git.bitcoin.ninja Git - rust-lightning/blob - c-bindings-gen/src/blocks.rs

   1 //! Printing logic for basic blocks of Rust-mapped code - parts of functions and declarations but
   2 //! not the full mapping logic.
   3
   4 use std::fs::File;
   5 use std::io::Write;
   6 use proc_macro2::{TokenTree, Span};
   7
   8 use crate::types::*;
   9
  10 /// Writes out a C++ wrapper class for the given type, which contains various utilities to access
  11 /// the underlying C-mapped type safely avoiding some common memory management issues by handling
  12 /// resource-freeing and prevending accidental raw copies.
  13 pub fn write_cpp_wrapper(cpp_header_file: &mut File, ty: &str, has_destructor: bool) {
  14         writeln!(cpp_header_file, "class {} {{", ty).unwrap();
  15         writeln!(cpp_header_file, "private:").unwrap();
  16         writeln!(cpp_header_file, "\tLDK{} self;", ty).unwrap();
  17         writeln!(cpp_header_file, "public:").unwrap();
  18         writeln!(cpp_header_file, "\t{}(const {}&) = delete;", ty, ty).unwrap();
  19         writeln!(cpp_header_file, "\t{}({}&& o) : self(o.self) {{ memset(&o, 0, sizeof({})); }}", ty, ty, ty).unwrap();
  20         writeln!(cpp_header_file, "\t{}(LDK{}&& m_self) : self(m_self) {{ memset(&m_self, 0, sizeof(LDK{})); }}", ty, ty, ty).unwrap();
  21         writeln!(cpp_header_file, "\toperator LDK{}() && {{ LDK{} res = self; memset(&self, 0, sizeof(LDK{})); return res; }}", ty, ty, ty).unwrap();
  22         if has_destructor {
  23                 writeln!(cpp_header_file, "\t~{}() {{ {}_free(self); }}", ty, ty).unwrap();
  24                 writeln!(cpp_header_file, "\t{}& operator=({}&& o) {{ {}_free(self); self = o.self; memset(&o, 0, sizeof({})); return *this; }}", ty, ty, ty, ty).unwrap();
  25         } else {
  26                 writeln!(cpp_header_file, "\t{}& operator=({}&& o) {{ self = o.self; memset(&o, 0, sizeof({})); return *this; }}", ty, ty, ty).unwrap();
  27         }
  28         writeln!(cpp_header_file, "\tLDK{}* operator &() {{ return &self; }}", ty).unwrap();
  29         writeln!(cpp_header_file, "\tLDK{}* operator ->() {{ return &self; }}", ty).unwrap();
  30         writeln!(cpp_header_file, "\tconst LDK{}* operator &() const {{ return &self; }}", ty).unwrap();
  31         writeln!(cpp_header_file, "\tconst LDK{}* operator ->() const {{ return &self; }}", ty).unwrap();
  32         writeln!(cpp_header_file, "}};").unwrap();
  33 }
  34
  35 /// Writes out a C-callable concrete Result<A, B> struct and utility methods
  36 pub fn write_result_block<W: std::io::Write>(w: &mut W, mangled_container: &str, ok_type: &str, err_type: &str) {
  37         writeln!(w, "#[repr(C)]").unwrap();
  38         writeln!(w, "pub union {}Ptr {{", mangled_container).unwrap();
  39         if ok_type != "()" {
  40                 writeln!(w, "\tpub result: *mut {},", ok_type).unwrap();
  41         } else {
  42                 writeln!(w, "\t/// Note that this value is always NULL, as there are no contents in the OK variant").unwrap();
  43                 writeln!(w, "\tpub result: *mut std::ffi::c_void,").unwrap();
  44         }
  45         if err_type != "()" {
  46                 writeln!(w, "\tpub err: *mut {},", err_type).unwrap();
  47         } else {
  48                 writeln!(w, "\t/// Note that this value is always NULL, as there are no contents in the Err variant").unwrap();
  49                 writeln!(w, "\tpub err: *mut std::ffi::c_void,").unwrap();
  50         }
  51         writeln!(w, "}}").unwrap();
  52         writeln!(w, "#[repr(C)]").unwrap();
  53         writeln!(w, "pub struct {} {{", mangled_container).unwrap();
  54         writeln!(w, "\tpub contents: {}Ptr,", mangled_container).unwrap();
  55         writeln!(w, "\tpub result_ok: bool,").unwrap();
  56         writeln!(w, "}}").unwrap();
  57
