理解Python中的RingBuffer环形缓冲区

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发布于 2022-10-03 10:02:42

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ringbuffer

Refered from Wikipedia, a ring buffer(环形缓冲区 or circular buffer, circular queue, cyclic buffer) is a data strcture that uses a single, fixed-size buffer as if it were connected end-to-end.

This structure lends itself easily to buffering data streams.

buffer

First, we should know what the “BUFFER” is in computer science.

According Wikipedia, a data buffer (or just buffer) is a region of a physical memory storage used to temporarily store data while it is being moved from one place to another.

Typically, the data is stored in a buffer as it is retrieved from an input device or just befor it is sent to an output device.

However, a buffer may be used when moving data between processes within a computer.

LMAX Disruptor 中 ringbuffer

LMAX是伦敦多元资产交易所的简称，https://www.lmax.com/

其开源的LMAX Disruptor可以处理数百万订单/秒。ringbuffer是其一大利器。

ringbuffer用于在不同上下文（线程）间传递数据的buffer。

ringbuffer是数据（数组内元素的内存地址是连续性存储的）比链表快。

Python中实现ringbuffer

网上相关资料不多。

自己实现

refer from ：

class RingBuffer:
def __init__(self, size):
self.data = [None for i in range(size)]
def append(self, x):
self.data.pop(0) # remove the last one which index = -1
self.data.append(x) # add at the index = -1
def get(self):
return self.data
buf = RingBuffer(4)
for i in range(10):
buf.append(i)
print(buf.get())

Python Cookbook by Alex Martelli, David Ascher 中有一种相对完善的实现：

class RingBuffer:
""" class that implements a not-yet-full buffer """
def __init__(self,size_max):
self.max = size_max
self.data = []
class __Full:
""" class that implements a full buffer """
def append(self, x):
""" Append an element overwriting the oldest one. """
self.data[self.cur] = x
self.cur = (self.cur+1) % self.max
def get(self):
""" return list of elements in correct order """
return self.data[self.cur:]+self.data[:self.cur]
def append(self,x):
"""append an element at the end of the buffer"""
self.data.append(x)
if len(self.data) == self.max:
self.cur = 0
# Permanently change self's class from non-full to full
self._ _class_ _ = self._ _Full
def get(self):
""" Return a list of elements from the oldest to the newest. """
return self.data
# sample usage
if _ _name_ _=='_ _main_ _':
x=RingBuffer(5)
x.append(1); x.append(2); x.append(3); x.append(4)
print x._ _class_ _, x.get(  )
x.append(5)
print x._ _class_ _, x.get(  )
x.append(6)
print x.data, x.get(  )
x.append(7); x.append(8); x.append(9); x.append(10)
print x.data, x.get(  )