diff options
Diffstat (limited to 'vendor/futures-macro')
| -rw-r--r-- | vendor/futures-macro/.cargo-checksum.json | 1 | ||||
| -rw-r--r-- | vendor/futures-macro/Cargo.toml | 34 | ||||
| -rw-r--r-- | vendor/futures-macro/LICENSE-APACHE | 202 | ||||
| -rw-r--r-- | vendor/futures-macro/LICENSE-MIT | 26 | ||||
| -rw-r--r-- | vendor/futures-macro/src/executor.rs | 55 | ||||
| -rw-r--r-- | vendor/futures-macro/src/join.rs | 143 | ||||
| -rw-r--r-- | vendor/futures-macro/src/lib.rs | 61 | ||||
| -rw-r--r-- | vendor/futures-macro/src/select.rs | 330 | ||||
| -rw-r--r-- | vendor/futures-macro/src/stream_select.rs | 113 |
9 files changed, 965 insertions, 0 deletions
diff --git a/vendor/futures-macro/.cargo-checksum.json b/vendor/futures-macro/.cargo-checksum.json new file mode 100644 index 000000000..4eda2b921 --- /dev/null +++ b/vendor/futures-macro/.cargo-checksum.json @@ -0,0 +1 @@ +{"files":{"Cargo.toml":"46ecfcda3cd6979538f7543858fcfecb52c319cec94d041ab369139723ffa69d","LICENSE-APACHE":"275c491d6d1160553c32fd6127061d7f9606c3ea25abfad6ca3f6ed088785427","LICENSE-MIT":"6652c868f35dfe5e8ef636810a4e576b9d663f3a17fb0f5613ad73583e1b88fd","src/executor.rs":"2a6c40ebf1fb70ac5bd0dfb991c7b945210c731b558b546f2ecb6d7a8976f3f6","src/join.rs":"e0d286558bd944fd02c1bd2501d13e62de2aa65e6bd3a2e0567488ac1a2374ed","src/lib.rs":"8324c4d5cc4e9e377b2f95afde751168d7e94196c1f2cb35802193c900ca0026","src/select.rs":"a7ed344932225fbe1b070d132a937184250c31385ac6764a8a6e6817413c7538","src/stream_select.rs":"5fb84834a40876ab1fd975c3af67594d0c5a4f8d724cb164db9bee71e70d14b1"},"package":"6dbd947adfffb0efc70599b3ddcf7b5597bb5fa9e245eb99f62b3a5f7bb8bd3c"}
\ No newline at end of file diff --git a/vendor/futures-macro/Cargo.toml b/vendor/futures-macro/Cargo.toml new file mode 100644 index 000000000..b192c17ff --- /dev/null +++ b/vendor/futures-macro/Cargo.toml @@ -0,0 +1,34 @@ +# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO +# +# When uploading crates to the registry Cargo will automatically +# "normalize" Cargo.toml files for maximal compatibility +# with all versions of Cargo and also rewrite `path` dependencies +# to registry (e.g., crates.io) dependencies. +# +# If you are reading this file be aware that the original Cargo.toml +# will likely look very different (and much more reasonable). +# See Cargo.toml.orig for the original contents. + +[package] +edition = "2018" +rust-version = "1.45" +name = "futures-macro" +version = "0.3.19" +description = "The futures-rs procedural macro implementations.\n" +homepage = "https://rust-lang.github.io/futures-rs" +license = "MIT OR Apache-2.0" +repository = "https://github.com/rust-lang/futures-rs" + +[lib] +proc-macro = true +[dependencies.proc-macro2] +version = "1.0" + +[dependencies.quote] +version = "1.0" + +[dependencies.syn] +version = "1.0.56" +features = ["full"] + +[features] diff --git a/vendor/futures-macro/LICENSE-APACHE b/vendor/futures-macro/LICENSE-APACHE new file mode 100644 index 000000000..9eb0b097f --- /dev/null +++ b/vendor/futures-macro/LICENSE-APACHE @@ -0,0 +1,202 @@ + Apache License + Version 2.0, January 2004 + http://www.apache.org/licenses/ + +TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION + +1. 