Convert all bool-returns to Results

Additionally:
* Make open2 fallible too
* Use a Result the entire time in open and open2, instead of going from Option to Result
* Specify c_int instead of i32 since apparently the size "may differ on some esoteric systems"; I suspect it won't compile on whatever those are but might as well improve the situation
* Avoid a maybe-possible panic in get_voice_type. Probably can't happen but I'm not 100% certain, so I made it fallible
* Add a missing null check to get_language

speech-dispatcher/examples/hello_world.rs

@@ -22,18 +22,18 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
             connection.client_id()
         ),
     );
-    connection.set_voice_rate(100);
+    connection.set_voice_rate(100)?;
     connection.say(Priority::Important, "This is faster.");
-    connection.set_voice_rate(0);
+    connection.set_voice_rate(0)?;
-    connection.set_spelling(true);
+    connection.set_spelling(true)?;
     connection.say(Priority::Important, "This is spelled.");
-    connection.set_spelling(false);
+    connection.set_spelling(false)?;
-    connection.set_punctuation(Punctuation::All);
+    connection.set_punctuation(Punctuation::All)?;
     connection.say(
         Priority::Important,
         "This statement, unlike others, has punctuation that is spoken!",
     );
-    connection.set_punctuation(Punctuation::None);
+    connection.set_punctuation(Punctuation::None)?;
     let mut _input = String::new();
     io::stdin().read_line(&mut _input).unwrap();
     Ok(())

speech-dispatcher/src/lib.rs

@@ -5,7 +5,7 @@ use std::{
     ffi::{CStr, CString},
     fmt,
     marker::Send,
-    os::raw::c_char,
+    os::raw::{c_char, c_int},
     sync::Mutex,
 };
 
@@ -82,8 +82,12 @@ pub enum CapitalLetters {
     Icon = SPDCapitalLetters::SPD_CAP_ICON,
 }
 
-fn i32_to_bool(v: i32) -> bool {
+/// Converts a `0` to a success and everything else to an error.
-    v == 1
+fn c_int_to_result(r: c_int) -> Result<(), SpeechDispatcherError> {
+    match r {
+        0 => Ok(()),
+        _ => Err(SpeechDispatcherError::OperationFailed),
+    }
 }
 
 #[derive(Default)]
@@ -151,7 +155,11 @@ unsafe extern "C" fn cb_im(msg_id: u64, client_id: u64, state: u32, index_mark:
 
 #[derive(Debug)]
 pub enum SpeechDispatcherError {
+    /// speech-dispatcher failed to initialize. Ensure speech-dispatcher is actually working on
+    /// your system; for example, does the command `spd-say hello` work?
     InitializationError,
+    /// The operation failed
+    OperationFailed,
 }
 
 impl std::error::Error for SpeechDispatcherError {}
@@ -161,6 +169,7 @@ impl fmt::Display for SpeechDispatcherError {
         use SpeechDispatcherError::*;
         match self {
             InitializationError => write!(f, "Failed to initialize"),
+            OperationFailed => write!(f, "Operation failed"),
         }
     }
 }
@@ -183,18 +192,14 @@ impl Connection {
                 mode as u32,
             );
             if c.is_null() {
-                None
+                Err(SpeechDispatcherError::InitializationError)
             } else {
-                Some(Self::setup_connection(c))
+                Ok(Self::setup_connection(c))
             }
         };
-        if let Some(connection) = connection {
+        let mut c = Self(connection?, 0);
-            let mut c = Self(connection, 0);
+        c.setup()?;
-            c.setup();
+        Ok(c)
-            Ok(c)
-        } else {
-            Err(SpeechDispatcherError::InitializationError)
-        }
     }
 
