deno_bindgen_macro 0.4.1

This tool aims to simplify glue code generation for Deno FFI libraries written in Rust.
Documentation 
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use crate::meta::Glue;
use crate::meta::Symbol;
use crate::meta::Type;
use syn::AttributeArgs;
use syn::FnArg;
use syn::ItemFn;
use syn::Meta;
use syn::NestedMeta;
use syn::ReturnType;

pub fn process_function(
  function: ItemFn,
  attr: AttributeArgs,
  metadata: &mut Glue,
) -> Result<Symbol, String> {
  let params = &function.sig.inputs;
  let mut parameters = Vec::with_capacity(params.len());

  for param in params.iter() {
    match param {
      FnArg::Typed(ref val) => {
        let val = val.clone();
        let ty = match *val.ty {
          syn::Type::Path(ref ty) => {
            let segment = ty.path.segments.first().unwrap();
            let ident = segment.ident.to_string();

            match ident.as_str() {
              "i8" => Type::I8,
              "u8" => Type::U8,
              "i16" => Type::I16,
              "u16" => Type::U16,
              "i32" => Type::I32,
              "u32" => Type::U32,
              "i64" => Type::I64,
              "u64" => Type::U64,
              "usize" => Type::Usize,
              "isize" => Type::Isize,
              _ => {
                metadata.type_defs.get(&ident).expect(&format!(
                  "Type definition not found for `{}` identifier",
                  &ident,
                ));

                Type::StructEnum { ident }
              }
            }
          }
          syn::Type::Reference(ref ty) => match *ty.elem {
            syn::Type::Path(ref ty) => {
              let segment = ty.path.segments.first().unwrap();
              let ident = segment.ident.to_string();

              match ident.as_str() {
                "str" => Type::Str,
                _ => unimplemented!(),
              }
            }
            syn::Type::Slice(ref slice) => match *slice.elem {
              syn::Type::Path(ref path) => {
                let segment = path.path.segments.first().unwrap();
                let ident = segment.ident.to_string();

                match ident.as_str() {
                  "u8" => {
                    if ty.mutability.is_some() {
                      Type::BufferMut
                    } else {
                      Type::Buffer
                    }
                  }
                  _ => unimplemented!(),
                }
              }
              _ => unimplemented!(),
            },
            _ => unimplemented!(),
          },
          _ => unimplemented!(),
        };

        parameters.push(ty);
      }
      _ => unimplemented!(),
    }
  }

  let result = match &function.sig.output {
    ReturnType::Default => Type::Void,
    ReturnType::Type(_, ref ty) => match ty.as_ref() {
      syn::Type::Path(ref ty) => {
        let segment = ty.path.segments.first().unwrap();
        let ident = segment.ident.to_string();

        match ident.as_str() {
          "i8" => Type::I8,
          "u8" => Type::U8,
          "i16" => Type::I16,
          "u16" => Type::U16,
          "i32" => Type::I32,
          "u32" => Type::U32,
          "i64" => Type::I64,
          "u64" => Type::U64,
          "usize" => Type::Usize,
          "isize" => Type::Isize,
          "f32" => Type::F32,
          "f64" => Type::F64,
          _ => panic!("{} return type not supported by Deno FFI", ident),
        }
      }
      syn::Type::Reference(ref ty) => match *ty.elem {
        syn::Type::Slice(ref slice) => match *slice.elem {
          syn::Type::Path(ref path) => {
            let segment = path.path.segments.first().unwrap();
            let ident = segment.ident.to_string();

            match ident.as_str() {
              "u8" => {
                if ty.mutability.is_some() {
                  Type::BufferMut
                } else {
                  Type::Buffer
                }
              }
              _ => unimplemented!(),
            }
          }
          _ => unimplemented!(),
        },
        _ => unimplemented!(),
      },
      _ => unimplemented!(),
    },
  };

  let symbol_name = function.sig.ident.to_string();
  let non_blocking = match attr.get(0).as_ref() {
    Some(NestedMeta::Meta(Meta::Path(ref attr_ident))) => {
      attr_ident.is_ident("non_blocking")
    }
    _ => false,
  };

  let symbol = Symbol {
    parameters,
    result,
    non_blocking,
  };
  metadata.symbols.insert(symbol_name, symbol.clone());

  Ok(symbol)
}