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//! Example implementation of hashed type ID
//!
//! This is a sample implementation of `core::any::type_id` built on top of `TypeInfo`. This is
//! freely implementable as additional crate. It doesn't need to live within ctti. It doesn't
//! use cryptographically secure hashing, but should be sufficient in regular cases.
use crate::*;
pub const fn type_id<T: TypeInfo>() -> u64 {
type_id_of_val(&T::INFO)
}
pub const fn type_id_of_val(info: &Type) -> u64 {
match info {
Unsized(ty) => hash_mul(&[1, type_id_of_val_inner(ty)]),
Sized(ty, inner) => hash_mul(&[
2,
type_id_of_val_inner(ty),
inner.size as u64,
inner.align as u64,
]),
}
}
pub const fn type_id_of_val_inner(info: &InnerType) -> u64 {
match info {
Primitive(ty) => hash_mul(&[
1,
match ty {
Boolean => 1,
Numeric(ty) => hash_mul(&[
2,
match ty {
Integer(ty) => hash_mul(&[
1,
match ty {
ty => {
hash_mul(&[hash_str(ty.name), ty.signed as u64, ty.size as u64])
}
},
]),
Float(ty) => hash_mul(&[2, ty.size as u64]),
},
]),
Textual(ty) => hash_mul(&[
3,
match ty {
Char => 1,
Str => 2,
},
]),
Never => 4,
},
]),
Sequence(ty) => hash_mul(&[
2,
match ty {
Tuple(ty) => hash_mul(&[1, {
let mut tmp = 0;
let mut i = 0;
while i < ty.fields.len() {
tmp = hash_mul(&[tmp, type_id_of_val(ty.fields[i])]);
i += 1;
}
tmp
}]),
Array(ty) => hash_mul(&[2, ty.size as u64, type_id_of_val(ty.ty)]),
Slice(ty) => hash_mul(&[3, type_id_of_val(ty.ty)]),
},
]),
User(ty) => hash_mul(&[
3,
match ty {
Struct(ty) => hash_mul(&[
1,
hash_repr(&ty.repr),
// FIXME: name is not sufficient for type uniqueness.
// Do we want the type ID represent layout compatibility or
// actual implementation identicalness, because tracking the
// latter is close to impossible.
hash_str(ty.name),
match ty.fields {
Named(fields) => {
hash_mul(&[1, {
let mut tmp = 0;
let mut i = 0;
while i < fields.len() {
// Intentionally do not hash field names, visibility, because they
// do not change the layout.
tmp = hash_mul(&[tmp, type_id_of_val(fields[i].inner.ty)]);
i += 1;
}
tmp
}])
}
Unnamed(fields) => {
hash_mul(&[2, {
let mut tmp = 0;
let mut i = 0;
while i < fields.len() {
// Intentionally do not hash field names, visibility, because they
// do not change the layout.
tmp = hash_mul(&[tmp, type_id_of_val(fields[i].ty)]);
i += 1;
}
tmp
}])
}
},
]),
Enum(ty) => hash_mul(&[
2,
hash_repr(&ty.repr),
// FIXME: name is not sufficient for type uniqueness.
// Do we want the type ID represent layout compatibility or
// actual implementation identicalness, because tracking the
// latter is close to impossible.
hash_str(ty.name),
{
const fn hash_variants<T: TypeInfo>(variants: &[EnumVariant<T>]) -> u64 {
let mut tmp = 0;
let mut i = 0;
while i < variants.len() {
let variant = &variants[i];
let mut tmp2 = 0;
let mut o = 0;
match variant.fields {
Named(fields) => {
while o < fields.len() {
tmp2 = hash_mul(&[
tmp2,
1,
type_id_of_val(fields[o].inner.ty),
]);
o += 1;
}
}
Unnamed(fields) => {
while o < fields.len() {
tmp2 =
hash_mul(&[tmp2, 2, type_id_of_val(fields[o].ty)]);
o += 1;
}
}
}
hash_mul(&[tmp, tmp2, hash_str(variant.name)]);
}
hash_mul(&[type_id::<T>(), tmp])
}
match ty.variants {
// Avoid clashing with I128 definition
C(v) => hash_mul(&[1, hash_variants(&v)]),
U8(v) => hash_variants(&v),
I8(v) => hash_variants(&v),
U16(v) => hash_variants(&v),
I16(v) => hash_variants(&v),
U32(v) => hash_variants(&v),
I32(v) => hash_variants(&v),
U64(v) => hash_variants(&v),
I64(v) => hash_variants(&v),
U128(v) => hash_variants(&v),
I128(v) => hash_variants(&v),
Usize(v) => hash_variants(&v),
Isize(v) => hash_variants(&v),
Undefined(v) => hash_variants(&v),
}
},
]),
Union(ty) => hash_mul(&[
3,
hash_repr(&ty.repr),
// FIXME: name is not sufficient for type uniqueness.
// Do we want the type ID represent layout compatibility or
// actual implementation identicalness, because tracking the
// latter is close to impossible.
hash_str(ty.name),
{
let mut tmp = 0;
let mut i = 0;
while i < ty.fields.len() {
// Intentionally do not hash field names, visibility, because they
// do not change the layout.
tmp = hash_mul(&[tmp, type_id_of_val(ty.fields[i].inner.ty)]);
i += 1;
}
tmp
},
]),
},
]),
Function(ty) => hash_mul(&[
4,
match ty {
_ => 0,
},
]),
Pointer(ty) => hash_mul(&[
5,
match &ty.indirection {
Indirection::Ref => 1,
Indirection::MutRef => 2,
Indirection::ConstPtr => 3,
Indirection::MutPtr => 4,
},
ty.sized as u64,
]),
}
}
const fn hash_repr(repr: &Repr) -> u64 {
hash_mul(&[
match repr.base {
BaseRepr::C => 1,
BaseRepr::Rust => 2,
BaseRepr::Transparent => 3,
BaseRepr::EnumSigned(s) => hash_mul(&[4, s as u64]),
BaseRepr::EnumUnsigned(s) => hash_mul(&[5, s as u64]),
},
repr.packed as u64,
if let Some(align) = repr.align {
align as u64
} else {
0
},
])
}
// Compile time hashing (not secure hashes).
const fn hash(mut x: u64) -> u64 {
x = (x ^ (x >> 30)).wrapping_mul(0xbf58476d1ce4e5b9u64);
x = (x ^ (x >> 27)).wrapping_mul(0x94d049bb133111ebu64);
x ^ (x >> 31)
}
const fn hash_str(s: &str) -> u64 {
let mut ret = 0u64;
let mut i = 0;
let b = s.as_bytes();
while i < b.len() {
ret = hash(ret.wrapping_add(b[i] as u64));
i += 1;
}
hash(ret)
}
const fn hash_mul(xs: &[u64]) -> u64 {
let mut ret = 0u64;
let mut i = 0;
while i < xs.len() {
ret = hash(ret.wrapping_add(xs[i]));
i += 1;
}
ret
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn check_different() {
assert_ne!(type_id::<u64>(), type_id::<usize>());
assert_ne!(type_id::<u64>(), type_id::<(u64,)>());
assert_ne!(type_id::<()>(), type_id::<(u64,)>());
assert_ne!(type_id::<()>(), type_id::<((),)>());
assert_ne!(type_id::<((),)>(), type_id::<((), ())>());
}
}