关于Google的SparseHashMap

关于Google的SparseHashMap

官方网站: http://google-sparsehash.googlecode.com

官方说,可以轻松的用dense_hash_map和sparse_hash_map替换掉hash_map或者unordered_map.
dense系列适用于"小字典",sparse系列适用于"大字典".

这货挺好使的,性能上也是不错的.
但是呢,有两点比较伤脑筋,这和其他的hashmap不兼容,
那就是要在dense要在插入之前必须执行一次set_empty_key,dense和sparse要在删除之前必须执行一次set_deleted_key.为了适配这个不兼容性,我整了这么个玩意:

#include  < google / dense_hash_map >
#include  < google / sparse_hash_map >
using  GOOGLE_NAMESPACE::dense_hash_map;
using  GOOGLE_NAMESPACE::sparse_hash_map;

template  < typename Value, typename Key  =  std:: string >
class  TStringDenseHashMap :  public  dense_hash_map < Key, Value >
{
public:
    TStringDenseHashMap()
    {
        set_empty_key( std::string("") );
        set_deleted_key( std::string(" ") );
    }
} ;
template  < typename Value, typename Key  =  std:: string >
class  TStringSparseHashMap :  public  sparse_hash_map < Key, Value >
{
public:
    TStringSparseHashMap()
    {
        set_deleted_key( (" ") );
    }
} ;

namespace  detail
{
    struct eqstr
    {
        bool operator()(const char* s1, const char* s2) const
        {
            return (s1 == s2) || (s1 && s2 && strcmp(s1, s2) == 0);
        }
    };
}
template  < typename Value, typename Key  =   const   char *>
class  TConstCharDenseHashMap :  public  dense_hash_map < Key, Value, stdext::hash_compare < Key > , detail::eqstr >
{
public:
    TConstCharDenseHashMap()
    {
        set_empty_key( ("") );
        set_deleted_key( (" ") );
    }
} ;
template  < typename Value, typename Key  =   const   char *>
class  TConstCharSparseHashMap :  public  sparse_hash_map < Key, Value, stdext::hash_compare < Key > , detail::eqstr >
{
public:
    TConstCharSparseHashMap()
    {
        set_deleted_key( (" ") );
    }
} ;

嗯,这样就可以很好的兼容了.
虽然.....很恶心.

以下附上测试代码:

void testGoogleHashMap()
{
{
typedef TStringDenseHashMap<std::string> StringDenseHashMap;
StringDenseHashMap map1;
size_t nSize = 0;

map1["张三"] = "张三";
map1["李四"] = "李四";
map1["王五"] = "王五";
nSize = map1.size();

StringDenseHashMap::iterator iter = map1.find("张三");
std::string strResult;
if (iter != map1.end())
{
strResult = iter->second;
}
std::cout << map1["张三"] << "," << map1["李四"] << "," << map1["王五"] << std::endl;

map1.erase("张三");
map1.erase("李四");
map1.erase("王五");
nSize = map1.size();
}

{
typedef TStringSparseHashMap<std::string> StringSparseHashMap;
StringSparseHashMap map1;
size_t nSize = 0;

map1["张三"] = "张三";
map1["李四"] = "李四";
map1["王五"] = "王五";
nSize = map1.size();

StringSparseHashMap::iterator iter = map1.find("张三");
std::string strResult;
if (iter != map1.end())
{
strResult = iter->second;
}
std::cout << map1["张三"] << "," << map1["李四"] << "," << map1["王五"] << std::endl;

map1.erase("张三");
map1.erase("李四");
map1.erase("王五");
nSize = map1.size();
}

{
typedef TConstCharDenseHashMap<const char*> ConstCharDenseHashMap;
ConstCharDenseHashMap map1;
size_t nSize = 0;

map1["张三"] = "张三";
map1["李四"] = "李四";
map1["王五"] = "王五";
nSize = map1.size();

ConstCharDenseHashMap::iterator iter = map1.find("张三");
std::string strResult;
if (iter != map1.end())
{
strResult = iter->second;
}
std::cout << map1["张三"] << "," << map1["李四"] << "," << map1["王五"] << std::endl;

map1.erase("张三");
map1.erase("李四");
map1.erase("王五");
nSize = map1.size();
}

{
typedef TConstCharSparseHashMap<std::string> ConstCharSparseHashMap;
ConstCharSparseHashMap map1;
size_t nSize = 0;

map1["张三"] = "张三";
map1["李四"] = "李四";
map1["王五"] = "王五";
nSize = map1.size();

ConstCharSparseHashMap::iterator iter = map1.find("张三");
std::string strResult;
if (iter != map1.end())
{
strResult = iter->second;
}
std::cout << map1["张三"] << "," << map1["李四"] << "," << map1["王五"] << std::endl;

map1.erase("张三");
map1.erase("李四");
map1.erase("王五");
nSize = map1.size();
}
} ;