coder_impl_slow.py

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#  or more contributor license agreements.  See the NOTICE file
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#  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
#
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import datetime
import decimal
import pickle
from abc import ABC, abstractmethod
from typing import List

import cloudpickle

from pyflink.common import Row, RowKind
from pyflink.common.time import Instant
from pyflink.datastream.window import TimeWindow, CountWindow
from pyflink.fn_execution.ResettableIO import ResettableIO
from pyflink.fn_execution.stream_slow import InputStream, OutputStream
from pyflink.table.utils import pandas_to_arrow, arrow_to_pandas

ROW_KIND_BIT_SIZE = 2


class LengthPrefixBaseCoderImpl(ABC):
    """
    LengthPrefixBaseCoder will be used in Operations and other coders will be the field coder of
    LengthPrefixBaseCoder.
    """

    def __init__(self, field_coder: 'FieldCoderImpl'):
        self._field_coder = field_coder
        self._data_out_stream = OutputStream()

    def _write_data_to_output_stream(self, out_stream: OutputStream):
        out_stream.write_var_int64(self._data_out_stream.size())
        out_stream.write(self._data_out_stream.get())
        self._data_out_stream.clear()


class FieldCoderImpl(ABC):
    @abstractmethod
    def encode_to_stream(self, value, out_stream: OutputStream):
        """
        Encodes `value` to the output stream.

        :param value: The output data
        :param out_stream: Output Stream
        """
        pass

    @abstractmethod
    def decode_from_stream(self, in_stream: InputStream, length: int = 0):
        """
        Decodes data from the input stream.

        :param in_stream: Input Stream
        :param length: The `length` size data of input stream will be decoded. The default value is
        0 which means the coder won't take use of the length to decode the data from input stream.
        :return: The decoded Data.
        """
        pass

    def encode(self, value):
        out = OutputStream()
        self.encode_to_stream(value, out)
        return out.get()

    def decode(self, encoded):
        return self.decode_from_stream(InputStream(encoded), len(encoded))


class IterableCoderImpl(LengthPrefixBaseCoderImpl):
    """
    Encodes iterable data to output stream. The output mode will decide whether write a special end
    message 0x00 to output stream after encoding data.
    """

    def __init__(self, field_coder: 'FieldCoderImpl', separated_with_end_message: bool):
        super(IterableCoderImpl, self).__init__(field_coder)
        self._separated_with_end_message = separated_with_end_message

    def encode_to_stream(self, value: List, out_stream: OutputStream):
        if value:
            for item in value:
                self._field_coder.encode_to_stream(item, self._data_out_stream)
                self._write_data_to_output_stream(out_stream)

        # write end message
        if self._separated_with_end_message:
            out_stream.write_var_int64(1)
            out_stream.write_byte(0x00)

    def decode_from_stream(self, in_stream: InputStream):
        while in_stream.size() > 0:
            yield self._field_coder.decode_from_stream(in_stream, in_stream.read_var_int64())


class ValueCoderImpl(LengthPrefixBaseCoderImpl):
    """
    Encodes a single data to output stream.
    """

    def __init__(self, field_coder: 'FieldCoderImpl'):
        super(ValueCoderImpl, self).__init__(field_coder)

    def encode_to_stream(self, value, out_stream: OutputStream):
        self._field_coder.encode_to_stream(value, self._data_out_stream)
        self._write_data_to_output_stream(out_stream)

    def decode_from_stream(self, in_stream: InputStream):
        return self._field_coder.decode_from_stream(in_stream, in_stream.read_var_int64())


class MaskUtils:
    """
    A util class used to encode mask value.
    """

    def __init__(self, field_count):
        self._field_count = field_count
        # the row kind uses the first 2 bits of the bitmap, the remaining bits are used for null
        # mask, for more details refer to:
        # https://github.com/apache/flink/blob/master/flink-core/src/main/java/org/apache/flink/api/java/typeutils/runtime/RowSerializer.java
        self._leading_complete_bytes_num = (self._field_count + ROW_KIND_BIT_SIZE) // 8
        self._remaining_bits_num = (self._field_count + ROW_KIND_BIT_SIZE) % 8
        self.null_mask_search_table = self.generate_null_mask_search_table()
        self.null_byte_search_table = (0x80, 0x40, 0x20, 0x10, 0x08, 0x04, 0x02, 0x01)
        self.row_kind_search_table = [0x00, 0x80, 0x40, 0xC0]

