Compact C Hex Dump Function w/ASCII to buffer

DumpHex.c

#include <stdio.h>

void dump_hex(const void *data, size_t size, char *output)
{
    char   ascii[17];
    size_t i, j;

    ascii[16] = '\0';
    for (i = 0; i < size; ++i)
    {
        if ((i % 16) == 0)
        {
            output += sprintf(output, "%08x   ", i);
        }
        output += sprintf(output, "%02X ", ((unsigned char *) data)[i]);
        if (((unsigned char *) data)[i] >= ' ' && ((unsigned char *) data)[i] <= '~')
        {
            ascii[i % 16] = ((unsigned char *) data)[i];
        }
        else
        {
            ascii[i % 16] = '.';
        }
        if ((i + 1) % 8 == 0 || i + 1 == size)
        {
            output += sprintf(output, "%c", ' ');
            if ((i + 1) % 16 == 0)
            {
                output += sprintf(output, " %s \n", ascii);
            }
            else if (i + 1 == size)
            {
                ascii[(i + 1) % 16] = '\0';
                if ((i + 1) % 16 <= 8)
                {
                    output += sprintf(output, "%c", ' ');
                }
                for (j = (i + 1) % 16; j < 16; ++j)
                {
                    output += sprintf(output, "%s", "   ");
                }
                output += sprintf(output, " %s \n", ascii);
            }
        }
    }
    *(output) = '\0';
}