Author: kpvdr Date: 2009-01-08 09:53:33 -0500 (Thu, 08 Jan 2009) New Revision: 3035 Modified: store/trunk/cpp/lib/MessageStoreImpl.cpp store/trunk/cpp/lib/MessageStoreImpl.h Log: Improved hash function gives more even distribution of queues across 29 dirs Modified: store/trunk/cpp/lib/MessageStoreImpl.cpp =================================================================== --- store/trunk/cpp/lib/MessageStoreImpl.cpp 2009-01-07 20:10:31 UTC (rev 3034) +++ store/trunk/cpp/lib/MessageStoreImpl.cpp 2009-01-08 14:53:33 UTC (rev 3035) @@ -1729,15 +1729,20 @@ return getJrnlDir(queue.getName().c_str()); } +u_int32_t MessageStoreImpl::bHash(const std::string str) +{ + // Daniel Bernstein hash fn + u_int32_t h = 0; + for (std::string::const_iterator i = str.begin(); i < str.end(); i++) + h = 33*h + *i; + return h; +} + std::string MessageStoreImpl::getJrnlDir(const char* queueName) //for exmaple /var/rhm/ + queueDir/ { std::stringstream dir; dir << getJrnlBaseDir() << std::hex << std::setfill('0') << std::setw(4); - u_int32_t count = 0; - for (u_int32_t i = 0; i < strlen(queueName); i++) { - count += queueName[i]; - } - dir << (count % 29); // Use a prime number for better distribution across dirs + dir << (bHash(queueName) % 29); // Use a prime number for better distribution across dirs dir << "/" << queueName << "/"; return dir.str(); } Modified: store/trunk/cpp/lib/MessageStoreImpl.h =================================================================== --- store/trunk/cpp/lib/MessageStoreImpl.h 2009-01-07 20:10:31 UTC (rev 3034) +++ store/trunk/cpp/lib/MessageStoreImpl.h 2009-01-08 14:53:33 UTC (rev 3035) @@ -241,6 +241,7 @@ // journal functions void createJrnlQueue(const qpid::broker::PersistableQueue& queue); + u_int32_t bHash(const std::string str); std::string getJrnlDir(const qpid::broker::PersistableQueue& queue); //for exmaple /var/rhm/ + queueDir/ std::string getJrnlDir(const char* queueName); std::string getJrnlBaseDir();