[GitHub] [arrow] mapleFU commented on pull request #15241: GH-14923: [C++][Parquet] Fix DELTA_BINARY_PACKED problem on reading the last block with malford bit-width

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mapleFU commented on PR #15241:
URL: https://github.com/apache/arrow/pull/15241#issuecomment-1377596076

   Let's go back to the original code:
   
   ```c++
         if (ARROW_PREDICT_FALSE(values_remaining_current_mini_block_ == 0)) {
           if (ARROW_PREDICT_FALSE(!first_block_initialized_)) {
             buffer[i++] = last_value_;
             DCHECK_EQ(i, 1);  // we're at the beginning of the page
             DCHECK_EQ(values_num_up_to_current_mini_block_, 0);
             values_num_up_to_current_mini_block_ = 1;
             if (ARROW_PREDICT_FALSE(i == max_values)) {
               // When block is uninitialized and i reaches max_values we have 
two
               // different possibilities:
               // 1. total_value_count_ == 1, which means that the page may 
have only
               // one value (encoded in the header), and we should not 
initialize
               // any block.
               // 2. total_value_count_ != 1, which means we should initialize 
the
               // incoming block for subsequent reads.
               if (total_value_count_ != 1) {
                 InitBlock();
               }
               break;
             }
             InitBlock();
           }
   ```
   
   And assume the page has 33 values:
   1. `total_value_count_ == 1`, call `InitBlock`
   2. `current_num_values = 0`, read block one, change to 32.
   3. `current_num_values = 32`, read block one, change to 64.
   
   But here, it should be `1` firstly.


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