add space between cjk & other chars

cjkpad.c

/*
gcc ./cjkpad.c -o cjkpad `pkg-config --libs --cflags icu-uc icu-io` && ./cjkpad
*/
#include <stdio.h>
#include <string.h>
#include <unicode/utext.h>
#include <unicode/ustdio.h>

static UErrorCode err = U_ZERO_ERROR;

// One grapheme?
typedef struct gra {
    UChar32 cp; // Code point
    UBlockCode block;  // unicode block
    size_t start;  // starting pos at the str[]
    size_t length; // number of char needed (cjk is mostly 3 char)
} gra;

bool isAlphaNum(gra *g) {
    return 'a' < g->cp && g->cp < 'z' || 'A' < g->cp && g->cp < 'Z' || '0' < g->cp && g->cp < '9';
}

bool isCjk(gra *g) {
    return g->block == UBLOCK_CJK_UNIFIED_IDEOGRAPHS;
}

void padCjk(const char str[]) {

    char formatted[1024] = {0}; // 1kiB
    gra Gra[1024];
    int graLength; // number of Gra

    { // 1st loop that analysis str
        UText *ut = utext_openUTF8(NULL, str, -1, &err);
        int begin, end;
        int i = 0;
        for (UChar32 cp = utext_next32From(ut, 0);
             cp > -1;
             cp = utext_next32(ut), i++) {

            end = utext_getNativeIndex(ut);

            Gra[i].cp = cp;
            Gra[i].block = ublock_getCode(cp);
            Gra[i].start = begin;
            Gra[i].length = end - begin;

            begin = end;
        }
        graLength = i;
    }

    { // 2nd loop that add spaces
        strncat(formatted, &str[Gra[0].start], Gra[0].length);
        for (int j = 1; j <= graLength; j++) {

            gra *prev = &Gra[j - 1];
            gra *curr = &Gra[j];
            gra *next = &Gra[j + 1];

            u_printf("%C%C%C\n", prev->cp, curr->cp, next->cp);

            if ((isAlphaNum(prev) && isCjk(curr))
                || (isCjk(prev) && isAlphaNum(curr))) {
                strcat(formatted, " ");
            }
            strncat(formatted, &str[curr->start], curr->length);
        }
    }

    printf("\n%s\n", formatted);
}

int main(void) {

    char str[] = "*你好world哈哈, 句子#中间you英文和，。/符号";

    padCjk(str);
}