    @staticmethod
    def generate_null_mask_search_table():
        """
        Each bit of one byte represents if the column at the corresponding position is None or not,
        e.g. 0x84 represents the first column and the sixth column are None.
        """
        null_mask = []
        for b in range(256):
            every_num_null_mask = [(b & 0x80) > 0, (b & 0x40) > 0, (b & 0x20) > 0, (b & 0x10) > 0,
                                   (b & 0x08) > 0, (b & 0x04) > 0, (b & 0x02) > 0, (b & 0x01) > 0]
            null_mask.append(tuple(every_num_null_mask))

        return tuple(null_mask)

    def write_mask(self, value, row_kind_value, out_stream: OutputStream):
        field_pos = 0
        null_byte_search_table = self.null_byte_search_table
        remaining_bits_num = self._remaining_bits_num

        # first byte contains the row kind bits
        b = self.row_kind_search_table[row_kind_value]
        for i in range(0, 8 - ROW_KIND_BIT_SIZE):
            if field_pos + i < len(value) and value[field_pos + i] is None:
                b |= null_byte_search_table[i + ROW_KIND_BIT_SIZE]
        field_pos += 8 - ROW_KIND_BIT_SIZE
        out_stream.write_byte(b)

        for _ in range(1, self._leading_complete_bytes_num):
            b = 0x00
            for i in range(0, 8):
                if value[field_pos + i] is None:
                    b |= null_byte_search_table[i]
            field_pos += 8
            out_stream.write_byte(b)

        if self._leading_complete_bytes_num >= 1 and remaining_bits_num:
            b = 0x00
            for i in range(remaining_bits_num):
                if value[field_pos + i] is None:
                    b |= null_byte_search_table[i]
            out_stream.write_byte(b)

    def read_mask(self, in_stream: InputStream):
        mask = []
        mask_search_table = self.null_mask_search_table
        remaining_bits_num = self._remaining_bits_num
        for _ in range(self._leading_complete_bytes_num):
            b = in_stream.read_byte()
            mask.extend(mask_search_table[b])

        if remaining_bits_num:
            b = in_stream.read_byte()
            mask.extend(mask_search_table[b][0:remaining_bits_num])
        return mask


class FlattenRowCoderImpl(FieldCoderImpl):
    """
    A coder for flatten row (List) object (without field names and row kind value is 0).
    """

    def __init__(self, field_coders: List[FieldCoderImpl]):
        self._field_coders = field_coders
        self._field_count = len(field_coders)
        self._mask_utils = MaskUtils(self._field_count)

    def encode_to_stream(self, value, out_stream: OutputStream):
        # encode mask value
        self._mask_utils.write_mask(value, 0, out_stream)

        # encode every field value
        for i in range(self._field_count):
            item = value[i]
            if item is not None:
                self._field_coders[i].encode_to_stream(item, out_stream)

    def decode_from_stream(self, in_stream: InputStream, length: int = 0):
        row_kind_and_null_mask = self._mask_utils.read_mask(in_stream)
        return [None if row_kind_and_null_mask[idx + ROW_KIND_BIT_SIZE] else
                self._field_coders[idx].decode_from_stream(in_stream)
                for idx in range(0, self._field_count)]

    def __repr__(self):
        return 'FlattenRowCoderImpl[%s]' % ', '.join(str(c) for c in self._field_coders)


class RowCoderImpl(FieldCoderImpl):
    """
    A coder for `Row` object.
    """

    def __init__(self, field_coders, field_names):
        self._field_coders = field_coders
        self._field_count = len(field_coders)
        self._field_names = field_names
        self._mask_utils = MaskUtils(self._field_count)

    def encode_to_stream(self, value: Row, out_stream: OutputStream):
        # encode mask value
        values = value.get_fields_by_names(self._field_names)
        self._mask_utils.write_mask(values, value.get_row_kind().value, out_stream)

