Squashed 'third_party/autocxx/' content from commit 629e8fa53

git-subtree-dir: third_party/autocxx
git-subtree-split: 629e8fa531a633164c0b52e2a3cab536d4cd0849
Signed-off-by: Brian Silverman <bsilver16384@gmail.com>
Change-Id: I62a03b0049f49adf029e0204639cdb5468dde1a1
diff --git a/engine/src/cxxbridge.rs b/engine/src/cxxbridge.rs
new file mode 100644
index 0000000..28163af
--- /dev/null
+++ b/engine/src/cxxbridge.rs
@@ -0,0 +1,45 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use proc_macro2::TokenStream;
+use quote::{ToTokens, TokenStreamExt};
+use syn::ItemMod;
+
+use crate::{do_cxx_cpp_generation, parse_file::CppBuildable, CppCodegenOptions, GeneratedCpp};
+
+/// A struct to represent a cxx::bridge (i.e. some manual bindings)
+/// found in a file. autocxx knows about them so that we can generate C++
+/// for both manual and automatic bindings using the same tooling.
+pub struct CxxBridge {
+    tokens: TokenStream,
+}
+
+impl From<ItemMod> for CxxBridge {
+    fn from(itm: ItemMod) -> Self {
+        Self {
+            tokens: itm.to_token_stream(),
+        }
+    }
+}
+
+impl ToTokens for CxxBridge {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        tokens.append_all(self.tokens.clone());
+    }
+}
+
+impl CppBuildable for CxxBridge {
+    fn generate_h_and_cxx(
+        &self,
+        cpp_codegen_options: &CppCodegenOptions,
+    ) -> Result<GeneratedCpp, cxx_gen::Error> {
+        let header_name = cpp_codegen_options.cxxgen_header_namer.name_header();
+        let fp = do_cxx_cpp_generation(self.tokens.clone(), cpp_codegen_options, header_name)?;
+        Ok(GeneratedCpp(vec![fp]))
+    }
+}