fix endianness in RHEL8.10

Signed-off-by: Himanshu Choudhary <Himanshu.Choudhary@amd.com>

Author: HimanshuChoudhary-Xilinx

src/cpp/common/uid_md5.h

@@ -5,8 +5,13 @@
 #define _AIEBU_COMMON_UID_MD5_H_
 
 #include <vector>
+#include <algorithm>
+#include <cstring>
+#include <iomanip>
+#include <<cstdint>>
+#include <sstream>
+#include <boost/version.hpp>
 #include <boost/uuid/detail/md5.hpp>
-#include <boost/algorithm/hex.hpp>
 
 namespace aiebu {
 
@@ -35,9 +40,28 @@ class uid_md5 {
 
     constexpr size_t element_size = sizeof(digest[0]);
 
-    // Early-exit doesn't work here. If sizeof(digest[0]] == 1
-    // then the compiler would complain about unreachable code
-    // because the if is compiled at compile time.
+    // Boost 1.71+ writes MD5 digest bytes in RFC 1321 order (little-endian per 32-bit
+    // word). Older Boost used host-endian byte layout in the digest buffer; the
+    // reverse below normalized that for stable output. Applying the reverse on 1.71+
+    // scrambles the digest (see boost/uuid/detail/md5.hpp, BOOST_UUID_DETAIL_MD5_BYTE_OUT).
+
+    // digest_type is either unsigned char[16] (element_size == 1) or unsigned int[4]
+    // (element_size == 4), depending on Boost. Pre-1.71 vs 1.71+ MD5 byte layout differs.
+
+    // BOOST_VERSION < 107100  and element_size ==1     -- reverse each 4-byte word
+    // BOOST_VERSION < 107100  and element_size !=1     -- do not reverse
+    // BOOST_VERSION >= 107100  and element_size !=1    -- reverse each element_size chunk
+    // BOOST_VERSION >= 107100  and element_size ==1    -- do not reverse
+#if BOOST_VERSION < 107100 || defined(BOOST_UUID_COMPAT_PRE_1_71_MD5)
+    // Pre-1.71 (or compat): element_size == 1 -> reverse each 4-byte MD5 word;
+    // element_size != 1 -> leave sig as memcpy'd from digest.
+    if constexpr (element_size == 1) {
+      for (size_t i = 0; i < md5_size; i += 4)
+        std::reverse(sig.data() + i, sig.data() + i + 4);
+    }
+#else
+    // Boost >= 1.71: element_size != 1 -> reverse each element-sized chunk;
+    // element_size == 1 -> leave as memcpy'd.
     if constexpr (element_size != 1) {
       // Different boost versions model digest_type differently:
       // 1. typedef unsigned int(digest_type)[4];
@@ -53,6 +77,7 @@ class uid_md5 {
         tcurr = tend;
       }
     }
+#endif
 
     return sig;
   }