[C++][Parquet] Fuzz using several batch sizes

[pitrou]

Describe the enhancement requested

Exercising several batch sizes in parquet::arrow::internal::FuzzReader may help find more reader/decoder bugs.

Component(s)

C++

[pitrou]

Something like this could work:

diff --git a/cpp/src/parquet/arrow/reader.cc b/cpp/src/parquet/arrow/reader.cc
index b57b5062a..717f49629 100644
--- a/cpp/src/parquet/arrow/reader.cc
+++ b/cpp/src/parquet/arrow/reader.cc
@@ -20,6 +20,7 @@
 #include <algorithm>
 #include <cstring>
 #include <memory>
+#include <optional>
 #include <unordered_set>
 #include <utility>
 #include <vector>
@@ -1385,13 +1386,21 @@ Status FuzzReader(std::unique_ptr<FileReader> reader) {
 
 Status FuzzReader(const uint8_t* data, int64_t size) {
   auto buffer = std::make_shared<::arrow::Buffer>(data, size);
-  auto file = std::make_shared<::arrow::io::BufferReader>(buffer);
-  FileReaderBuilder builder;
-  RETURN_NOT_OK(builder.Open(std::move(file)));
+  auto st = Status::OK();
+
+  for (auto batch_size : std::vector<std::optional<int>>{std::nullopt, 1, 13, 300}) {
+    auto file = std::make_shared<::arrow::io::BufferReader>(buffer);
+    FileReaderBuilder builder;
+    RETURN_NOT_OK(builder.Open(std::move(file)));
 
-  std::unique_ptr<FileReader> reader;
-  RETURN_NOT_OK(builder.Build(&reader));
-  return FuzzReader(std::move(reader));
+    std::unique_ptr<FileReader> reader;
+    RETURN_NOT_OK(builder.Build(&reader));
+    if (batch_size) {
+      reader->set_batch_size(*batch_size);
+    }
+    st &= FuzzReader(std::move(reader));
+  }
+  return st;
 }
 
 }  // namespace internal

[mapleFU]

I'd like to pickup this issue, but I need to learn fuzz first :)

[mapleFU]

take