From 9d415f0513f7b34daf4fadaf96b138d23ae850e6 Mon Sep 17 00:00:00 2001
From: Niels Lohmann <mail@nlohmann.me>
Date: Wed, 30 Sep 2026 07:33:12 +0200
Subject: [PATCH] Cast number_integer to number_unsigned_t only once in
 to_msgpack()

Addresses review comment by @gregmarr.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---
 include/nlohmann/detail/output/binary_writer.hpp | 9 +++++----
 single_include/nlohmann/json.hpp                 | 9 +++++----
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/include/nlohmann/detail/output/binary_writer.hpp b/include/nlohmann/detail/output/binary_writer.hpp
index d9b9fa521..4f39f0537 100644
--- a/include/nlohmann/detail/output/binary_writer.hpp
+++ b/include/nlohmann/detail/output/binary_writer.hpp
@@ -337,24 +337,25 @@ class binary_writer
                     // MessagePack does not differentiate between positive
                     // signed integers and unsigned integers. Therefore, we used
                     // the code from the value_t::number_unsigned case here.
-                    if (static_cast<typename BasicJsonType::number_unsigned_t>(j.m_data.m_value.number_integer) < 128)
+                    const auto value_as_unsigned = static_cast<typename BasicJsonType::number_unsigned_t>(j.m_data.m_value.number_integer);
+                    if (value_as_unsigned < 128)
                     {
                         // positive fixnum
                         write_number(static_cast<std::uint8_t>(j.m_data.m_value.number_integer));
                     }
-                    else if (static_cast<typename BasicJsonType::number_unsigned_t>(j.m_data.m_value.number_integer) <= (std::numeric_limits<std::uint8_t>::max)())
+                    else if (value_as_unsigned <= (std::numeric_limits<std::uint8_t>::max)())
                     {
                         // uint 8
                         oa.write_character(to_char_type(0xCC));
                         write_number(static_cast<std::uint8_t>(j.m_data.m_value.number_integer));
                     }
-                    else if (static_cast<typename BasicJsonType::number_unsigned_t>(j.m_data.m_value.number_integer) <= (std::numeric_limits<std::uint16_t>::max)())
+                    else if (value_as_unsigned <= (std::numeric_limits<std::uint16_t>::max)())
                     {
                         // uint 16
                         oa.write_character(to_char_type(0xCD));
                         write_number(static_cast<std::uint16_t>(j.m_data.m_value.number_integer));
                     }
-                    else if (static_cast<typename BasicJsonType::number_unsigned_t>(j.m_data.m_value.number_integer) <= (std::numeric_limits<std::uint32_t>::max)())
+                    else if (value_as_unsigned <= (std::numeric_limits<std::uint32_t>::max)())
                     {
                         // uint 32
                         oa.write_character(to_char_type(0xCE));
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index ee9c86afd..937a08782 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -20667,24 +20667,25 @@ class binary_writer
                     // MessagePack does not differentiate between positive
                     // signed integers and unsigned integers. Therefore, we used
                     // the code from the value_t::number_unsigned case here.
-                    if (static_cast<typename BasicJsonType::number_unsigned_t>(j.m_data.m_value.number_integer) < 128)
+                    const auto value_as_unsigned = static_cast<typename BasicJsonType::number_unsigned_t>(j.m_data.m_value.number_integer);
+                    if (value_as_unsigned < 128)
                     {
                         // positive fixnum
                         write_number(static_cast<std::uint8_t>(j.m_data.m_value.number_integer));
                     }
-                    else if (static_cast<typename BasicJsonType::number_unsigned_t>(j.m_data.m_value.number_integer) <= (std::numeric_limits<std::uint8_t>::max)())
+                    else if (value_as_unsigned <= (std::numeric_limits<std::uint8_t>::max)())
                     {
                         // uint 8
                         oa.write_character(to_char_type(0xCC));
                         write_number(static_cast<std::uint8_t>(j.m_data.m_value.number_integer));
                     }
-                    else if (static_cast<typename BasicJsonType::number_unsigned_t>(j.m_data.m_value.number_integer) <= (std::numeric_limits<std::uint16_t>::max)())
+                    else if (value_as_unsigned <= (std::numeric_limits<std::uint16_t>::max)())
                     {
                         // uint 16
                         oa.write_character(to_char_type(0xCD));
                         write_number(static_cast<std::uint16_t>(j.m_data.m_value.number_integer));
                     }
-                    else if (static_cast<typename BasicJsonType::number_unsigned_t>(j.m_data.m_value.number_integer) <= (std::numeric_limits<std::uint32_t>::max)())
+                    else if (value_as_unsigned <= (std::numeric_limits<std::uint32_t>::max)())
                     {
                         // uint 32
                         oa.write_character(to_char_type(0xCE));