     pub unsafe fn open2<S: Into<String>>(
@@ -204,7 +209,7 @@ impl Connection {
         mode: Mode,
         address: *mut Address,
         autospawn: bool,
-    ) -> Self {
+    ) -> Result<Self, SpeechDispatcherError> {
         let auto_spawn = if autospawn { 1 } else { 0 };
         let error_result = vec![CString::new("").unwrap().into_raw()].as_mut_ptr();
         let clientname = CString::new(client_name.into()).unwrap();
@@ -220,11 +225,15 @@ impl Connection {
                 auto_spawn,
                 error_result,
             );
-            Self::setup_connection(c)
+            if c.is_null() {
+                Err(SpeechDispatcherError::InitializationError)
+            } else {
+                Ok(Self::setup_connection(c))
+            }
         };
-        let mut c = Self(connection, 0);
+        let mut c = Self(connection?, 0);
-        c.setup();
+        c.setup()?;
-        c
+        Ok(c)
     }
 
     unsafe fn setup_connection(c: *mut SPDConnection) -> *mut SPDConnection {
@@ -237,7 +246,7 @@ impl Connection {
         c
     }
 
-    fn setup(&mut self) {
+    fn setup(&mut self) -> Result<(), SpeechDispatcherError> {
         let client_id = self.send_data("HISTORY GET CLIENT_ID\r\n", true);
         if let Some(client_id) = client_id {
             let client_id: Vec<&str> = client_id.split("\r\n").collect();
@@ -252,7 +261,9 @@ impl Connection {
             }
         }
         callbacks.lock().unwrap().insert(self.1, Default::default());
-        self.set_notification_on(Notification::All);
+        self.set_notification_on(Notification::All)
+            .map_err(|_| SpeechDispatcherError::InitializationError)?;
+        Ok(())
     }
 
     pub fn close(&self) {
@@ -281,107 +292,123 @@ impl Connection {
         }
     }
 
-    pub fn stop(&self) -> bool {
+    pub fn stop(&self) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_stop(self.0) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn stop_all(&self) -> bool {
+    pub fn stop_all(&self) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_stop_all(self.0) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn stop_uid(&self, target_uid: i32) -> bool {
+    pub fn stop_uid(&self, target_uid: i32) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_stop_uid(self.0, target_uid) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn cancel(&self) -> bool {
+    pub fn cancel(&self) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_cancel(self.0) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn cancel_all(&self) -> bool {
+    pub fn cancel_all(&self) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_cancel_all(self.0) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn cancel_uid(&self, target_uid: i32) -> bool {
+    pub fn cancel_uid(&self, target_uid: i32) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_cancel_uid(self.0, target_uid) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn pause(&self) -> bool {
+    pub fn pause(&self) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_pause(self.0) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn pause_all(&self) -> bool {
+    pub fn pause_all(&self) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_pause_all(self.0) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn pause_uid(&self, target_uid: i32) -> bool {
+    pub fn pause_uid(&self, target_uid: i32) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_pause_uid(self.0, target_uid) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn resume(&self) -> bool {
+    pub fn resume(&self) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_resume(self.0) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn resume_all(&self) -> bool {
+    pub fn resume_all(&self) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_resume_all(self.0) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn resume_uid(&self, target_uid: i32) -> bool {
+    pub fn resume_uid(&self, target_uid: i32) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_resume_uid(self.0, target_uid) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn key<S: Into<String>>(&self, priority: Priority, key_name: S) -> bool {
+    pub fn key<S: Into<String>>(
+        &self,
+        priority: Priority,
+        key_name: S,
+    ) -> Result<(), SpeechDispatcherError> {
         let param = CString::new(key_name.into()).unwrap();
         let v = unsafe { spd_key(self.0, priority as u32, param.as_ptr()) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn char<S: Into<String>>(&self, priority: Priority, char: S) -> bool {
+    pub fn char<S: Into<String>>(
+        &self,
+        priority: Priority,
+        char: S,
+    ) -> Result<(), SpeechDispatcherError> {
         let param = CString::new(char.into()).unwrap();
         let v = unsafe { spd_char(self.0, priority as u32, param.as_ptr()) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn wchar(&self, priority: Priority, wchar: i32) -> bool {
+    pub fn wchar(&self, priority: Priority, wchar: i32) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_wchar(self.0, priority as u32, wchar as wchar_t) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn sound_icon<S: Into<String>>(&self, priority: Priority, icon_name: S) -> bool {
+    pub fn sound_icon<S: Into<String>>(
+        &self,
+        priority: Priority,
+        icon_name: S,
+    ) -> Result<(), SpeechDispatcherError> {
         let param = CString::new(icon_name.into()).unwrap();
         let v = unsafe { spd_char(self.0, priority as u32, param.as_ptr()) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_voice_type(&self, voice_type: VoiceType) -> bool {
+    pub fn set_voice_type(&self, voice_type: VoiceType) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_set_voice_type(self.0, voice_type as u32) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_voice_type_all(&self, voice_type: VoiceType) -> bool {
+    pub fn set_voice_type_all(&self, voice_type: VoiceType) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_set_voice_type_all(self.0, voice_type as u32) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_voice_type_uid(&self, voice_type: VoiceType, target_uid: u32) -> bool {
+    pub fn set_voice_type_uid(
+        &self,
+        voice_type: VoiceType,
+        target_uid: u32,
+    ) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_set_voice_type_uid(self.0, voice_type as u32, target_uid) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn get_voice_type(&self) -> VoiceType {
+    pub fn get_voice_type(&self) -> Result<VoiceType, SpeechDispatcherError> {
         let v = unsafe { spd_get_voice_type(self.0) };
-        match v {
+        Ok(match v {
             SPDVoiceType::SPD_MALE1 => VoiceType::Male1,
             SPDVoiceType::SPD_MALE2 => VoiceType::Male2,
             SPDVoiceType::SPD_MALE3 => VoiceType::Male3,
@@ -390,213 +417,282 @@ impl Connection {
             SPDVoiceType::SPD_FEMALE3 => VoiceType::Female3,
             SPDVoiceType::SPD_CHILD_MALE => VoiceType::ChildMale,
             SPDVoiceType::SPD_CHILD_FEMALE => VoiceType::ChildFemale,
-            _ => panic!("Invalid voice type"),
+            _ => return Err(SpeechDispatcherError::OperationFailed), // can this happen?
-        }
+        })
     }
 
