quote-bot/levenshtein.c

#define _POSIX_C_SOURCE 200809L /* strnlen */
#include <string.h>             /* memset */
#include <stdlib.h>             /* malloc */

#include "levenshtein.h"

/* <https://rosettacode.org/wiki/Levenshtein_distance#C>
 * TODO: use this for quote duplicate removal */
static int levenshtein_dist(const char *s, const char *t, int *d, int ls, int lt, int i, int j) {
    int x, y;
    int *n = d + i * ls + j;

    if (*n >= 0)
        return *n;

    if (i == ls)
        x = lt - j;
    else if (j == lt)
        x = ls - i;
    else if (s[i] == t[j])
        x = levenshtein_dist(s, t, d, ls, lt, i + 1, j + 1);
    else {
        x = levenshtein_dist(s, t, d, ls, lt, i + 1, j + 1);

        if ((y = levenshtein_dist(s, t, d, ls, lt, i, j + 1)) < x)
            x = y;
        if ((y = levenshtein_dist(s, t, d, ls, lt, i + 1, j)) < x)
            x = y;
        x++;
    }
    return *n = x;
}

int levenshtein(const char *s, const char *t) {
    int i, j, n;
    int ls = (int)strnlen(s, 128), lt = (int)strnlen(t, 128);
    int *d;
    size_t size;
    size = sizeof(int) * (unsigned long)((ls + 1) * (lt + 1));
    d = (int *)malloc(size);
    memset(d, 0, size);
    for (i = 0; i <= ls; i++)
        for (j = 0; j <= lt; j++)
            *(d + i * ls + j) = -1;
    n = levenshtein_dist(s, t, d, ls, lt, 0, 0);
    free(d);
    d = NULL;
    return n;
}