#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};

    ret.cap = wordsSize;
    ret.data = calloc(ret.cap, sizeof(*ret.data));

    for ( int i = 0; i < wordsSize; ++i ) {
        char *cstr = words[i];
        unsigned long wsize = 0;
        unsigned long wcap = 32;
        while ( *cstr != '\0' ) {
            if ( *cstr == separator ) {
                if ( wsize > 0 ) {
                    ret.data[ret.size][wsize++] = 0;
                    ++ret.size;
                }
                wsize = 0;
                wcap = 32;
                if ( ret.size >= ret.cap ) {
                    ret.cap *= 2;
                    ret.data = realloc(ret.data, sizeof(*ret.data) * ret.cap);
                    for ( unsigned long j = ret.size; j < ret.cap; ++j ) {
                        ret.data[j] = NULL;
                    }
                }
                ++cstr;
                continue;
            }
            if ( ret.data[ret.size] == NULL ) { ret.data[ret.size] = malloc(wcap); }
            ret.data[ret.size][wsize++] = *cstr;
            if ( wsize >= wcap ) {
                wcap *= 2;
                ret.data[ret.size] = realloc(ret.data[ret.size], wcap);
            }
            ++cstr;
        }
        if ( wsize != 0 ) {
            ret.data[ret.size++][wsize++] = 0;
            if ( ret.size >= ret.cap ) {
                ret.cap *= 2;
                ret.data = realloc(ret.data, sizeof(*ret.data) * ret.cap);
                for ( unsigned long j = ret.size; j < ret.cap; ++j ) {
                    ret.data[j] = NULL;
                }
            }
        }
    }

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

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

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

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