(arrow) branch main updated: GH-46094: [C++][Docs] Add note to RleDecoder::Get's doc comment (#46874)

[kou]

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The following commit(s) were added to refs/heads/main by this push:
     new 3573f54888 GH-46094: [C++][Docs] Add note to RleDecoder::Get's doc 
comment (#46874)
3573f54888 is described below

commit 3573f548881af39dd09cfd96b12c3a2b742f4699
Author: Hadrian Reppas <hadr...@uchicago.edu>
AuthorDate: Sun Jun 22 21:02:10 2025 -0500

    GH-46094: [C++][Docs] Add note to RleDecoder::Get's doc comment (#46874)
    
    ### Rationale for this change
    
    The behavior of `RleDecoder::Get` caused some confusion in 
https://github.com/apache/arrow/issues/46094.
    
    ### What changes are included in this PR?
    
    Improvement to `RleDecoder::Get`'s doc comment.
    
    ### Are these changes tested?
    
    N/A
    
    ### Are there any user-facing changes?
    
    No.
    * GitHub Issue: #46094
    
    Authored-by: Hadrian Reppas <hadr...@hudson-trading.com>
    Signed-off-by: Sutou Kouhei <k...@clear-code.com>
---
 cpp/src/arrow/util/rle_encoding_internal.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/cpp/src/arrow/util/rle_encoding_internal.h 
b/cpp/src/arrow/util/rle_encoding_internal.h
index 6f133f15b0..fab8c50512 100644
--- a/cpp/src/arrow/util/rle_encoding_internal.h
+++ b/cpp/src/arrow/util/rle_encoding_internal.h
@@ -112,6 +112,12 @@ class RleDecoder {
   }
 
   /// Gets the next value.  Returns false if there are no more.
+  ///
+  /// NB: Because the encoding only supports literal runs with lengths
+  /// that are multiples of 8, RleEncoder sometimes pads the end of its
+  /// input with zeros. Since the encoding does not differentiate between
+  /// input values and padding, Get() returns true even for these padding
+  /// values.
   template <typename T>
   bool Get(T* val);