refactor(state): create_state from whisper context wrapper

src/whisper_ctx_wrapper.rs

@@ -0,0 +1,37 @@
+use std::sync::Arc;
+
+use crate::{WhisperContext, WhisperContextParameters, WhisperError, WhisperState};
+
+pub struct WhisperContextWrapper {
+    ctx: Arc<WhisperContext>,
+}
+
+impl WhisperContextWrapper {
+    /// wrapper of WhisperContext::new_with_params.
+    pub fn new_with_params(
+        path: &str,
+        parameters: WhisperContextParameters,
+    ) -> Result<Self, WhisperError> {
+        let ctx = WhisperContext::new_with_params(path, parameters)?;
+        Ok(Self { ctx: Arc::new(ctx) })
+    }
+
+    // we don't implement `whisper_init()` here since i have zero clue what `whisper_model_loader` does
+
+    /// Create a new state object, ready for use.
+    ///
+    /// # Returns
+    /// Ok(WhisperState) on success, Err(WhisperError) on failure.
+    ///
+    /// # C++ equivalent
+    /// `struct whisper_state * whisper_init_state(struct whisper_context * ctx);`
+    pub fn create_state(&self) -> Result<WhisperState, WhisperError> {
+        let state = unsafe { whisper_rs_sys::whisper_init_state(self.ctx.ctx) };
+        if state.is_null() {
+            Err(WhisperError::InitError)
+        } else {
+            // SAFETY: this is known to be a valid pointer to a `whisper_state` struct
+            Ok(WhisperState::new(self.ctx.clone(), state))
+        }
+    }
+}