Expose struct method calls on trait structs to C++ directly
[ldk-c-bindings] / c-bindings-gen / src / main.rs
index 9693e3d560a04575cf51863ec180ce1d37956434..c8adf7df1b6e7238c0a907c8aa4662019dc3b70b 100644 (file)
@@ -237,7 +237,9 @@ fn writeln_trait<'a, 'b, W: std::io::Write>(w: &mut W, t: &'a syn::ItemTrait, ty
        writeln!(w, "\t/// An opaque pointer which is passed to your function implementations as an argument.").unwrap();
        writeln!(w, "\t/// This has no meaning in the LDK, and can be NULL or any other value.").unwrap();
        writeln!(w, "\tpub this_arg: *mut c_void,").unwrap();
-       let mut generated_fields = Vec::new(); // Every field's (name, is_clonable) except this_arg, used in Clone generation
+       // We store every field's (name, Option<clone_fn>, docs) except this_arg, used in Clone generation
+       // docs is only set if its a function which should be callable on the object itself in C++
+       let mut generated_fields = Vec::new();
        for item in t.items.iter() {
                match item {
                        &syn::TraitItem::Method(ref m) => {
@@ -271,14 +273,14 @@ fn writeln_trait<'a, 'b, W: std::io::Write>(w: &mut W, t: &'a syn::ItemTrait, ty
                                                // happen) as well as provide an Option<>al function pointer which is
                                                // called when the trait method is called which allows updating on the fly.
                                                write!(w, "\tpub {}: ", m.sig.ident).unwrap();
-                                               generated_fields.push((format!("{}", m.sig.ident), true));
+                                               generated_fields.push((format!("{}", m.sig.ident), None, None));
                                                types.write_c_type(w, &*r.elem, Some(&meth_gen_types), false);
                                                writeln!(w, ",").unwrap();
                                                writeln!(w, "\t/// Fill in the {} field as a reference to it will be given to Rust after this returns", m.sig.ident).unwrap();
                                                writeln!(w, "\t/// Note that this takes a pointer to this object, not the this_ptr like other methods do").unwrap();
                                                writeln!(w, "\t/// This function pointer may be NULL if {} is filled in when this object is created and never needs updating.", m.sig.ident).unwrap();
                                                writeln!(w, "\tpub set_{}: Option<extern \"C\" fn(&{})>,", m.sig.ident, trait_name).unwrap();
-                                               generated_fields.push((format!("set_{}", m.sig.ident), true));
+                                               generated_fields.push((format!("set_{}", m.sig.ident), None, None));
                                                // Note that cbindgen will now generate
                                                // typedef struct Thing {..., set_thing: (const struct Thing*), ...} Thing;
                                                // which does not compile since Thing is not defined before it is used.
@@ -290,8 +292,12 @@ fn writeln_trait<'a, 'b, W: std::io::Write>(w: &mut W, t: &'a syn::ItemTrait, ty
                                        writeln!(w, "\t#[must_use]").unwrap();
                                }
 
