mirror of
https://github.com/TheAlgorithms/Python.git
synced 2024-11-30 16:31:08 +00:00
882fb2f3c9
* rewrite of base85.py * changed maps to list comprehension * Apply suggestions from code review Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com> --------- Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>
59 lines
1.8 KiB
Python
59 lines
1.8 KiB
Python
"""
|
|
Base85 (Ascii85) encoding and decoding
|
|
|
|
https://en.wikipedia.org/wiki/Ascii85
|
|
"""
|
|
|
|
|
|
def _base10_to_85(d: int) -> str:
|
|
return "".join(chr(d % 85 + 33)) + _base10_to_85(d // 85) if d > 0 else ""
|
|
|
|
|
|
def _base85_to_10(digits: list) -> int:
|
|
return sum(char * 85**i for i, char in enumerate(reversed(digits)))
|
|
|
|
|
|
def ascii85_encode(data: bytes) -> bytes:
|
|
"""
|
|
>>> ascii85_encode(b"")
|
|
b''
|
|
>>> ascii85_encode(b"12345")
|
|
b'0etOA2#'
|
|
>>> ascii85_encode(b"base 85")
|
|
b'@UX=h+?24'
|
|
"""
|
|
binary_data = "".join(bin(ord(d))[2:].zfill(8) for d in data.decode("utf-8"))
|
|
null_values = (32 * ((len(binary_data) // 32) + 1) - len(binary_data)) // 8
|
|
binary_data = binary_data.ljust(32 * ((len(binary_data) // 32) + 1), "0")
|
|
b85_chunks = [int(_s, 2) for _s in map("".join, zip(*[iter(binary_data)] * 32))]
|
|
result = "".join(_base10_to_85(chunk)[::-1] for chunk in b85_chunks)
|
|
return bytes(result[:-null_values] if null_values % 4 != 0 else result, "utf-8")
|
|
|
|
|
|
def ascii85_decode(data: bytes) -> bytes:
|
|
"""
|
|
>>> ascii85_decode(b"")
|
|
b''
|
|
>>> ascii85_decode(b"0etOA2#")
|
|
b'12345'
|
|
>>> ascii85_decode(b"@UX=h+?24")
|
|
b'base 85'
|
|
"""
|
|
null_values = 5 * ((len(data) // 5) + 1) - len(data)
|
|
binary_data = data.decode("utf-8") + "u" * null_values
|
|
b85_chunks = map("".join, zip(*[iter(binary_data)] * 5))
|
|
b85_segments = [[ord(_s) - 33 for _s in chunk] for chunk in b85_chunks]
|
|
results = [bin(_base85_to_10(chunk))[2::].zfill(32) for chunk in b85_segments]
|
|
char_chunks = [
|
|
[chr(int(_s, 2)) for _s in map("".join, zip(*[iter(r)] * 8))] for r in results
|
|
]
|
|
result = "".join("".join(char) for char in char_chunks)
|
|
offset = int(null_values % 5 == 0)
|
|
return bytes(result[: offset - null_values], "utf-8")
|
|
|
|
|
|
if __name__ == "__main__":
|
|
import doctest
|
|
|
|
doctest.testmod()
|