define a shared struct to hold the result of a decoding step

backends/trtllm/include/ffi.h

@@ -60,7 +60,8 @@ namespace huggingface::tgi::backends {
         size_t StreamTokens(
                 const RequestId requestId,
                 huggingface::tgi::backends::GenerationContext *ctx,
-                rust::Fn<void(huggingface::tgi::backends::GenerationContext *, uint32_t, float_t, bool)> callback);
+                rust::Fn<void(huggingface::tgi::backends::GenerationContext *,
+                              huggingface::tgi::backends::GenerationStep)> callback);
     };
 
     /***

backends/trtllm/src/backend.rs

@@ -20,13 +20,11 @@ use tracing::{instrument, Level, span};
 
 use text_generation_router::{FinishReason, Token};
 use text_generation_router::infer::{Backend, GeneratedText, InferError, InferStreamResponse};
-use text_generation_router::validation::{
-    Chunk, ValidationError, ValidGenerateRequest, ValidParameters,
-};
+use text_generation_router::validation::{Chunk, ValidationError, ValidGenerateRequest};
 use text_generation_router::validation::ValidationError::UnsupportedModality;
 
 use crate::errors::TensorRtLlmBackendError;
-use crate::ffi::{create_tensorrt_llm_backend, TensorRtLlmBackendImpl};
+use crate::ffi::{create_tensorrt_llm_backend, GenerationStep, TensorRtLlmBackendImpl};
 
 // Value used to poll the state of the generation stream
 static POLLING_INTERVAL_US: OnceLock<u64> = OnceLock::new();
@@ -208,14 +206,11 @@ impl TensorRtLlmBackend {
                             executor_w.pin_mut().stream_tokens(
                                 request_id,
                                 ctx_,
-                                |ctx: *mut GenerationContext,
-                                 token_id: u32,
-                                 logprob: f32,
-                                 is_final: bool| {
+                                |ctx: *mut GenerationContext, step: GenerationStep| {
                                     let inner_ctx = &mut *ctx;
 
                                     // Insert the latest generated token to the tracker
-                                    inner_ctx.tokens.push(token_id);
+                                    inner_ctx.tokens.push(step.token_id);
 
                                     // Update the timestamp at which the request started effectively
                                     // Can be a bit off, would need to be before the callback, let's see
@@ -224,7 +219,7 @@ impl TensorRtLlmBackend {
                                     // Decode the token
                                     let text = inner_ctx
                                         .tokenizer
-                                        .decode(&[token_id], true)
+                                        .decode(&[step.token_id], true)
                                         .expect("Failed to decode token");
 
                                     let special = inner_ctx
@@ -234,13 +229,13 @@ impl TensorRtLlmBackend {
 
                                     // Create the structure holding the token
                                     let token = Token {
-                                        id: token_id,
+                                        id: step.token_id,
                                         text,
-                                        logprob,
+                                        logprob: step.log_prob,
                                         special,
                                     };
 
-                                    let out = if is_final {
+                                    let out = if step.is_final {
                                         inner_ctx.done.store(true, Ordering::Relaxed);
                                         let generated_text = inner_ctx
                                             .tokenizer

backends/trtllm/src/ffi.cpp

@@ -6,6 +6,7 @@
 #include <cmath>
 #include <exception>
 #include <filesystem>
+#include <limits>
 #include <iterator>
 #include <vector>
 
@@ -36,10 +37,12 @@ uint64_t huggingface::tgi::backends::TensorRtLlmBackendImpl::Submit(
 size_t huggingface::tgi::backends::TensorRtLlmBackendImpl::StreamTokens(
         const uint64_t requestId,
         huggingface::tgi::backends::GenerationContext *ctx,
-        rust::Fn<void(huggingface::tgi::backends::GenerationContext *, uint32_t, float_t, bool)> callback) {
+        rust::Fn<void(huggingface::tgi::backends::GenerationContext *,
+                      huggingface::tgi::backends::GenerationStep)> callback) {
 
     size_t numTokens = 0;
     for (const auto &item: Poll(requestId)) {
+        GenerationStep step;
         if (!item.hasError()) {
             SPDLOG_DEBUG("\tStreamTokens -> Decoding token...");
             const auto decoded = item.getResult();
@@ -51,13 +54,15 @@ size_t huggingface::tgi::backends::TensorRtLlmBackendImpl::StreamTokens(
             ++numTokens;
 
             SPDLOG_DEBUG(FMT_STRING("\tStreamTokens -> {:d} {:.2f} (final = {})"), token, logProb, isFinal);
-            callback(std::move(ctx), token, logProb, isFinal);
+            step = huggingface::tgi::backends::GenerationStep{static_cast<uint32_t>(token), logProb, isFinal};
             SPDLOG_DEBUG("\tStreamTokens -> Post callback");
         } else {
             // TODO : Return rest::Result with error
             SPDLOG_WARN("\tStreamTokens -> Got error while decoding: {}", item.getErrorMsg());
-            callback(std::move(ctx), 0, 0.0, true);
+            step = huggingface::tgi::backends::GenerationStep{std::numeric_limits<uint32_t>::max(), 0.0, true};
         }
+
+        callback(std::move(ctx), std::move(step));
     }
 
     return numTokens;

backends/trtllm/src/lib.rs

@@ -1,12 +1,20 @@
-pub use backend::TensorRtLlmBackend;
-
-use crate::backend::GenerationContext;
+pub use backend::{GenerationContext, TensorRtLlmBackend};
 
 mod backend;
 pub mod errors;
 
 #[cxx::bridge(namespace = "huggingface::tgi::backends")]
 mod ffi {
+
+    /// Struct used as shared type between rust and C++ to represent the result
+    /// of a single decoding iteration
+    #[derive(Copy, Clone)]
+    pub struct GenerationStep {
+        token_id: u32,
+        log_prob: f32,
+        is_final: bool,
+    }
+
     extern "Rust" {
         type GenerationContext;
     }
@@ -60,7 +68,7 @@ mod ffi {
             self: Pin<&mut TensorRtLlmBackendImpl>,
             request_id: u64,
             ctx: *mut GenerationContext,
-            cb: unsafe fn(*mut GenerationContext, u32, f32, bool),
+            cb: unsafe fn(*mut GenerationContext, GenerationStep),
         ) -> usize;
 
         // #[rust_name = "shutdown"]