fst_reader.cpp

/*********************************************************************
 * File:	fst_reader.cpp 
 * Desc:	
 *
 *********************************************************************/

#include <fstream>
#include <indexlib/fst/fst_reader.h>
#include <indexlib/fst/fstlib.h>

using namespace std;
	
FstReader::FstReader(): m_keyCnt(0), m_size(0), m_fstByteArr(NULL) {}

FstReader::~FstReader() {
    if (m_fstByteArr) {
        delete m_fstByteArr;
        m_fstByteArr = NULL;
    }
    
    m_size = 0;
}

bool FstReader::Init(const std::string &fstMmapFile) {
    ifstream fin(fstMmapFile, ios_base::binary);
    if (!fin) { 
//         LOG(ERROR, "cannot open: %s", fstMmapFile.c_str());
        return false;
	}
    
    fin.seekg(0, ios_base::end);
    auto size = fin.tellg();
    fin.seekg(0, ios_base::beg);

    m_keyCnt = 0;
    fin.read((char*)(&m_keyCnt), sizeof(size_t));
//     LOG(INFO, "read fst file: %s, file size=%lu, key count=%lu", fstMmapFile.c_str(), m_keyCnt, size);

    if (0 == m_keyCnt) return true;

    size -= sizeof(size_t);
    m_size = size;
    m_fstByteArr = new char[m_size];
    fin.read(m_fstByteArr, m_size);

    fin.close();
    return true;
}

bool FstReader::ExactMatch(const char *key, output_t &pMatchPos) {
    if (0 == m_keyCnt) return false;

    auto outputs = fst::exact_match_search<output_t>(m_fstByteArr, m_size, key);
 
    if(outputs.empty()) {
        pMatchPos = -1;
    } else {
        pMatchPos = (output_t)(outputs[0]);
    }

	return (pMatchPos != -1);
}

output_t FstReader::GetUnitPos(const char *key)
{
    output_t matchPos = -1;
    ExactMatch(key, matchPos);

    return matchPos;
}

uint32_t FstReader::GetSlotNum()
{
	return m_keyCnt;
}