tabby/crates/llama-cpp-bindings/src/lib.rs

use std::sync::{Arc, Mutex};

use async_trait::async_trait;
use derive_builder::Builder;
use ffi::create_engine;
use stop_words::StopWords;
use tabby_inference::{TextGeneration, TextGenerationOptions};
use tokenizers::tokenizer::Tokenizer;

#[cxx::bridge(namespace = "llama")]
mod ffi {
    unsafe extern "C++" {
        include!("llama-cpp-bindings/include/engine.h");

        type TextInferenceEngine;

        fn create_engine(model_path: &str) -> SharedPtr<TextInferenceEngine>;

        fn start(&self, prompt: &str) -> u32;
        fn step(&self, next_token_id: u32) -> u32;
    }
}

unsafe impl Send for ffi::TextInferenceEngine {}
unsafe impl Sync for ffi::TextInferenceEngine {}

#[derive(Builder, Debug)]
pub struct LlamaEngineOptions {
    model_path: String,
    tokenizer_path: String,
}

pub struct LlamaEngine {
    engine: Mutex<cxx::SharedPtr<ffi::TextInferenceEngine>>,
    tokenizer: Arc<Tokenizer>,
    stop_words: StopWords,
}

impl LlamaEngine {
    pub fn create(options: LlamaEngineOptions) -> Self {
        LlamaEngine {
            engine: Mutex::new(create_engine(&options.model_path)),
            tokenizer: Arc::new(Tokenizer::from_file(&options.tokenizer_path).unwrap()),
            stop_words: StopWords::default(),
        }
    }
}

#[async_trait]
impl TextGeneration for LlamaEngine {
    async fn generate(&self, prompt: &str, options: TextGenerationOptions) -> String {
        let engine = self.engine.lock().unwrap();
        let mut next_token_id = engine.start(prompt);
        let mut n_remains = options.max_decoding_length - 1;
        let mut output_ids = vec![next_token_id];

        let mut stop_condition = self
            .stop_words
            .create_condition(self.tokenizer.clone(), options.stop_words);

        // FIXME(meng): supports cancellation.
        while n_remains > 0 {
            next_token_id = engine.step(next_token_id);
            if stop_condition.next_token(next_token_id) {
                break;
            }
            output_ids.push(next_token_id);
            n_remains -= 1;
        }

        self.tokenizer.decode(&output_ids, true).unwrap()
    }
}