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Message-ID: <20230523170405.3c229965.gary@garyguo.net>
Date: Tue, 23 May 2023 17:04:05 +0100
From: Gary Guo <gary@...yguo.net>
To: Benno Lossin <benno.lossin@...ton.me>
Cc: Miguel Ojeda <ojeda@...nel.org>,
Alex Gaynor <alex.gaynor@...il.com>,
Wedson Almeida Filho <wedsonaf@...il.com>,
Boqun Feng <boqun.feng@...il.com>,
Björn Roy Baron <bjorn3_gh@...tonmail.com>,
rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
patches@...ts.linux.dev
Subject: Re: [PATCH 2/4] rust: macros: refactor generics parsing of
`#[pin_data]` into its own function
On Mon, 24 Apr 2023 08:11:38 +0000
Benno Lossin <benno.lossin@...ton.me> wrote:
> Other macros might also want to parse generics. Additionally this makes
> the code easier to read, as the next commit will introduce more code in
> `#[pin_data]`. Also add more comments to explain how parsing generics
> work.
>
> Signed-off-by: Benno Lossin <benno.lossin@...ton.me>
Reviewed-by: Gary Guo <gary@...yguo.net>
> ---
> rust/macros/helpers.rs | 86 ++++++++++++++++++++++++++++++++++++++++-
> rust/macros/pin_data.rs | 70 +++++----------------------------
> 2 files changed, 94 insertions(+), 62 deletions(-)
>
> diff --git a/rust/macros/helpers.rs b/rust/macros/helpers.rs
> index b2bdd4d8c958..afb0f2e3a36a 100644
> --- a/rust/macros/helpers.rs
> +++ b/rust/macros/helpers.rs
> @@ -1,6 +1,6 @@
> // SPDX-License-Identifier: GPL-2.0
>
> -use proc_macro::{token_stream, Group, TokenTree};
> +use proc_macro::{token_stream, Group, Punct, Spacing, TokenStream, TokenTree};
>
> pub(crate) fn try_ident(it: &mut token_stream::IntoIter) -> Option<String> {
> if let Some(TokenTree::Ident(ident)) = it.next() {
> @@ -69,3 +69,87 @@ pub(crate) fn expect_end(it: &mut token_stream::IntoIter) {
> panic!("Expected end");
> }
> }
> +
> +pub(crate) struct Generics {
> + pub(crate) impl_generics: Vec<TokenTree>,
> + pub(crate) ty_generics: Vec<TokenTree>,
> +}
> +
> +/// Parses the given `TokenStream` into `Generics` and the rest.
> +///
> +/// The generics are not present in the rest, but a where clause might remain.
> +pub(crate) fn parse_generics(input: TokenStream) -> (Generics, Vec<TokenTree>) {
> + // `impl_generics`, the declared generics with their bounds.
> + let mut impl_generics = vec![];
> + // Only the names of the generics, without any bounds.
> + let mut ty_generics = vec![];
> + // Tokens not related to the generics e.g. the `where` token and definition.
> + let mut rest = vec![];
> + // The current level of `<`.
> + let mut nesting = 0;
> + let mut toks = input.into_iter();
> + // If we are at the beginning of a generic parameter.
> + let mut at_start = true;
> + for tt in &mut toks {
> + match tt.clone() {
> + TokenTree::Punct(p) if p.as_char() == '<' => {
> + if nesting >= 1 {
> + // This is inside of the generics and part of some bound.
> + impl_generics.push(tt);
> + }
> + nesting += 1;
> + }
> + TokenTree::Punct(p) if p.as_char() == '>' => {
> + // This is a parsing error, so we just end it here.
> + if nesting == 0 {
> + break;
> + } else {
> + nesting -= 1;
> + if nesting >= 1 {
> + // We are still inside of the generics and part of some bound.
> + impl_generics.push(tt);
> + }
> + if nesting == 0 {
> + break;
> + }
> + }
> + }
> + tt => {
> + if nesting == 1 {
> + // Here depending on the token, it might be a generic variable name.
> + match &tt {
> + // Ignore const.