-    pub fn set_synthesis_voice<S: Into<String>>(&self, voice_name: S) -> bool {
+    pub fn set_synthesis_voice<S: Into<String>>(
+        &self,
+        voice_name: S,
+    ) -> Result<(), SpeechDispatcherError> {
         let param = CString::new(voice_name.into()).unwrap();
         let v = unsafe { spd_set_synthesis_voice(self.0, param.as_ptr()) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_synthesis_voice_all<S: Into<String>>(&self, voice_name: S) -> bool {
+    pub fn set_synthesis_voice_all<S: Into<String>>(
+        &self,
+        voice_name: S,
+    ) -> Result<(), SpeechDispatcherError> {
         let param = CString::new(voice_name.into()).unwrap();
         let v = unsafe { spd_set_synthesis_voice_all(self.0, param.as_ptr()) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_synthesis_voice_uid<S: Into<String>>(&self, voice_name: S, target_uid: u32) -> bool {
+    pub fn set_synthesis_voice_uid<S: Into<String>>(
+        &self,
+        voice_name: S,
+        target_uid: u32,
+    ) -> Result<(), SpeechDispatcherError> {
         let param = CString::new(voice_name.into()).unwrap();
         let v = unsafe { spd_set_synthesis_voice_uid(self.0, param.as_ptr(), target_uid) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_data_mode(&self, mode: DataMode) -> bool {
+    pub fn set_data_mode(&self, mode: DataMode) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_set_data_mode(self.0, mode as u32) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_notification_on(&self, notification: Notification) -> bool {
+    pub fn set_notification_on(
+        &self,
+        notification: Notification,
+    ) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_set_notification_on(self.0, notification as u32) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_notification_off(&self, notification: Notification) -> bool {
+    pub fn set_notification_off(
+        &self,
+        notification: Notification,
+    ) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_set_notification_off(self.0, notification as u32) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_notification<S: Into<String>>(&self, notification: Notification, state: S) -> bool {
+    pub fn set_notification<S: Into<String>>(
+        &self,
+        notification: Notification,
+        state: S,
+    ) -> Result<(), SpeechDispatcherError> {
         let param = CString::new(state.into()).unwrap();
         let v = unsafe { spd_set_notification(self.0, notification as u32, param.as_ptr()) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_voice_rate(&self, rate: i32) -> bool {
+    pub fn set_voice_rate(&self, rate: i32) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_set_voice_rate(self.0, rate) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_voice_rate_all(&self, rate: i32) -> bool {
+    pub fn set_voice_rate_all(&self, rate: i32) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_set_voice_rate_all(self.0, rate) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_voice_rate_uid(&self, rate: i32, target_uid: u32) -> bool {
+    pub fn set_voice_rate_uid(
+        &self,
+        rate: i32,
+        target_uid: u32,
+    ) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_set_voice_rate_uid(self.0, rate, target_uid) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
     pub fn get_voice_rate(&self) -> i32 {
         unsafe { spd_get_voice_rate(self.0) }
     }
 