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We also recommend that a + file or class name and description of purpose be included on the + same "printed page" as the copyright notice for easier + identification within third-party archives. + +Copyright (c) 2016 Alex Crichton +Copyright (c) 2017 The Tokio Authors + +Licensed under the Apache License, Version 2.0 (the "License"); +you may not use this file except in compliance with the License. +You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + +Unless required by applicable law or agreed to in writing, software +distributed under the License is distributed on an "AS IS" BASIS, +WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +See the License for the specific language governing permissions and +limitations under the License. diff --git a/vendor/futures-macro/LICENSE-MIT b/vendor/futures-macro/LICENSE-MIT new file mode 100644 index 000000000..8ad082ec4 --- /dev/null +++ b/vendor/futures-macro/LICENSE-MIT @@ -0,0 +1,26 @@ +Copyright (c) 2016 Alex Crichton +Copyright (c) 2017 The Tokio Authors + +Permission is hereby granted, free of charge, to any +person obtaining a copy of this software and associated +documentation files (the "Software"), to deal in the +Software without restriction, including without +limitation the rights to use, copy, modify, merge, +publish, distribute, sublicense, and/or sell copies of +the Software, and to permit persons to whom the Software +is furnished to do so, subject to the following +conditions: + +The above copyright notice and this permission notice +shall be included in all copies or substantial portions +of the Software. + +THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF +ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED +TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A +PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT +SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY +CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION +OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR +IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER +DEALINGS IN THE SOFTWARE. diff --git a/vendor/futures-macro/src/executor.rs b/vendor/futures-macro/src/executor.rs new file mode 100644 index 000000000..40a091f94 --- /dev/null +++ b/vendor/futures-macro/src/executor.rs @@ -0,0 +1,55 @@ +use proc_macro::TokenStream; +use proc_macro2::Span; +use quote::{quote, quote_spanned, ToTokens}; + +pub(crate) fn test(args: TokenStream, item: TokenStream) -> TokenStream { + if !args.is_empty() { + return syn::Error::new_spanned(proc_macro2::TokenStream::from(args), "invalid argument") + .to_compile_error() + .into(); + } + + let mut input = syn::parse_macro_input!(item as syn::ItemFn); + + if input.sig.asyncness.take().is_none() { + return syn::Error::new_spanned(input.sig.fn_token, "Only async functions are supported") + .to_compile_error() + .into(); + } + + // If type mismatch occurs, the current rustc points to the last statement. + let (last_stmt_start_span, last_stmt_end_span) = { + let mut last_stmt = input + .block + .stmts + .last() + .map(ToTokens::into_token_stream) + .unwrap_or_default() + .into_iter(); + // `Span` on stable Rust has a limitation that only points to the first + // token, not the whole tokens. We can work around this limitation by + // using the first/last span of the tokens like + // `syn::Error::new_spanned` does. + let start = last_stmt.next().map_or_else(Span::call_site, |t| t.span()); + let end = last_stmt.last().map_or(start, |t| t.span()); + (start, end) + }; + + let path = quote_spanned! {last_stmt_start_span=> + ::futures_test::__private + }; + let body = &input.block; + input.block.stmts = vec![syn::Stmt::Expr( + syn::parse2(quote_spanned! {last_stmt_end_span=> + #path::block_on(async #body) + }) + .unwrap(), + )]; + + let gen = quote! { + #[::core::prelude::v1::test] + #input + }; + + gen.into() +} diff --git a/vendor/futures-macro/src/join.rs b/vendor/futures-macro/src/join.rs new file mode 100644 index 000000000..d427da27a --- /dev/null +++ b/vendor/futures-macro/src/join.rs @@ -0,0 +1,143 @@ +//! The futures-rs `join! macro implementation. + +use proc_macro::TokenStream; +use proc_macro2::{Span, TokenStream as TokenStream2}; +use