shm: hide picosha2 from header

fairmq/shmem/Common.cxx

@@ -0,0 +1,48 @@
+/********************************************************************************
+ *    Copyright (C) 2021 GSI Helmholtzzentrum fuer Schwerionenforschung GmbH    *
+ *                                                                              *
+ *              This software is distributed under the terms of the             *
+ *              GNU Lesser General Public Licence (LGPL) version 3,             *
+ *                  copied verbatim in the file "LICENSE"                       *
+ ********************************************************************************/
+
+#include "Common.h"
+
+#include <picosha2.h>
+
+#include <unistd.h>
+
+#include <sstream>
+#include <string>
+
+namespace fair::mq::shmem
+{
+
+std::string makeShmIdStr(const std::string& sessionId, const std::string& userId)
+{
+    std::string seed(userId + 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());
+
+    return picosha2::bytes_to_hex_string(hash.begin(), hash.end());
+}
+
+std::string makeShmIdStr(const std::string& sessionId)
+{
+    return makeShmIdStr(sessionId, std::to_string(geteuid()));
+}
+
+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;
+}
+
+
+}   // namespace fair::mq::shmem