RustPython/stdlib/src/pystruct.rs at main · github-roushan/RustPython · GitHub

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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::{

AsObject, Py, PyObjectRef, PyPayload, PyResult, TryFromObject, VirtualMachine,

buffer::{FormatSpec, new_struct_error, struct_error_type},

builtins::{PyBytes, PyStr, PyStrRef, PyTupleRef, PyTypeRef},

function::{ArgBytesLike, ArgMemoryBuffer, PosArgs},

match_class,

protocol::PyIterReturn,

types::{Constructor, IterNext, Iterable, SelfIter},

};

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 => s.is_ascii().then_some(s),

b @ PyBytes => ascii::AsciiStr::from_ascii(&b)

.ok()

.map(|s| vm.ctx.new_str(s)),

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_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()

}

RustPython/stdlib/src/pystruct.rs at main · github-roushan/RustPython · GitHub

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