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use crate::ty::Type;
use std::fmt;
#[derive(Clone)]
pub enum Seg<'a> {
NamedIndex(usize, &'a str),
Index(usize),
}
impl<'a> fmt::Debug for Seg<'a> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self {
Seg::NamedIndex(_, name) => f.write_str(name),
Seg::Index(i) => write!(f, "{}", i),
}
}
}
#[derive(Clone, Debug)]
pub struct MemberVariableRouting<'a> {
pub sym: Vec<Seg<'a>>,
pub offset: usize,
pub ty: &'a Type,
}
struct WalkFrame<'a> {
sym_stem: Option<Vec<Seg<'a>>>,
base_offset: usize,
ty: &'a Type,
i: usize,
}
pub struct Walk<'a> {
inner: Vec<WalkFrame<'a>>,
}
impl<'a> Walk<'a> {
pub fn new(ty: &'a Type) -> Walk<'a> {
let frame = WalkFrame {
sym_stem: None,
base_offset: 0,
ty: ty,
i: 0,
};
Walk { inner: vec![frame] }
}
}
impl<'a> Iterator for Walk<'a> {
type Item = MemberVariableRouting<'a>;
fn next(&mut self) -> Option<MemberVariableRouting<'a>> {
fn get_child_ty_offset_seg<'a>(
ty: &'a Type,
i: usize,
) -> Option<(&'a Type, usize, Seg<'a>)> {
match ty {
Type::Struct(struct_ty) => {
let member = struct_ty.members.get(i)?;
let seg = if let Some(name) = &member.name {
Seg::NamedIndex(i, &name)
} else {
Seg::Index(i)
};
Some((&member.ty, member.offset.unwrap_or_default(), seg))
}
Type::Array(arr_ty) => {
// Unsized buffer are treated as 0-sized.
if i < arr_ty.nelement.unwrap_or_default() as usize {
Some((
&arr_ty.element_ty,
arr_ty.stride.unwrap_or_default() * i,
Seg::Index(i),
))
} else {
None
}
}
_ => None,
}
}
enum LoopEnd<'a> {
Push(WalkFrame<'a>),
PopReturn(MemberVariableRouting<'a>),
}
loop {
// If used, this field will be filled with the next frame to be
// pushed at the back of the walk stack; or the last frame will be
// popped if the field is kept `None`.
let loop_end = if let Some(frame) = self.inner.last_mut() {
if let Some((child_ty, offset, seg)) = get_child_ty_offset_seg(frame.ty, frame.i) {
frame.i += 1; // Step member.
let offset = frame.base_offset + offset;
let ty = child_ty;
let sym = if let Some(sym_stem) = &frame.sym_stem {
let mut sym = sym_stem.clone();
sym.push(seg);
sym
} else {
vec![seg]
};
if child_ty.is_struct() || child_ty.is_array() {
// Found composite type, step into it.
LoopEnd::Push(WalkFrame {
sym_stem: Some(sym),
base_offset: offset,
ty,
i: 0,
})
} else {
// Return directly if it's not a composite type.
return Some(MemberVariableRouting { sym, offset, ty });
}
} else {
// Here can be reached only when the first frame's type is
// neither an array nor a struct; or a later frame's
// composite type's elements has been exhausted.
let ty = frame.ty;
let offset = frame.base_offset;
let sym = frame.sym_stem.clone().unwrap_or_default();
LoopEnd::PopReturn(MemberVariableRouting { sym, offset, ty })
}
} else {
// We have exhausted all types we have, including the root type
// of walk.
return None;
};
match loop_end {
LoopEnd::Push(frame) => self.inner.push(frame),
LoopEnd::PopReturn(route) => {
self.inner.pop();
return Some(route);
}
}
}
}
}