Add protoc-gen-prost crate, a protoc codegen plugin

Cargo.toml

@@ -21,6 +21,7 @@ members = [
   "prost-derive",
   "prost-types",
   "protobuf",
+  "protoc-gen-prost",
   "tests",
   "tests-2015",
   "tests-no-std",

protoc-gen-prost/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "protoc-gen-prost"
+version = "0.7.0"
+authors = ["Tokio Contributors <[email protected]>"]
+license = "Apache-2.0"
+repository = "https://github.com/tokio-rs/prost"
+documentation = "https://docs.rs/prost-build"
+readme = "README.md"
+description = "A Protocol Buffers implementation for the Rust Language."
+edition = "2018"
+
+[dependencies]
+prost = { version = "0.7.0", path = "..", default-features = false }
+prost-build = { version = "0.7.0", path = "../prost-build", default-features = false }
+prost-types = { version = "0.7.0", path = "../prost-types", default-features = false }

protoc-gen-prost/src/main.rs

@@ -0,0 +1,26 @@
+use std::io::{Read, Result, Write};
+
+use prost::Message;
+use prost_build::Config;
+use prost_types::compiler::CodeGeneratorRequest;
+
+fn main() {
+    if let Err(e) = faillible_main() {
+        eprintln!("{}", e);
+        std::process::exit(1);
+    }
+}
+
+fn faillible_main() -> Result<()> {
+    let mut buf = Vec::new();
+    std::io::stdin().read_to_end(&mut buf)?;
+
+    let req = CodeGeneratorRequest::decode(buf.as_slice()).unwrap();
+    let res = Config::new_from_opts(req.parameter(), true).compile_request(req);
+
+    buf.clear();
+    res.encode(&mut buf).unwrap();
+    std::io::stdout().write_all(&buf)?;
+
+    Ok(())
+}