-    pub fn set_voice_pitch(&self, pitch: i32) -> bool {
+    pub fn set_voice_pitch(&self, pitch: i32) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_set_voice_pitch(self.0, pitch) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_voice_pitch_all(&self, pitch: i32) -> bool {
+    pub fn set_voice_pitch_all(&self, pitch: i32) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_set_voice_pitch_all(self.0, pitch) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_voice_pitch_uid(&self, pitch: i32, target_uid: u32) -> bool {
+    pub fn set_voice_pitch_uid(
+        &self,
+        pitch: i32,
+        target_uid: u32,
+    ) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_set_voice_pitch_uid(self.0, pitch, target_uid) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
     pub fn get_voice_pitch(&self) -> i32 {
         unsafe { spd_get_voice_pitch(self.0) }
     }
 
-    pub fn set_volume(&self, volume: i32) -> bool {
+    pub fn set_volume(&self, volume: i32) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_set_volume(self.0, volume) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_volume_all(&self, volume: i32) -> bool {
+    pub fn set_volume_all(&self, volume: i32) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_set_volume_all(self.0, volume) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_volume_uid(&self, volume: i32, target_uid: u32) -> bool {
+    pub fn set_volume_uid(
+        &self,
+        volume: i32,
+        target_uid: u32,
+    ) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_set_volume_uid(self.0, volume, target_uid) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
     pub fn get_volume(&self) -> i32 {
         unsafe { spd_get_volume(self.0) }
     }
 
