feat: optionally use system liblsl

lsl-sys/Cargo.toml

@@ -10,5 +10,16 @@ keywords = ["lsl", "ffi"]
 categories = ["external-ffi-bindings"]
 links = "lsl"
 
+[features]
+system = ["dep:pkg-config", "dep:vcpkg"]
+bundled = ["dep:cmake"]
+bindgen = ["dep:bindgen"]
+default = ["system", "bundled", "bindgen"]
+
 [build-dependencies]
-cmake = "0.1.44"
+cmake = { version = "0.1.44", optional = true }
+bindgen = { version = "0.72", optional = true }
+pkg-config = { version = "0.3", optional = true }
+
+[target.'cfg(windows)'.build-dependencies]
+vcpkg = { version = "0.2", optional = true }

lsl-sys/build.rs

@@ -1,29 +1,80 @@
 use std::env;
+use std::path::{Path, PathBuf};
 
 fn main() {
-    // TODO: find out if liblsl already present on system and usable (if so, link to that instead)
-    // println!("cargo:warning={}", "rebuilding...");
-    build_liblsl();
+    let include_dirs = resolve_lsl();
+
+    #[cfg(feature = "bindgen")]
+    {
+        let header = find_header(&include_dirs, "lsl_c.h").unwrap_or_else(|| {
+            panic!(
+                "lsl_c.h not found in any resolved include dir: {include_dirs:?}.\n\
+                 If liblsl is installed in a non-standard location, make sure pkg-config \
+                 can find its .pc file (set PKG_CONFIG_PATH), or on Windows that vcpkg \
+                 knows about the 'lsl' port."
+            )
+        });
+        run_bindgen(&header, &include_dirs);
+    }
+
+    let _ = include_dirs;
+}
+
+#[cfg(all(feature = "system", feature = "bundled"))]
+fn resolve_lsl() -> Vec<PathBuf> {
+    try_system().unwrap_or_else(build_liblsl)
+}
+
+#[cfg(all(feature = "system", not(feature = "bundled")))]
+fn resolve_lsl() -> Vec<PathBuf> {
+    try_system().unwrap_or_else(|| {
+        panic!(
+            "liblsl not found via pkg-config (or vcpkg on Windows). Install liblsl's \
+             development package, or enable the 'bundled' feature to build it from source."
+        )
+    })
 }
 
-// Build the liblsl library from source using cmake
-fn build_liblsl() {
+#[cfg(all(not(feature = "system"), feature = "bundled"))]
+fn resolve_lsl() -> Vec<PathBuf> {
+    build_liblsl()
+}
+
+#[cfg(not(any(feature = "system", feature = "bundled")))]
+fn resolve_lsl() -> Vec<PathBuf> {
+    compile_error!("at least one of the 'system' or 'bundled' features must be enabled")
+}
+
+#[cfg(feature = "system")]
+fn try_system() -> Option<Vec<PathBuf>> {
+    println!("cargo:rerun-if-env-changed=PKG_CONFIG_PATH");
+
+    if let Ok(lib) = pkg_config::Config::new().probe("lsl") {
+        return Some(lib.include_paths);
+    }
+
+    #[cfg(windows)]
+    if let Ok(lib) = vcpkg::find_package("lsl") {
+        return Some(lib.include_paths);
+    }
+
+    None
+}
+
+fn find_header(dirs: &[PathBuf], name: &str) -> Option<PathBuf> {
+    dirs.iter().map(|d| d.join(name)).find(|p| p.exists())
+}
+
+#[cfg(feature = "bundled")]
+fn build_liblsl() -> Vec<PathBuf> {
     let target = env::var("TARGET").unwrap();
-
-    // build with cmake
+
     let mut cfg = cmake::Config::new("liblsl");
-    cfg
-        .define("LSL_NO_FANCY_LIBNAME", "ON")
+    cfg.define("LSL_NO_FANCY_LIBNAME", "ON")
         .define("LSL_BUILD_STATIC", "ON");
     if target.contains("msvc") {
-        // override some C/CXX flags that the cmake crate splices in on Windows
-        // (these cause the build to fail)...
-        // * /EHsc sets the correct exception handling mode
-        // * /GR enables RTTI
-        // * /MD links in the msvcrt as a DLL instead of statically
         let cxx_args = " /nologo /EHsc /MD /GR";
-        cfg 
-            .define("WIN32", "1")
+        cfg.define("WIN32", "1")
             .define("_WINDOWS", "1")
             .define("CMAKE_C_FLAGS", cxx_args)
             .define("CMAKE_CXX_FLAGS", cxx_args)
@@ -34,23 +85,37 @@ fn build_liblsl() {
     }
     let install_dir = cfg.build();
 
-    // emit link directives
     let libdir = install_dir.join("lib");
-    let libname = "lsl";
-    println!(
-        "cargo:rustc-link-search=native={}",
-        libdir.to_str().unwrap()
-    );
-    println!("cargo:rustc-link-lib=static={}", libname);
-
-    // make sure we also link some additional libs
+    println!("cargo:rustc-link-search=native={}", libdir.display());
+    println!("cargo:rustc-link-lib=static=lsl");
+
     if target.contains("linux") {
         println!("cargo:rustc-link-lib=dylib=stdc++");
     } else if target.contains("windows") {
-        // TODO: this is a shortcoming in the current cmake file, which should be       
-        //       linking in this library (once this is fixed, we should remove this)
         println!("cargo:rustc-link-lib=dylib=bcrypt");
     } else {
         println!("cargo:rustc-link-lib=dylib=c++");
     }
+
+    vec![install_dir.join("include")]
+}
+
+#[cfg(feature = "bindgen")]
+fn run_bindgen(header: &Path, include_dirs: &[PathBuf]) {
+    let mut builder = bindgen::Builder::default()
+        .header(header.to_str().expect("header path is not valid UTF-8"))
+        .allowlist_function("^lsl_.*")
+        .allowlist_var("^lsl_.*")
+        .allowlist_type("^lsl_.*");
+
+    for dir in include_dirs {
+        builder = builder.clang_arg(format!("-I{}", dir.display()));
+    }
+
+    let bindings = builder.generate().expect("failed to generate liblsl bindings");
+
+    let out = PathBuf::from(env::var("OUT_DIR").unwrap()).join("generated.rs");
+    bindings
+        .write_to_file(&out)
+        .expect("failed to write liblsl bindings");
 }

lsl-sys/src/lib.rs

@@ -1,7 +1,19 @@
 #[allow(non_camel_case_types)]
 #[allow(non_upper_case_globals)]
+#[cfg(not(feature = "bindgen"))]
 mod generated;
 
+#[allow(non_camel_case_types)]
+#[allow(non_upper_case_globals)]
+#[cfg(feature = "bindgen")]
+mod generated {
+    include!(concat!(env!("OUT_DIR"), "/generated.rs"));
+}
+
+#[cfg(feature = "system")]
+#[link(name = "lsl")]
+extern "C" {}
+
 pub use generated::*;
 
 #[cfg(test)]