        # encode every field value
        for i in range(self._field_count):
            item = values[i]
            if item is not None:
                self._field_coders[i].encode_to_stream(item, out_stream)

    def decode_from_stream(self, in_stream: InputStream, length=0) -> Row:
        row_kind_and_null_mask = self._mask_utils.read_mask(in_stream)
        fields = [None if row_kind_and_null_mask[idx + ROW_KIND_BIT_SIZE] else
                  self._field_coders[idx].decode_from_stream(in_stream)
                  for idx in range(0, self._field_count)]

        # compute the row_kind value
        row_kind_value = 0
        for i in range(ROW_KIND_BIT_SIZE):
            row_kind_value += int(row_kind_and_null_mask[i]) * 2 ** i

        row = Row(*fields)
        row.set_field_names(self._field_names)
        row.set_row_kind(RowKind(row_kind_value))
        return row

    def __repr__(self):
        return 'RowCoderImpl[%s, %s]' % \
               (', '.join(str(c) for c in self._field_coders), self._field_names)


class ArrowCoderImpl(FieldCoderImpl):
    """
    A coder for arrow format data.
    """

    def __init__(self, schema, row_type, timezone):
        self._schema = schema
        self._field_types = row_type.field_types()
        self._timezone = timezone
        self._resettable_io = ResettableIO()
        self._batch_reader = ArrowCoderImpl._load_from_stream(self._resettable_io)

    def encode_to_stream(self, cols, out_stream: OutputStream):
        import pyarrow as pa

        self._resettable_io.set_output_stream(out_stream)
        batch_writer = pa.RecordBatchStreamWriter(self._resettable_io, self._schema)
        batch_writer.write_batch(
            pandas_to_arrow(self._schema, self._timezone, self._field_types, cols))

    def decode_from_stream(self, in_stream: InputStream, length=0):
        return self.decode_one_batch_from_stream(in_stream, length)

    def decode_one_batch_from_stream(self, in_stream: InputStream, size: int) -> List:
        self._resettable_io.set_input_bytes(in_stream.read(size))
        # there is only one arrow batch in the underlying input stream
        return arrow_to_pandas(self._timezone, self._field_types, [next(self._batch_reader)])

    @staticmethod
    def _load_from_stream(stream):
        import pyarrow as pa

        while stream.readable():
            reader = pa.ipc.open_stream(stream)
            yield reader.read_next_batch()

    def __repr__(self):
        return 'ArrowCoderImpl[%s]' % self._schema


class OverWindowArrowCoderImpl(FieldCoderImpl):
    """
    A coder for over window with arrow format data.
    The data structure: [window data][arrow format data].
    """

    def __init__(self, arrow_coder_impl: ArrowCoderImpl):
        self._arrow_coder = arrow_coder_impl
        self._int_coder = IntCoderImpl()

    def encode_to_stream(self, cols, out_stream: OutputStream):
        self._arrow_coder.encode_to_stream(cols, out_stream)

    def decode_from_stream(self, in_stream: InputStream, length=0):
        window_num = self._int_coder.decode_from_stream(in_stream)
        length -= 4
        window_boundaries_and_arrow_data = []
        for _ in range(window_num):
            window_size = self._int_coder.decode_from_stream(in_stream)
            length -= 4
            window_boundaries_and_arrow_data.append(
                [self._int_coder.decode_from_stream(in_stream)
                 for _ in range(window_size)])
            length -= 4 * window_size
        window_boundaries_and_arrow_data.append(
            self._arrow_coder.decode_one_batch_from_stream(in_stream, length))
        return window_boundaries_and_arrow_data