quote::{format_ident, quote}; +use syn::parse::{Parse, ParseStream}; +use syn::{Expr, Ident, Token}; + +#[derive(Default)] +struct Join { + fut_exprs: Vec<Expr>, +} + +impl Parse for Join { + fn parse(input: ParseStream<'_>) -> syn::Result<Self> { + let mut join = Self::default(); + + while !input.is_empty() { + join.fut_exprs.push(input.parse::<Expr>()?); + + if !input.is_empty() { + input.parse::<Token![,]>()?; + } + } + + Ok(join) + } +} + +fn bind_futures(fut_exprs: Vec<Expr>, span: Span) -> (Vec<TokenStream2>, Vec<Ident>) { + let mut future_let_bindings = Vec::with_capacity(fut_exprs.len()); + let future_names: Vec<_> = fut_exprs + .into_iter() + .enumerate() + .map(|(i, expr)| { + let name = format_ident!("_fut{}", i, span = span); + future_let_bindings.push(quote! { + // Move future into a local so that it is pinned in one place and + // is no longer accessible by the end user. + let mut #name = __futures_crate::future::maybe_done(#expr); + }); + name + }) + .collect(); + + (future_let_bindings, future_names) +} + +/// The `join!` macro. +pub(crate) fn join(input: TokenStream) -> TokenStream { + let parsed = syn::parse_macro_input!(input as Join); + + // should be def_site, but that's unstable + let span = Span::call_site(); + + let (future_let_bindings, future_names) = bind_futures(parsed.fut_exprs, span); + + let poll_futures = future_names.iter().map(|fut| { + quote! { + __all_done &= __futures_crate::future::Future::poll( + unsafe { __futures_crate::Pin::new_unchecked(&mut #fut) }, __cx).is_ready(); + } + }); + let take_outputs = future_names.iter().map(|fut| { + quote! { + unsafe { __futures_crate::Pin::new_unchecked(&mut #fut) }.take_output().unwrap(), + } + }); + + TokenStream::from(quote! { { + #( #future_let_bindings )* + + __futures_crate::future::poll_fn(move |__cx: &mut __futures_crate::task::Context<'_>| { + let mut __all_done = true; + #( #poll_futures )* + if __all_done { + __futures_crate::task::Poll::Ready(( + #( #take_outputs )* + )) + } else { + __futures_crate::task::Poll::Pending + } + }).await + } }) +} + +/// The `try_join!` macro. +pub(crate) fn try_join(input: TokenStream) -> TokenStream { + let parsed = syn::parse_macro_input!(input as Join); + + // should be def_site, but that's unstable + let span = Span::call_site(); + + let (future_let_bindings, future_names) = bind_futures(parsed.fut_exprs, span); + + let poll_futures = future_names.iter().map(|fut| { + quote! { + if __futures_crate::future::Future::poll( + unsafe { __futures_crate::Pin::new_unchecked(&mut #fut) }, __cx).is_pending() + { + __all_done = false; + } else if unsafe { __futures_crate::Pin::new_unchecked(&mut #fut) }.output_mut().unwrap().is_err() { + // `.err().unwrap()` rather than `.unwrap_err()` so that we don't introduce + // a `T: Debug` bound. + // Also, for an error type of ! any code after `err().unwrap()` is unreachable. + #[allow(unreachable_code)] + return __futures_crate::task::Poll::Ready( + __futures_crate::Err( + unsafe { __futures_crate::Pin::new_unchecked(&mut #fut) }.take_output().unwrap().err().unwrap() + ) + ); + } + } + }); + let take_outputs = future_names.iter().map(|fut| { + quote! { + // `.ok().unwrap()` rather than `.unwrap()` so that we don't introduce + // an `E: Debug` bound. + // Also, for an ok type of ! any code after `ok().unwrap()` is unreachable. + #[allow(unreachable_code)] + unsafe { __futures_crate::Pin::new_unchecked(&mut #fut) }.take_output().unwrap().ok().unwrap(), + } + }); + + TokenStream::from(quote! { { + #( #future_let_bindings )* + + #[allow(clippy::diverging_sub_expression)] + __futures_crate::future::poll_fn(move |__cx: &mut __futures_crate::task::Context<'_>| { + let mut __all_done = true; + #( #poll_futures )* + if __all_done { + __futures_crate::task::Poll::Ready( + __futures_crate::Ok(( + #( #take_outputs )* + )) + ) + } else { + __futures_crate::task::Poll::Pending + } + }).await + } }) +} diff --git a/vendor/futures-macro/src/lib.rs b/vendor/futures-macro/src/lib.rs new file mode 100644 index 000000000..0afe34b83 --- /dev/null +++ b/vendor/futures-macro/src/lib.rs @@ -0,0 +1,61 @@ +//! The futures-rs procedural macro implementations. + +#![warn(rust_2018_idioms, single_use_lifetimes, unreachable_pub)] +#![doc(test( + no_crate_inject, + attr( + deny(warnings, rust_2018_idioms, single_use_lifetimes), + allow(dead_code, unused_assignments, unused_variables) + ) +))] + +// Since https://github.com/rust-lang/cargo/pull/7700 `proc_macro` is part of the prelude for +// proc-macro crates, but to support older compilers we still need this explicit `extern crate`. +#[allow(unused_extern_crates)] +extern crate proc_macro; + +use proc_macro::TokenStream; + +mod executor; +mod join; +mod select; +mod stream_select; + +/// The `join!` macro. +#[proc_macro] +pub fn join_internal(input: TokenStream) -> TokenStream { + crate::join::join(input) +} + +/// The `try_join!` macro. +#[proc_macro] +pub fn try_join_internal(input: TokenStream) -> TokenStream { + crate::join::try_join(input) +} + +/// The `select!` macro. +#[proc_macro] +pub fn select_internal(input: TokenStream) -> TokenStream { + crate::select::select(input) +} + +/// The `select_biased!` macro. +#[proc_macro] +pub fn select_biased_internal(input: TokenStream) -> TokenStream { + crate::select::select_biased(input) +} + +// TODO: Change this to doc comment once rustdoc bug fixed: https://github.com/rust-lang/futures-rs/pull/2435 +// The `test` attribute. +#[proc_macro_attribute] +pub fn test_internal(input: TokenStream, item: TokenStream) -> TokenStream { + crate::executor::test(input, item) +} + +/// The `stream_select!` macro. +#[proc_macro] +pub fn stream_select_internal(input: TokenStream) -> TokenStream { + crate::stream_select::stream_select(input.into()) + .unwrap_or_else(syn::Error::into_compile_error) + .into() +} diff --git a/vendor/futures-macro/src/select.rs b/vendor/futures-macro/src/select.rs new file mode 100644 index 000000000..0c8e5f1ca --- /dev/null +++ b/vendor/futures-macro/src/select.rs @@ -0,0 +1,330 @@ +//! The futures-rs `select! macro implementation. + +use proc_macro::TokenStream; +use proc_macro2::Span; +use quote::{format_ident, quote}; +use syn::parse::{Parse, ParseStream}; +use syn::{parse_quote, Expr, Ident, Pat, Token}; + +mod kw { + syn::custom_keyword!(complete); +} + +struct Select { + // span of `complete`, then expression after `=> ...` + complete: Option<Expr>, + default: Option<Expr>, + normal_fut_exprs: Vec<Expr>, + normal_fut_handlers: Vec<(Pat, Expr)>, +} + +#[allow(clippy::large_enum_variant)] +enum CaseKind { + Complete, + Default, + Normal(Pat, Expr), +} + +impl Parse for Select { + fn parse(input: ParseStream<'_>) -> syn::Result<Self> { + let mut select = Self { + complete: None, + default: None, + normal_fut_exprs: vec![], + normal_fut_handlers: vec![], + }; + + while !input.is_empty() { + let case_kind = if input.peek(kw::complete) { + // `complete` + if select.complete.is_some() { + return Err(input.error("multiple `complete` cases found, only one allowed")); + } + input.parse::<kw::complete>()?; + CaseKind::Complete + } else if input.peek(Token![default]) { + // `default` + if select.default.is_some() { + return Err(input.error("multiple `default` cases found, only one allowed")); + } + input.parse::<Ident>()?; + CaseKind::Default + } else { + // `<pat> = <expr>` + let pat = input.parse()?; + input.parse::<Token![=]>()?; + let expr = input.parse()?; + CaseKind::Normal(pat, expr) + }; + + // `=> <expr>` + input.parse::<Token![=>]>()?; + let