utils.h

#ifndef PQTABLE_UTILS_H
#define PQTABLE_UTILS_H

//#include <opencv2/opencv.hpp>
#include <fstream>
#include <time.h>
#include <vector>


namespace pqtable {

	// Iterative reader class for reading .ivecs or .fvecs files.
	// The next vector (std::vector<float>) is read by Next() function.
	//
	// Usage:
	//   ItrReader reader("data.fvecs", "fvecs");
	//   while(!reader.IsEnd()){
	//     std::vector<float> vec = reader.Next();
	//     /* some stuff for vec */
	//   }
	//
	// Optional wrapper interface:
	//   int top_n = 100;
	//   std::vector<std::vector<float> > vecs = ReadTopN("data.fvecs", "fvecs", top_n);

	// Interface (abstract basic class) of iterative reader
	class I_ItrReader {
	public:
		virtual ~I_ItrReader() {}
		virtual bool IsEnd() = 0;
		virtual std::vector<float> Next()=0;
		virtual std::vector<int> NextInt()=0;

	};

	// Iterative reader for fvec file
	class FvecsItrReader : I_ItrReader {
	public:
		FvecsItrReader(std::string filename);
		bool IsEnd();
		std::vector<float> Next();
		std::vector<int> NextInt();
	private:
		FvecsItrReader(); // prohibit default construct
		std::ifstream ifs;
		std::vector<float> vec; // store the next vec
		bool eof_flag;
	};
	
	// Iterative reader for ivec file
	class IvecsItrReader : I_ItrReader {
	public:
		IvecsItrReader(std::string filename);
		bool IsEnd();
		std::vector<float> Next();
		std::vector<int> NextInt();
	private:
		IvecsItrReader(); // prohibit default construct
		std::ifstream ifs;
		std::vector<int> vec; // store the next vec
		bool eof_flag;
	};

	// Proxy class
	class ItrReader {
	public:
		// ext must be "fvecs" or "ivecs"
		ItrReader(std::string filename, std::string ext);
		~ItrReader();

		bool IsEnd();
		std::vector<float> Next();
		std::vector<int> NextInt();

	private:
		ItrReader();
		I_ItrReader *m_reader;
	};

	// Wrapper. Read top-N vectors
	// If top_n = -1, then read all vectors
	std::vector<std::vector<float> > ReadTopN(std::string filename, std::string ext, int top_n = -1);
	std::vector<std::vector<int> > ReadTopNI(std::string filename, std::string ext, int top_n = -1);
}

#endif // PQTABLE_UTILS_H