理解Python中的RingBuffer环形缓冲区

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

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 = -1self.data.append(x) # add at the index = -1def get(self):return self.databuf = 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_maxself.data = []class __Full:""" class that implements a full buffer """def append(self, x):""" Append an element overwriting the oldest one. """self.data[self.cur] = xself.cur = (self.cur+1) % self.maxdef 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 fullself._ _class_ _ = self._ _Fulldef 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(  )