Add lo_set_external_plugin_paths()

To allow the external plugins paths to be provided, overriding the
defaults.

ffi/src/handle.rs

@@ -28,7 +28,9 @@ use loadorder::GameSettings;
 use loadorder::WritableLoadOrder;
 
 use crate::constants::*;
-use crate::helpers::{error, handle_error, to_c_string, to_c_string_array, to_str};
+use crate::helpers::{
+    error, handle_error, to_c_string, to_c_string_array, to_path_buf_vec, to_str,
+};
 
 /// A structure that holds all game-specific data used by libloadorder.
 ///
@@ -354,3 +356,43 @@ pub unsafe extern "C" fn lo_get_active_plugins_file_path(
     })
     .unwrap_or(LIBLO_ERROR_PANICKED)
 }
+
+/// Sets the external plugin paths to be recognised by the given handle.
+///
+/// If the load order contains plugins that are installed outside of the game's plugins directory,
+/// this function can be used to provide the paths to those plugins so that libloadorder is able to
+/// find them.
+///
+/// If external plugins exist, this function must be called before performing any operations on
+/// the load order to avoid any unexpected behaviour.
+///
+/// Returns `LIBLO_OK` if successful, otherwise a `LIBLO_ERROR_*` code is returned.
+#[no_mangle]
+pub unsafe extern "C" fn lo_set_external_plugin_paths(
+    handle: lo_game_handle,
+    paths: *const *const c_char,
+    num_paths: size_t,
+) -> c_uint {
+    catch_unwind(|| {
+        if handle.is_null() || paths.is_null() {
+            return error(LIBLO_ERROR_INVALID_ARGS, "Null pointer passed");
+        }
+
+        let mut handle = match (*handle).write() {
+            Err(e) => return error(LIBLO_ERROR_POISONED_THREAD_LOCK, &e.to_string()),
+            Ok(h) => h,
+        };
+
+        let plugin_paths = match to_path_buf_vec(paths, num_paths) {
+            Ok(x) => x,
+            Err(x) => return error(x, "A filename contained a null byte"),
+        };
+
+        handle
+            .game_settings_mut()
+            .set_external_plugin_paths(plugin_paths);
+
+        LIBLO_OK
+    })
+    .unwrap_or(LIBLO_ERROR_PANICKED)
+}

ffi/src/helpers.rs

@@ -19,6 +19,7 @@
 use std::ffi::{CStr, CString};
 use std::io;
 use std::mem;
+use std::path::PathBuf;
 use std::slice;
 
 use libc::{c_char, c_uint, size_t};
@@ -114,3 +115,13 @@ pub unsafe fn to_str_vec<'a>(
         .map(|c| to_str(*c))
         .collect()
 }
+
+pub unsafe fn to_path_buf_vec(
+    array: *const *const c_char,
+    array_size: usize,
+) -> Result<Vec<PathBuf>, u32> {
+    slice::from_raw_parts(array, array_size)
+        .iter()
+        .map(|c| to_str(*c).map(PathBuf::from))
+        .collect()
+}

ffi/tests/ffi.c

@@ -154,6 +154,17 @@ void test_lo_get_active_plugins_file_path() {
   lo_destroy_handle(handle);
 }
 
+void test_lo_set_external_plugin_paths() {
+printf("testing lo_set_external_plugin_paths()...\n");
+  lo_game_handle handle = create_handle();
+
+  const char * paths[] = { "Blank.esm" };
+  unsigned int return_code = lo_set_external_plugin_paths(handle, paths, 1);
+
+  assert(return_code == 0);
+  lo_destroy_handle(handle);
+}
+
 void test_lo_set_active_plugins() {
   printf("testing lo_set_active_plugins()...\n");
   lo_game_handle handle = create_handle();
@@ -300,6 +311,7 @@ int main(void) {
   test_lo_fix_plugin_lists();
   test_lo_get_implicitly_active_plugins();
   test_lo_get_active_plugins_file_path();
+  test_lo_set_external_plugin_paths();
 
   test_lo_set_active_plugins();
   test_lo_get_active_plugins();

ffi/tests/ffi.cpp

@@ -157,6 +157,17 @@ void test_lo_get_active_plugins_file_path() {
   lo_destroy_handle(handle);
 }
 
+void test_lo_set_external_plugin_paths() {
+printf("testing lo_set_external_plugin_paths()...\n");
+  lo_game_handle handle = create_handle();
+
+  const char * paths[] = { "Blank.esm" };
+  unsigned int return_code = lo_set_external_plugin_paths(handle, paths, 1);
+
+  assert(return_code == 0);
+  lo_destroy_handle(handle);
+}
+
 void test_lo_set_active_plugins() {
   printf("testing lo_set_active_plugins()...\n");
   lo_game_handle handle = create_handle();
@@ -325,6 +336,7 @@ int main(void) {
   test_lo_fix_plugin_lists();
   test_lo_get_implicitly_active_plugins();
   test_lo_get_active_plugins_file_path();
+  test_lo_set_external_plugin_paths();
 
   test_lo_set_active_plugins();
   test_lo_get_active_plugins();