byte_pos + space_left
                  self.buffer[self.current_pos:self.buffer_size] = bytes[byte_pos:new_byte_pos]
                  write_int(self.buffer_size, self.wrapped)
                  self.wrapped.write(self.buffer)
                  byte_remaining -= space_left
                  byte_pos = new_byte_pos
                  self.current_pos = 0
  
      def close(self):
          # if there is anything left in the buffer, write it out first
          if self.current_pos > 0:
              write_int(self.current_pos, self.wrapped)
              self.wrapped.write(self.buffer[:self.current_pos])
          # -1 length indicates to the receiving end that we're done.
          write_int(-1, self.wrapped)
          self.wrapped.close()
  
  
  if __name__ == '__main__':
      import doctest
      (failure_count, test_count) = doctest.testmod()
      if failure_count:
          exit(-1)
  