  58         writeln!(w, "#[no_mangle]").unwrap();
  59         if ok_type != "()" {
  60                 writeln!(w, "pub extern \"C\" fn {}_ok(o: {}) -> {} {{", mangled_container, ok_type, mangled_container).unwrap();
  61         } else {
  62                 writeln!(w, "pub extern \"C\" fn {}_ok() -> {} {{", mangled_container, mangled_container).unwrap();
  63         }
  64         writeln!(w, "\t{} {{", mangled_container).unwrap();
  65         writeln!(w, "\t\tcontents: {}Ptr {{", mangled_container).unwrap();
  66         if ok_type != "()" {
  67                 writeln!(w, "\t\t\tresult: Box::into_raw(Box::new(o)),").unwrap();
  68         } else {
  69                 writeln!(w, "\t\t\tresult: std::ptr::null_mut(),").unwrap();
  70         }
  71         writeln!(w, "\t\t}},").unwrap();
  72         writeln!(w, "\t\tresult_ok: true,").unwrap();
  73         writeln!(w, "\t}}").unwrap();
  74         writeln!(w, "}}").unwrap();
  75
  76         writeln!(w, "#[no_mangle]").unwrap();
  77         if err_type != "()" {
  78                 writeln!(w, "pub extern \"C\" fn {}_err(e: {}) -> {} {{", mangled_container, err_type, mangled_container).unwrap();
  79         } else {
  80                 writeln!(w, "pub extern \"C\" fn {}_err() -> {} {{", mangled_container, mangled_container).unwrap();
  81         }
  82         writeln!(w, "\t{} {{", mangled_container).unwrap();
  83         writeln!(w, "\t\tcontents: {}Ptr {{", mangled_container).unwrap();
  84         if err_type != "()" {
  85                 writeln!(w, "\t\t\terr: Box::into_raw(Box::new(e)),").unwrap();
  86         } else {
  87                 writeln!(w, "\t\t\terr: std::ptr::null_mut(),").unwrap();
  88         }
  89         writeln!(w, "\t\t}},").unwrap();
  90         writeln!(w, "\t\tresult_ok: false,").unwrap();
  91         writeln!(w, "\t}}").unwrap();
  92         writeln!(w, "}}").unwrap();
  93
  94         writeln!(w, "#[no_mangle]").unwrap();
  95         writeln!(w, "pub extern \"C\" fn {}_free(_res: {}) {{ }}", mangled_container, mangled_container).unwrap();
  96         writeln!(w, "impl Drop for {} {{", mangled_container).unwrap();
  97         writeln!(w, "\tfn drop(&mut self) {{").unwrap();
  98         writeln!(w, "\t\tif self.result_ok {{").unwrap();
  99         if ok_type != "()" {
 100                 writeln!(w, "\t\t\tif unsafe {{ !(self.contents.result as *mut ()).is_null() }} {{").unwrap();
 101                 writeln!(w, "\t\t\t\tlet _ = unsafe {{ Box::from_raw(self.contents.result) }};").unwrap();
 102                 writeln!(w, "\t\t\t}}").unwrap();
 103         }
 104         writeln!(w, "\t\t}} else {{").unwrap();
 105         if err_type != "()" {
 106                 writeln!(w, "\t\t\tif unsafe {{ !(self.contents.err as *mut ()).is_null() }} {{").unwrap();
 107                 writeln!(w, "\t\t\t\tlet _ = unsafe {{ Box::from_raw(self.contents.err) }};").unwrap();
 108                 writeln!(w, "\t\t\t}}").unwrap();
 109         }
 110         writeln!(w, "\t\t}}").unwrap();
 111         writeln!(w, "\t}}").unwrap();
 112         writeln!(w, "}}").unwrap();
 113
 114         // TODO: Templates should use () now that they can, too
 115         let templ_ok_type = if ok_type != "()" { ok_type } else { "u8" };
 116         let templ_err_type = if err_type != "()" { err_type } else { "u8" };
 117
 118         writeln!(w, "impl From<crate::c_types::CResultTempl<{}, {}>> for {} {{", templ_ok_type, templ_err_type, mangled_container).unwrap();
 119         writeln!(w, "\tfn from(mut o: crate::c_types::CResultTempl<{}, {}>) -> Self {{", templ_ok_type, templ_err_type).unwrap();
 120         writeln!(w, "\t\tlet contents = if o.result_ok {{").unwrap();
 121         if ok_type != "()" {
 122                 writeln!(w, "\t\t\tlet result = unsafe {{ o.contents.result }};").unwrap();