expr = input.parse::<Expr>()?; + + // Commas after the expression are only optional if it's a `Block` + // or it is the last branch in the `match`. + let is_block = match expr { + Expr::Block(_) => true, + _ => false, + }; + if is_block || input.is_empty() { + input.parse::<Option<Token![,]>>()?; + } else { + input.parse::<Token![,]>()?; + } + + match case_kind { + CaseKind::Complete => select.complete = Some(expr), + CaseKind::Default => select.default = Some(expr), + CaseKind::Normal(pat, fut_expr) => { + select.normal_fut_exprs.push(fut_expr); + select.normal_fut_handlers.push((pat, expr)); + } + } + } + + Ok(select) + } +} + +// Enum over all the cases in which the `select!` waiting has completed and the result +// can be processed. +// +// `enum __PrivResult<_1, _2, ...> { _1(_1), _2(_2), ..., Complete }` +fn declare_result_enum( + result_ident: Ident, + variants: usize, + complete: bool, + span: Span, +) -> (Vec<Ident>, syn::ItemEnum) { + // "_0", "_1", "_2" + let variant_names: Vec<Ident> = + (0..variants).map(|num| format_ident!("_{}", num, span = span)).collect(); + + let type_parameters = &variant_names; + let variants = &variant_names; + + let complete_variant = if complete { Some(quote!(Complete)) } else { None }; + + let enum_item = parse_quote! { + enum #result_ident<#(#type_parameters,)*> { + #( + #variants(#type_parameters), + )* + #complete_variant + } + }; + + (variant_names, enum_item) +} + +/// The `select!` macro. +pub(crate) fn select(input: TokenStream) -> TokenStream { + select_inner(input, true) +} + +/// The `select_biased!` macro. +pub(crate) fn select_biased(input: TokenStream) -> TokenStream { + select_inner(input, false) +} + +fn select_inner(input: TokenStream, random: bool) -> TokenStream { + let parsed = syn::parse_macro_input!(input as Select); + + // should be def_site, but that's unstable + let span = Span::call_site(); + + let enum_ident = Ident::new("__PrivResult", span); + + let (variant_names, enum_item) = declare_result_enum( + enum_ident.clone(), + parsed.normal_fut_exprs.len(), + parsed.complete.is_some(), + span, + ); + + // bind non-`Ident` future exprs w/ `let` + let mut future_let_bindings = Vec::with_capacity(parsed.normal_fut_exprs.len()); + let bound_future_names: Vec<_> = parsed + .normal_fut_exprs + .into_iter() + .zip(variant_names.iter()) + .map(|(expr, variant_name)| { + match expr { + syn::Expr::Path(path) => { + // Don't bind futures that are already a path. + // This prevents creating redundant stack space + // for them. + // Passing Futures by path requires those Futures to implement Unpin. + // We check for this condition here in order to be able to + // safely use Pin::new_unchecked(&mut #path) later on. + future_let_bindings.push(quote! { + __futures_crate::async_await::assert_fused_future(&#path); + __futures_crate::async_await::assert_unpin(&#path); + }); + path + } + _ => { + // Bind and pin the resulting Future on the stack. This is + // necessary to support direct select! calls on !Unpin + // Futures. The Future is not explicitly pinned here with + // a Pin call, but assumed as pinned. The actual Pin is + // created inside the poll() function below to defer the + // creation of the temporary pointer, which would otherwise + // increase the size of the generated Future. + // Safety: This is safe since the lifetime of the Future + // is totally constraint to the lifetime of the select! + // expression, and the Future can't get moved inside it + // (it is shadowed). + future_let_bindings.push(quote! { + let mut #variant_name = #expr; + }); + parse_quote! { #variant_name } + } + } + }) + .collect(); + + // For each future, make an `&mut dyn FnMut(&mut Context<'_>) -> Option<Poll<__PrivResult<...