bindgen: pre-generate bindings (#402)

README.md

@@ -34,6 +34,14 @@ $ git submodule update --init --recursive # if you just cloned the repository
 $ cargo build
 ```
 
+Bindings are pre-generated for x86_64 Linux. For other platforms, bindings are generated at compile time.
+
+If the content in librocksdb_sys/crocksdb/crocksdb/c.h is updated, you may need to regenerate bindings:
+
+```
+$ ./scripts/generate-bindings.sh
+```
+
 ## Running
 
 ###### Cargo.toml

librocksdb_sys/Cargo.toml

@@ -23,6 +23,7 @@ sse = ["libtitan_sys/sse"]
 [build-dependencies]
 cc = "1.0.3"
 cmake = "0.1"
+bindgen = "0.52"
 
 [dependencies.jemalloc-sys]
 version = "0.1.8"

librocksdb_sys/build.rs

@@ -11,6 +11,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+extern crate bindgen;
 extern crate cc;
 extern crate cmake;
 
@@ -24,7 +25,52 @@ use std::{env, str};
 // See https://github.com/gnzlbg/jemallocator/blob/bfc89192971e026e6423d9ee5aaa02bc56585c58/jemalloc-sys/build.rs#L45
 const NO_JEMALLOC_TARGETS: &[&str] = &["android", "dragonfly", "musl", "darwin"];
 
+// Generate the bindings to rocksdb C-API.
+// Try to disable the generation of platform-related bindings.
+fn bindgen_rocksdb(file_path: &PathBuf) {
+    let bindings = bindgen::Builder::default()
+        .header("crocksdb/crocksdb/c.h")
+        .ctypes_prefix("libc")
+        .generate()
+        .expect("unable to generate rocksdb bindings");
+
+    bindings
+        .write_to_file(file_path)
+        .expect("unable to write rocksdb bindings");
+}
+
+// Determine if need to update bindings. Supported platforms do not
+// need to be updated by default unless the UPDATE_BIND is specified.
+// Other platforms use bindgen to generate the bindings every time.
+fn config_binding_path() {
+    let file_path: PathBuf;
+
+    match env::var("TARGET").unwrap_or("".to_owned()).as_str() {
+        "x86_64-unknown-linux-gnu" => {
+            file_path = PathBuf::from(env::var("CARGO_MANIFEST_DIR").unwrap())
+                .join("bindings")
+                .join("x86_64-unknown-linux-gnu-bindings.rs");
+            if env::var("UPDATE_BIND")
+                .map(|s| s == "1".to_owned())
+                .unwrap_or(false)
+            {
+                bindgen_rocksdb(&file_path);
+            }
+        }
+        _ => {
+            file_path = PathBuf::from(env::var("OUT_DIR").unwrap()).join("rocksdb-bindings.rs");
+            bindgen_rocksdb(&file_path);
+        }
+    };
+    println!(
+        "cargo:rustc-env=BINDING_PATH={}",
+        file_path.to_str().unwrap()
+    );
+}
+
 fn main() {
+    println!("cargo:rerun-if-env-changed=UPDATE_BIND");
+
     let mut build = build_rocksdb();
 
     build.cpp(true).file("crocksdb/c.cc");
@@ -134,6 +180,8 @@ fn build_rocksdb() -> Build {
         build.define("OS_FREEBSD", None);
     }
 
+    config_binding_path();
+
     let cur_dir = env::current_dir().unwrap();
     build.include(cur_dir.join("rocksdb").join("include"));
     build.include(cur_dir.join("rocksdb"));

scripts/generate-bindings.sh

+#!/bin/bash
+
+# NOTE: 
+# This script is only used when you want to generate bindings yourself.
+# The generated bindings will overwrite librocksdb_sys/bindings/*
+
+export UPDATE_BIND=1
+cargo build  --target x86_64-unknown-linux-gnu
+rustfmt librocksdb_sys/bindings/*