 123                 writeln!(w, "\t\t\tunsafe {{ o.contents.result = std::ptr::null_mut() }};").unwrap();
 124                 writeln!(w, "\t\t\t{}Ptr {{ result }}", mangled_container).unwrap();
 125         } else {
 126                 writeln!(w, "\t\t\tlet _ = unsafe {{ Box::from_raw(o.contents.result) }};").unwrap();
 127                 writeln!(w, "\t\t\to.contents.result = std::ptr::null_mut();").unwrap();
 128                 writeln!(w, "\t\t\t{}Ptr {{ result: std::ptr::null_mut() }}", mangled_container).unwrap();
 129         }
 130         writeln!(w, "\t\t}} else {{").unwrap();
 131         if err_type != "()" {
 132                 writeln!(w, "\t\t\tlet err = unsafe {{ o.contents.err }};").unwrap();
 133                 writeln!(w, "\t\t\tunsafe {{ o.contents.err = std::ptr::null_mut(); }}").unwrap();
 134                 writeln!(w, "\t\t\t{}Ptr {{ err }}", mangled_container).unwrap();
 135         } else {
 136                 writeln!(w, "\t\t\tlet _ = unsafe {{ Box::from_raw(o.contents.err) }};").unwrap();
 137                 writeln!(w, "\t\t\to.contents.err = std::ptr::null_mut();").unwrap();
 138                 writeln!(w, "\t\t\t{}Ptr {{ err: std::ptr::null_mut() }}", mangled_container).unwrap();
 139         }
 140         writeln!(w, "\t\t}};").unwrap();
 141         writeln!(w, "\t\tSelf {{").unwrap();
 142         writeln!(w, "\t\t\tcontents,").unwrap();
 143         writeln!(w, "\t\t\tresult_ok: o.result_ok,").unwrap();
 144         writeln!(w, "\t\t}}").unwrap();
 145         writeln!(w, "\t}}").unwrap();
 146         writeln!(w, "}}").unwrap();
 147 }
 148
 149 /// Writes out a C-callable concrete Vec<A> struct and utility methods
 150 pub fn write_vec_block<W: std::io::Write>(w: &mut W, mangled_container: &str, inner_type: &str) {
 151         writeln!(w, "#[repr(C)]").unwrap();
 152         writeln!(w, "pub struct {} {{", mangled_container).unwrap();
 153         writeln!(w, "\tpub data: *mut {},", inner_type).unwrap();
 154         writeln!(w, "\tpub datalen: usize").unwrap();
 155         writeln!(w, "}}").unwrap();
 156
 157         writeln!(w, "impl {} {{", mangled_container).unwrap();
 158         writeln!(w, "\t#[allow(unused)] pub(crate) fn into_rust(&mut self) -> Vec<{}> {{", inner_type).unwrap();
 159         writeln!(w, "\t\tif self.datalen == 0 {{ return Vec::new(); }}").unwrap();
 160         writeln!(w, "\t\tlet ret = unsafe {{ Box::from_raw(std::slice::from_raw_parts_mut(self.data, self.datalen)) }}.into();").unwrap();
 161         writeln!(w, "\t\tself.data = std::ptr::null_mut();").unwrap();
 162         writeln!(w, "\t\tself.datalen = 0;").unwrap();
 163         writeln!(w, "\t\tret").unwrap();
 164         writeln!(w, "\t}}").unwrap();
 165         writeln!(w, "\t#[allow(unused)] pub(crate) fn as_slice(&self) -> &[{}] {{", inner_type).unwrap();
 166         writeln!(w, "\t\tunsafe {{ std::slice::from_raw_parts_mut(self.data, self.datalen) }}").unwrap();
 167         writeln!(w, "\t}}").unwrap();
 168         writeln!(w, "}}").unwrap();
 169
 170         writeln!(w, "impl From<Vec<{}>> for {} {{", inner_type, mangled_container).unwrap();
 171         writeln!(w, "\tfn from(v: Vec<{}>) -> Self {{", inner_type).unwrap();
 172         writeln!(w, "\t\tlet datalen = v.len();").unwrap();
 173         writeln!(w, "\t\tlet data = Box::into_raw(v.into_boxed_slice());").unwrap();
 174         writeln!(w, "\t\tSelf {{ datalen, data: unsafe {{ (*data).as_mut_ptr() }} }}").unwrap();
 175         writeln!(w, "\t}}").unwrap();
 176         writeln!(w, "}}").unwrap();
 177
 178         writeln!(w, "#[no_mangle]").unwrap();
 179         writeln!(w, "pub extern \"C\" fn {}_free(_res: {}) {{ }}", mangled_container, mangled_container).unwrap();
 180         writeln!(w, "impl Drop for {} {{", mangled_container).unwrap();
 181         writeln!(w, "\tfn drop(&mut self) {{").unwrap();
 182         writeln!(w, "\t\tif self.datalen == 0 {{ return; }}").unwrap();
