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

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

tachyonwill commented on a change in pull request #12365:
URL: https://github.com/apache/arrow/pull/12365#discussion_r801164114



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File path: cpp/src/parquet/encoding.cc
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@@ -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:
       I worry that this is the wrong place to put it though. The basic contract of these decoders seems to be, 'give me how many values you want, I will give you min(what you want, what is left) and then return how many were actually given'. Changing this one to throw an exception if 'what you want > what is left' would make it unlike the others, even if I only expect the caller to request more than is what is available if the caller has a bug or the file is malformed.




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