feat: add back streaming for ctranslate2

crates/ctranslate2-bindings/src/lib.rs

@@ -1,5 +1,6 @@
 use std::sync::Arc;
 
+use async_stream::stream;
 use async_trait::async_trait;
 use derive_builder::Builder;
 use futures::stream::BoxStream;
@@ -8,6 +9,7 @@ use tabby_inference::{
     helpers, TextGeneration, TextGenerationOptions,
 };
 use tokenizers::tokenizer::Tokenizer;
+use tokio::sync::mpsc::{channel, Sender};
 use tokio_util::sync::CancellationToken;
 
 #[cxx::bridge(namespace = "tabby")]
@@ -70,13 +72,22 @@ pub struct CTranslate2EngineOptions {
 }
 
 pub struct InferenceContext {
+    sender: Sender<String>,
     decoding: IncrementalDecoding,
     cancel: CancellationToken,
 }
 
 impl InferenceContext {
-    fn new(decoding: IncrementalDecoding, cancel: CancellationToken) -> Self {
-        InferenceContext { decoding, cancel }
+    fn new(
+        sender: Sender<String>,
+        decoding: IncrementalDecoding,
+        cancel: CancellationToken,
+    ) -> Self {
+        InferenceContext {
+            sender,
+            decoding,
+            cancel,
+        }
     }
 }
 
@@ -108,33 +119,8 @@ impl CTranslate2Engine {
 #[async_trait]
 impl TextGeneration for CTranslate2Engine {
     async fn generate(&self, prompt: &str, options: TextGenerationOptions) -> String {
-        let encoding = self.tokenizer.encode(prompt, true).unwrap();
-        let engine = self.engine.clone();
-
-        let cancel = CancellationToken::new();
-        let cancel_for_inference = cancel.clone();
-        let _guard = cancel.drop_guard();
-
-        let decoding = self.decoding_factory.create_incremental_decoding(
-            self.tokenizer.clone(),
-            truncate_tokens(encoding.get_ids(), options.max_input_length),
-            options.stop_words,
-        );
-
-        let context = InferenceContext::new(decoding, cancel_for_inference);
-        let output_ids = tokio::task::spawn_blocking(move || {
-            let context = Box::new(context);
-            engine.inference(
-                context,
-                inference_callback,
-                truncate_tokens(encoding.get_tokens(), options.max_input_length),
-                options.max_decoding_length,
-                options.sampling_temperature,
-            )
-        })
-        .await
-        .expect("Inference failed");
-        self.tokenizer.decode(&output_ids, true).unwrap()
+        let s = self.generate_stream(prompt, options).await;
+        helpers::stream_to_string(s).await
     }
 
     async fn generate_stream(
@@ -142,7 +128,35 @@ impl TextGeneration for CTranslate2Engine {
         prompt: &str,
         options: TextGenerationOptions,
     ) -> BoxStream<String> {
-        helpers::string_to_stream(self.generate(prompt, options).await).await
+        let encoding = self.tokenizer.encode(prompt, true).unwrap();
+        let decoding = self.decoding_factory.create_incremental_decoding(
+            self.tokenizer.clone(),
+            truncate_tokens(encoding.get_ids(), options.max_input_length),
+            options.stop_words,
+        );
+
+        let cancel = CancellationToken::new();
+        let engine = self.engine.clone();
+        let (sender, mut receiver) = channel::<String>(8);
+        let context = InferenceContext::new(sender, decoding, cancel.clone());
+        tokio::task::spawn(async move {
+            let context = Box::new(context);
+            engine.inference(
+                context,
+                inference_callback,
+                truncate_tokens(encoding.get_tokens(), options.max_input_length),
+                options.max_decoding_length,
+                options.sampling_temperature,
+            );
+        });
+
+        let s = stream! {
+            let _guard = cancel.drop_guard();
+            while let Some(text) = receiver.recv().await {
+                yield text;
+            }
+        };
+        Box::pin(s)
     }
 }
 
@@ -163,7 +177,10 @@ fn inference_callback(
 ) -> bool {
     if context.cancel.is_cancelled() {
         true
+    } else if let Some(new_text) = context.decoding.next_token(token_id) {
+        let _ = context.sender.blocking_send(new_text);
+        false
     } else {
-        !context.decoding.next_token(token_id).is_some()
+        true
     }
 }