>>` + // to use for polling that individual future. These will then be put in an array. + let poll_functions = bound_future_names.iter().zip(variant_names.iter()).map( + |(bound_future_name, variant_name)| { + // Below we lazily create the Pin on the Future below. + // This is done in order to avoid allocating memory in the generator + // for the Pin variable. + // Safety: This is safe because one of the following condition applies: + // 1. The Future is passed by the caller by name, and we assert that + // it implements Unpin. + // 2. The Future is created in scope of the select! function and will + // not be moved for the duration of it. It is thereby stack-pinned + quote! { + let mut #variant_name = |__cx: &mut __futures_crate::task::Context<'_>| { + let mut #bound_future_name = unsafe { + __futures_crate::Pin::new_unchecked(&mut #bound_future_name) + }; + if __futures_crate::future::FusedFuture::is_terminated(&#bound_future_name) { + __futures_crate::None + } else { + __futures_crate::Some(__futures_crate::future::FutureExt::poll_unpin( + &mut #bound_future_name, + __cx, + ).map(#enum_ident::#variant_name)) + } + }; + let #variant_name: &mut dyn FnMut( + &mut __futures_crate::task::Context<'_> + ) -> __futures_crate::Option<__futures_crate::task::Poll<_>> = &mut #variant_name; + } + }, + ); + + let none_polled = if parsed.complete.is_some() { + quote! { + __futures_crate::task::Poll::Ready(#enum_ident::Complete) + } + } else { + quote! { + panic!("all futures in select! were completed,\ + but no `complete =>` handler was provided") + } + }; + + let branches = parsed.normal_fut_handlers.into_iter().zip(variant_names.iter()).map( + |((pat, expr), variant_name)| { + quote! { + #enum_ident::#variant_name(#pat) => { #expr }, + } + }, + ); + let branches = quote! { #( #branches )* }; + + let complete_branch = parsed.complete.map(|complete_expr| { + quote! { + #enum_ident::Complete => { #complete_expr }, + } + }); + + let branches = quote! { + #branches + #complete_branch + }; + + let await_select_fut = if parsed.default.is_some() { + // For select! with default this returns the Poll result + quote! { + __poll_fn(&mut __futures_crate::task::Context::from_waker( + __futures_crate::task::noop_waker_ref() + )) + } + } else { + quote! { + __futures_crate::future::poll_fn(__poll_fn).await + } + }; + + let execute_result_expr = if let Some(default_expr) = &parsed.default { + // For select! with default __select_result is a Poll, otherwise not + quote! { + match __select_result { + __futures_crate::task::Poll::Ready(result) => match result { + #branches + }, + _ => #default_expr + } + } + } else { + quote! { + match __select_result { + #branches + } + } + }; + + let shuffle = if random { + quote! { + __futures_crate::async_await::shuffle(&mut __select_arr); + } + } else { + quote!() + }; + + TokenStream::from(quote! { { + #enum_item + + let __select_result = { + #( #future_let_bindings )* + + let mut __poll_fn = |__cx: &mut __futures_crate::task::Context<'_>| { + let mut __any_polled = false; + + #( #poll_functions )* + + let mut __select_arr = [#( #variant_names ),*]; + #shuffle + for poller in &mut __select_arr { + let poller: &mut &mut dyn FnMut( + &mut __futures_crate::task::Context<'_> + ) -> __futures_crate::Option<__futures_crate::task::Poll<_>> = poller; + match poller(__cx) { + __futures_crate::Some(x @ __futures_crate::task::Poll::Ready(_)) => + return x, + __futures_crate::Some(__futures_crate::task::Poll::Pending) => { + __any_polled = true; + } + __futures_crate::None => {} + } + } + + if !