c++ - How to add strings to cuckoo filter? -


i running modified version of example provided @ cuckoo filter repository: https://github.com/efficient/cuckoofilter/blob/master/example/test.cc

i want add strings cuckoo filter. although string added when check if exists in filter, returns false. can point out what's wrong approach?

size_t total_items  = 1000000; cuckoofilter<string, 12> filter(total_items);  // insert items cuckoo filter string temp1 = "sample"; if (filter.add(temp1) != cuckoofilter::ok) {         cout<<"not added"<<endl; }      // check if inserted items in filter string temp2 = "sample"; assert(filter.contain(temp2) == cuckoofilter::ok);

the assertion should true false in case. why?

a quick glance @ source of https://github.com/efficient/cuckoofilter/blob/master/src/cuckoofilter.h#l65 reveals uses function 

inline void generateindextaghash(const itemtype &item, size_t* index, uint32_t* tag) const {     std::string hashed_key = hashutil::sha1hash(         (const char*) &item,         sizeof(item)     );  // ... rest skipped brevity  }

to generate initial index , fingerprint (tag) of item. problem hashes actual object passed. simplify, this:

// filter.add(temp1) inside hashutil::sha1hash((const char*) &temp1, sizeof(temp1));  // filter.contain(temp2) inside hashutil::sha1hash((const char*) &temp2, sizeof(temp2));

basically, hashes 2 different objects which, expected, generate different hashes , map different buckets.

for work in case need call hashutil::sha1hash() in way hashes actual string data, is:

// should hashutil::sha1hash(     temp1.c_str(), // <-- notice pass pointer actual character data rather pointer instance of std::string()     temp1.length() );   hashutil::sha1hash(     temp2.c_str(), // <-- notice pass pointer actual character data rather pointer instance of std::string()     temp2.length() );

this should answer why? question.

can point out what's wrong approach?

there nothing wrong approach per-se doesn't work might've expected, because library not support such use case.


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