 183         writeln!(w, "\t\tunsafe {{ Box::from_raw(std::slice::from_raw_parts_mut(self.data, self.datalen)) }};").unwrap();
 184         writeln!(w, "\t}}").unwrap();
 185         writeln!(w, "}}").unwrap();
 186         if inner_type == "u8" || mangled_container == "CVec_SpendableOutputDescriptorZ" { // XXX
 187                 writeln!(w, "impl Clone for {} {{", mangled_container).unwrap();
 188                 writeln!(w, "\tfn clone(&self) -> Self {{").unwrap();
 189                 writeln!(w, "\t\tlet mut res = Vec::new();").unwrap();
 190                 writeln!(w, "\t\tif self.datalen == 0 {{ return Self::from(res); }}").unwrap();
 191                 writeln!(w, "\t\tres.extend_from_slice(unsafe {{ std::slice::from_raw_parts_mut(self.data, self.datalen) }});").unwrap();
 192                 writeln!(w, "\t\tSelf::from(res)").unwrap();
 193                 writeln!(w, "\t}}").unwrap();
 194                 writeln!(w, "}}").unwrap();
 195         }
 196 }
 197
 198 /// Prints the docs from a given attribute list unless its tagged no export
 199 pub fn writeln_docs<W: std::io::Write>(w: &mut W, attrs: &[syn::Attribute], prefix: &str) {
 200         for attr in attrs.iter() {
 201                 let tokens_clone = attr.tokens.clone();
 202                 let mut token_iter = tokens_clone.into_iter();
 203                 if let Some(token) = token_iter.next() {
 204                         match token {
 205                                 TokenTree::Punct(c) if c.as_char() == '=' => {
 206                                         // syn gets '=' from '///' or '//!' as it is syntax for #[doc = ""]
 207                                 },
 208                                 TokenTree::Group(_) => continue, // eg #[derive()]
 209                                 _ => unimplemented!(),
 210                         }
 211                 } else { continue; }
 212                 match attr.style {
 213                         syn::AttrStyle::Inner(_) => {
 214                                 match token_iter.next().unwrap() {
 215                                         TokenTree::Literal(lit) => {
 216                                                 // Drop the first and last chars from lit as they are always "
 217                                                 let doc = format!("{}", lit);
 218                                                 writeln!(w, "{}//!{}", prefix, &doc[1..doc.len() - 1]).unwrap();
 219                                         },
 220                                         _ => unimplemented!(),
 221                                 }
 222                         },
 223                         syn::AttrStyle::Outer => {
 224                                 match token_iter.next().unwrap() {
 225                                         TokenTree::Literal(lit) => {
 226                                                 // Drop the first and last chars from lit as they are always "
 227                                                 let doc = format!("{}", lit);
 228                                                 writeln!(w, "{}///{}", prefix, &doc[1..doc.len() - 1]).unwrap();
 229                                         },
 230                                         _ => unimplemented!(),
 231                                 }
 232                         },
 233                 }
 234         }
 235 }
 236
 237 /// Print the parameters in a method declaration, starting after the open parenthesis, through and
 238 /// including the closing parenthesis and return value, but not including the open bracket or any
 239 /// trailing semicolons.
 240 ///
 241 /// Usable both for a function definition and declaration.
 242 ///
 243 /// this_param is used when returning Self or accepting a self parameter, and should be the
 244 /// concrete, mapped type.
