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//! Generates an expression that calculates the size (in bits) of a data type
use crate::{GeneratedField, GeneratedType, GeneratedTypeKind};
use canadensis_dsdl_frontend::compiled::Extent;
use canadensis_dsdl_frontend::types::{
ImplicitField, PrimitiveType, ResolvedScalarType, ResolvedType,
};
use std::fmt::{Display, Formatter, Result};
pub(crate) struct SizeBitsExpr<'t, 'c>(pub &'t GeneratedType<'c>);
impl Display for SizeBitsExpr<'_, '_> {
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
let size_min = self.0.size.min_value();
let size_max = self.0.size.max_value();
if size_min == size_max {
// Just a single precalculated value
write!(f, "{}", size_min)
} else {
write_complex_size_expression(f, self.0)
}
}
}
fn write_complex_size_expression(f: &mut Formatter, ty: &GeneratedType) -> Result {
// This is similar to generating the serialize implementation, but we have to manually
// add 32 bits for delimiter headers of delimited composite types.
match &ty.kind {
GeneratedTypeKind::Struct(gstruct) => {
for field in &gstruct.fields {
match field {
GeneratedField::Data(field) => {
Display::fmt(
&WriteFieldSize {
ty: field.cyphal_ty,
expr: &format!("self.{}", field.name),
},
f,
)?;
}
GeneratedField::Padding(bits) => write!(f, "{}", *bits)?,
}
// End of field
write!(f, " + ")?;
}
// Last field, make the expression end in + 0
write!(f, "0")?;
}
GeneratedTypeKind::Enum(genum) => {
write!(f, "{} + match self {{", genum.discriminant_bits)?;
for variant in genum.variants.iter() {
// Match arm (inner value is called `inner`)
writeln!(f, "{}::{}(inner) => {{", ty.name.type_name, variant.name)?;
if let Some(ty) = &variant.ty {
Display::fmt(
&WriteFieldSize {
ty: &ty.cyphal_ty,
expr: "inner",
},
f,
)?;
} else {
// No data, no size, nothing to do
}
// End match arm
writeln!(f, "}}")?;
}
// End match
write!(f, "}}")?;
}
}
Ok(())
}
struct WriteFieldSize<'t> {
ty: &'t ResolvedType,
expr: &'t str,
}
impl Display for WriteFieldSize<'_> {
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
match &self.ty {
ResolvedType::Scalar(scalar) => Display::fmt(
&WriteScalarSize {
ty: scalar,
expr: self.expr,
},
f,
)?,
ResolvedType::FixedArray { inner, .. } => {
Display::fmt(
&WriteArrayElementSizes {
ty: inner,
expr: self.expr,
},
f,
)?;
}
ResolvedType::VariableArray { inner, .. } => {
// Add something for the length
match self.ty.implicit_field() {
Some(ImplicitField::ArrayLength { bits }) => {
write!(f, "{} +", bits)?;
}
_ => panic!("Variable-length array has no implicit length"),
}
// Then the elements
Display::fmt(
&WriteArrayElementSizes {
ty: inner,
expr: self.expr,
},
f,
)?;
}
}
Ok(())
}
}
struct WriteArrayElementSizes<'t> {
ty: &'t ResolvedScalarType,
expr: &'t str,
}
impl Display for WriteArrayElementSizes<'_> {
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
let element_size = self.ty.size();
let size_min = element_size.min_value();
if size_min == element_size.max_value() {
// Element size is fixed
// Add space for the delimiter header if the element type is delimited
let element_size = match self.ty.extent() {
Extent::Delimited(_) => 32 + size_min,
Extent::Sealed => size_min,
};
writeln!(
f,
"({}).len() * {}_usize.next_multiple_of({})",
self.expr,
element_size,
self.ty.alignment()
)
} else {
// In general, we need to iterate over every element and add up the
// lengths.
write!(
f,
"({}).iter().map(|element| {}).sum::<usize>()",
self.expr,
WriteScalarSize {
ty: self.ty,
expr: "element"
}
)
}
}
}
/// Writes the size of a scalar type
struct WriteScalarSize<'t> {
ty: &'t ResolvedScalarType,
expr: &'t str,
}
impl Display for WriteScalarSize<'_> {
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
match &self.ty {
ResolvedScalarType::Composite { inner, .. } => {
if matches!(inner.extent(), Extent::Delimited(_)) {
// Add 32 bits for the delimiter header
write!(f, "32 + ")?;
}
let inner_min_size = inner.bit_length().min_value();
let inner_max_size = inner.bit_length().max_value();
if inner_min_size == inner_max_size {
// Fixed-size type, use a literal
write!(
f,
"{}",
inner_min_size.next_multiple_of(self.ty.alignment().into())
)?;
} else {
// Call size_bits() on the inner type
write!(
f,
"({}).size_bits().next_multiple_of({})",
self.expr,
self.ty.alignment()
)?;
}
}
ResolvedScalarType::Primitive(primitive) => match primitive {
PrimitiveType::Boolean => write!(f, "1")?,
PrimitiveType::Byte | PrimitiveType::Utf8 => write!(f, "8")?,
PrimitiveType::Int { bits } => write!(f, "{}", *bits)?,
PrimitiveType::UInt { bits, .. } => write!(f, "{}", *bits)?,
PrimitiveType::Float16 { .. } => write!(f, "16")?,
PrimitiveType::Float32 { .. } => write!(f, "32")?,
PrimitiveType::Float64 { .. } => write!(f, "64")?,
},
ResolvedScalarType::Void { bits } => write!(f, "{}", *bits)?,
}
Ok(())
}
}