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iterator.rs
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164 lines (153 loc) · 5.35 KB
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/*
* utilities to support iteration.
*/
use crate::builtins::int::{self, PyInt};
use crate::builtins::iter::PySequenceIterator;
use crate::exceptions::PyBaseExceptionRef;
use crate::pyobject::{BorrowValue, PyObjectRef, PyResult, PyValue, TryFromObject, TypeProtocol};
use crate::vm::VirtualMachine;
use num_traits::Signed;
/*
* This helper function is called at multiple places. First, it is called
* in the vm when a for loop is entered. Next, it is used when the builtin
* function 'iter' is called.
*/
pub fn get_iter(vm: &VirtualMachine, iter_target: PyObjectRef) -> PyResult {
let getiter = {
let cls = iter_target.class();
cls.mro_find_map(|x| x.slots.iter.load())
};
if let Some(getiter) = getiter {
let iter = getiter(iter_target, vm)?;
let cls = iter.class();
let is_iter = cls.iter_mro().any(|x| x.slots.iternext.load().is_some());
if is_iter {
drop(cls);
Ok(iter)
} else {
Err(vm.new_type_error(format!(
"iter() returned non-iterator of type '{}'",
cls.name
)))
}
} else {
vm.get_method_or_type_error(iter_target.clone(), "__getitem__", || {
format!("'{}' object is not iterable", iter_target.class().name)
})?;
Ok(PySequenceIterator::new_forward(iter_target)
.into_ref(vm)
.into_object())
}
}
pub fn call_next(vm: &VirtualMachine, iter_obj: &PyObjectRef) -> PyResult {
let iternext = {
let cls = iter_obj.class();
cls.mro_find_map(|x| x.slots.iternext.load())
.ok_or_else(|| vm.new_type_error(format!("'{}' object is not an iterator", cls.name)))?
};
iternext(iter_obj, vm)
}
/*
* Helper function to retrieve the next object (or none) from an iterator.
*/
pub fn get_next_object(
vm: &VirtualMachine,
iter_obj: &PyObjectRef,
) -> PyResult<Option<PyObjectRef>> {
let next_obj: PyResult = call_next(vm, iter_obj);
match next_obj {
Ok(value) => Ok(Some(value)),
Err(next_error) => {
// Check if we have stopiteration, or something else:
if next_error.isinstance(&vm.ctx.exceptions.stop_iteration) {
Ok(None)
} else {
Err(next_error)
}
}
}
}
/* Retrieve all elements from an iterator */
pub fn get_all<T: TryFromObject>(vm: &VirtualMachine, iter_obj: &PyObjectRef) -> PyResult<Vec<T>> {
let cap = length_hint(vm, iter_obj.clone())?.unwrap_or(0);
// TODO: fix extend to do this check (?), see test_extend in Lib/test/list_tests.py,
// https://github.com/python/cpython/blob/master/Objects/listobject.c#L934-L940
if cap >= isize::max_value() as usize {
return Ok(Vec::new());
}
let mut elements = Vec::with_capacity(cap);
while let Some(element) = get_next_object(vm, iter_obj)? {
elements.push(T::try_from_object(vm, element)?);
}
elements.shrink_to_fit();
Ok(elements)
}
pub fn try_map<F, R>(vm: &VirtualMachine, iter_obj: &PyObjectRef, mut f: F) -> PyResult<Vec<R>>
where
F: FnMut(PyObjectRef) -> PyResult<R>,
{
let cap = length_hint(vm, iter_obj.clone())?.unwrap_or(0);
// TODO: fix extend to do this check (?), see test_extend in Lib/test/list_tests.py,
// https://github.com/python/cpython/blob/v3.9.0/Objects/listobject.c#L922-L928
if cap >= isize::max_value() as usize {
return Ok(Vec::new());
}
let mut results = Vec::with_capacity(cap);
while let Some(element) = get_next_object(vm, iter_obj)? {
results.push(f(element)?);
}
results.shrink_to_fit();
Ok(results)
}
pub fn stop_iter_with_value(val: PyObjectRef, vm: &VirtualMachine) -> PyBaseExceptionRef {
let stop_iteration_type = vm.ctx.exceptions.stop_iteration.clone();
vm.new_exception(stop_iteration_type, vec![val])
}
pub fn stop_iter_value(vm: &VirtualMachine, exc: &PyBaseExceptionRef) -> PyResult {
let args = exc.args();
let val = vm.unwrap_or_none(args.borrow_value().first().cloned());
Ok(val)
}
pub fn length_hint(vm: &VirtualMachine, iter: PyObjectRef) -> PyResult<Option<usize>> {
if let Some(len) = vm.obj_len_opt(&iter) {
match len {
Ok(len) => return Ok(Some(len)),
Err(e) => {
if !e.isinstance(&vm.ctx.exceptions.type_error) {
return Err(e);
}
}
}
}
let hint = match vm.get_method(iter, "__length_hint__") {
Some(hint) => hint?,
None => return Ok(None),
};
let result = match vm.invoke(&hint, ()) {
Ok(res) => res,
Err(e) => {
return if e.isinstance(&vm.ctx.exceptions.type_error) {
Ok(None)
} else {
Err(e)
}
}
};
let result = result
.payload_if_subclass::<PyInt>(vm)
.ok_or_else(|| {
vm.new_type_error(format!(
"'{}' object cannot be interpreted as an integer",
result.class().name
))
})?
.borrow_value();
if result.is_negative() {
return Err(vm.new_value_error("__length_hint__() should return >= 0".to_owned()));
}
let hint = int::try_to_primitive(result, vm)?;
Ok(Some(hint))
}
// pub fn seq_iter_method(obj: PyObjectRef) -> PySequenceIterator {
// PySequenceIterator::new_forward(obj)
// }