 245 pub fn write_method_params<W: std::io::Write>(w: &mut W, sig: &syn::Signature, this_param: &str, types: &mut TypeResolver, generics: Option<&GenericTypes>, self_ptr: bool, fn_decl: bool) {
 246         if sig.constness.is_some() || sig.asyncness.is_some() || sig.unsafety.is_some() ||
 247                         sig.abi.is_some() || sig.variadic.is_some() {
 248                 unimplemented!();
 249         }
 250         if sig.generics.lt_token.is_some() {
 251                 for generic in sig.generics.params.iter() {
 252                         match generic {
 253                                 syn::GenericParam::Type(_)|syn::GenericParam::Lifetime(_) => {
 254                                         // We ignore these, if they're not on skipped args, we'll blow up
 255                                         // later, and lifetimes we just hope the C client enforces.
 256                                 },
 257                                 _ => unimplemented!(),
 258                         }
 259                 }
 260         }
 261
 262         let mut first_arg = true;
 263         let mut num_unused = 0;
 264         for inp in sig.inputs.iter() {
 265                 match inp {
 266                         syn::FnArg::Receiver(recv) => {
 267                                 if !recv.attrs.is_empty() || recv.reference.is_none() { unimplemented!(); }
 268                                 write!(w, "this_arg: {}{}",
 269                                         match (self_ptr, recv.mutability.is_some()) {
 270                                                 (true, true) => "*mut ",
 271                                                 (true, false) => "*const ",
 272                                                 (false, true) => "&mut ",
 273                                                 (false, false) => "&",
 274                                         }, this_param).unwrap();
 275                                 assert!(first_arg);
 276                                 first_arg = false;
 277                         },
 278                         syn::FnArg::Typed(arg) => {
 279                                 if types.skip_arg(&*arg.ty, generics) { continue; }
 280                                 if !arg.attrs.is_empty() { unimplemented!(); }
 281                                 // First get the c type so that we can check if it ends up being a reference:
 282                                 let mut c_type = Vec::new();
 283                                 types.write_c_type(&mut c_type, &*arg.ty, generics, false);
 284                                 match &*arg.pat {
 285                                         syn::Pat::Ident(ident) => {
 286                                                 if !ident.attrs.is_empty() || ident.subpat.is_some() {
 287                                                         unimplemented!();
 288                                                 }
 289                                                 write!(w, "{}{}{}: ", if first_arg { "" } else { ", " }, if !fn_decl || c_type[0] == '&' as u8 || c_type[0] == '*' as u8 { "" } else { "mut " }, ident.ident).unwrap();
 290                                                 first_arg = false;
 291                                         },
 292                                         syn::Pat::Wild(wild) => {
 293                                                 if !wild.attrs.is_empty() { unimplemented!(); }
 294                                                 write!(w, "{}unused_{}: ", if first_arg { "" } else { ", " }, num_unused).unwrap();
 295                                                 num_unused += 1;
 296                                         },
 297                                         _ => unimplemented!(),
 298                                 }
 299                                 w.write(&c_type).unwrap();
 300                         }
 301                 }
 302         }
 303         write!(w, ")").unwrap();
 304         match &sig.output {
 305                 syn::ReturnType::Type(_, rtype) => {
 306                         write!(w, " -> ").unwrap();
 307                         if let Some(mut remaining_path) = first_seg_self(&*rtype) {
 308                                 if remaining_path.next().is_none() {
 309                                         write!(w, "{}", this_param).unwrap();
 310                                         return;
 311                                 }
 312                         }
 313                         if let syn::Type::Reference(r) = &**rtype {
 314                                 // We can't return a reference, cause we allocate things on the stack.
 315                                 types.write_c_type(w, &*r.elem, generics, true);
 316                         } else {
 317                                 types.write_c_type(w, &*rtype, generics, true);
 318                         }
 319                 },
 320                 _ => {},
 321         }
 322 }
 323
 324 /// Print the main part of a method declaration body, starting with a newline after the function
 325 /// open bracket and converting each function parameter to or from C-mapped types. Ends with "let
 326 /// mut ret = " assuming the next print will be the unmapped Rust function to call followed by the
 327 /// parameters we mapped to/from C here.
