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#!/usr/bin/env python

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# -*- coding: utf-8 -*-

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# This file is part of Beremiz

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# Copyright (C) 2021: Edouard TISSERANT

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#

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# See COPYING file for copyrights details.

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# Based on Eelco Hoogendoorn stackoverflow answer about RingBuffer with numpy

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import numpy as np

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class RingBuffer(object):

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    def __init__(self, width=None, size=131072, padding=None):

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        self.size = size

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        self.padding = size if padding is None else padding

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        shape = (self.size+self.padding,)

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        if width :

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            shape += (width,)

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        self.buffer = np.zeros(shape)

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        self.cursor = 0

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    def append(self, data):

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        """this is an O(n) operation"""

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        data = data[-self.size:]

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        n = len(data)

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        if self.size + self.padding - self.cursor < n:

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            self.compact()

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        self.buffer[self.cursor:][:n] = data

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        self.cursor += n

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    @property

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    def count(self):

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        return min(self.size, self.cursor)

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    @property

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    def view(self):

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        """this is always an O(1) operation"""

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        return self.buffer[max(0, self.cursor - self.size):][:self.count]

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    def compact(self):

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        """

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        note: only when this function is called, is an O(size) performance hit incurred,

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        and this cost is amortized over the whole padding space

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        """

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        print 'compacting'

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        self.buffer[:self.count] = self.view

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        self.cursor -= self.size

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