Add support for building with io_uring on Linux. (rust-rocksdb#621)

Cargo.toml

@@ -22,6 +22,7 @@ members = ["librocksdb-sys"]
 [features]
 default = ["snappy", "lz4", "zstd", "zlib", "bzip2"]
 jemalloc = ["librocksdb-sys/jemalloc"]
+io-uring = ["librocksdb-sys/io-uring"]
 valgrind = []
 snappy = ["librocksdb-sys/snappy"]
 lz4 = ["librocksdb-sys/lz4"]

librocksdb-sys/Cargo.toml

@@ -15,6 +15,7 @@ links = "rocksdb"
 default = [ "static" ]
 jemalloc = ["tikv-jemalloc-sys"]
 static = ["libz-sys?/static", "bzip2-sys?/static"]
+io-uring = ["pkg-config"]
 snappy = []
 lz4 = ["lz4-sys"]
 zstd = ["zstd-sys"]
@@ -38,3 +39,4 @@ uuid = { version = "1.0", features = ["v4"] }
 cc = { version = "1.0", features = ["parallel"] }
 bindgen = { version = "0.60", default-features = false, features = ["runtime"] }
 glob = "0.3"
+pkg-config = { version = "0.3", optional = true }

librocksdb-sys/build.rs

@@ -222,6 +222,13 @@ fn build_rocksdb() {
         config.define("WITH_JEMALLOC", "ON");
     }
 
+    #[cfg(feature = "io-uring")]
+    if target.contains("linux") {
+        pkg_config::probe_library("liburing")
+            .expect("The io-uring feature was requested but the library is not available");
+        config.define("ROCKSDB_IOURING_PRESENT", Some("1"));
+    }
+
     if target.contains("msvc") {
         config.flag("-EHsc");
         config.flag("-std:c++17");