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pystruct.rs
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321 lines (292 loc) · 10.2 KB
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//! Python struct module.
//!
//! Docs: https://docs.python.org/3/library/struct.html
//!
//! Use this rust module to do byte packing:
//! https://docs.rs/byteorder/1.2.6/byteorder/
pub(crate) use _struct::make_module;
#[pymodule]
pub(crate) mod _struct {
use crate::vm::{
buffer::{new_struct_error, struct_error_type, FormatSpec},
builtins::{PyBytes, PyStr, PyStrRef, PyTupleRef, PyTypeRef},
function::{ArgBytesLike, ArgMemoryBuffer, PosArgs},
match_class,
protocol::PyIterReturn,
types::{Constructor, IterNext, Iterable, SelfIter},
AsObject, Py, PyObjectRef, PyPayload, PyResult, TryFromObject, VirtualMachine,
};
use crossbeam_utils::atomic::AtomicCell;
#[derive(Traverse)]
struct IntoStructFormatBytes(PyStrRef);
impl TryFromObject for IntoStructFormatBytes {
fn try_from_object(vm: &VirtualMachine, obj: PyObjectRef) -> PyResult<Self> {
// CPython turns str to bytes but we do reversed way here
// The only performance difference is this transition cost
let fmt = match_class! {
match obj {
s @ PyStr => if s.is_ascii() {
Some(s)
} else {
None
},
b @ PyBytes => if b.is_ascii() {
Some(unsafe {
PyStr::new_ascii_unchecked(b.as_bytes().to_vec())
}.into_ref(&vm.ctx))
} else {
None
},
other => return Err(vm.new_type_error(format!("Struct() argument 1 must be a str or bytes object, not {}", other.class().name()))),
}
}.ok_or_else(|| vm.new_unicode_decode_error("Struct format must be a ascii string".to_owned()))?;
Ok(IntoStructFormatBytes(fmt))
}
}
impl IntoStructFormatBytes {
fn format_spec(&self, vm: &VirtualMachine) -> PyResult<FormatSpec> {
FormatSpec::parse(self.0.as_str().as_bytes(), vm)
}
}
fn get_buffer_offset(
buffer_len: usize,
offset: isize,
needed: usize,
is_pack: bool,
vm: &VirtualMachine,
) -> PyResult<usize> {
let offset_from_start = if offset < 0 {
if (-offset) as usize > buffer_len {
return Err(new_struct_error(
vm,
format!("offset {offset} out of range for {buffer_len}-byte buffer"),
));
}
buffer_len - (-offset as usize)
} else {
let offset = offset as usize;
let (op, op_action) = if is_pack {
("pack_into", "packing")
} else {
("unpack_from", "unpacking")
};
if offset >= buffer_len {
let msg = format!(
"{op} requires a buffer of at least {required} bytes for {op_action} {needed} \
bytes at offset {offset} (actual buffer size is {buffer_len})",
op = op,
op_action = op_action,
required = needed + offset,
needed = needed,
offset = offset,
buffer_len = buffer_len
);
return Err(new_struct_error(vm, msg));
}
offset
};
if (buffer_len - offset_from_start) < needed {
Err(new_struct_error(
vm,
if is_pack {
format!("no space to pack {needed} bytes at offset {offset}")
} else {
format!("not enough data to unpack {needed} bytes at offset {offset}")
},
))
} else {
Ok(offset_from_start)
}
}
#[pyfunction]
fn pack(fmt: IntoStructFormatBytes, args: PosArgs, vm: &VirtualMachine) -> PyResult<Vec<u8>> {
fmt.format_spec(vm)?.pack(args.into_vec(), vm)
}
#[pyfunction]
fn pack_into(
fmt: IntoStructFormatBytes,
buffer: ArgMemoryBuffer,
offset: isize,
args: PosArgs,
vm: &VirtualMachine,
) -> PyResult<()> {
let format_spec = fmt.format_spec(vm)?;
let offset = get_buffer_offset(buffer.len(), offset, format_spec.size, true, vm)?;
buffer.with_ref(|data| format_spec.pack_into(&mut data[offset..], args.into_vec(), vm))
}
#[pyfunction]
fn unpack(
fmt: IntoStructFormatBytes,
buffer: ArgBytesLike,
vm: &VirtualMachine,
) -> PyResult<PyTupleRef> {
let format_spec = fmt.format_spec(vm)?;
buffer.with_ref(|buf| format_spec.unpack(buf, vm))
}
#[derive(FromArgs)]
struct UpdateFromArgs {
buffer: ArgBytesLike,
#[pyarg(any, default = "0")]
offset: isize,
}
#[pyfunction]
fn unpack_from(
fmt: IntoStructFormatBytes,
args: UpdateFromArgs,
