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# SPDX-FileCopyrightText: © 2025 ZeldaRET
# SPDX-License-Identifier: CC0-1.0
import struct
import abc
from typing import Sequence, Any
# NOTE: this system does NOT handle struct alignment/padding automatically, it should be made explicit
# this system voluntarily does not handle variable length arrays. which is not a valid "type" in C anyway (?)
# having variable-sized data is too messy to handle, because it needs a size at some point anyway
# This choice allows the root CData ABC to have a size as a guaranteed attribute
# BOSA = "Byte Order, Size, and Alignment" for the struct module
# Big Endian
STRUCT_BOSA_CHAR = ">"
class CData(abc.ABC):
@abc.abstractmethod
def __init__(self, size: int):
self.size = size
# Unpack
@abc.abstractmethod
def unpack_from(self, data: memoryview, offset: int = 0) -> Any: ...
class CData_Value(CData):
def __init__(self, format_char: str):
assert format_char in set("bBhHiIfd")
self.unpack_struct = struct.Struct(STRUCT_BOSA_CHAR + format_char)
super().__init__(self.unpack_struct.size)
def unpack_from(self, data: memoryview, offset: int = 0):
return self.unpack_struct.unpack_from(data, offset)[0]
s8: "CData_Value"
u8: "CData_Value"
s16: "CData_Value"
u16: "CData_Value"
s32: "CData_Value"
u32: "CData_Value"
f32: "CData_Value"
f64: "CData_Value"
pointer: "CData_Value"
CData_Value.s8 = CData_Value("b")
CData_Value.u8 = CData_Value("B")
CData_Value.s16 = CData_Value("h")
CData_Value.u16 = CData_Value("H")
CData_Value.s32 = CData_Value("i")
CData_Value.u32 = CData_Value("I")
CData_Value.f32 = CData_Value("f")
CData_Value.f64 = CData_Value("d")
CData_Value.pointer = CData_Value("I")
class CData_Array(CData):
def __init__(self, element_cdata: CData, length: int):
assert length > 0
self.element_cdata = element_cdata
self.length = length
super().__init__(element_cdata.size * length)
def unpack_from(self, data: memoryview, offset: int = 0):
array_unpacked = []
for i in range(self.length):
unpacked = self.element_cdata.unpack_from(data, offset)
array_unpacked.append(unpacked)
offset += self.element_cdata.size
assert len(array_unpacked) == self.length
return array_unpacked
class CData_Struct(CData):
def __init__(self, members: Sequence[tuple[str, CData]]):
# assert all members have different names
assert len(members) == len(
set(member_name for member_name, member_cdata in members)
), members
self.members = members
super().__init__(
sum(member_cdata.size for member_name, member_cdata in members)
)
if __debug__:
# Check alignment
# This may mess up with CData instances other than CData_Value, Array and Struct
def get_required_alignment(cdata: CData):
if isinstance(cdata, CData_Struct):
return max(
get_required_alignment(cdata_member_cdata)
for cdata_member_name, cdata_member_cdata in cdata.members
)
elif isinstance(cdata, CData_Array):
return get_required_alignment(cdata.element_cdata)
else:
# Assume the alignment requirement corresponds to the size
# (e.g. this is correct for CData_Value)
return cdata.size
# Check alignment of the members of the struct
offset = 0
for member_name, member_cdata in members:
alignment = get_required_alignment(member_cdata)
assert offset % alignment == 0, (member_name, offset, alignment)
offset += member_cdata.size
# Check alignment of the struct size
alignment = get_required_alignment(self)
assert self.size % alignment == 0, (self.size, alignment)
def unpack_from(self, data: memoryview, offset: int = 0):
struct_unpacked = dict()
for member_name, member_cdata in self.members:
member_unpacked = member_cdata.unpack_from(data, offset)
struct_unpacked[member_name] = member_unpacked
offset += member_cdata.size
return struct_unpacked
def try_stuff():
"""
struct {
s8 fun;
// u8 pad;
s16 games;
} array[] = { { 1, 2 }, { 3, 4 } };
u8 varLenArray[] = { 1, 2, 3 };
struct {
u8* ptr;
u16 len;
struct {
s32 secret1;
u32 secret2;
} mySubStruct;
} data = { varLenArray, 3, { 421, 0x01020304 } };
"""
array_bytes = memoryview(
bytes(
[
1,
0,
*(0, 2),
3,
0,
*(0, 4),
]
)
)
varLenArray_bytes = memoryview(bytes([1, 2, 3]))
data_bytes = memoryview(
bytes(
[
*(0x12, 0x34, 0x56, 0x78),
*(0, 3),
0,
0,
*(0, 0, 421 >> 8, 421 & 0xFF),
*(1, 2, 3, 4),
]
)
)
arrayElem_CData_Struct = CData_Struct(
(
("fun", CData_Value.s8),
("pad1", CData_Value.s8),
("games", CData_Value.s16),
)
)
array_CData_Array = CData_Array(arrayElem_CData_Struct, 2)
print(array_CData_Array.unpack_from(array_bytes))
mySubStruct_CData_Struct = CData_Struct(
(
("secret1", CData_Value.s32),
("secret2", CData_Value.u32),
)
)
data_CData_Struct = CData_Struct(
(
("ptr", CData_Value.pointer),
("len", CData_Value.u16),
("pad_6", CData_Value.s16),
("mySubStruct", mySubStruct_CData_Struct),
)
)
data_unpacked = data_CData_Struct.unpack_from(data_bytes)
print(data_unpacked)
varLenArray_CData_Array = CData_Array(CData_Value.u8, data_unpacked["len"])
print(varLenArray_CData_Array.unpack_from(varLenArray_bytes))
data_integratedSubStruct_CData_Struct = CData_Struct(
(
("ptr", CData_Value.pointer),
("len", CData_Value.u16),
("pad_6", CData_Value.s16),
(
"mySubStruct",
CData_Struct(
(
("secret1", CData_Value.s32),
("secret2", CData_Value.u32),
)
),
),
)
)
data_unpacked = data_integratedSubStruct_CData_Struct.unpack_from(data_bytes)
print(data_unpacked)
if __name__ == "__main__":
try_stuff()
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