lib11sht/lib11sht.c

/* ************************************************************************ *
 *    lib11sht.c, v1.0                                                      *
 *    Fuzzy comparison library implementation                               *
 *                                                                          *
 *    Copyright (C) 2025 by Ruben Carlo Benante <rcb@beco.cc>               *
 *    GNU GPL version 2 or later.                                           *
 * ************************************************************************ */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <errno.h>

#include "lib11sht.h"

/* Internal helpers — kept private to this translation unit. */
static int   uselesschar(int c);
static void  trim(char *s);
static void  asciify(const char *src, char *dest);
static int   ulen(unsigned char c);
static float shit11(char *s1, char *s2);
static float fmin3(float a, float b, float c);
static float fmax2(float a, float b);

/* ---------------------------------------------------------------------- */
int fequal(float a, float b, float delta)
{
    if(a < b - delta)
        return -1;
    if(a > b + delta)
        return  1;

    /* b-delta <= a <= b+delta */
    return 0;
}

/* ---------------------------------------------------------------------- */
int sequal(char *a, char *b, float thr, float *ratio, char *s1, char *s2)
{
    int i;

    if(!a || !b || !s1 || !s2 || !ratio)
    {
        errno = EINVAL;
        return 0;
    }

    /* remove accents */
    asciify(a, s1);
    asciify(b, s2);

    /* trim spaces (leading, trailing, and internal collapse) */
    trim(s1);
    trim(s2);

    /* lowercase */
    for(i=0; i<LEVN_SBUFF && s1[i]; i++)
        s1[i] = (char)tolower((unsigned char)s1[i]);
    for(i=0; i<LEVN_SBUFF && s2[i]; i++)
        s2[i] = (char)tolower((unsigned char)s2[i]);

    i=strcmp(s1, s2);
    if(!i)
    {
        *ratio=1.0;
        return 0;
    }
    *ratio = shit11(s1, s2);
    if(*ratio > thr)
        return 0;
    return (i < 0)? -1 : 1;
}

/* ---------------------------------------------------------------------- */
/* Levenshtein similarity ratio 0.0..1.0 */
static float shit11(char *s1, char *s2)
{
    int len1, len2;
    int i, j, cost;

    len1 = strlen(s1);
    len2 = strlen(s2);

    if(len1 == 0 && len2 == 0)
        return 1.0;                 /* both empty == identical */
    if(len1 == 0 || len2 == 0)
        return 0.0;                 /* one empty == no similarity */

    int d[len1+1][len2+1];

    for(i=0; i<=len1; i++)
        d[i][0] = i;
    for(j=0; j<=len2; j++)
        d[0][j] = j;

    for(i=1; i <= len1; i++)
        for(j=1; j <= len2; j++)
        {
            cost = (s1[i-1] == s2[j-1])? 0 : 1;
            d[i][j] = fmin3(d[i-1][j] + 1, d[i][j-1] + 1, d[i-1][j-1] + cost);
        }
    return 1.0 - d[len1][len2] / fmax2(len1, len2);
}

/* ---------------------------------------------------------------------- */
static float fmin3(float a, float b, float c)
{
    float m=a;
    if(b<m)
        m=b;
    if(c<m)
        m=c;
    return m;
}

/* ---------------------------------------------------------------------- */
static float fmax2(float a, float b)
{
    return (a>b)? a : b;
}

/* ---------------------------------------------------------------------- */
static int uselesschar(int c)
{
    if(c == ' ') return 1;
    if(c == '\t') return 1;
    if(c == '\n') return 1;
    if(c == '\r') return 1;
    if(c == 0xC2) return 1;
    if(c == 0xA0) return 1;
    return 0;
}

/* ---------------------------------------------------------------------- */
/* remove leading/trailing whitespace + collapse internal multiple whitespace */
static void trim(char *s)
{
    int len, i, j, fin = 0;

    if(!s)
        return;
    /* remove leading spaces */
    i = 0;
    while(uselesschar(s[i]))
        i++;
    if(i > 0)
        memmove(s, s + i, strlen(s + i) + 1);
    /* remove trailing spaces */
    len = strlen(s);
    while(len > 0 && uselesschar(s[len - 1]))
        s[--len] = '\0';
    /* remove double spaces in between */
    i=j=0;
    while(s[i] != '\0')
    {
        if(uselesschar(s[i]))
        {
            if(!fin)
            {
                s[j++] = ' ';
                fin = 1;
            }
        }
        else
        {
            s[j++] = s[i];
            fin = 0;
        }
        i++;
    }
    s[j] = '\0';
}

/* ---------------------------------------------------------------------- */
static int ulen(unsigned char c)
{
    if((c & 0xE0) == 0xC0) return 2; /* UTF8 lead 2 bytes 110xxxxx */
    if((c & 0xF0) == 0xE0) return 3; /* UTF8 lead 3 bytes 1110xxxx */
    if((c & 0xF8) == 0xF0) return 4; /* UTF8 lead 4 bytes 11110xxx */
    return 1; /* ASCII or invalid or UTF continuation byte */
}

/* ---------------------------------------------------------------------- */
static void asciify(const char *src, char *dest)
{
    int len, i, k, j, found;
    char ch[5]; /* UTF8 multibyte char */
    const char transclear[] =
    "AEIOUAEIOUAEIOUAEIOUAEIOU"
    "aeiouaeiouaeiouaeiouaeiou"
    "aoCcNn123"
    " ";                                /* NBSP → space */
    const char *translit[] = {
        "Á","É","Í","Ó","Ú", "À","È","Ì","Ò","Ù",
        "Ã","Ẽ","Ĩ","Õ","Ũ", "Â","Ê","Î","Ô","Û",
        "Ä","Ë","Ï","Ö","Ü", "á","é","í","ó","ú",
        "à","è","ì","ò","ù", "ã","ẽ","ĩ","õ","ũ",
        "â","ê","î","ô","û", "ä","ë","ï","ö","ü",
        "ª","º","Ç","ç","Ñ", "ñ","¹","²","³",
        "\xC2\xA0"};                    /* NBSP */

    if(!src || !dest)
        return;
    if(*src=='\0')
    {
        dest[0] = '\0';            /* maintain "dest is a valid C string" contract */
        return;
    }

    j=i=0;
    while(src[i]!='\0' && i < LEVN_SBUFF)
    {
        if(((unsigned char)src[i] & 0xc0) == 0x80) /* non ASCII, UTF continuation char */
        {
            i++;
            continue;
        }

        len = ulen((unsigned char)src[i]);
        memcpy(ch, &src[i], len);
        ch[len]='\0';
        if(((unsigned char)src[i]) < 0x80) /* ASCII */
        {
            dest[j++] = ch[0];
            i++;
            continue;
        }

        found = 0;
        for(k=0; k<(int)(sizeof(translit)/sizeof(translit[0])); k++)
            if(strcmp(ch, translit[k])==0)
            {
                dest[j++] = transclear[k];
                found = 1;
                break;
            }
        if(!found)
            dest[j++] = '?';
        i+=len;
    }
    dest[j]='\0';
}

/* ---------------------------------------------------------------------- */
/* vi: set ai et ts=4 sw=4 tw=0 wm=0 fo=croql : C config for Vim modeline */