shm: make shmId also available as uint64_t

fairmq/shmem/Common.h

@@ -11,6 +11,7 @@
 #include <picosha2.h>
 
 #include <atomic>
+#include <sstream>
 #include <string>
 #include <functional> // std::equal_to
 
@@ -194,15 +195,25 @@ struct RegionBlock
 
 // find id for unique shmem name:
 // a hash of user id + session id, truncated to 8 characters (to accommodate for name size limit on some systems (MacOS)).
-inline std::string buildShmIdFromSessionIdAndUserId(const std::string& sessionId)
+inline std::string makeShmIdStr(const std::string& sessionId)
 {
     std::string seed((std::to_string(geteuid()) + sessionId));
     // generate a 8-digit hex value out of sha256 hash
     std::vector<unsigned char> hash(4);
     picosha2::hash256(seed.begin(), seed.end(), hash.begin(), hash.end());
-    std::string shmId = picosha2::bytes_to_hex_string(hash.begin(), hash.end());
 
-    return shmId;
+    return picosha2::bytes_to_hex_string(hash.begin(), hash.end());
+}
+
+inline uint64_t makeShmIdUint64(const std::string& sessionId)
+{
+    std::string shmId = makeShmIdStr(sessionId);
+    uint64_t id = 0;
+    std::stringstream ss;
+    ss << std::hex << shmId;
+    ss >> id;
+
+    return id;
 }
 
 struct SegmentSize : public boost::static_visitor<size_t>