[GitHub] [arrow] pitrou commented on a diff in pull request #14191: ARROW-17798: [C++][Parquet] Add DELTA_BINARY_PACKED encoder to Parquet writer

[GitBox]

pitrou commented on code in PR #14191:
URL: https://github.com/apache/arrow/pull/14191#discussion_r1030575454


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cpp/src/arrow/util/bit_stream_utils.h:
##########
@@ -204,8 +204,8 @@ class BitReader {
 
 inline bool BitWriter::PutValue(uint64_t v, int num_bits) {
   // TODO: revisit this limit if necessary (can be raised to 64 by fixing some 
edge cases)
-  DCHECK_LE(num_bits, 32);
-  DCHECK_EQ(v >> num_bits, 0) << "v = " << v << ", num_bits = " << num_bits;
+  DCHECK_LE(num_bits, 64);
+  //  DCHECK_EQ(v >> num_bits, 0) << "v = " << v << ", num_bits = " << 
num_bits;

Review Comment:
   However, the `v >> (num_bits - bit_offset_)` operation below might be 
undefined if `num_bits - bit_offset_` is 64.
   So I would change:
   ```c++
       buffered_values_ = v >> (num_bits - bit_offset_);
   ```
   into:
   ```c++
       buffered_values_ = (num_bits - bit_offset_ == 64) ? 0 : (v >> (num_bits 
- bit_offset_));
   ```
   



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