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#!/usr/bin/env python
# License: GPLv3 Copyright: 2025, Kovid Goyal <kovid at kovidgoyal.net>
import os
from typing import NamedTuple
class BitField(NamedTuple):
name: str
bits: int
def typename_for_bitsize(bits: int) -> str:
if bits <= 8:
return 'uint8'
if bits <= 16:
return 'uint16'
if bits <= 32:
return 'uint32'
return 'uint64'
def make_bitfield(dest: str, typename: str, *fields_: str, add_package: bool = True) -> tuple[str, str]:
output_path = os.path.join(dest, f'{typename.lower()}_generated.go')
ans = [f'package {os.path.basename(dest)}', '']
a = ans.append
if not add_package:
del ans[0]
def fieldify(spec: str) -> BitField:
name, num = spec.partition(' ')[::2]
return BitField(name, int(num))
fields = tuple(map(fieldify, fields_))
total_size = sum(x.bits for x in fields)
if total_size > 64:
raise ValueError(f'Total size of bit fields: {total_size} for {typename} is larger than 64 bits')
a(f'// Total number of bits used: {total_size}')
itype = typename_for_bitsize(total_size)
a(f'type {typename} {itype}')
a('')
shift = 0
for bf in reversed(fields):
tn = typename_for_bitsize(bf.bits)
mask = '0b' + '1' * bf.bits
a(f'func (s {typename}) {bf.name.capitalize()}() {tn} {{') # }}
if shift:
a(f' return {tn}((s >> {shift}) & {mask})')
else:
a(f' return {tn}(s & {mask})')
a('}')
a('')
a(f'func (s *{typename}) Set_{bf.name}(val {tn}) {{') # }}
if shift:
a(f' *s &^= {mask} << {shift}')
a(f' *s |= {typename}(val&{mask}) << {shift}')
else:
a(f' *s &^= {mask}')
a(f' *s |= {typename}(val & {mask})')
a('}')
a('')
shift += bf.bits
return output_path, '\n'.join(ans)
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