__any_polled { + #none_polled + } else { + __futures_crate::task::Poll::Pending + } + }; + + #await_select_fut + }; + + #execute_result_expr + } }) +} diff --git a/vendor/futures-macro/src/stream_select.rs b/vendor/futures-macro/src/stream_select.rs new file mode 100644 index 000000000..9927b5307 --- /dev/null +++ b/vendor/futures-macro/src/stream_select.rs @@ -0,0 +1,113 @@ +use proc_macro2::TokenStream; +use quote::{format_ident, quote, ToTokens}; +use syn::{parse::Parser, punctuated::Punctuated, Expr, Index, Token}; + +/// The `stream_select!` macro. +pub(crate) fn stream_select(input: TokenStream) -> Result<TokenStream, syn::Error> { + let args = Punctuated::<Expr, Token![,]>::parse_terminated.parse2(input)?; + if args.len() < 2 { + return Ok(quote! { + compile_error!("stream select macro needs at least two arguments.") + }); + } + let generic_idents = (0..args.len()).map(|i| format_ident!("_{}", i)).collect::<Vec<_>>(); + let field_idents = (0..args.len()).map(|i| format_ident!("__{}", i)).collect::<Vec<_>>(); + let field_idents_2 = (0..args.len()).map(|i| format_ident!("___{}", i)).collect::<Vec<_>>(); + let field_indices = (0..args.len()).map(Index::from).collect::<Vec<_>>(); + let args = args.iter().map(|e| e.to_token_stream()); + + Ok(quote! { + { + #[derive(Debug)] + struct StreamSelect<#(#generic_idents),*> (#(Option<#generic_idents>),*); + + enum StreamEnum<#(#generic_idents),*> { + #( + #generic_idents(#generic_idents) + ),*, + None, + } + + impl<ITEM, #(#generic_idents),*> __futures_crate::stream::Stream for StreamEnum<#(#generic_idents),*> + where #(#generic_idents: __futures_crate::stream::Stream<Item=ITEM> + ::std::marker::Unpin,)* + { + type Item = ITEM; + + fn poll_next(mut self: ::std::pin::Pin<&mut Self>, cx: &mut __futures_crate::task::Context<'_>) -> __futures_crate::task::Poll<Option<Self::Item>> { + match self.get_mut() { + #( + Self::#generic_idents(#generic_idents) => ::std::pin::Pin::new(#generic_idents).poll_next(cx) + ),*, + Self::None => panic!("StreamEnum::None should never be polled!"), + } + } + } + + impl<ITEM, #(#generic_idents),*> __futures_crate::stream::Stream for StreamSelect<#(#generic_idents),*> + where #(#generic_idents: __futures_crate::stream::Stream<Item=ITEM> + ::std::marker::Unpin,)* + { + type Item = ITEM; + + fn poll_next(mut self: ::std::pin::Pin<&mut Self>, cx: &mut __futures_crate::task::Context<'_>) -> __futures_crate::task::Poll<Option<Self::Item>> { + let Self(#(ref mut #field_idents),*) = self.get_mut(); + #( + let mut #field_idents_2 = false; + )* + let mut any_pending = false; + { + let mut stream_array = [#(#field_idents.as_mut().map(|f| StreamEnum::#generic_idents(f)).unwrap_or(StreamEnum::None)),*]; + __futures_crate::async_await::shuffle(&mut stream_array); + + for mut s in stream_array { + if let StreamEnum::None = s { + continue; + } else { + match __futures_crate::stream::Stream::poll_next(::std::pin::Pin::new(&mut s), cx) { + r @ __futures_crate::task::Poll::Ready(Some(_)) => { + return r; + }, + __futures_crate::task::Poll::Pending => { + any_pending = true; + }, + __futures_crate::task::Poll::Ready(None) => { + match s { + #( + StreamEnum::#generic_idents(_) => { #field_idents_2 = true; } + ),*, + StreamEnum::None => panic!("StreamEnum::None should never be polled!"), + } + }, + } + } + } + } + #( + if #field_idents_2 { + *#field_idents = None; + } + )* + if any_pending { + __futures_crate::task::Poll::Pending + } else { + __futures_crate::task::Poll::Ready(None) + } + } + + fn size_hint(&self) -> (usize, Option<usize>) { + let mut s = (0, Some(0)); + #( + if let Some(new_hint) = self.#field_indices.as_ref().map(|s| s.size_hint()) { + s.0 += new_hint.0; + // We can change this out for `.zip` when the MSRV is 1.46.0 or higher. + s.1 = s.1.and_then(|a| new_hint.1.map(|b| a + b)); + } + )* + s + } + } + + StreamSelect(#(Some(#args)),*) + + } + }) +} |