feat: add comments, xllm header.

Author: magicheng0816

xllm/core/framework/sampling/constrained_decoding.h

@@ -26,10 +26,21 @@ class ConstrainedDecoding {
  public:
   virtual ~ConstrainedDecoding();
 
+  // Precompute and cache fixed constraint masks (e.g., static vocabulary
+  // whitelists) to avoid redundant calculations during token generation.
+  // Returns: true if cache built successfully, false otherwise
   virtual bool build_mask_cache();
 
-  // Input generated_token_list: [sequence_num][generated_token_ids]
-  // Output: mask tensor[sequence_num,vocab_size]
+  // Generate dynamic constraint mask based on already generated token
+  // sequences. This mask will be applied to filter invalid tokens.
+  //
+  // Input: generated_token_list - 2D vector of token IDs, where each inner
+  // vector represents the generated tokens for a single sequence in the batch
+  // (format:[sequence_num][token_ids])
+  // Output: tensor of shape [sequence_num, vocab_size], where 0.0f
+  // indicates allowed tokens and a large negative number indicates forbidden
+  // tokens for each sequence, the usage is to filter invalid tokens by adding
+  // the mask to the model logits.
   virtual torch::Tensor generate_mask(
       const std::vector<std::vector<int32_t>>& generated_token_list);
 };

xllm/core/framework/sampling/rec_constrained_decoding.cpp

@@ -1,3 +1,18 @@
+/* Copyright 2025 The xLLM Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    https://github.com/jd-opensource/xllm/blob/main/LICENSE
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
 #include "rec_constrained_decoding.h"
 
 #include <c10/core/TensorOptions.h>