    def __repr__(self):
        return 'OverWindowArrowCoderImpl[%s]' % self._arrow_coder


class TinyIntCoderImpl(FieldCoderImpl):
    """
    A coder for tiny int value (from -128 to 127).
    """

    def encode_to_stream(self, value, out_stream: OutputStream):
        out_stream.write_int8(value)

    def decode_from_stream(self, in_stream: InputStream, length=0):
        return in_stream.read_int8()


class SmallIntCoderImpl(FieldCoderImpl):
    """
    A coder for small int value (from -32,768 to 32,767).
    """

    def encode_to_stream(self, value, out_stream: OutputStream):
        out_stream.write_int16(value)

    def decode_from_stream(self, in_stream: InputStream, length=0):
        return in_stream.read_int16()


class IntCoderImpl(FieldCoderImpl):
    """
    A coder for int value (from -2,147,483,648 to 2,147,483,647).
    """

    def encode_to_stream(self, value, out_stream: OutputStream):
        out_stream.write_int32(value)

    def decode_from_stream(self, in_stream: InputStream, length=0):
        return in_stream.read_int32()


class BigIntCoderImpl(FieldCoderImpl):
    """
    A coder for big int value (from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807).
    """

    def encode_to_stream(self, value, out_stream: OutputStream):
        out_stream.write_int64(value)

    def decode_from_stream(self, in_stream: InputStream, length=0):
        return in_stream.read_int64()


class BooleanCoderImpl(FieldCoderImpl):
    """
    A coder for a boolean value.
    """

    def encode_to_stream(self, value, out_stream: OutputStream):
        out_stream.write_byte(value)

    def decode_from_stream(self, in_stream: InputStream, length=0):
        return not not in_stream.read_byte()


class FloatCoderImpl(FieldCoderImpl):
    """
    A coder for a float value (4-byte single precision floating point number).
    """

    def encode_to_stream(self, value, out_stream: OutputStream):
        out_stream.write_float(value)

    def decode_from_stream(self, in_stream: InputStream, length=0):
        return in_stream.read_float()


class DoubleCoderImpl(FieldCoderImpl):
    """
    A coder for a double value (8-byte double precision floating point number).
    """

    def encode_to_stream(self, value, out_stream: OutputStream):
        out_stream.write_double(value)

    def decode_from_stream(self, in_stream: InputStream, length=0):
        return in_stream.read_double()


class BinaryCoderImpl(FieldCoderImpl):
    """
    A coder for a bytes value.
    """

    def encode_to_stream(self, value, out_stream: OutputStream):
        out_stream.write_bytes(value, len(value))

    def decode_from_stream(self, in_stream: InputStream, length=0):
        return in_stream.read_bytes()


class CharCoderImpl(FieldCoderImpl):
    """
    A coder for a str value.
    """

    def encode_to_stream(self, value, out_stream: OutputStream):
        bytes_value = value.encode("utf-8")
        out_stream.write_bytes(bytes_value, len(bytes_value))

    def decode_from_stream(self, in_stream: InputStream, length=0):
        return in_stream.read_bytes().decode("utf-8")


class DecimalCoderImpl(FieldCoderImpl):
    """
    A coder for a decimal value (with fixed precision and scale).
    """

    def __init__(self, precision, scale):
        self.context = decimal.Context(prec=precision)
        self.scale_format = decimal.Decimal(10) ** -scale

    def encode_to_stream(self, value, out_stream: OutputStream):
        user_context = decimal.getcontext()
        decimal.setcontext(self.context)
        value = value.quantize(self.scale_format)
        bytes_value = str(value).encode("utf-8")
        out_stream.write_bytes(bytes_value, len(bytes_value))
        decimal.setcontext(user_context)

