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51 lines
1.7 KiB
Python
51 lines
1.7 KiB
Python
"""
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In a multi-threaded download, this algorithm could be used to provide
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each worker thread with a block of non-overlapping bytes to download.
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For example:
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for i in allocation_list:
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requests.get(url,headers={'Range':f'bytes={i}'})
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"""
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from __future__ import annotations
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def allocation_num(number_of_bytes: int, partitions: int) -> list[str]:
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"""
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Divide a number of bytes into x partitions.
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:param number_of_bytes: the total of bytes.
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:param partitions: the number of partition need to be allocated.
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:return: list of bytes to be assigned to each worker thread
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>>> allocation_num(16647, 4)
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['1-4161', '4162-8322', '8323-12483', '12484-16647']
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>>> allocation_num(50000, 5)
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['1-10000', '10001-20000', '20001-30000', '30001-40000', '40001-50000']
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>>> allocation_num(888, 999)
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Traceback (most recent call last):
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...
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ValueError: partitions can not > number_of_bytes!
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>>> allocation_num(888, -4)
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Traceback (most recent call last):
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...
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ValueError: partitions must be a positive number!
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"""
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if partitions <= 0:
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raise ValueError("partitions must be a positive number!")
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if partitions > number_of_bytes:
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raise ValueError("partitions can not > number_of_bytes!")
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bytes_per_partition = number_of_bytes // partitions
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allocation_list = []
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for i in range(partitions):
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start_bytes = i * bytes_per_partition + 1
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end_bytes = (
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number_of_bytes if i == partitions - 1 else (i + 1) * bytes_per_partition
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)
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allocation_list.append(f"{start_bytes}-{end_bytes}")
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return allocation_list
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if __name__ == "__main__":
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import doctest
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doctest.testmod()
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