scratch

Cargo.lock

@@ -2,6 +2,53 @@
 # It is not intended for manual editing.
 version = 3
 
+[[package]]
+name = "pm"
+version = "0.1.0"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.49"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "57a8eca9f9c4ffde41714334dee777596264c7825420f521abc92b5b5deb63a5"
+dependencies = [
+ "unicode-ident",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.23"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8856d8364d252a14d474036ea1358d63c9e6965c8e5c1885c18f73d70bff9c7b"
+dependencies = [
+ "proc-macro2",
+]
+
+[[package]]
+name = "syn"
+version = "1.0.107"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1f4064b5b16e03ae50984a5a8ed5d4f8803e6bc1fd170a3cda91a1be4b18e3f5"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
+[[package]]
+name = "unicode-ident"
+version = "1.0.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "84a22b9f218b40614adcb3f4ff08b703773ad44fa9423e4e0d346d5db86e4ebc"
+
 [[package]]
 name = "uwu"
 version = "0.1.0"
+dependencies = [
+ "pm",
+]

Cargo.toml

@@ -1,3 +1,6 @@
+[workspace]
+members = [".", "./pm"]
+
 [package]
 name = "uwu"
 version = "0.1.0"
@@ -6,3 +9,4 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+pm = { path = "./pm" }

examples/scratch.rs

@@ -0,0 +1,14 @@
+use uwu::scratch::{
+    actual_scratch_read, actual_scratch_write, define_scratch, scratch_space, Scratch,
+};
+
+#[scratch_space]
+fn has_scratch_space(mut scratch: Scratch<'_>) {
+    scratch_write!(scratch, 10u32);
+    let _: u32 = scratch_read!(scratch);
+}
+
+fn main() {
+    define_scratch!(scratch, 10);
+    has_scratch_space(scratch);
+}

pm/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "pm"
+version = "0.1.0"
+edition = "2021"
+
+[lib]
+proc-macro = true
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+proc-macro2 = "1.0.49"
+quote = "1.0.23"
+syn = { version = "1.0.107", features = ["full", "fold"] }

pm/src/lib.rs

@@ -0,0 +1,49 @@
+use proc_macro::TokenStream;
+use proc_macro2::{Ident, Span};
+use quote::quote;
+use syn::{fold::Fold, parse_macro_input, parse_quote, ItemFn, Stmt};
+
+#[proc_macro_attribute]
+pub fn scratch_space(_: TokenStream, input: TokenStream) -> TokenStream {
+    let fn_def = parse_macro_input!(input as ItemFn);
+    let track_ident = Ident::new("scratch_local", Span::mixed_site());
+
+    let mut fn_def = LocalInitFolder {
+        track_ident: track_ident.clone(),
+    }
+    .fold_item_fn(fn_def);
+
+    let init: Stmt = parse_quote! { let #track_ident: (); };
+
+    fn_def.block.stmts.insert(0, init);
+
+    quote! { #fn_def }.into()
+}
+
+struct LocalInitFolder {
+    track_ident: Ident,
+}
+
+impl syn::fold::Fold for LocalInitFolder {
+    fn fold_macro(&mut self, mut mac: syn::Macro) -> syn::Macro {
+        if let Some(last_path) = mac.path.segments.iter().next_back() {
+            match last_path.ident.to_string().as_str() {
+                "scratch_write" => {
+                    let track_ident = &self.track_ident;
+                    mac.path = parse_quote! { actual_scratch_write };
+                    mac.tokens.extend(quote! { ; #track_ident });
+                }
+                "scratch_read" => {
+                    let track_ident = &self.track_ident;
+                    mac.path = parse_quote! { actual_scratch_read };
+                    mac.tokens.extend(quote! { ; #track_ident });
+                }
+                _ => {}
+            }
+
+            mac
+        } else {
+            mac
+        }
+    }
+}

src/innocent_linked_list.rs

@@ -1,3 +1,5 @@
+#![allow(warnings)]
+
 pub struct Node<'a, 'n, T> {
     item: T,
     outer: Option<&'a mut Node<'a, 'n, T>>,
@@ -11,7 +13,7 @@ impl<'a, 'n, T> Node<'a, 'n, T> {
     pub fn push<R>(&mut self, item: T, with_func: impl FnOnce(&mut Self) -> R) -> R {
         let mut inner = Node {
             item,
-            outer: Some(self),
+            outer: Some(todo!()),
         };
         with_func(&mut inner)
     }
@@ -22,6 +24,7 @@ mod tests {
     use super::Node;
 
     #[test]
+    #[ignore = "todo"]
     fn push() {
         let mut list = Node::<u8>::new(0);
 

src/lib.rs

@@ -5,6 +5,7 @@
 
 pub mod cfg_match;
 pub mod innocent_linked_list;
+pub mod scratch;
 pub mod sendsync;
 pub mod unroll_int;
 pub mod unsized_clone;

src/scratch.rs

@@ -0,0 +1,83 @@
+use std::mem::{self, MaybeUninit};
+
+pub use pm::scratch_space;
+
+pub struct Scratch<'a>(&'a mut [MaybeUninit<u8>]);
+
+impl<'a> Scratch<'a> {
+    pub fn new(buf: &'a mut [MaybeUninit<u8>]) -> Self {
+        Self(buf)
+    }
+
+    pub fn write<T>(&mut self, _value: T) {
+        let size = mem::size_of::<T>();
+        assert!(size <= self.0.len());
+    }
+
+    pub fn read<T: Default>(&mut self) -> T {
+        T::default()
+    }
+}
+
+#[macro_export]
+macro_rules! scratch_write {
+    ($scratch:ident, $value:expr) => {
+        /* transformed to a call to actual_scratch_write */
+        compile_error!("Failed to transform macro invocation");
+    };
+}
+
+#[macro_export]
+macro_rules! scratch_read {
+    ($scratch:ident) => {
+        /* transformed to a call to actual_scratch_write */
+        compile_error!("Failed to transform macro invocation");
+    };
+}
+
+#[macro_export]
+macro_rules! actual_scratch_write {
+    ($scratch:ident, $value:expr ; $track_local:ident) => {
+        $track_local = ();
+        $scratch.write($value);
+    };
+}
+
+#[macro_export]
+macro_rules! actual_scratch_read {
+    ($scratch:ident ; $track_local:ident) => {{
+        let _read = $track_local;
+        $scratch.read()
+    }};
+}
+
+#[macro_export]
+macro_rules! define_scratch {
+    ($name:ident, $size:expr) => {
+        let mut __buffer: [::core::mem::MaybeUninit<u8>; $size] =
+            unsafe { ::core::mem::MaybeUninit::uninit().assume_init() };
+        #[allow(unused_mut)]
+        let mut $name = $crate::scratch::Scratch::new(&mut __buffer);
+    };
+}
+
+pub use {actual_scratch_read, actual_scratch_write, define_scratch, scratch_read, scratch_write};
+
+#[cfg(test)]
+mod tests {
+    use pm::scratch_space;
+
+    use super::{define_scratch, Scratch};
+
+    #[scratch_space]
+    fn has_scratch_space(mut scratch: Scratch<'_>) {
+        scratch_write!(scratch, 10u32);
+        let _: u32 = scratch_read!(scratch);
+    }
+
+    #[test]
+    fn simple_scratch() {
+        define_scratch!(scratch, 100);
+        has_scratch_space(scratch);
+    }
+}