 328 pub fn write_method_var_decl_body<W: std::io::Write>(w: &mut W, sig: &syn::Signature, extra_indent: &str, types: &TypeResolver, generics: Option<&GenericTypes>, to_c: bool) {
 329         let mut num_unused = 0;
 330         for inp in sig.inputs.iter() {
 331                 match inp {
 332                         syn::FnArg::Receiver(_) => {},
 333                         syn::FnArg::Typed(arg) => {
 334                                 if types.skip_arg(&*arg.ty, generics) { continue; }
 335                                 if !arg.attrs.is_empty() { unimplemented!(); }
 336                                 macro_rules! write_new_var {
 337                                         ($ident: expr, $ty: expr) => {
 338                                                 if to_c {
 339                                                         if types.write_to_c_conversion_new_var(w, &$ident, &$ty, generics, false) {
 340                                                                 write!(w, "\n\t{}", extra_indent).unwrap();
 341                                                         }
 342                                                 } else {
 343                                                         if types.write_from_c_conversion_new_var(w, &$ident, &$ty, generics) {
 344                                                                 write!(w, "\n\t{}", extra_indent).unwrap();
 345                                                         }
 346                                                 }
 347                                         }
 348                                 }
 349                                 match &*arg.pat {
 350                                         syn::Pat::Ident(ident) => {
 351                                                 if !ident.attrs.is_empty() || ident.subpat.is_some() {
 352                                                         unimplemented!();
 353                                                 }
 354                                                 write_new_var!(ident.ident, *arg.ty);
 355                                         },
 356                                         syn::Pat::Wild(w) => {
 357                                                 if !w.attrs.is_empty() { unimplemented!(); }
 358                                                 write_new_var!(syn::Ident::new(&format!("unused_{}", num_unused), Span::call_site()), *arg.ty);
 359                                                 num_unused += 1;
 360                                         },
 361                                         _ => unimplemented!(),
 362                                 }
 363                         }
 364                 }
 365         }
 366         match &sig.output {
 367                 syn::ReturnType::Type(_, _) => {
 368                         write!(w, "let mut ret = ").unwrap();
 369                 },
 370                 _ => {},
 371         }
 372 }
 373
 374 /// Prints the parameters in a method call, starting after the open parenthesis and ending with a
 375 /// final return statement returning the method's result. Should be followed by a single closing
 376 /// bracket.
 377 ///
 378 /// The return value is expected to be bound to a variable named `ret` which is available after a
 379 /// method-call-ending semicolon.
 380 pub fn write_method_call_params<W: std::io::Write>(w: &mut W, sig: &syn::Signature, extra_indent: &str, types: &TypeResolver, generics: Option<&GenericTypes>, this_type: &str, to_c: bool) {
 381         let mut first_arg = true;
 382         let mut num_unused = 0;
 383         for inp in sig.inputs.iter() {
 384                 match inp {
 385                         syn::FnArg::Receiver(recv) => {
 386                                 if !recv.attrs.is_empty() || recv.reference.is_none() { unimplemented!(); }
 387                                 if to_c {
 388                                         write!(w, "self.this_arg").unwrap();
 389                                         first_arg = false;
 390                                 }
 391                         },
 392                         syn::FnArg::Typed(arg) => {
 393                                 if types.skip_arg(&*arg.ty, generics) {
 394                                         if !to_c {
 395                                                 if !first_arg {
 396                                                         write!(w, ", ").unwrap();
 397                                                 }
 398                                                 first_arg = false;
 399                                                 types.no_arg_to_rust(w, &*arg.ty, generics);
 400                                         }
 401                                         continue;
 402                                 }
 403                                 if !arg.attrs.is_empty() { unimplemented!(); }
 404                                 macro_rules! write_ident {
 405                                         ($ident: expr) => {
 406                                                 if !first_arg {
 407                                                         write!(w, ", ").unwrap();
 408                                                 }
 409                                                 first_arg = false;
 410                                                 if to_c {
 411                                                         types.write_to_c_conversion_inline_prefix(w, &*arg.ty, generics, false);
 412                                                         write!(w, "{}", $ident).unwrap();
 413                                                         types.write_to_c_conversion_inline_suffix(w, &*arg.ty, generics, false);
 414                                                 } else {
 415                                                         types.write_from_c_conversion_prefix(w, &*arg.ty, generics);
 416                                                         write!(w, "{}", $ident).unwrap();
 417                                                         types.write_from_c_conversion_suffix(w, &*arg.ty, generics);
 418                                                 }
 419                                         }
 420                                 }
 421                                 match &*arg.pat {
 422                                         syn::Pat::Ident(ident) => {
 423                                                 if !ident.attrs.is_empty() || ident.subpat.is_some() {
 424                                                         unimplemented!();
 425                                                 }
 426                                                 write_ident!(ident.ident);
 427                                         },
 428                                         syn::Pat::Wild(w) => {
 429                                                 if !w.attrs.is_empty() { unimplemented!(); }
 430                                                 write_ident!(format!("unused_{}", num_unused));
 431                                                 num_unused += 1;
 432                                         },
 433                                         _ => unimplemented!(),
 434                                 }
 435                         }
 436                 }
 437         }
 438         write!(w, ")").unwrap();
 439         match &sig.output {
 440                 syn::ReturnType::Type(_, rtype) => {
 441                         write!(w, ";\n\t{}", extra_indent).unwrap();
 442
 443                         let self_segs_iter = first_seg_self(&*rtype);
 444                         if to_c && first_seg_self(&*rtype).is_some() {
 445                                 // Assume rather blindly that we're returning an associated trait from a C fn call to a Rust trait object.