vm: &VirtualMachine,
) -> PyResult<PyTupleRef> {
let format_spec = fmt.format_spec(vm)?;
let offset =
get_buffer_offset(args.buffer.len(), args.offset, format_spec.size, false, vm)?;
args.buffer
.with_ref(|buf| format_spec.unpack(&buf[offset..][..format_spec.size], vm))
}
#[pyattr]
#[pyclass(name = "unpack_iterator", traverse)]
#[derive(Debug, PyPayload)]
struct UnpackIterator {
#[pytraverse(skip)]
format_spec: FormatSpec,
buffer: ArgBytesLike,
#[pytraverse(skip)]
offset: AtomicCell<usize>,
}
impl UnpackIterator {
fn new(
vm: &VirtualMachine,
format_spec: FormatSpec,
buffer: ArgBytesLike,
) -> PyResult<UnpackIterator> {
if format_spec.size == 0 {
Err(new_struct_error(
vm,
"cannot iteratively unpack with a struct of length 0".to_owned(),
))
} else if buffer.len() % format_spec.size != 0 {
Err(new_struct_error(
vm,
format!(
"iterative unpacking requires a buffer of a multiple of {} bytes",
format_spec.size
),
))
} else {
Ok(UnpackIterator {
format_spec,
buffer,
offset: AtomicCell::new(0),
})
}
}
}
#[pyclass(with(IterNext, Iterable))]
impl UnpackIterator {
#[pymethod(magic)]
fn length_hint(&self) -> usize {
self.buffer.len().saturating_sub(self.offset.load()) / self.format_spec.size
}
}
impl SelfIter for UnpackIterator {}
impl IterNext for UnpackIterator {
fn next(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<PyIterReturn> {
let size = zelf.format_spec.size;
let offset = zelf.offset.fetch_add(size);
zelf.buffer.with_ref(|buf| {
if let Some(buf) = buf.get(offset..offset + size) {
zelf.format_spec
.unpack(buf, vm)
.map(|x| PyIterReturn::Return(x.into()))
} else {
Ok(PyIterReturn::StopIteration(None))
}
})
}
}
#[pyfunction]
fn iter_unpack(
fmt: IntoStructFormatBytes,
buffer: ArgBytesLike,
vm: &VirtualMachine,
) -> PyResult<UnpackIterator> {
let format_spec = fmt.format_spec(vm)?;
UnpackIterator::new(vm, format_spec, buffer)
}
#[pyfunction]
fn calcsize(fmt: IntoStructFormatBytes, vm: &VirtualMachine) -> PyResult<usize> {
Ok(fmt.format_spec(vm)?.size)
}
#[pyattr]
#[pyclass(name = "Struct", traverse)]
#[derive(Debug, PyPayload)]
struct PyStruct {
#[pytraverse(skip)]
spec: FormatSpec,
format: PyStrRef,
}
impl Constructor for PyStruct {
type Args = IntoStructFormatBytes;
fn py_new(cls: PyTypeRef, fmt: Self::Args, vm: &VirtualMachine) -> PyResult {
let spec = fmt.format_spec(vm)?;
let format = fmt.0;
PyStruct { spec, format }
.into_ref_with_type(vm, cls)
.map(Into::into)
}
}
#[pyclass(with(Constructor))]
impl PyStruct {
#[pygetset]
fn format(&self) -> PyStrRef {
self.format.clone()
}
#[pygetset]
#[inline]
fn size(&self) -> usize {
self.spec.size
}
#[pymethod]
fn pack(&self, args: PosArgs, vm: &VirtualMachine) -> PyResult<Vec<u8>> {
self.spec.pack(args.into_vec(), vm)
}
#[pymethod]
fn pack_into(
&self,
buffer: ArgMemoryBuffer,
offset: isize,
args: PosArgs,
vm: &VirtualMachine,
) -> PyResult<()> {
let offset = get_buffer_offset(buffer.len(), offset, self.size(), true, vm)?;
buffer.with_ref(|data| {
self.spec
.pack_into(&mut data[offset..], args.into_vec(), vm)
})
}
#[pymethod]
fn unpack(&self, data: ArgBytesLike, vm: &VirtualMachine) -> PyResult<PyTupleRef> {
data.with_ref(|buf| self.spec.unpack(buf, vm))
}
#[pymethod]
fn unpack_from(&self, args: UpdateFromArgs, vm: &VirtualMachine) -> PyResult<PyTupleRef> {
let offset = get_buffer_offset(args.buffer.len(), args.offset, self.size(), false, vm)?;
args.buffer
.with_ref(|buf| self.spec.unpack(&buf[offset..][..self.size()], vm))
}
#[pymethod]
fn iter_unpack(
&self,
buffer: ArgBytesLike,
vm: &VirtualMachine,
) -> PyResult<UnpackIterator> {
UnpackIterator::new(vm, self.spec.clone(), buffer)
}
}
// seems weird that this is part of the "public" API, but whatever
// TODO: implement a format code->spec cache like CPython does?
#[pyfunction]
fn _clearcache() {}
#[pyattr(name = "error")]
fn error_type(vm: &VirtualMachine) -> PyTypeRef {
struct_error_type(vm).clone()
}
}