    def decode_from_stream(self, in_stream: InputStream, length=0):
        user_context = decimal.getcontext()
        decimal.setcontext(self.context)
        value = decimal.Decimal(in_stream.read_bytes().decode("utf-8")).quantize(self.scale_format)
        decimal.setcontext(user_context)
        return value


class BigDecimalCoderImpl(FieldCoderImpl):
    """
    A coder for a big decimal value (without fixed precision and scale).
    """

    def encode_to_stream(self, value, out_stream: OutputStream):
        bytes_value = str(value).encode("utf-8")
        out_stream.write_bytes(bytes_value, len(bytes_value))

    def decode_from_stream(self, in_stream: InputStream, length=0):
        return decimal.Decimal(in_stream.read_bytes().decode("utf-8"))


class DateCoderImpl(FieldCoderImpl):
    """
    A coder for a datetime.date value.
    """

    EPOCH_ORDINAL = datetime.datetime(1970, 1, 1).toordinal()

    def encode_to_stream(self, value, out_stream: OutputStream):
        out_stream.write_int32(self.date_to_internal(value))

    def decode_from_stream(self, in_stream: InputStream, length=0):
        value = in_stream.read_int32()
        return self.internal_to_date(value)

    def date_to_internal(self, d):
        return d.toordinal() - self.EPOCH_ORDINAL

    def internal_to_date(self, v):
        return datetime.date.fromordinal(v + self.EPOCH_ORDINAL)


class TimeCoderImpl(FieldCoderImpl):
    """
    A coder for a datetime.time value.
    """

    def encode_to_stream(self, value, out_stream: OutputStream):
        out_stream.write_int32(self.time_to_internal(value))

    def decode_from_stream(self, in_stream: InputStream, length=0):
        value = in_stream.read_int32()
        return self.internal_to_time(value)

    @staticmethod
    def time_to_internal(t):
        milliseconds = (t.hour * 3600000
                        + t.minute * 60000
                        + t.second * 1000
                        + t.microsecond // 1000)
        return milliseconds

    @staticmethod
    def internal_to_time(v):
        seconds, milliseconds = divmod(v, 1000)
        minutes, seconds = divmod(seconds, 60)
        hours, minutes = divmod(minutes, 60)
        return datetime.time(hours, minutes, seconds, milliseconds * 1000)


class TimestampCoderImpl(FieldCoderImpl):
    """
    A coder for a datetime.datetime value.
    """

    def __init__(self, precision):
        self.precision = precision

    def is_compact(self):
        return self.precision <= 3

    def encode_to_stream(self, value, out_stream: OutputStream):
        milliseconds, nanoseconds = self.timestamp_to_internal(value)
        if self.is_compact():
            assert nanoseconds == 0
            out_stream.write_int64(milliseconds)
        else:
            out_stream.write_int64(milliseconds)
            out_stream.write_int32(nanoseconds)

    def decode_from_stream(self, in_stream: InputStream, length=0):
        if self.is_compact():
            milliseconds = in_stream.read_int64()
            nanoseconds = 0
        else:
            milliseconds = in_stream.read_int64()
            nanoseconds = in_stream.read_int32()
        return self.internal_to_timestamp(milliseconds, nanoseconds)

    @staticmethod
    def timestamp_to_internal(timestamp):
        seconds = int(timestamp.replace(tzinfo=datetime.timezone.utc).timestamp())
        microseconds_of_second = timestamp.microsecond
        milliseconds = seconds * 1000 + microseconds_of_second // 1000
        nanoseconds = microseconds_of_second % 1000 * 1000
        return milliseconds, nanoseconds

    def internal_to_timestamp(self, milliseconds, nanoseconds):
        second, microsecond = (milliseconds // 1000,
                               milliseconds % 1000 * 1000 + nanoseconds // 1000)
        return datetime.datetime.utcfromtimestamp(second).replace(microsecond=microsecond)


