Fix remaining_length accounting after Huffman decode in RegressionPredictor / ComposedPredictor

include/SZ3/predictor/ComposedPredictor.hpp

@@ -72,8 +72,12 @@ class ComposedPredictor : public concepts::PredictorInterface<T, N> {
         if (selection_size > 0) {
             HuffmanEncoder<int> selection_encoder;
             selection_encoder.load(c, remaining_length);
+            /// decode() advances `c` past the encoded stream but does not update `remaining_length`;
+            /// account for exactly the bytes it consumed so the bound stays tight for later reads.
+            const uchar *decode_start = c;
             this->selection = selection_encoder.decode(c, selection_size);
             selection_encoder.postprocess_decode();
+            remaining_length -= static_cast<size_t>(c - decode_start);
         }
     }
 

include/SZ3/predictor/RegressionPredictor.hpp

@@ -114,9 +114,14 @@ class RegressionPredictor : public concepts::PredictorInterface<T, N> {
             quantizer_liner.load(c, remaining_length);
             HuffmanEncoder<int> encoder = HuffmanEncoder<int>();
             encoder.load(c, remaining_length);
+            /// decode() advances `c` past the encoded stream but does not update `remaining_length`;
+            /// account for exactly the bytes it consumed. The previous `coeff_size * sizeof(int)` used the
+            /// uncompressed index count, which overshoots the (Huffman-compressed) stream and understates
+            /// remaining_length, making a later encoder.load() bound check spuriously reject valid data.
+            const uchar *decode_start = c;
             regression_coeff_quant_inds = encoder.decode(c, coeff_size);
             encoder.postprocess_decode();
-            remaining_length -= coeff_size * sizeof(int);
+            remaining_length -= static_cast<size_t>(c - decode_start);
             std::fill(current_coeffs.begin(), current_coeffs.end(), 0);
             regression_coeff_index = 0;
         }