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

/**
 * Note: The returned array must be malloced, assume caller calls free().
 */
char**
splitWordsBySeparator(char** words, int wordsSize, char separator,
                      int* returnSize)
{
    struct {
        char **data;
        unsigned long cap;
        unsigned long size;
    } ret = {0};
    char buf[21] = {0};

    ret.cap = wordsSize;
    for ( int i = 0; i < wordsSize; ++i ) {
        char *cstr = words[i];
        while ( *cstr != '\0' ) {
            ret.cap += ( *cstr == separator );
            ++cstr;
        }
    }
    ret.data = malloc((ret.cap+1) * sizeof(*ret.data));
    memset(ret.data, 0, (ret.cap+1) * sizeof(*ret.data));

    ret.size = 0;
    for ( int i = 0; i < wordsSize; ++i ) {
        unsigned long wsize = 0;

        char *cstr = words[i];
        while ( *cstr != '\0' ) {
            if ( *cstr == separator ) {
                ++cstr;
                if ( wsize == 0 ) { continue; }
                ret.data[ret.size] = calloc(wsize + 1, sizeof(char));
                memcpy(ret.data[ret.size], buf, wsize);
                ++ret.size;
                wsize = 0;
                continue;
            }
            buf[wsize++] = *cstr;
            ++cstr;
        }

        if ( wsize == 0 ) { continue; }
        ret.data[ret.size] = calloc(wsize + 1, sizeof(char));
        memcpy(ret.data[ret.size], buf, wsize);
        ++ret.size;
    }

    *returnSize = ret.size;
    return ret.data;
}

void
r(char **ws, int s, char sep)
{
    int ret_size = 0;
    char **retorig = splitWordsBySeparator(ws, s, sep, &ret_size);
    printf("RetSize = %d\n", ret_size);
    if ( retorig == NULL ) return;
    char **ret = retorig;

    printf("Ret = [");
    while ( *ret != NULL ) {
        printf("\"%s\", ", *ret);
        free(*ret++);
    }
    printf("]\n");
    free(retorig);
}

int
main(void)
{
    char *words[] = {"one.two.three","four.five","six"};
    r(words, 3, '.');
    return 0;
}