+                               let mut cpp_docs = Vec::new();
+                               writeln_docs(&mut cpp_docs, &m.attrs, "\t * ");
+                               let docs_string = "\t/**\n".to_owned() + &String::from_utf8(cpp_docs).unwrap().replace("///", "") + "\t */\n";
+
                                write!(w, "\tpub {}: extern \"C\" fn (", m.sig.ident).unwrap();
-                               generated_fields.push((format!("{}", m.sig.ident), true));
+                               generated_fields.push((format!("{}", m.sig.ident), None, Some(docs_string)));
                                write_method_params(w, &m.sig, "c_void", types, Some(&meth_gen_types), true, false);
                                writeln!(w, ",").unwrap();
                        },
@@ -300,55 +306,53 @@ fn writeln_trait<'a, 'b, W: std::io::Write>(w: &mut W, t: &'a syn::ItemTrait, ty
                }
        }
        // Add functions which may be required for supertrait implementations.
-       let mut requires_clone = false;
-       walk_supertraits!(t, Some(&types), (
-               ("Clone", _) => requires_clone = true,
-               (_, _) => {}
-       ) );
        walk_supertraits!(t, Some(&types), (
                ("Clone", _) => {
-                       writeln!(w, "\t/// Creates a copy of the object pointed to by this_arg, for a copy of this {}.", trait_name).unwrap();
-                       writeln!(w, "\t/// Note that the ultimate copy of the {} will have all function pointers the same as the original.", trait_name).unwrap();
-                       writeln!(w, "\t/// May be NULL if no action needs to be taken, the this_arg pointer will be copied into the new {}.", trait_name).unwrap();
-                       writeln!(w, "\tpub clone: Option<extern \"C\" fn (this_arg: *const c_void) -> *mut c_void>,").unwrap();
-                       generated_fields.push(("clone".to_owned(), true));
+                       writeln!(w, "\t/// Called, if set, after this {} has been cloned into a duplicate object.", trait_name).unwrap();
+                       writeln!(w, "\t/// The new {} is provided, and should be mutated as needed to perform a", trait_name).unwrap();
+                       writeln!(w, "\t/// deep copy of the object pointed to by this_arg or avoid any double-freeing.").unwrap();
+                       writeln!(w, "\tpub cloned: Option<extern \"C\" fn (new_{}: &mut {})>,", trait_name, trait_name).unwrap();
+                       generated_fields.push(("cloned".to_owned(), None, None));
                },
                ("std::cmp::Eq", _)|("core::cmp::Eq", _) => {
-                       writeln!(w, "\t/// Checks if two objects are equal given this object's this_arg pointer and another object.").unwrap();
+                       let eq_docs = "Checks if two objects are equal given this object's this_arg pointer and another object.";
+                       writeln!(w, "\t/// {}", eq_docs).unwrap();
                        writeln!(w, "\tpub eq: extern \"C\" fn (this_arg: *const c_void, other_arg: &{}) -> bool,", trait_name).unwrap();
-                       generated_fields.push(("eq".to_owned(), true));
+                       generated_fields.push(("eq".to_owned(), None, Some(format!("\t/** {} */\n", eq_docs))));
                },
                ("std::hash::Hash", _)|("core::hash::Hash", _) => {
-                       writeln!(w, "\t/// Calculate a succinct non-cryptographic hash for an object given its this_arg pointer.").unwrap();
-                       writeln!(w, "\t/// This is used, for example, for inclusion of this object in a hash map.").unwrap();
+                       let hash_docs_a = "Calculate a succinct non-cryptographic hash for an object given its this_arg pointer.";
+                       let hash_docs_b = "This is used, for example, for inclusion of this object in a hash map.";
+                       writeln!(w, "\t/// {}", hash_docs_a).unwrap();
+                       writeln!(w, "\t/// {}", hash_docs_b).unwrap();
                        writeln!(w, "\tpub hash: extern \"C\" fn (this_arg: *const c_void) -> u64,").unwrap();
-                       generated_fields.push(("hash".to_owned(), true));
+                       generated_fields.push(("hash".to_owned(), None,
+                               Some(format!("\t/**\n\t * {}\n\t * {}\n\t */\n", hash_docs_a, hash_docs_b))));
                },
                ("Send", _) => {}, ("Sync", _) => {},
                (s, i) => {
+                       // TODO: Both of the below should expose supertrait methods in C++, but doing so is
+                       // nontrivial.
                        generated_fields.push(if types.crate_types.traits.get(s).is_none() {
                                let (docs, name, ret) = convert_trait_impl_field(s);
                                writeln!(w, "\t/// {}", docs).unwrap();
                                writeln!(w, "\tpub {}: extern \"C\" fn (this_arg: *const c_void) -> {},", name, ret).unwrap();
-                               (name, true) // Assume clonable
+                               (name, None, None) // Assume clonable
                        } else {
                                // For in-crate supertraits, just store a C-mapped copy of the supertrait as a member.
                                writeln!(w, "\t/// Implementation of {} for this object.", i).unwrap();
-                               writeln!(w, "\tpub {}: crate::{},", i, s).unwrap();
                                let is_clonable = types.is_clonable(s);
-                               if !is_clonable && requires_clone {
-                                       writeln!(w, "\t/// Creates a copy of the {}, for a copy of this {}.", i, trait_name).unwrap();
-                                       writeln!(w, "\t/// Because {} doesn't natively support copying itself, you have to provide a full copy implementation here.", i).unwrap();
-                                       writeln!(w, "\tpub {}_clone: extern \"C\" fn (orig_{}: &{}) -> {},", i, i, i, i).unwrap();
-                               }
-                               (format!("{}", i), is_clonable)
+                               writeln!(w, "\tpub {}: crate::{},", i, s).unwrap();
+                               (format!("{}", i), if !is_clonable {
+                                       Some(format!("crate::{}_clone_fields", s))
+                               } else { None }, None)
                        });
                }
        ) );
        writeln!(w, "\t/// Frees any resources associated with this object given its this_arg pointer.").unwrap();
        writeln!(w, "\t/// Does not need to free the outer struct containing function pointers and may be NULL is no resources need to be freed.").unwrap();
        writeln!(w, "\tpub free: Option<extern \"C\" fn(this_arg: *mut c_void)>,").unwrap();
-       generated_fields.push(("free".to_owned(), true));
+       generated_fields.push(("free".to_owned(), None, None));
        writeln!(w, "}}").unwrap();
 
