From 665e433697247c4a43e055830dee7a72afdb810f Mon Sep 17 00:00:00 2001
From: Amlal El Mahrouss <amlal@nekernel.org>
Date: Thu, 1 Jan 2026 12:52:28 +0100
Subject: feat: FIX Checksum API for OCL.FIX.

Signed-off-by: Amlal El Mahrouss <amlal@nekernel.org>
---
 include/ocl/fix/checksum.hpp | 43 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 42 insertions(+), 1 deletion(-)

(limited to 'include')

diff --git a/include/ocl/fix/checksum.hpp b/include/ocl/fix/checksum.hpp
index c075b13..31aee75 100644
--- a/include/ocl/fix/checksum.hpp
+++ b/include/ocl/fix/checksum.hpp
@@ -9,9 +9,50 @@
 #define __OCL_FIX_CHECKSUM
 
 #include <ocl/fix/detail/config.hpp>
+#include <ocl/fix/parser.hpp>
+#include <boost/core/detail/string_view.hpp>
 
 namespace ocl::fix
 {
-}
+
+	/// \brief Returns the checksum index of a FIX message.
+	/// \param range the range_buffer containing the message.
+	/// \throws runtime_error if the FIX message is invalid (missing tag "8").
+	inline std::string try_index_checksum(range_buffer& fix)
+	{
+		if (fix.is_valid())
+			return fix["10"];
+		else
+			detail::throw_runtime_error();
+	}
+
+	/// \brief FIX message operators namespace.
+	namespace operators::fix
+	{
+		using checksum_type = long long;
+
+		/// \brief Calculates the FIX protocol checksum for a message.
+		/// \param in_ Pointer to the message buffer.
+		/// \param len Length of the message in bytes.
+		/// \return The checksum value (sum of all bytes modulo 256).
+		inline checksum_type
+			checksum(const char* in_,
+				 const long  len)
+		{
+			if (len < 1)
+				return 0L;
+
+			long long cks{};
+
+			for (long idx{}; idx < len; ++idx)
+			{
+				cks += static_cast<unsigned char>(in_[idx]);
+			}
+
+			return cks % 256;
+		}
+	} // namespace operators::fix
+
+} // namespace ocl::fix
 
 #endif
-- 
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