WritableUtils.py

#!/usr/bin/env python
# ========================================================================
# 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.
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# limitations under the License.

import six


def intToByte(version):
    if six.PY2:
        return chr(version % 256)
    else:
        return version.to_bytes(1, 'little', signed=True)

def readVInt(data_input):
    return readVLong(data_input)

def readVLong(data_input):
    first_byte = data_input.readByte()
    length = decodeVIntSize(first_byte)
    if length == 1:
        return first_byte

    i = 0
    for _idx in range(length - 1):
        b = data_input.readUByte()
        i = i << 8
        i = i | b

    return (i ^ -1) if isNegativeVInt(first_byte) else i

def writeVInt(data_output, value):
    return writeVLong(data_output, value)

def writeVLong(data_output, value):
    if value >= -112 and value <= 127:
        data_output.writeByte(value)
        return

    length = -112
    if value < 0:
        value ^= -1
        length -= 120

    temp = value
    while temp != 0:
        temp = temp >> 8
        length -= 1

    data_output.writeByte(length)
    length = -(length + 120) if (length < -120) else -(length + 112)
    for idx in reversed(range(length)):
        shiftbits = idx << 3
        mask = 0xFF << shiftbits

        x = (value & mask) >> shiftbits
        data_output.writeUByte(x)

def isNegativeVInt(value):
    return value < -120 or (value >= -112 and value < 0)

def decodeVIntSize(value):
    if value >= -112:
        return 1
    elif value < -120:
        return -119 - value
    return -111 - value