Initial UniFFI C++ Bindgen

.changeset/add_cpp_bindgen_command.md

@@ -0,0 +1,5 @@
+---
+livekit-ffi: patch
+---
+
+Add a workspace-owned command for generating C++ bindings from `livekit-ffi` with the pinned LiveKit UniFFI C++ generator.

livekit-ffi/Cargo.toml

@@ -44,7 +44,7 @@ downcast-rs = "1.2"
 console-subscriber = { workspace = true, features = ["parking_lot"], optional = true }
 bytes = { workspace = true }
 from_variants = "1.0.2"
-uniffi = { workspace = true, features = ["scaffolding-ffi-buffer-fns"] }
+uniffi = { workspace = true, features = ["scaffolding-ffi-buffer-fns", "tokio"] }
 
 [target.'cfg(target_os = "android")'.dependencies]
 jni = "0.21.1"

tools/bindgens/src/bin/uniffi-bindgen-cpp.rs

@@ -0,0 +1,85 @@
+// Copyright 2026 LiveKit, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! The pinned UniFFI C++ bindgen CLI used by LiveKit SDK consumers.
+//!
+//! The C++ generator is a binary-only crate, so this workspace command installs
+//! the pinned revision into the workspace target directory and forwards all
+//! arguments to it. Generate C++ bindings from `livekit-ffi`, for example:
+//! `cargo run -p bindgens --bin uniffi-bindgen-cpp -- \
+//!     --library target/debug/liblivekit_ffi.dylib --out-dir <dir>`
+
+use std::{
+    env,
+    path::{Path, PathBuf},
+    process::{Command, ExitCode},
+};
+
+const REPOSITORY: &str = "https://github.com/livekit/uniffi-bindgen-cpp.git";
+const REVISION: &str = "7d54c1c56e0e4c46772ef4c2b5be3cb26396cbdb";
+
+fn main() -> ExitCode {
+    match run() {
+        Ok(code) => code,
+        Err(error) => {
+            eprintln!("uniffi-bindgen-cpp: {error}");
+            ExitCode::FAILURE
+        }
+    }
+}
+
+fn run() -> Result<ExitCode, String> {
+    let install_root = install_root();
+    let executable =
+        install_root.join("bin").join(format!("uniffi-bindgen-cpp{}", env::consts::EXE_SUFFIX));
+
+    if !executable.is_file() {
+        install(&install_root)?;
+    }
+
+    let status = Command::new(&executable)
+        .args(env::args_os().skip(1))
+        .status()
+        .map_err(|error| format!("failed to run {}: {error}", executable.display()))?;
+
+    match status.code() {
+        Some(code) if (0..=u8::MAX as i32).contains(&code) => Ok(ExitCode::from(code as u8)),
+        Some(code) => Err(format!("generator exited with unsupported status {code}")),
+        None => Err("generator terminated without an exit status".to_owned()),
+    }
+}
+
+fn install_root() -> PathBuf {
+    Path::new(env!("CARGO_MANIFEST_DIR"))
+        .join("../..")
+        .join("target")
+        .join("uniffi-bindgen-cpp")
+        .join(REVISION)
+}
+
+fn install(install_root: &Path) -> Result<(), String> {
+    let cargo = env::var_os("CARGO").unwrap_or_else(|| "cargo".into());
+    let status = Command::new(cargo)
+        .args(["install", "--locked", "--git", REPOSITORY, "--rev", REVISION, "--root"])
+        .arg(install_root)
+        .arg("uniffi-bindgen-cpp")
+        .status()
+        .map_err(|error| format!("failed to install pinned C++ generator: {error}"))?;
+
+    if status.success() {
+        Ok(())
+    } else {
+        Err(format!("installing pinned C++ generator failed with {status}"))
+    }
+}