-    pub fn set_punctuation(&self, punctuation: Punctuation) -> bool {
+    pub fn set_punctuation(&self, punctuation: Punctuation) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_set_punctuation(self.0, punctuation as u32) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_punctuation_all(&self, punctuation: Punctuation) -> bool {
+    pub fn set_punctuation_all(
+        &self,
+        punctuation: Punctuation,
+    ) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_set_punctuation_all(self.0, punctuation as u32) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_punctuation_uid(&self, punctuation: Punctuation, target_uid: u32) -> bool {
+    pub fn set_punctuation_uid(
+        &self,
+        punctuation: Punctuation,
+        target_uid: u32,
+    ) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_set_punctuation_uid(self.0, punctuation as u32, target_uid) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_capital_letters(&self, capital_letters: CapitalLetters) -> bool {
+    pub fn set_capital_letters(
+        &self,
+        capital_letters: CapitalLetters,
+    ) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_set_capital_letters(self.0, capital_letters as u32) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_capital_letters_all(&self, capital_letters: CapitalLetters) -> bool {
+    pub fn set_capital_letters_all(
+        &self,
+        capital_letters: CapitalLetters,
+    ) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_set_capital_letters_all(self.0, capital_letters as u32) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
     pub fn set_capital_letters_uid(
         &self,
         capital_letters: CapitalLetters,
         target_uid: u32,
-    ) -> bool {
+    ) -> Result<(), SpeechDispatcherError> {
         let v = unsafe { spd_set_capital_letters_uid(self.0, capital_letters as u32, target_uid) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_spelling(&self, spelling: bool) -> bool {
+    pub fn set_spelling(&self, spelling: bool) -> Result<(), SpeechDispatcherError> {
         let s = if spelling {
             SPDSpelling::SPD_SPELL_ON
         } else {
             SPDSpelling::SPD_SPELL_OFF
         };
         let v = unsafe { spd_set_spelling(self.0, s) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_spelling_all(&self, spelling: bool) -> bool {
+    pub fn set_spelling_all(&self, spelling: bool) -> Result<(), SpeechDispatcherError> {
         let s = if spelling {
             SPDSpelling::SPD_SPELL_ON
         } else {
             SPDSpelling::SPD_SPELL_OFF
         };
         let v = unsafe { spd_set_spelling_all(self.0, s) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_spelling_uid(&self, spelling: bool, target_uid: u32) -> bool {
+    pub fn set_spelling_uid(
+        &self,
+        spelling: bool,
+        target_uid: u32,
+    ) -> Result<(), SpeechDispatcherError> {
         let s = if spelling {
             SPDSpelling::SPD_SPELL_ON
         } else {
             SPDSpelling::SPD_SPELL_OFF
         };
         let v = unsafe { spd_set_spelling_uid(self.0, s, target_uid) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_language<S: Into<String>>(&self, language: S) -> bool {
+    pub fn set_language<S: Into<String>>(&self, language: S) -> Result<(), SpeechDispatcherError> {
         let param = CString::new(language.into()).unwrap();
         let v = unsafe { spd_set_language(self.0, param.as_ptr()) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_language_all<S: Into<String>>(&self, language: S) -> bool {
+    pub fn set_language_all<S: Into<String>>(
+        &self,
+        language: S,
+    ) -> Result<(), SpeechDispatcherError> {
         let param = CString::new(language.into()).unwrap();
         let v = unsafe { spd_set_language_all(self.0, param.as_ptr()) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_language_uid<S: Into<String>>(&self, language: S, target_uid: u32) -> bool {
+    pub fn set_language_uid<S: Into<String>>(
+        &self,
+        language: S,
+        target_uid: u32,
+    ) -> Result<(), SpeechDispatcherError> {
         let param = CString::new(language.into()).unwrap();
         let v = unsafe { spd_set_language_uid(self.0, param.as_ptr(), target_uid) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn get_language(&self) -> &str {
+    pub fn get_language(&self) -> Result<&str, SpeechDispatcherError> {
-        let v = unsafe { CStr::from_ptr(spd_get_language(self.0)) };
+        let language = unsafe { spd_get_language(self.0) };
-        v.to_str().unwrap()
+        if language.is_null() {
+            Err(SpeechDispatcherError::OperationFailed)
+        } else {
+            let language = unsafe { CStr::from_ptr(language) };
+            language
+                .to_str()
+                .map_err(|_| SpeechDispatcherError::OperationFailed)
+        }
     }
 
-    pub fn set_output_module<S: Into<String>>(&self, output_module: S) -> bool {
+    pub fn set_output_module<S: Into<String>>(
+        &self,
+        output_module: S,
+    ) -> Result<(), SpeechDispatcherError> {
         let param = CString::new(output_module.into()).unwrap();
         let v = unsafe { spd_set_output_module(self.0, param.as_ptr()) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
-    pub fn set_output_module_all<S: Into<String>>(&self, output_module: S) -> bool {
+    pub fn set_output_module_all<S: Into<String>>(
+        &self,
+        output_module: S,
+    ) -> Result<(), SpeechDispatcherError> {
         let param = CString::new(output_module.into()).unwrap();
         let v = unsafe { spd_set_output_module_all(self.0, param.as_ptr()) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
     pub fn set_output_module_uid<S: Into<String>>(
         &self,
         output_module: S,
         target_uid: u32,
-    ) -> bool {
+    ) -> Result<(), SpeechDispatcherError> {
         let param = CString::new(output_module.into()).unwrap();
         let v = unsafe { spd_set_output_module_uid(self.0, param.as_ptr(), target_uid) };
-        i32_to_bool(v)
+        c_int_to_result(v)
     }
 
     pub fn send_data<S: Into<String>>(&self, data: S, wait_for_reply: bool) -> Option<String> {