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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.
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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.
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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。
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Python中实现ringbuffer
网上相关资料不多。
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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 = -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( ) -
Python模块collections.deque
class collections.deque([iterable[, maxlen]])deque对象返回一个新的双向队列对象。
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Python模块pyringbuf
这个模块在2015年之后就没有更新了
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References
- 剖析Disruptor:为什么会这么快？（一）Ringbuffer的特别之处
- 并发框架Disruptor译文
- disruptor – BlogsAndArticles.wiki
- Trisha’s Ramblings
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