        macro_rules! impl_trait_for_c {
@@ -427,7 +431,9 @@ fn writeln_trait<'a, 'b, W: std::io::Write>(w: &mut W, t: &'a syn::ItemTrait, ty
                                                }
                                                write_method_var_decl_body(w, &m.sig, "\t", $type_resolver, Some(&meth_gen_types), true);
                                                write!(w, "(self{}.{})(", $impl_accessor, m.sig.ident).unwrap();
-                                               write_method_call_params(w, &m.sig, "\t", $type_resolver, Some(&meth_gen_types), "", true);
+                                               let mut args = Vec::new();
+                                               write_method_call_params(&mut args, &m.sig, "\t", $type_resolver, Some(&meth_gen_types), "", true);
+                                               w.write_all(String::from_utf8(args).unwrap().replace("self", &format!("self{}", $impl_accessor)).as_bytes()).unwrap();
 
                                                writeln!(w, "\n\t}}").unwrap();
                                        },
@@ -451,6 +457,20 @@ fn writeln_trait<'a, 'b, W: std::io::Write>(w: &mut W, t: &'a syn::ItemTrait, ty
        writeln!(w, "unsafe impl Send for {} {{}}", trait_name).unwrap();
        writeln!(w, "unsafe impl Sync for {} {{}}", trait_name).unwrap();
 
