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# SPDX-License-Identifier: BSD-2-Clause
# SPDX-FileCopyrightText: Copyright (c) 2025 Runxi Yu <https://runxiyu.org>
import base64
import hashlib
import sys
import struct
def validate_bit_zeros(bs: bytes, n: int) -> bool:
q, r = divmod(n, 8)
if any(b != 0 for b in bs[:q]):
return False
if r and (bs[q] & (0xFF << (8 - r))):
return False
return True
if len(sys.argv) < 3:
print(f"usage: {sys.argv[0]} <base64 identifier> <difficulty>", file=sys.stderr)
sys.exit(1)
decoded = base64.b64decode(sys.argv[1])
difficulty = int(sys.argv[2])
next_val = 0
while True:
h = hashlib.sha256(decoded + struct.pack("Q", next_val)).digest()
if validate_bit_zeros(h, difficulty):
break
next_val = (next_val + 1) & 0xFFFFFFFFFFFFFFFF
if next_val == 0:
raise ValueError("overflow")
print(base64.b64encode(struct.pack("Q", next_val)).decode())
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