On Thu, Jun 05, 2025 at 12:11:24PM +0200, Paolo Bonzini wrote:
> Date: Thu, 5 Jun 2025 12:11:24 +0200
> From: Paolo Bonzini <pbonz...@redhat.com>
> Subject: [PATCH 3/3] scripts/qapi: generate high-level Rust bindings
> X-Mailer: git-send-email 2.49.0
>
> From: Marc-André Lureau <marcandre.lur...@redhat.com>
>
> Generate high-level idiomatic Rust code for the QAPI types, with to/from
> translations for the C FFI.
>
> - char* is mapped to String, scalars to there corresponding Rust types
>
> - enums are simply aliased from FFI
>
> - has_foo/foo members are mapped to Option<T>
>
> - lists are represented as Vec<T>
>
> - structures have Rust versions, with To/From FFI conversions
>
> - alternate are represented as Rust enum
>
> - unions are represented in a similar way as in C: a struct S with a "u"
> member (since S may have extra 'base' fields). However, the discriminant
> isn't a member of S, since Rust enum already include it.
Why not map the C union to rust union directly (in `pub enum
%(rs_name)sVariant`)?
(latter comments are all about format nits)
...
> +%(cfg)s
> +impl From<&%(rs_name)sVariant> for %(tag)s {
> + fn from(e: &%(rs_name)sVariant) -> Self {
> + match e {
> + ''',
> + cfg=ifcond.rsgen(),
> + rs_name=rs_name(name),
> + tag=rs_type(variants.tag_member.type.c_type(), ''))
> +
> + for var in variants.variants:
> + type_name = var.type.name
> + var_name = to_camel_case(rs_name(var.name))
> + patt = '(_)'
> + if type_name == 'q_empty':
> + patt = ''
> + ret += mcgen('''
> + %(cfg)s
This introduces extra \n, which will generate a blank line if there's
no cfg.
> + %(rs_name)sVariant::%(var_name)s%(patt)s => Self::%(var_name)s,
So, I think it should be:
%(cfg)s %(rs_name)sVariant::%(var_name)s%(patt)s => Self::%(var_name)s,
> +''',
> + cfg=var.ifcond.rsgen(),
> + rs_name=rs_name(name),
> + var_name=var_name,
> + patt=patt)
> +
> + ret += mcgen('''
> + }
> + }
> +}
> +''')
> + return ret
> +
> +
> +def gen_rs_variants(name: str,
> + ifcond: QAPISchemaIfCond,
> + variants: Optional[QAPISchemaVariants]) -> str:
> + ret = mcgen('''
> +
> +%(cfg)s
> +#[derive(Clone,Debug)]
> +pub enum %(rs_name)sVariant {
> +''',
> + cfg=ifcond.rsgen(),
> + rs_name=rs_name(name))
> +
> + for var in variants.variants:
> + type_name = var.type.name
> + var_name = to_camel_case(rs_name(var.name, False))
> + if type_name == 'q_empty':
> + ret += mcgen('''
> + %(cfg)s
> + %(var_name)s,
ditto,
%(cfg)s %(var_name)s,
> +''',
> + cfg=var.ifcond.rsgen(),
> + var_name=var_name)
> + else:
> + c_type = var.type.c_unboxed_type()
> + if c_type.endswith('_wrapper'):
> + c_type = c_type[6:-8] # remove q_obj*-wrapper
> + ret += mcgen('''
> + %(cfg)s
> + %(var_name)s(%(rs_type)s),
%(cfg)s %(var_name)s(%(rs_type)s),
> +''',
> + cfg=var.ifcond.rsgen(),
> + var_name=var_name,
> + rs_type=rs_type(c_type, ''))
> +
> + ret += mcgen('''
> +}
> +''')
> +
> + ret += gen_rs_variants_to_tag(name, ifcond, variants)
> +
> + return ret
> +
> +
> +def gen_rs_members(members: List[QAPISchemaObjectTypeMember],
> + exclude: List[str] = None) -> str:
> + exclude = exclude or []
> + return [f"{m.ifcond.rsgen()} {to_snake_case(rs_name(m.name))}"
> + for m in members if m.name not in exclude]
> +
> +
> +def gen_struct_members(members: List[QAPISchemaObjectTypeMember]) -> str:
> + ret = ''
> + for memb in members:
> + typ = rs_type(memb.type.c_type(), '', optional=memb.optional,
> box=True)
> + ret += mcgen('''
> + %(cfg)s
> + pub %(rs_name)s: %(rs_type)s,
%(cfg)s pub %(rs_name)s: %(rs_type)s,
> +''',
> + cfg=memb.ifcond.rsgen(),
> + rs_type=typ,
> + rs_name=to_snake_case(rs_name(memb.name)))
> + return ret
> +
> +
...
> +%(cfg)s
> +#[repr(u32)]
> +#[derive(Copy, Clone, Debug, PartialEq, Eq, qemu_api_macros::TryInto)]
> +pub enum %(rs_name)s {
> +''',
> + cfg=ifcond.rsgen(),
> + rs_name=rs_name(name))
> +
> + for member in enum_members:
> + ret += mcgen('''
> + %(cfg)s
> + %(c_enum)s,
%(cfg)s %(c_enum)s,
> +''',
> + cfg=member.ifcond.rsgen(),
> + c_enum=to_camel_case(rs_name(member.name)))
> + # picked the first, since that's what malloc0 does
> + # but arguably could use _MAX instead, or a qapi annotation
> + default = to_camel_case(rs_name(enum_members[0].name))
> + ret += mcgen('''
> +}
> +
...
> +def gen_rs_alternate(name: str,
> + ifcond: QAPISchemaIfCond,
> + variants: Optional[QAPISchemaVariants]) -> str:
> + if name in objects_seen:
> + return ''
> +
> + ret = ''
> + objects_seen.add(name)
> +
> + ret += mcgen('''
> +%(cfg)s
> +#[derive(Clone, Debug)]
> +pub enum %(rs_name)s {
> +''',
> + cfg=ifcond.rsgen(),
> + rs_name=rs_name(name))
> +
> + for var in variants.variants:
> + if var.type.name == 'q_empty':
> + continue
> + ret += mcgen('''
> + %(cfg)s
> + %(mem_name)s(%(rs_type)s),
%(cfg)s %(mem_name)s(%(rs_type)s),
> +''',
> + cfg=var.ifcond.rsgen(),
> + rs_type=rs_type(var.type.c_unboxed_type(), ''),
> + mem_name=to_camel_case(rs_name(var.name)))
> +
> + ret += mcgen('''
> +}
> +''')
> + return ret
