AtomicId.cc

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#include <algorithm>
#include <cstddef>
#include <cstdlib>
#include <cstring>
#include <mutex>
#include <set>

#include "FWCore/Utilities/interface/thread_safety_macros.h"
#include "PhysicsTools/MVAComputer/interface/AtomicId.h"

namespace { // anonymous
    struct StringLess {
        bool operator()(const char *id1, const char *id2) const
        { return std::strcmp(id1, id2) < 0; }
    };

    class IdCache {
        public:
        ~IdCache();

        inline const char *findOrInsert(const char *string) throw();

        private:
        typedef std::multiset<const char *, StringLess> IdSet;

        IdSet           idSet;
        std::allocator<char>    stringAllocator;
                std::mutex          mutex;
    };
} // anonymous namespace

IdCache::~IdCache()
{
    for(std::multiset<const char*, StringLess>::iterator iter =
        idSet.begin(); iter != idSet.end(); iter++)
        stringAllocator.deallocate(const_cast<char*>(*iter),
                                   std::strlen(*iter));
}

const char *IdCache::findOrInsert(const char *string) throw()
{
    std::lock_guard<std::mutex> scoped_lock(mutex);

    IdSet::iterator pos = idSet.lower_bound(string);
    if (pos != idSet.end() && std::strcmp(*pos, string) == 0)
        return *pos;

    std::size_t size = std::strlen(string) + 1;
    char *unique = stringAllocator.allocate(size);
    std::memcpy(unique, string, size);

    idSet.insert(pos, unique);

    return unique;
}

namespace PhysicsTools {

static IdCache &getAtomicIdCache()
{
    CMS_THREAD_SAFE static IdCache atomicIdCache;
    return atomicIdCache;
}

const char *AtomicId::lookup(const char *string) throw()
{
    if (string)
        return getAtomicIdCache().findOrInsert(string);

    return nullptr;
}

} // namespace PhysicsTools