class LocalZonedTimestampCoderImpl(TimestampCoderImpl):
    """
    A coder for a datetime.datetime with time zone value.
    """

    def __init__(self, precision, timezone):
        super(LocalZonedTimestampCoderImpl, self).__init__(precision)
        self.timezone = timezone

    def internal_to_timestamp(self, milliseconds, nanoseconds):
        return self.timezone.localize(
            super(LocalZonedTimestampCoderImpl, self).internal_to_timestamp(
                milliseconds, nanoseconds))


class InstantCoderImpl(FieldCoderImpl):
    """
    A coder for Instant.
    """
    def __init__(self):
        self._null_seconds = -9223372036854775808
        self._null_nanos = -2147483648

    def encode_to_stream(self, value: Instant, out_stream: OutputStream):
        if value is None:
            out_stream.write_int64(self._null_seconds)
            out_stream.write_int32(self._null_nanos)
        else:
            out_stream.write_int64(value.seconds)
            out_stream.write_int32(value.nanos)

    def decode_from_stream(self, in_stream: InputStream, length: int = 0):
        seconds = in_stream.read_int64()
        nanos = in_stream.read_int32()
        if seconds == self._null_seconds and nanos == self._null_nanos:
            return None
        else:
            return Instant(seconds, nanos)


class CloudPickleCoderImpl(FieldCoderImpl):
    """
    A coder used with cloudpickle for all kinds of python object.
    """

    def __init__(self):
        self.field_coder = BinaryCoderImpl()

    def encode_to_stream(self, value, out_stream: OutputStream):
        coded_data = cloudpickle.dumps(value)
        self.field_coder.encode_to_stream(coded_data, out_stream)

    def decode_from_stream(self, in_stream: InputStream, length=0):
        return self._decode_one_value_from_stream(in_stream)

    def _decode_one_value_from_stream(self, in_stream: InputStream):
        real_data = self.field_coder.decode_from_stream(in_stream)
        value = cloudpickle.loads(real_data)
        return value

    def __repr__(self) -> str:
        return 'CloudPickleCoderImpl[%s]' % str(self.field_coder)


class PickleCoderImpl(FieldCoderImpl):
    """
    A coder used with pickle for all kinds of python object.
    """

    def __init__(self):
        self.field_coder = BinaryCoderImpl()

    def encode_to_stream(self, value, out_stream: OutputStream):
        coded_data = pickle.dumps(value)
        self.field_coder.encode_to_stream(coded_data, out_stream)

    def decode_from_stream(self, in_stream: InputStream, length=0):
        real_data = self.field_coder.decode_from_stream(in_stream)
        value = pickle.loads(real_data)
        return value

    def __repr__(self) -> str:
        return 'PickleCoderImpl[%s]' % str(self.field_coder)


class TupleCoderImpl(FieldCoderImpl):
    """
    A coder for a tuple value.
    """

    def __init__(self, field_coders):
        self._field_coders = field_coders
        self._field_count = len(field_coders)

    def encode_to_stream(self, value, out_stream: OutputStream):
        field_coders = self._field_coders
        for i in range(self._field_count):
            field_coders[i].encode_to_stream(value[i], out_stream)

    def decode_from_stream(self, stream: InputStream, length=0):
        decoded_list = [field_coder.decode_from_stream(stream)
                        for field_coder in self._field_coders]
        return (*decoded_list,)

    def __repr__(self) -> str:
        return 'TupleCoderImpl[%s]' % ', '.join(str(c) for c in self._field_coders)


class GenericArrayCoderImpl(FieldCoderImpl):
    """
    A coder for object array value (the element of array could be any kind of Python object).
    """

    def __init__(self, elem_coder: FieldCoderImpl):
        self._elem_coder = elem_coder

    def encode_to_stream(self, value, out_stream: OutputStream):
        out_stream.write_int32(len(value))
        for elem in value:
            if elem is None:
                out_stream.write_byte(False)
            else:
                out_stream.write_byte(True)
                self._elem_coder.encode_to_stream(elem, out_stream)