+       writeln!(w, "#[no_mangle]").unwrap();
+       writeln!(w, "pub(crate) extern \"C\" fn {}_clone_fields(orig: &{}) -> {} {{", trait_name, trait_name, trait_name).unwrap();
+       writeln!(w, "\t{} {{", trait_name).unwrap();
+       writeln!(w, "\t\tthis_arg: orig.this_arg,").unwrap();
+       for (field, clone_fn, _) in generated_fields.iter() {
+               if let Some(f) = clone_fn {
+                       // If the field isn't clonable, blindly assume its a trait and hope for the best.
+                       writeln!(w, "\t\t{}: {}(&orig.{}),", field, f, field).unwrap();
+               } else {
+                       writeln!(w, "\t\t{}: Clone::clone(&orig.{}),", field, field).unwrap();
+               }
+       }
+       writeln!(w, "\t}}\n}}").unwrap();
+
        // Implement supertraits for the C-mapped struct.
        walk_supertraits!(t, Some(&types), (
                ("std::cmp::Eq", _)|("core::cmp::Eq", _) => {
@@ -467,17 +487,9 @@ fn writeln_trait<'a, 'b, W: std::io::Write>(w: &mut W, t: &'a syn::ItemTrait, ty
                        writeln!(w, "#[no_mangle]").unwrap();
                        writeln!(w, "/// Creates a copy of a {}", trait_name).unwrap();
                        writeln!(w, "pub extern \"C\" fn {}_clone(orig: &{}) -> {} {{", trait_name, trait_name, trait_name).unwrap();
-                       writeln!(w, "\t{} {{", trait_name).unwrap();
-                       writeln!(w, "\t\tthis_arg: if let Some(f) = orig.clone {{ (f)(orig.this_arg) }} else {{ orig.this_arg }},").unwrap();
-                       for (field, clonable) in generated_fields.iter() {
-                               if *clonable {
-                                       writeln!(w, "\t\t{}: Clone::clone(&orig.{}),", field, field).unwrap();
-                               } else {
-                                       writeln!(w, "\t\t{}: (orig.{}_clone)(&orig.{}),", field, field, field).unwrap();
-                                       writeln!(w, "\t\t{}_clone: orig.{}_clone,", field, field).unwrap();
-                               }
-                       }
-                       writeln!(w, "\t}}\n}}").unwrap();
+                       writeln!(w, "\tlet mut res = {}_clone_fields(orig);", trait_name).unwrap();
+                       writeln!(w, "\tif let Some(f) = orig.cloned {{ (f)(&mut res) }};").unwrap();
+                       writeln!(w, "\tres\n}}").unwrap();
                        writeln!(w, "impl Clone for {} {{", trait_name).unwrap();
                        writeln!(w, "\tfn clone(&self) -> Self {{").unwrap();
                        writeln!(w, "\t\t{}_clone(self)", trait_name).unwrap();
@@ -522,7 +534,8 @@ fn writeln_trait<'a, 'b, W: std::io::Write>(w: &mut W, t: &'a syn::ItemTrait, ty
        writeln!(w, "\t\t\tf(self.this_arg);").unwrap();
        writeln!(w, "\t\t}}\n\t}}\n}}").unwrap();
 
-       write_cpp_wrapper(cpp_headers, &trait_name, true);
+       write_cpp_wrapper(cpp_headers, &trait_name, true, Some(generated_fields.drain(..)
+               .filter_map(|(name, _, docs)| if let Some(docs) = docs { Some((name, docs)) } else { None }).collect()));
 }
 
 /// Write out a simple "opaque" type (eg structs) which contain a pointer to the native Rust type
@@ -567,7 +580,7 @@ fn writeln_opaque<W: std::io::Write>(w: &mut W, ident: &syn::Ident, struct_name:
        writeln!(w, "\t\tret").unwrap();
        writeln!(w, "\t}}\n}}").unwrap();
 
-       write_cpp_wrapper(cpp_headers, &format!("{}", ident), true);
+       write_cpp_wrapper(cpp_headers, &format!("{}", ident), true, None);
 }
 
