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228 lines (185 loc) · 7.56 KB
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# -*- coding: utf-8 -*-
# MinIO Python Library for Amazon S3 Compatible Cloud Storage, (C)
# 2019 MinIO, Inc.
#
# 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.
"""
minio.select.reader
~~~~~~~~~~~~~~~
This module implements the reader for SelectObject response body.
:copyright: (c) 2019 by MinIO, Inc.
:license: Apache 2.0, see LICENSE for more details.
"""
from __future__ import absolute_import
import io
import sys
from xml.etree import ElementTree
from .errors import SelectCRCValidationError, SelectMessageError
from .helpers import (ERROR, EVENT, EVENT_CONTENT_TYPE, EVENT_RECORDS,
EVENT_STATS, byte_int, calculate_crc, validate_crc)
def _extract_header(header_bytes):
"""
populates the header map after reading the header in bytes
"""
header_map = {}
header_byte_parsed = 0
# While loop ends when all the headers present are read
# header contains multipe headers
while header_byte_parsed < len(header_bytes):
header_name_byte_length = byte_int(
header_bytes[header_byte_parsed:header_byte_parsed+1])
header_byte_parsed += 1
header_name = header_bytes[
header_byte_parsed:header_byte_parsed+header_name_byte_length
]
header_byte_parsed += header_name_byte_length
# Header Value Type is of 1 bytes and is skipped
header_byte_parsed += 1
value_string_byte_length = byte_int(
header_bytes[header_byte_parsed:header_byte_parsed+2]
)
header_byte_parsed += 2
header_value = header_bytes[
header_byte_parsed:header_byte_parsed+value_string_byte_length
]
header_byte_parsed += value_string_byte_length
header_map[header_name.decode(
"utf-8").lstrip(":")] = header_value.decode("utf-8").lstrip(":")
return header_map
def _parse_stats(stats):
"""
Parses stats XML and populates the stat dict.
"""
stat = {}
for attribute in ElementTree.fromstring(stats):
if attribute.tag == 'BytesScanned':
stat['BytesScanned'] = attribute.text
elif attribute.tag == 'BytesProcessed':
stat['BytesProcessed'] = attribute.text
elif attribute.tag == 'BytesReturned':
stat['BytesReturned'] = attribute.text
return stat
class SelectObjectReader:
"""
SelectObjectReader returns a Reader that upon read
returns queried data, but stops when the response ends.
LimitedRandomReader is compatible with BufferedIOBase.
"""
def __init__(self, response):
self.response = response
self.remaining_bytes = bytes()
self.stat = {}
self.prog = {}
def readable(self): # pylint: disable=no-self-use
"""Return this is readable."""
return True
def writeable(self): # pylint: disable=no-self-use
"""Return this is not writeable."""
return False
def close(self):
"""Close response."""
self.response.close()
def stats(self):
"""Get stats information."""
return self.stat
def progress(self):
"""Get progress information."""
return self.prog
def __extract_message(self):
"""
Process the response sent from server.
https://docs.aws.amazon.com/AmazonS3/latest/API/RESTObjectSELECTContent.html
"""
crc_bytes = io.BytesIO()
total_bytes_len = self.response.read(4)
if not total_bytes_len:
return {}
total_length = byte_int(total_bytes_len)
header_bytes_len = self.response.read(4)
if not header_bytes_len:
return {}
header_len = byte_int(header_bytes_len)
crc_bytes.write(total_bytes_len)
crc_bytes.write(header_bytes_len)
prelude_bytes_crc = self.response.read(4)
if not validate_crc(crc_bytes.getvalue(), prelude_bytes_crc):
raise SelectCRCValidationError(
{"Checksum Mismatch, PreludeCRC of " +
str(calculate_crc(crc_bytes.getvalue())) +
" does not equal expected CRC of " +
str(byte_int(prelude_bytes_crc))})
crc_bytes.write(prelude_bytes_crc)
header_bytes = self.response.read(header_len)
if not header_bytes:
raise SelectMessageError(
"Premature truncation of select message header" +
<
7AFF
/div> ", server is sending corrupt message?")
crc_bytes.write(header_bytes)
header_map = _extract_header(header_bytes)
payload_length = total_length - header_len - int(16)
payload_bytes = b''
event_type = header_map["event-type"]
if header_map["message-type"] == ERROR:
raise SelectMessageError(
header_map["error-code"] + ":\"" +
header_map["error-message"] + "\"")
if header_map["message-type"] != EVENT:
raise SelectMessageError(
"Unrecognized message-type {0}".format(
header_map["message-type"])
)
if event_type == EVENT_STATS:
content_type = header_map["content-type"]
if content_type != EVENT_CONTENT_TYPE:
raise SelectMessageError(
"Unrecognized content-type {0}".format(content_type))
payload_bytes = self.response.read(payload_length)
self.stat = _parse_stats(payload_bytes)
elif event_type == EVENT_RECORDS:
payload_bytes = self.response.read(payload_length)
crc_bytes.write(payload_bytes)
message_crc = self.response.read(4)
if not message_crc:
return {}
if not validate_crc(crc_bytes.getvalue(), message_crc):
raise SelectCRCValidationError(
{"Checksum Mismatch, MessageCRC of " +
str(calculate_crc(crc_bytes.getvalue())) +
" does not equal expected CRC of " +
str(byte_int(message_crc))})
message = {event_type: payload_bytes}
return message
def stream(self, num_bytes=32*1024):
"""
extract each record from the response body ... and buffer it.
send only up to requested bytes such as message[:num_bytes]
rest is buffered and added to the next iteration.
caller should call self.close() to close the stream.
"""
while not self.response.isclosed():
if not self.remaining_bytes:
message = self.__extract_message()
if EVENT_RECORDS not in message:
continue
self.remaining_bytes = message.get(EVENT_RECORDS, b'')
result = self.remaining_bytes
if num_bytes < len(self.remaining_bytes):
result = self.remaining_bytes[:num_bytes]
self.remaining_bytes = self.remaining_bytes[len(result):]
if result == b'':
break
if sys.version_info.major == 3:
yield result.decode('utf-8', errors='ignore')
else:
# Python 2.x needs explicit conversion.
yield result.decode('utf-8', errors='ignore').encode('utf-8')
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