    def decode_from_stream(self, in_stream: InputStream, length=0):
        size = in_stream.read_int32()
        elements = [self._elem_coder.decode_from_stream(in_stream)
                    if in_stream.read_byte() else None for _ in range(size)]
        return elements

    def __repr__(self):
        return 'GenericArrayCoderImpl[%s]' % repr(self._elem_coder)


class PrimitiveArrayCoderImpl(FieldCoderImpl):
    """
    A coder for primitive array value (the element of array won't be null).
    """

    def __init__(self, elem_coder: FieldCoderImpl):
        self._elem_coder = elem_coder

    def encode_to_stream(self, value, out_stream: OutputStream):
        out_stream.write_int32(len(value))
        for elem in value:
            self._elem_coder.encode_to_stream(elem, out_stream)

    def decode_from_stream(self, in_stream: InputStream, length=0):
        size = in_stream.read_int32()
        elements = [self._elem_coder.decode_from_stream(in_stream) for _ in range(size)]
        return elements

    def __repr__(self):
        return 'PrimitiveArrayCoderImpl[%s]' % repr(self._elem_coder)


class MapCoderImpl(FieldCoderImpl):
    """
    A coder for map value (dict with same type key and same type value).
    """

    def __init__(self, key_coder: FieldCoderImpl, value_coder: FieldCoderImpl):
        self._key_coder = key_coder
        self._value_coder = value_coder

    def encode_to_stream(self, map_value, out_stream: OutputStream):
        out_stream.write_int32(len(map_value))
        for key in map_value:
            self._key_coder.encode_to_stream(key, out_stream)
            value = map_value[key]
            if value is None:
                out_stream.write_byte(True)
            else:
                out_stream.write_byte(False)
                self._value_coder.encode_to_stream(map_value[key], out_stream)

    def decode_from_stream(self, in_stream: InputStream, length=0):
        size = in_stream.read_int32()
        map_value = {}
        for _ in range(size):
            key = self._key_coder.decode_from_stream(in_stream)
            is_null = in_stream.read_byte()
            if is_null:
                map_value[key] = None
            else:
                value = self._value_coder.decode_from_stream(in_stream)
                map_value[key] = value
        return map_value

    def __repr__(self):
        return 'MapCoderImpl[%s]' % ' : '.join([repr(self._key_coder), repr(self._value_coder)])


class TimeWindowCoderImpl(FieldCoderImpl):
    """
    A coder for TimeWindow.
    """

    def encode_to_stream(self, value, out_stream: OutputStream):
        out_stream.write_int64(value.start)
        out_stream.write_int64(value.end)

    def decode_from_stream(self, in_stream: InputStream, length=0):
        start = in_stream.read_int64()
        end = in_stream.read_int64()
        return TimeWindow(start, end)


class CountWindowCoderImpl(FieldCoderImpl):
    """
    A coder for CountWindow.
    """

    def encode_to_stream(self, value, out_stream: OutputStream):
        out_stream.write_int64(value.id)

    def decode_from_stream(self, in_stream: InputStream, length=0):
        return CountWindow(in_stream.read_int64())


class DataViewFilterCoderImpl(FieldCoderImpl):
    """
    A coder for data view filter.
    """
    def __init__(self, udf_data_view_specs):
        self._udf_data_view_specs = udf_data_view_specs
        self._pickle_coder = PickleCoderImpl()

    def encode_to_stream(self, value, out_stream: OutputStream):
        self._pickle_coder.encode_to_stream(self._filter_data_views(value), out_stream)

    def decode_from_stream(self, in_stream: InputStream, length=0):
        return self._pickle_coder.decode_from_stream(in_stream)

    def _filter_data_views(self, row):
        i = 0
        for specs in self._udf_data_view_specs:
            for spec in specs:
                row[i][spec.field_index] = None
            i += 1
        return row