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# 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.
from __future__ import annotations
import binascii
import struct
from pyiceberg.avro.codecs.codec import Codec
STRUCT_CRC32 = struct.Struct(">I") # big-endian unsigned int
try:
import snappy
class SnappyCodec(Codec):
@staticmethod
def _check_crc32(bytes_: bytes, checksum: bytes) -> None:
"""Incrementally compute CRC-32 from bytes and compare to a checksum.
Args:
bytes_ (bytes): The bytes to check against `checksum`
checksum (bytes): Byte representation of a checksum
Raises:
ValueError: If the computed CRC-32 does not match the checksum
"""
if binascii.crc32(bytes_) & 0xFFFFFFFF != STRUCT_CRC32.unpack(checksum)[0]:
raise ValueError("Checksum failure")
@staticmethod
def compress(data: bytes) -> tuple[bytes, int]:
compressed_data = snappy.compress(data)
# A 4-byte, big-endian CRC32 checksum
compressed_data += STRUCT_CRC32.pack(binascii.crc32(data) & 0xFFFFFFFF)
return compressed_data, len(compressed_data)
@staticmethod
def decompress(data: bytes) -> bytes:
# Compressed data includes a 4-byte CRC32 checksum
data = data[0:-4]
uncompressed = snappy.decompress(data)
checksum = data[-4:]
SnappyCodec._check_crc32(uncompressed, checksum)
return uncompressed
except ImportError:
class SnappyCodec(Codec): # type: ignore
@staticmethod
def compress(data: bytes) -> tuple[bytes, int]:
raise ImportError("Snappy support not installed, please install using `pip install pyiceberg[snappy]`")
@staticmethod
def decompress(data: bytes) -> bytes:
raise ImportError("Snappy support not installed, please install using `pip install pyiceberg[snappy]`")
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