> + TokenTree::Ident(i) if i.to_string() == "const" => {}
> + TokenTree::Ident(_) if at_start => {
> + ty_generics.push(tt.clone());
> + // We also already push the `,` token, this makes it easier to append
> + // generics.
> + ty_generics.push(TokenTree::Punct(Punct::new(',', Spacing::Alone)));
> + at_start = false;
> + }
> + TokenTree::Punct(p) if p.as_char() == ',' => at_start = true,
> + // Lifetimes begin with `'`.
> + TokenTree::Punct(p) if p.as_char() == '\'' && at_start => {
> + ty_generics.push(tt.clone());
> + }
> + _ => {}
> + }
> + }
> + if nesting >= 1 {
> + impl_generics.push(tt);
> + } else if nesting == 0 {
> + // If we haven't entered the generics yet, we still want to keep these tokens.
> + rest.push(tt);
> + }
> + }
> + }
> + }
> + rest.extend(toks);
> + (
> + Generics {
> + impl_generics,
> + ty_generics,
> + },
> + rest,
> + )
> +}
> diff --git a/rust/macros/pin_data.rs b/rust/macros/pin_data.rs
> index 954149d77181..c593b05d9e8c 100644
> --- a/rust/macros/pin_data.rs
> +++ b/rust/macros/pin_data.rs
> @@ -1,71 +1,19 @@
> // SPDX-License-Identifier: Apache-2.0 OR MIT
>
> -use proc_macro::{Punct, Spacing, TokenStream, TokenTree};
> +use crate::helpers::{parse_generics, Generics};
> +use proc_macro::TokenStream;
>
> pub(crate) fn pin_data(args: TokenStream, input: TokenStream) -> TokenStream {
> // This proc-macro only does some pre-parsing and then delegates the actual parsing to
> // `kernel::__pin_data!`.
> - //
> - // In here we only collect the generics, since parsing them in declarative macros is very
> - // elaborate. We also do not need to analyse their structure, we only need to collect them.
>
> - // `impl_generics`, the declared generics with their bounds.
> - let mut impl_generics = vec![];
> - // Only the names of the generics, without any bounds.
> - let mut ty_generics = vec![];
> - // Tokens not related to the generics e.g. the `impl` token.
> - let mut rest = vec![];
> - // The current level of `<`.
> - let mut nesting = 0;
> - let mut toks = input.into_iter();
> - // If we are at the beginning of a generic parameter.
> - let mut at_start = true;
> - for tt in &mut toks {
> - match tt.clone() {
> - TokenTree::Punct(p) if p.as_char() == '<' => {
> - if nesting >= 1 {
> - impl_generics.push(tt);
> - }
> - nesting += 1;
> - }
> - TokenTree::Punct(p) if p.as_char() == '>' => {
> - if nesting == 0 {
> - break;
> - } else {
> - nesting -= 1;
> - if nesting >= 1 {
> - impl_generics.push(tt);
> - }
> - if nesting == 0 {
> - break;
> - }
> - }
> - }
> - tt => {
> - if nesting == 1 {
> - match &tt {
> - TokenTree::Ident(i) if i.to_string() == "const" => {}
> - TokenTree::Ident(_) if at_start => {
> - ty_generics.push(tt.clone());
> - ty_generics.push(TokenTree::Punct(Punct::new(',', Spacing::Alone)));
> - at_start = false;
> - }
> - TokenTree::Punct(p) if p.as_char() == ',' => at_start = true,
> - TokenTree::Punct(p) if p.as_char() == '\'' && at_start => {
> - ty_generics.push(tt.clone());
> - }
> - _ => {}
> - }
> - }
> - if nesting >= 1 {
> - impl_generics.push(tt);
> - } else if nesting == 0 {
> - rest.push(tt);
> - }
> - }
> - }
> - }
> - rest.extend(toks);
> + let (
> + Generics {
> + impl_generics,
> + ty_generics,
> + },
> + mut rest,
> + ) = parse_generics(input);
> // This should be the body of the struct `{...}`.
> let last = rest.pop();
> quote!(::kernel::__pin_data! {
> --
> 2.40.0
>
>
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