Borsch traits using bindgen

program/rust/Cargo.toml

@@ -7,8 +7,13 @@ edition = "2021"
 license = "Apache 2.0"
 publish = false
 
+[build-dependencies]
+bindgen = "0.60.1"
+
 [dependencies]
 solana-program = "=1.10.29"
+borsh = "0.9"
+
 
 [lib]
 crate-type = ["cdylib", "lib"]

program/rust/build.rs

@@ -1,3 +1,26 @@
+mod build_utils;
+use bindgen::Builder;
+use std::vec::Vec;
+
 fn main() {
     println!("cargo:rustc-link-search=../c/target");
+
+    let borsh_derives = ["BorshSerialize".to_string(), "BorshDeserialize".to_string()];
+
+    //make a parser and to it type, traits pairs
+    let mut parser = build_utils::DeriveAdderParserCallback::new();
+    parser.register_traits("cmd_hdr", borsh_derives.to_vec());
+    parser.register_traits("pc_acc", borsh_derives.to_vec());
+
+
+    //generate and write bindings
+    let bindings = Builder::default()
+        .header("./src/bindings.h")
+        .parse_callbacks(Box::new(parser))
+        .rustfmt_bindings(true)
+        .generate()
+        .expect("Unable to generate bindings");
+    bindings
+        .write_to_file("./bindings.rs")
+        .expect("Couldn't write bindings!");
 }

program/rust/build_utils.rs

@@ -0,0 +1,35 @@
+use bindgen::callbacks::ParseCallbacks;
+use std::collections::HashMap;
+use std::panic::UnwindSafe;
+///This type stores a hashmap from structnames
+///to vectors of trait names, and ensures
+///that the traits of each struct are added to its
+///definition when an instance of this struct
+///is provided as a ParseCallback for bindgen
+#[derive(Debug, Default)]
+pub struct DeriveAdderParserCallback<'a> {
+    pub types_to_traits: HashMap<&'a str, Vec<String>>,
+}
+
+impl<'a> DeriveAdderParserCallback<'a> {
+    ///create a parser that does not add any traits
+    pub fn new() -> Self {
+        Default::default()
+    }
+    //add pairs of types and their desired traits
+    pub fn register_traits(&mut self, type_name: &'a str, traits: Vec<String>) {
+        self.types_to_traits.insert(&type_name, traits);
+    }
+}
+
+//this is required to implement the callback trait
+impl UnwindSafe for DeriveAdderParserCallback<'_> {}
+
+impl ParseCallbacks for DeriveAdderParserCallback<'_> {
+    fn add_derives(&self, _name: &str) -> Vec<String> {
+        self.types_to_traits
+            .get(_name)
+            .unwrap_or(&Vec::<String>::new())
+            .to_vec()
+    }
+}

program/rust/src/c_oracle_header.rs

@@ -0,0 +1,11 @@
+#![allow(non_upper_case_globals)]
+#![allow(non_camel_case_types)]
+#![allow(non_snake_case)]
+//we do not use all the variables in oracle.h, so this helps with the warnings
+#![allow(unused_variables)]
+#![allow(dead_code)]
+//All the custom trait imports should go here
+use borsh::{BorshDeserialize, BorshSerialize};
+//bindings.rs is generated by build.rs to include
+//things defined in bindings.h
+include!("../bindings.rs");

program/rust/src/lib.rs

@@ -1,8 +1,23 @@
-//c_oracle_header is auto generated by build_bpf.sh
-//to reflect the current status of oracle.h
 mod c_oracle_header;
 mod time_machine_types;
 
+//Below is a high lever description of the rust/c setup.
+
+//As we migrate from C to Rust, our Rust code needs to be able to interract with C
+//build-bpf.sh is set up to compile the C code into a bpf archive file, that build.rs
+//is set up to link the rust targets to. This enables to interact with the c_entrypoint
+//as well as similarly declare other C functions in Rust and call them
+
+//We also generate bindings for the types and constants in oracle.h (as well as other things
+//included in bindings.h), these bindings can be accessed through c_oracle_header.rs
+//Bindings allow us to access type definitions, function definitions and constants. In order to
+//add traits to the bindings, we use the parser in build.rs. The traits must be defined/included
+//at the the top of c_oracle_headers.rs. One of the most important traits we deal are the Borsh
+//serialization traits.
+
+//the only limitation of our set up is that we can not unit test in rust, anything that calls
+//a c function. Though we can test functions that use constants/types defined in oracle.h
+
 //do not link with C during unit tests (which are built in native architecture, unlike libpyth.o)
 #[cfg(target_arch = "bpf")]
 #[link(name = "cpyth")]

scripts/build-bpf.sh

@@ -40,8 +40,6 @@ rm ./target/*-keypair.json
 
 #build Rust and link it with C
 cd "${RUST_DIR}"
-cargo install bindgen
-bindgen ./src/bindings.h -o ./src/c_oracle_header.rs
 cargo clean
 cargo test
 cargo clean