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Optimize set_value with mask caching and combined operations #2894

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Optimize set_value with mask caching and combined operations #2894

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9 changes: 6 additions & 3 deletions opendbc/can/packer.py
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Original file line number Diff line number Diff line change
Expand Up @@ -54,18 +54,21 @@ def make_can_msg(self, name_or_addr, bus: int, values: dict[str, float]):
return 0, b'', bus
return addr, bytes(dat), bus

_MASKS: list[int] = [(1 << k) - 1 for k in range(9)]

def set_value(msg: bytearray, sig: Signal, ival: int) -> None:
i = sig.lsb // 8
bits = sig.size
if sig.size < 64:
ival &= (1 << sig.size) - 1

while 0 <= i < len(msg) and bits > 0:
shift = sig.lsb % 8 if (sig.lsb // 8) == i else 0
size = min(bits, 8 - shift)
mask = ((1 << size) - 1) << shift
msg[i] &= ~mask
msg[i] |= (ival & ((1 << size) - 1)) << shift
size_mask = _MASKS[size] if size <= 8 else (1 << size) - 1
mask = size_mask << shift
msgval = msg[i]
msg[i] = (msgval & ~mask) | ((ival & size_mask) << shift)
bits -= size
ival >>= size
i = i + 1 if sig.is_little_endian else i - 1