[GitHub] [arrow] pitrou commented on a change in pull request #12365: PARQUET-2119: Fix DeltaBitPackDecoder fuzzer found issue.

[GitBox <gi...@apache.org>]

pitrou commented on a change in pull request #12365:
URL: https://github.com/apache/arrow/pull/12365#discussion_r801589517



##########
File path: cpp/src/parquet/encoding.cc
##########
@@ -2424,7 +2426,12 @@ class DeltaByteArrayDecoder : public DecoderImpl,
       return max_values;
     }
 
-    suffix_decoder_.Decode(buffer, max_values);
+    int suffix_read = suffix_decoder_.Decode(buffer, max_values);
+    if (ARROW_PREDICT_FALSE(suffix_read != max_values)) {
+      ParquetException::EofException("Read " + std::to_string(suffix_read) +
+                                     "Expecting " + std::to_string(max_values) +
+                                     " from suffix decoder");

Review comment:
       ```suggestion
         ParquetException::EofException("Read " + std::to_string(suffix_read) +
                                        ", expecting " + std::to_string(max_values) +
                                        " from suffix decoder");
   ```

##########
File path: cpp/src/parquet/encoding.cc
##########
@@ -2181,12 +2181,14 @@ class DeltaBitPackDecoder : public DecoderImpl, virtual public TypedDecoder<DTyp
   }
 
   int GetInternal(T* buffer, int max_values) {
-    max_values = std::min(max_values, this->num_values_);
+    int total_value_count = static_cast<int>(std::min(
+        total_value_count_, static_cast<uint32_t>(std::numeric_limits<int>::max())));
+    max_values = std::min(max_values, total_value_count);
+    DCHECK_GE(max_values, 0);

Review comment:
       What is this check for? Is there a situation where `max_values` can be negative (except the caller passing a negative value)?

##########
File path: cpp/src/parquet/encoding.cc
##########
@@ -2181,12 +2181,14 @@ class DeltaBitPackDecoder : public DecoderImpl, virtual public TypedDecoder<DTyp
   }
 
   int GetInternal(T* buffer, int max_values) {
-    max_values = std::min(max_values, this->num_values_);
+    int total_value_count = static_cast<int>(std::min(
+        total_value_count_, static_cast<uint32_t>(std::numeric_limits<int>::max())));
+    max_values = std::min(max_values, total_value_count);

Review comment:
       This is extremely convoluted. How about:
   ```suggestion
       max_values = static_cast<int>(std::min<int64_t>(max_values, total_value_count_));
   ```




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