add zc_config_from_env function

docs/api.rst

@@ -399,6 +399,7 @@ Functions
 .. doxygenfunction:: z_config_default
 .. doxygenfunction:: z_config_client
 .. doxygenfunction:: z_config_peer
+.. doxygenfunction:: zc_config_from_env
 .. doxygenfunction:: zc_config_from_file
 .. doxygenfunction:: zc_config_from_str
 .. doxygenfunction:: zc_config_insert_json

include/zenoh_commons.h

@@ -3548,6 +3548,12 @@ z_error_t z_view_string_wrap(struct z_view_string_t *this_,
 ZENOHC_API
 z_error_t z_whatami_to_view_string(enum z_whatami_t whatami,
                                    struct z_view_string_t *str_out);
+/**
+ * Constructs a configuration by parsing a file path stored in ZENOH_CONFIG environmental variable.
+ *
+ * Returns 0 in case of success, negative error code otherwise.
+ */
+ZENOHC_API z_error_t zc_config_from_env(struct z_owned_config_t *this_);
 /**
  * Constructs a configuration by parsing a file at `path`. Currently supported format is JSON5, a superset of JSON.
  *

src/config.rs

@@ -294,6 +294,26 @@ pub unsafe extern "C" fn zc_config_from_file(
     res
 }
 
+/// Constructs a configuration by parsing a file path stored in ZENOH_CONFIG environmental variable.
+///
+/// Returns 0 in case of success, negative error code otherwise.
+#[allow(clippy::missing_safety_doc)]
+#[no_mangle]
+pub unsafe extern "C" fn zc_config_from_env(
+    this: &mut MaybeUninit<z_owned_config_t>,
+) -> errors::z_error_t {
+    match Config::from_env() {
+        Ok(c) => {
+            this.as_rust_type_mut_uninit().write(Some(c));
+            errors::Z_OK
+        }
+        Err(e) => {
+            tracing::error!("{}", e);
+            errors::Z_EIO
+        }
+    }
+}
+
 /// Constructs a default peer mode configuration.
 #[allow(clippy::missing_safety_doc)]
 #[no_mangle]