strings_util.cpp

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#include "strings_util.h"
 
#include <algorithm>
#include <cstring>
 
std::string hhunter::util::to_lowercase(std::string str)
{
    std::transform(str.begin(), str.end(), str.begin(), tolower);
    return str;
}
 
bool hhunter::util::is_cstr_equal(char const *a, char const *b, const size_t max_len)
{
    for (size_t i = 0; i < max_len; ++i) {
        if (tolower(a[i]) != tolower(b[i])) {
            return false;
        }
        if (tolower(a[i]) == '\0') break;
    }
    return true;
}
 
#define MIN(x,y) ((x) < (y) ? (x) : (y))
 
size_t hhunter::util::levenshtein_distance(const char s1[], const char s2[])
{
    const size_t MAX_LEN = 100;
    const size_t len1 = strlen(s1);
    const size_t len2 = strlen(s2);
 
    if (len1 >= MAX_LEN || len2 >= MAX_LEN) return(-1);
 
    //init the distance matrix
    int dist[MAX_LEN][MAX_LEN] = { 0 };
    for (int i = 0;i <= len1;i++) {
        dist[0][i] = i;
    }
    for (int j = 0;j <= len2; j++) {
        dist[j][0] = j;
    }
    // calculate
    for (int j = 1;j <= len1; j++) {
        for (int i = 1;i <= len2; i++) {
            int track = 1;
            if (s1[i - 1] == s2[j - 1]) {
                track = 0;
            }
            int t = MIN((dist[i - 1][j] + 1), (dist[i][j - 1] + 1));
            dist[i][j] = MIN(t, (dist[i - 1][j - 1] + track));
        }
    }
    return dist[len2][len1];
}
 
size_t hhunter::util::str_hist_diffrence(const char s1[], const char s2[])
{
    const size_t MAX_LEN = 255;
    size_t hist1[MAX_LEN] = { 0 };
    size_t hist2[MAX_LEN] = { 0 };
 
    const size_t len1 = strlen(s1);
    const size_t len2 = strlen(s2);
 
    for (size_t i = 0; i < len1; i++) {
        char c = tolower(s1[i]);
        hist1[c]++;
    }
 
    for (size_t i = 0; i < len2; i++) {
        char c = tolower(s2[i]);
        hist2[c]++;
    }
 
    size_t diffs = 0;
    for (size_t i = 0; i < MAX_LEN; i++) {
        if (hist2[i] == hist1[i]) continue;
        diffs++;
    }
    return diffs;
}
 
hhunter::util::stringsim_type hhunter::util::is_string_similar(const std::string &param, const std::string &filter)
{
    bool sim_found = (param.find(filter) != std::string::npos) || (filter.find(param) != std::string::npos);
    if (sim_found) return SIM_SUBSTR;
 
    size_t dist = util::levenshtein_distance(filter.c_str(), param.c_str());
    if (dist <= (param.length() / 2)) {
        sim_found = true;
    }
    if (dist >= param.length() || dist >= filter.length()) {
        sim_found = false;
    }
    if (sim_found) return SIM_LAV_DIST;
 
    size_t diff = util::str_hist_diffrence(filter.c_str(), param.c_str());
    if (diff <= (param.length() / 2) || diff <= (filter.length() / 2)) {
        sim_found = true;
    }
    if (diff >= param.length() || diff >= filter.length()) {
        sim_found = false;
    }
    if (sim_found) return SIM_HIST;
    return SIM_NONE;
}