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/**
* @file lltypeinfolookup.h
* @author Nat Goodspeed
* @date 2012-04-08
* @brief Template data structure like std::map<std::type_info*, T>
*
* $LicenseInfo:firstyear=2012&license=viewerlgpl$
* Copyright (c) 2012, Linden Research, Inc.
* $/LicenseInfo$
*/
#if ! defined(LL_LLTYPEINFOLOOKUP_H)
#define LL_LLTYPEINFOLOOKUP_H
#include "llsortedvector.h"
#include <typeinfo>
/**
* LLTypeInfoLookup is specifically designed for use cases for which you might
* consider std::map<std::type_info*, VALUE>. We have several such data
* structures in the viewer. The trouble with them is that at least on Linux,
* you can't rely on always getting the same std::type_info* for a given type:
* different load modules will produce different std::type_info*.
* LLTypeInfoLookup contains a workaround to address this issue.
*
* Specifically, when we don't find the passed std::type_info*,
* LLTypeInfoLookup performs a linear search over registered entries to
* compare name() strings. Presuming that this succeeds, we cache the new
* (previously unrecognized) std::type_info* to speed future lookups.
*
* This worst-case fallback search (linear search with string comparison)
* should only happen the first time we look up a given type from a particular
* load module other than the one from which we initially registered types.
* (However, a lookup which wouldn't succeed anyway will always have
* worst-case performance.) This class is probably best used with less than a
* few dozen different types.
*/
template <typename VALUE>
class LLTypeInfoLookup
{
public:
typedef LLTypeInfoLookup<VALUE> self;
typedef LLSortedVector<const std::type_info*, VALUE> vector_type;
typedef typename vector_type::key_type key_type;
typedef typename vector_type::mapped_type mapped_type;
typedef typename vector_type::value_type value_type;
typedef typename vector_type::iterator iterator;
typedef typename vector_type::const_iterator const_iterator;
LLTypeInfoLookup() {}
iterator begin() { return mVector.begin(); }
iterator end() { return mVector.end(); }
const_iterator begin() const { return mVector.begin(); }
const_iterator end() const { return mVector.end(); }
bool empty() const { return mVector.empty(); }
std::size_t size() const { return mVector.size(); }
std::pair<iterator, bool> insert(const std::type_info* key, const VALUE& value)
{
return insert(value_type(key, value));
}
std::pair<iterator, bool> insert(const value_type& pair)
{
return mVector.insert(pair);
}
// const find() forwards to non-const find(): this can alter mVector!
const_iterator find(const std::type_info* key) const
{
return const_cast<self*>(this)->find(key);
}
// non-const find() caches previously-unknown type_info* to speed future
// lookups.
iterator find(const std::type_info* key)
{
iterator found = mVector.find(key);
if (found != mVector.end())
{
// If LLSortedVector::find() found, great, we're done.
return found;
}
// Here we didn't find the passed type_info*. On Linux, though, even
// for the same type, typeid(sametype) produces a different type_info*
// when used in different load modules. So the fact that we didn't
// find the type_info* we seek doesn't mean this type isn't
// registered. Scan for matching name() string.
for (typename vector_type::iterator ti(mVector.begin()), tend(mVector.end());
ti != tend; ++ti)
{
if (std::string(ti->first->name()) == key->name())
{
// This unrecognized 'key' is for the same type as ti->first.
// To speed future lookups, insert a new entry that lets us
// look up ti->second using this same 'key'.
return insert(key, ti->second).first;
}
}
// We simply have never seen a type with this type_info* from any load
// module.
return mVector.end();
}
private:
vector_type mVector;
};
#endif /* ! defined(LL_LLTYPEINFOLOOKUP_H) */
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