 /// Writes out all the relevant mappings for a Rust struct, deferring to writeln_opaque to generate
@@ -803,13 +816,10 @@ fn writeln_impl<W: std::io::Write>(w: &mut W, i: &syn::ItemImpl, types: &mut Typ
                                                        }
                                                }
                                                let mut requires_clone = false;
-                                               walk_supertraits!(trait_obj, Some(&types), (
-                                                       ("Clone", _) => requires_clone = true,
-                                                       (_, _) => {}
-                                               ) );
                                                walk_supertraits!(trait_obj, Some(&types), (
                                                        ("Clone", _) => {
-                                                               writeln!(w, "\t\tclone: Some({}_clone_void),", ident).unwrap();
+                                                               requires_clone = true;
+                                                               writeln!(w, "\t\tcloned: Some({}_{}_cloned),", trait_obj.ident, ident).unwrap();
                                                        },
                                                        ("Sync", _) => {}, ("Send", _) => {},
                                                        ("std::marker::Sync", _) => {}, ("std::marker::Send", _) => {},
@@ -827,9 +837,6 @@ fn writeln_impl<W: std::io::Write>(w: &mut W, i: &syn::ItemImpl, types: &mut Typ
                                                                                }
                                                                        }
                                                                        write!(w, "\t\t}},\n").unwrap();
-                                                                       if !types.is_clonable(s) && requires_clone {
-                                                                               writeln!(w, "\t\t{}_clone: {}_{}_clone,", t, ident, t).unwrap();
-                                                                       }
                                                                } else {
                                                                        write_trait_impl_field_assign(w, s, ident);
                                                                }
@@ -914,27 +921,21 @@ fn writeln_impl<W: std::io::Write>(w: &mut W, i: &syn::ItemImpl, types: &mut Typ
                                                                _ => unimplemented!(),
                                                        }
                                                }
-                                               walk_supertraits!(trait_obj, Some(&types), (
-                                                       (s, t) => {
-                                                               if let Some(supertrait_obj) = types.crate_types.traits.get(s) {
-                                                                       if !types.is_clonable(s) && requires_clone {
-                                                                               writeln!(w, "extern \"C\" fn {}_{}_clone(orig: &crate::{}) -> crate::{} {{", ident, t, s, s).unwrap();
-                                                                               writeln!(w, "\tcrate::{} {{", s).unwrap();
-                                                                               writeln!(w, "\t\tthis_arg: orig.this_arg,").unwrap();
-                                                                               writeln!(w, "\t\tfree: None,").unwrap();
-                                                                               for item in supertrait_obj.items.iter() {
-                                                                                       match item {
-                                                                                               syn::TraitItem::Method(m) => {
-                                                                                                       write_meth!(m, supertrait_obj, "");
-                                                                                               },
-                                                                                               _ => {},
-                                                                                       }
-                                                                               }
-                                                                               write!(w, "\t}}\n}}\n").unwrap();
+                                               if requires_clone {
+                                                       writeln!(w, "extern \"C\" fn {}_{}_cloned(new_obj: &mut crate::{}) {{", trait_obj.ident, ident, full_trait_path).unwrap();
+                                                       writeln!(w, "\tnew_obj.this_arg = {}_clone_void(new_obj.this_arg);", ident).unwrap();
+                                                       writeln!(w, "\tnew_obj.free = Some({}_free_void);", ident).unwrap();
+                                                       walk_supertraits!(trait_obj, Some(&types), (
+                                                               (s, t) => {
+                                                                       if types.crate_types.traits.get(s).is_some() {
+                                                                               assert!(!types.is_clonable(s)); // We don't currently support cloning with a clonable supertrait
+                                                                               writeln!(w, "\tnew_obj.{}.this_arg = new_obj.this_arg;", t).unwrap();
+                                                                               writeln!(w, "\tnew_obj.{}.free = None;", t).unwrap();
                                                                        }
                                                                }
-                                                       }
-                                               ) );
+                                                       ) );
+                                                       writeln!(w, "}}").unwrap();
+                                               }
                                                write!(w, "\n").unwrap();
                                        } else if path_matches_nongeneric(&trait_path.1, &["From"]) {
                                        } else if path_matches_nongeneric(&trait_path.1, &["Default"]) {
@@ -1372,7 +1373,7 @@ fn writeln_enum<'a, 'b, W: std::io::Write>(w: &mut W, e: &'a syn::ItemEnum, type
        writeln!(w, "pub extern \"C\" fn {}_clone(orig: &{}) -> {} {{", e.ident, e.ident, e.ident).unwrap();
        writeln!(w, "\torig.clone()").unwrap();
        writeln!(w, "}}").unwrap();
-       write_cpp_wrapper(cpp_headers, &format!("{}", e.ident), needs_free);
+       write_cpp_wrapper(cpp_headers, &format!("{}", e.ident), needs_free, None);
 }
 
 fn writeln_fn<'a, 'b, W: std::io::Write>(w: &mut W, f: &'a syn::ItemFn, types: &mut TypeResolver<'b, 'a>) {
@@ -1756,7 +1757,7 @@ fn main() {
        // For container templates which we created while walking the crate, make sure we add C++
        // mapped types so that C++ users can utilize the auto-destructors available.
        for (ty, has_destructor) in libtypes.templates_defined.borrow().iter() {
-               write_cpp_wrapper(&mut cpp_header_file, ty, *has_destructor);
+               write_cpp_wrapper(&mut cpp_header_file, ty, *has_destructor, None);
        }
        writeln!(cpp_header_file, "}}").unwrap();