From b5af5fbe70acaba9bf80f146dde8df61c2bde1f8 Mon Sep 17 00:00:00 2001
From: hodasemi <superschneider@t-online.de>
Date: Wed, 1 Feb 2023 13:10:52 +0100
Subject: [PATCH] Add custom macro for ReprC impl

---
 Cargo.toml                      |  1 +
 src/lib.rs                      |  3 ++
 src/prelude.rs                  |  3 ++
 src/repr_c.rs                   | 36 +++++++++++++++++++
 src/reprc_proc_macro/Cargo.toml | 13 +++++++
 src/reprc_proc_macro/src/lib.rs | 62 +++++++++++++++++++++++++++++++++
 6 files changed, 118 insertions(+)
 create mode 100644 src/repr_c.rs
 create mode 100644 src/reprc_proc_macro/Cargo.toml
 create mode 100644 src/reprc_proc_macro/src/lib.rs

diff --git a/Cargo.toml b/Cargo.toml
index bca37ff..0f3db86 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -10,6 +10,7 @@ rand = "0.8.5"
 backtrace = "0.3.67"
 assetpath = { git = "https://gavania.de/hodasemi/vulkan_lib.git" }
 anyhow = { version = "1.0.68", features = ["backtrace"] }
+reprc_proc_macro = { path = "src/reprc_proc_macro" }
 
 # networking
 serde = { version = "1.0.152", features = ["derive"] }
diff --git a/src/lib.rs b/src/lib.rs
index 878d738..2e8dca8 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -14,4 +14,7 @@ pub mod try_lock_guard;
 pub mod arc_unique_vec;
 pub mod rc_unique_vec;
 
+#[macro_use]
+mod repr_c;
+
 pub mod unsafe_life_time;
diff --git a/src/prelude.rs b/src/prelude.rs
index b19f64d..4be0e39 100644
--- a/src/prelude.rs
+++ b/src/prelude.rs
@@ -27,3 +27,6 @@ pub use crate::try_lock_guard::TryLockGuard;
 
 // unsafe life time trickery
 pub use crate::unsafe_life_time::*;
+
+pub use crate::repr_c::ReprC;
+pub use reprc_proc_macro::DeriveReprC;
diff --git a/src/repr_c.rs b/src/repr_c.rs
new file mode 100644
index 0000000..416166b
--- /dev/null
+++ b/src/repr_c.rs
@@ -0,0 +1,36 @@
+use reprc_proc_macro::DeriveReprC;
+
+#[macro_export]
+macro_rules! impl_reprc {
+    (
+        $(#[$meta: meta])*
+        $v:vis struct $struct_name:ident {
+            $( $(#[$field_meta:meta])* $member:ident : $t:ty, )+
+        }
+    ) => {
+        #[repr(C)]
+        #[derive(Debug, Clone, DeriveReprC)]
+        $(#[$meta])*
+        $v struct $struct_name {
+            $(
+                $( #[$field_meta] )*
+                pub $member: $t,
+            )+
+        }
+    };
+}
+
+impl_reprc!(
+    struct Test {
+        #[assume_reprc]
+        i1: i32,
+        #[assume_reprc]
+        i2: i32,
+        #[assume_reprc]
+        v1: Vec<i32>,
+    }
+);
+
+pub unsafe trait ReprC {
+    fn is_repr_c(&self) -> bool;
+}
diff --git a/src/reprc_proc_macro/Cargo.toml b/src/reprc_proc_macro/Cargo.toml
new file mode 100644
index 0000000..3f44c9e
--- /dev/null
+++ b/src/reprc_proc_macro/Cargo.toml
@@ -0,0 +1,13 @@
+[package]
+name = "reprc_proc_macro"
+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]
+syn = { version = "1.0.107", features = ["full", "fold"] }
+quote = "1.0.23"
\ No newline at end of file
diff --git a/src/reprc_proc_macro/src/lib.rs b/src/reprc_proc_macro/src/lib.rs
new file mode 100644
index 0000000..6d5d9f9
--- /dev/null
+++ b/src/reprc_proc_macro/src/lib.rs
@@ -0,0 +1,62 @@
+use proc_macro::TokenStream;
+use quote::{quote, ToTokens};
+use syn::{parse_macro_input, Data, DeriveInput, Ident};
+
+const REPRC_ATTRIBUTE: &'static str = "assume_reprc";
+
+#[proc_macro_derive(DeriveReprC, attributes(assume_reprc))]
+pub fn reprc_builder(item: TokenStream) -> TokenStream {
+    let ast = parse_macro_input!(item as DeriveInput);
+
+    let struct_name = ast.ident;
+    let generics = ast.generics.to_token_stream();
+
+    match ast.data {
+        Data::Struct(data_struct) => match data_struct.fields {
+            syn::Fields::Named(named_fields) => {
+                let reprc_fields: Vec<Ident> = named_fields
+                    .named
+                    .iter()
+                    .filter_map(|field| {
+                        if field
+                            .attrs
+                            .iter()
+                            .find(|attribute| {
+                                let segments = &attribute.path.segments;
+
+                                if segments.len() < 1 {
+                                    return false;
+                                }
+
+                                segments[0].ident == REPRC_ATTRIBUTE
+                            })
+                            .is_some()
+                        {
+                            None
+                        } else {
+                            Some(field.ident.clone())
+                        }
+                    })
+                    .map(|i| i.unwrap())
+                    .collect();
+
+                TokenStream::from(quote! {
+                    unsafe impl #generics ReprC for #struct_name #generics {
+                        fn is_repr_c(&self) -> bool {
+                            true
+
+                            #(
+                                && self. #reprc_fields.to_tokens() .is_repr_c()
+                            )*
+                        }
+                    }
+                })
+            }
+            syn::Fields::Unnamed(_) => todo!("Unnamed Field not supported"),
+            syn::Fields::Unit => todo!("Unit not supported"),
+        },
+
+        Data::Enum(_) => todo!("Enum not supported"),
+        Data::Union(_) => todo!("Union not supported"),
+    }
+}