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https://github.com/notwa/mm
synced 2024-11-05 02:49:02 -08:00
69 lines
1.4 KiB
Python
69 lines
1.4 KiB
Python
# Based on uCON64's N64 checksum algorithm by Andreas Sterbenz
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crc_seeds = {
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6101: 0xF8CA4DDC,
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6102: 0xF8CA4DDC,
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6103: 0xA3886759,
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6105: 0xDF26F436,
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6106: 0x1FEA617A,
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}
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MAX32 = 0xFFFFFFFF
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def ROL(i, b):
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return ((i << b) | (i >> (32 - b))) & MAX32
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def R4(b):
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return b[0]*0x1000000 + b[1]*0x10000 + b[2]*0x100 + b[3]
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def crc(f, bootcode=6105):
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seed = crc_seeds[bootcode]
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t1 = t2 = t3 = t4 = t5 = t6 = seed
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if bootcode == 6105:
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f.seek(0x0710 + 0x40)
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lookup = f.read(0x100)
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f.seek(0x1000)
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for i in range(0x1000, 0x101000, 4):
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d = R4(f.read(4))
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if ((t6 + d) & MAX32) < t6:
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t4 += 1
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t4 &= MAX32
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t6 += d
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t6 &= MAX32
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t3 ^= d
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b = d & 0x1F
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r = (d << b) | (d >> (32 - b))
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r &= MAX32
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t5 += r
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t5 &= MAX32
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if t2 > d:
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t2 ^= r
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else:
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t2 ^= t6 ^ d
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if bootcode == 6105:
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o = i & 0xFF
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temp = R4(lookup[o:o + 4])
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else:
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temp = t5
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t1 += temp ^ d
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t1 &= MAX32
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if bootcode == 6103:
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crc1 = (t6 ^ t4) + t3
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crc2 = (t5 ^ t2) + t1
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elif bootcode == 6106:
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crc1 = t6*t4 + t3
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crc2 = t5*t2 + t1
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else:
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crc1 = t6 ^ t4 ^ t3
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crc2 = t5 ^ t2 ^ t1
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return crc1 & MAX32, crc2 & MAX32
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