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import json
import json.decoder
from ..errors import StreamParseError
json_decoder = json.JSONDecoder()
def stream_as_text(stream):
"""
Given a stream of bytes or text, if any of the items in the stream
are bytes convert them to text.
This function can be removed once we return text streams
instead of byte streams.
"""
for data in stream:
if not isinstance(data, str):
data = data.decode('utf-8', 'replace')
yield data
def json_splitter(buffer):
"""Attempt to parse a json object from a buffer. If there is at least one
object, return it and the rest of the buffer, otherwise return None.
"""
buffer = buffer.strip()
try:
obj, index = json_decoder.raw_decode(buffer)
rest = buffer[json.decoder.WHITESPACE.match(buffer, index).end():]
return obj, rest
except ValueError:
return None
def json_stream(stream):
"""Given a stream of text, return a stream of json objects.
This handles streams which are inconsistently buffered (some entries may
be newline delimited, and others are not).
"""
return split_buffer(stream, json_splitter, json_decoder.decode)
def line_splitter(buffer, separator='\n'):
index = buffer.find(str(separator))
if index == -1:
return None
return buffer[:index + 1], buffer[index + 1:]
def split_buffer(stream, splitter=None, decoder=lambda a: a):
"""Given a generator which yields strings and a splitter function,
joins all input, splits on the separator and yields each chunk.
Unlike string.split(), each chunk includes the trailing
separator, except for the last one if none was found on the end
of the input.
"""
splitter = splitter or line_splitter
buffered = ''
for data in stream_as_text(stream):
buffered += data
while True:
buffer_split = splitter(buffered)
if buffer_split is None:
break
item, buffered = buffer_split
yield item
if buffered:
try:
yield decoder(buffered)
except Exception as e:
raise StreamParseError(e)
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