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ring_buffer.py
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67 lines (55 loc) · 1.94 KB
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from rpython.rlib.rarithmetic import r_uint
from pixie.vm.primitives import nil
empty_slot = (nil, nil)
class RingBuffer(object):
def __init__(self, size):
assert isinstance(size, r_uint)
self._array = [empty_slot] * size
self._array_len = size
self._length = size
self._head = r_uint(0)
self._tail = r_uint(0)
def pending(self):
return self._array_len - self._length
def pop(self):
if not self._length == 0:
x = self._array[self._tail]
self._array[self._tail] = empty_slot
self._tail = (self._tail + 1) % self._array_len
self._length -= 1
return x
return empty_slot
def push(self, x):
self._array[self._head] = x
self._head = (self._head + 1) % self._array_len
self._length += 1
def unbounded_push(self, x):
if self._length == 0:
self.resize()
self.push(x)
def resize(self):
new_arr_size = self._array_len * 2
new_arr = [None] * new_arr_size
if self._tail < self._head:
array_copy(self._array, self._tail, new_arr, 0, self._length)
self._tail = 0
self._head = self._length
self._array = new_arr
self._array_len = new_arr_size
elif self._tail > self._head:
array_copy(self._array, self._tail, new_arr, 0, self._array_len - self._tail)
array_copy(self._array, 0, new_arr, self._array_len - self._tail, self._head)
self._tail = 0
self._head = self._length
self._array = new_arr
self._array_len = new_arr_size
else:
self._tail = 0
self._head = 0
self._array = new_arr
self._array_len = new_arr_size
def array_copy(src, src_pos, dest, dest_pos, count):
x = r_uint(0)
while x < count:
dest[dest_pos + x] = src[src_pos + x]
x += 1