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use super::{
config::{
Config,
ReprKind,
},
field_config::{
FieldConfig,
SkipWhich,
},
BitfieldStruct,
};
use crate::errors::CombineError;
use core::convert::TryFrom;
use quote::quote;
use std::collections::HashMap;
use syn::{
self,
parse::Result,
spanned::Spanned as _,
};
impl TryFrom<(&mut Config, syn::ItemStruct)> for BitfieldStruct {
type Error = syn::Error;
fn try_from((config, item_struct): (&mut Config, syn::ItemStruct)) -> Result<Self> {
Self::ensure_has_fields(&item_struct)?;
Self::ensure_no_generics(&item_struct)?;
Self::extract_attributes(&item_struct.attrs, config)?;
Self::analyse_config_for_fields(&item_struct, config)?;
config.ensure_no_conflicts()?;
Ok(Self { item_struct })
}
}
impl BitfieldStruct {
/// Returns an error if the input struct does not have any fields.
fn ensure_has_fields(item_struct: &syn::ItemStruct) -> Result<()> {
if let unit @ syn::Fields::Unit = &item_struct.fields {
return Err(format_err_spanned!(
unit,
"encountered invalid bitfield struct without fields"
))
}
Ok(())
}
/// Returns an error if the input struct is generic.
fn ensure_no_generics(item_struct: &syn::ItemStruct) -> Result<()> {
if !item_struct.generics.params.is_empty() {
return Err(format_err_spanned!(
item_struct,
"encountered invalid generic bitfield struct"
))
}
Ok(())
}
/// Extracts the `#[repr(uN)]` annotations from the given `#[bitfield]` struct.
fn extract_repr_attribute(attr: &syn::Attribute, config: &mut Config) -> Result<()> {
let path = &attr.path;
let args = &attr.tokens;
let meta: syn::MetaList = syn::parse2::<_>(quote! { #path #args })?;
let mut retained_reprs = vec![];
for nested_meta in meta.nested {
let meta_span = nested_meta.span();
match nested_meta {
syn::NestedMeta::Meta(syn::Meta::Path(path)) => {
let repr_kind = if path.is_ident("u8") {
Some(ReprKind::U8)
} else if path.is_ident("u16") {
Some(ReprKind::U16)
} else if path.is_ident("u32") {
Some(ReprKind::U32)
} else if path.is_ident("u64") {
Some(ReprKind::U64)
} else if path.is_ident("u128") {
Some(ReprKind::U128)
} else {
// If other repr such as `transparent` or `C` have been found we
// are going to re-expand them into a new `#[repr(..)]` that is
// ignored by the rest of this macro.
retained_reprs.push(syn::NestedMeta::Meta(syn::Meta::Path(path)));
None
};
if let Some(repr_kind) = repr_kind {
config.repr(repr_kind, meta_span)?;
}
}
unknown => retained_reprs.push(unknown),
}
}
if !retained_reprs.is_empty() {
// We only push back another re-generated `#[repr(..)]` if its contents
// contained some non-bitfield representations and thus is not empty.
let retained_reprs_tokens = quote! {
( #( #retained_reprs ),* )
};
config.push_retained_attribute(syn::Attribute {
pound_token: attr.pound_token,
style: attr.style,
bracket_token: attr.bracket_token,
path: attr.path.clone(),
tokens: retained_reprs_tokens,
});
}
Ok(())
}
/// Extracts the `#[derive(Debug)]` annotations from the given `#[bitfield]` struct.
fn extract_derive_debug_attribute(
attr: &syn::Attribute,
config: &mut Config,
) -> Result<()> {
let path = &attr.path;
let args = &attr.tokens;
let meta: syn::MetaList = syn::parse2::<_>(quote! { #path #args })?;
let mut retained_derives = vec![];
for nested_meta in meta.nested {
let meta_span = nested_meta.span();
match nested_meta {
syn::NestedMeta::Meta(syn::Meta::Path(path)) => {
if path.is_ident("Debug") {
config.derive_debug(meta_span)?;
} else if path.is_ident("BitfieldSpecifier") {
config.derive_specifier(meta_span)?;
} else {
// Other derives are going to be re-expanded them into a new
// `#[derive(..)]` that is ignored by the rest of this macro.
