Source code for monai.data.thread_buffer

# Copyright 2020 - 2021 MONAI Consortium
# 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
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from queue import Empty, Full, Queue
from threading import Thread


[docs]class ThreadBuffer: """ Iterates over values from self.src in a separate thread but yielding them in the current thread. This allows values to be queued up asynchronously. The internal thread will continue running so long as the source has values or until the stop() method is called. One issue raised by using a thread in this way is that during the lifetime of the thread the source object is being iterated over, so if the thread hasn't finished another attempt to iterate over it will raise an exception or yield unexpected results. To ensure the thread releases the iteration and proper cleanup is done the stop() method must be called which will join with the thread. Args: src: Source data iterable buffer_size: Number of items to buffer from the source timeout: Time to wait for an item from the buffer, or to wait while the buffer is full when adding items """ def __init__(self, src, buffer_size=1, timeout=0.01): self.src = src self.buffer_size = buffer_size self.timeout = timeout self.buffer = Queue(self.buffer_size) self.gen_thread = None self.is_running = False def enqueue_values(self): for src_val in self.src: while self.is_running: try: self.buffer.put(src_val, timeout=self.timeout) except Full: pass # try to add the item again else: break # successfully added the item, quit trying else: # quit the thread cleanly when requested to stop break def stop(self): self.is_running = False # signal the thread to exit if self.gen_thread is not None: self.gen_thread.join() self.gen_thread = None def __iter__(self): self.is_running = True self.gen_thread = Thread(target=self.enqueue_values, daemon=True) self.gen_thread.start() try: while self.is_running and (self.gen_thread.is_alive() or not self.buffer.empty()): try: yield self.buffer.get(timeout=self.timeout) except Empty: pass # queue was empty this time, try again finally: self.stop() # ensure thread completion