 446                                 write!(w, "ret").unwrap();
 447                         } else if !to_c && self_segs_iter.is_some() && self_segs_iter.unwrap().next().is_none() {
 448                                 // If we're returning "Self" (and not "Self::X"), just do it manually
 449                                 write!(w, "{} {{ inner: Box::into_raw(Box::new(ret)), is_owned: true }}", this_type).unwrap();
 450                         } else if to_c {
 451                                 let new_var = types.write_from_c_conversion_new_var(w, &syn::Ident::new("ret", Span::call_site()), rtype, generics);
 452                                 if new_var {
 453                                         write!(w, "\n\t{}", extra_indent).unwrap();
 454                                 }
 455                                 types.write_from_c_conversion_prefix(w, &*rtype, generics);
 456                                 write!(w, "ret").unwrap();
 457                                 types.write_from_c_conversion_suffix(w, &*rtype, generics);
 458                         } else {
 459                                 let ret_returned = if let syn::Type::Reference(_) = &**rtype { true } else { false };
 460                                 let new_var = types.write_to_c_conversion_new_var(w, &syn::Ident::new("ret", Span::call_site()), &rtype, generics, true);
 461                                 if new_var {
 462                                         write!(w, "\n\t{}", extra_indent).unwrap();
 463                                 }
 464                                 types.write_to_c_conversion_inline_prefix(w, &rtype, generics, true);
 465                                 write!(w, "{}ret", if ret_returned && !new_var { "*" } else { "" }).unwrap();
 466                                 types.write_to_c_conversion_inline_suffix(w, &rtype, generics, true);
 467                         }
 468                 }
 469                 _ => {},
 470         }
 471 }
 472
 473 /// Prints concrete generic parameters for a struct/trait/function, including the less-than and
 474 /// greater-than symbols, if any generic parameters are defined.
 475 pub fn maybe_write_generics<W: std::io::Write>(w: &mut W, generics: &syn::Generics, types: &TypeResolver, concrete_lifetimes: bool) {
 476         let mut gen_types = GenericTypes::new();
 477         assert!(gen_types.learn_generics(generics, types));
 478         if !generics.params.is_empty() {
 479                 write!(w, "<").unwrap();
 480                 for (idx, generic) in generics.params.iter().enumerate() {
 481                         match generic {
 482                                 syn::GenericParam::Type(type_param) => {
 483                                         let mut printed_param = false;
 484                                         for bound in type_param.bounds.iter() {
 485                                                 if let syn::TypeParamBound::Trait(trait_bound) = bound {
 486                                                         assert_simple_bound(&trait_bound);
 487                                                         write!(w, "{}{}", if idx != 0 { ", " } else { "" }, gen_types.maybe_resolve_ident(&type_param.ident).unwrap()).unwrap();
 488                                                         if printed_param {
 489                                                                 unimplemented!("Can't print generic params that have multiple non-lifetime bounds");
 490                                                         }
 491                                                         printed_param = true;
 492                                                 }
 493                                         }
 494                                 },
 495                                 syn::GenericParam::Lifetime(lt) => {
 496                                         if concrete_lifetimes {
 497                                                 write!(w, "'static").unwrap();
 498                                         } else {
 499                                                 write!(w, "{}'{}", if idx != 0 { ", " } else { "" }, lt.lifetime.ident).unwrap();
 500                                         }
 501                                 },
 502                                 _ => unimplemented!(),
 503                         }
 504                 }
 505                 write!(w, ">").unwrap();
 506         }
 507 }
 508
 509