retained_derives
.push(syn::NestedMeta::Meta(syn::Meta::Path(path)));
};
}
unknown => retained_derives.push(unknown),
}
}
if !retained_derives.is_empty() {
// We only push back another re-generated `#[derive(..)]` if its contents
// contain some remaining derives and thus is not empty.
let retained_derives_tokens = quote! {
( #( #retained_derives ),* )
};
config.push_retained_attribute(syn::Attribute {
pound_token: attr.pound_token,
style: attr.style,
bracket_token: attr.bracket_token,
path: attr.path.clone(),
tokens: retained_derives_tokens,
});
}
Ok(())
}
/// Analyses and extracts the `#[repr(uN)]` or other annotations from the given struct.
fn extract_attributes(
attributes: &[syn::Attribute],
config: &mut Config,
) -> Result<()> {
for attr in attributes {
if attr.path.is_ident("repr") {
Self::extract_repr_attribute(attr, config)?;
} else if attr.path.is_ident("derive") {
Self::extract_derive_debug_attribute(attr, config)?;
} else {
config.push_retained_attribute(attr.clone());
}
}
Ok(())
}
/// Analyses and extracts the configuration for all bitfield fields.
fn analyse_config_for_fields(
item_struct: &syn::ItemStruct,
config: &mut Config,
) -> Result<()> {
for (index, field) in Self::fields(item_struct) {
let span = field.span();
let field_config = Self::extract_field_config(field)?;
config.field_config(index, span, field_config)?;
}
Ok(())
}
/// Extracts the `#[bits = N]` and `#[skip(..)]` attributes for a given field.
fn extract_field_config(field: &syn::Field) -> Result<FieldConfig> {
let mut config = FieldConfig::default();
for attr in &field.attrs {
if attr.path.is_ident("bits") {
let path = &attr.path;
let args = &attr.tokens;
let name_value: syn::MetaNameValue =
syn::parse2::<_>(quote! { #path #args })?;
let span = name_value.span();
match name_value.lit {
syn::Lit::Int(lit_int) => {
config.bits(lit_int.base10_parse::<usize>()?, span)?;
}
_ => {
return Err(format_err!(
span,
"encountered invalid value type for #[bits = N]"
))
}
}
} else if attr.path.is_ident("skip") {
let path = &attr.path;
let args = &attr.tokens;
let meta: syn::Meta = syn::parse2::<_>(quote! { #path #args })?;
let span = meta.span();
match meta {
syn::Meta::Path(path) => {
assert!(path.is_ident("skip"));
config.skip(SkipWhich::All, span)?;
}
syn::Meta::List(meta_list) => {
let mut which = HashMap::new();
for nested_meta in &meta_list.nested {
match nested_meta {
syn::NestedMeta::Meta(syn::Meta::Path(path)) => {
if path.is_ident("getters") {
if let Some(previous) =
which.insert(SkipWhich::Getters, span)
{
return Err(format_err!(
span,
"encountered duplicate #[skip(getters)]"
)
.into_combine(format_err!(
previous,
"previous found here"
)))
}
} else if path.is_ident("setters") {
if let Some(previous) =
which.insert(SkipWhich::Setters, span)
{
return Err(format_err!(
span,
"encountered duplicate #[skip(setters)]"
)
.into_combine(format_err!(
previous,
"previous found here"
)))
}
} else {
return Err(format_err!(
nested_meta.span(),
"encountered unknown or unsupported #[skip(..)] specifier"
))
}
}
_ => return Err(format_err!(span, "encountered invalid #[skip] field attribute argument"))
}
}
if which.is_empty()
|| which.contains_key(&SkipWhich::Getters)
&& which.contains_key(&SkipWhich::Setters)
{
config.skip(SkipWhich::All, span)?;
} else if which.contains_key(&SkipWhich::Getters) {
config.skip(SkipWhich::Getters, span)?;
} else if which.contains_key(&SkipWhich::Setters) {
config.skip(SkipWhich::Setters, span)?;
}
}
_ => {
return Err(format_err!(
span,
"encountered invalid format for #[skip] field attribute"
))
}
}
} else {
config.retain_attr(attr.clone());
}
}
Ok(config)
}
}