Support libsodium

Cargo.toml

@@ -24,11 +24,12 @@ default = ["zmq_has"]
 # this feature is a no-op and only present for backward-compatibility;
 # it will be removed in the next API-breaking release.
 zmq_has = []
+libsodium = ["zmq-sys/libsodium"]
 
 [dependencies]
 bitflags = "1.0"
 libc = "0.2.15"
-zmq-sys = { version = "0.12.0", path = "zmq-sys" }
+zmq-sys = { version = "0.12.1", path = "zmq-sys" }
 
 [dev-dependencies]
 trybuild = { version = "1" }

zmq-sys/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "zmq-sys"
-version = "0.12.0"
+version = "0.12.1"
 authors = [
     "[email protected]",
     "[email protected]",
@@ -14,9 +14,11 @@ build = "build/main.rs"
 links = "zmq"
 
 [features]
+libsodium = ["dep:libsodium-sys-stable"]
 
 [dependencies]
 libc = "0.2.15"
+libsodium-sys-stable = { version = "1.0", optional = true }
 
 [build-dependencies]
 system-deps = "6"

zmq-sys/build/main.rs

@@ -1,3 +1,5 @@
+use std::env;
+
 pub fn configure() {
     println!("cargo:rerun-if-changed=build/main.rs");
     println!("cargo:rerun-if-env-changed=PROFILE");
@@ -6,8 +8,19 @@ pub fn configure() {
     // relying on `tweetnacl`. However since this `tweetnacl` [has never been
     // audited nor is ready for production](https://github.com/zeromq/libzmq/issues/3006),
     // we link against `libsodium` to enable `ZMQ_CURVE`.
+    let maybe_libsodium = if cfg!(feature = "libsodium") {
+        let lib_dir = env::var("DEP_SODIUM_LIB")
+            .expect("build metadata `DEP_SODIUM_LIB` required");
+        let include_dir = env::var("DEP_SODIUM_INCLUDE")
+            .expect("build metadata `DEP_SODIUM_INCLUDE` required");
+
+        Some(zeromq_src::LibLocation::new(lib_dir, include_dir))
+    } else {
+        None
+    };
+
     zeromq_src::Build::new()
-        .with_libsodium(None)
+        .with_libsodium(maybe_libsodium)
         .build();
 }