main.c

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

int main(int argc, const char * argv[])
{
    int left, offset=0;
    char *target = "daniel&vivid<daniel>,\"vivid\'";
    char c, *dest;
    const char *inp;
    
    inp = target;
    
    left = 32*5;
    dest = (char *)calloc(left+1, 1);
    
    while ((c = (char)*inp++) && (left >= 6))
    {
        printf("%c,", c);

        switch (c)
        {
            case '>':
                dest[offset++] = '&';
                dest[offset++] = 'g';
                dest[offset++] = 't';
                dest[offset++] = ';';
                left -= 4;
                break;
            case '<':
                dest[offset++] = '&';
                dest[offset++] = 'l';
                dest[offset++] = 't';
                dest[offset++] = ';';
                left -= 4;
                break;
            case '&':
                dest[offset++] = '&';
                dest[offset++] = 'a';
                dest[offset++] = 'm';
                dest[offset++] = 'p';
                dest[offset++] = ';';
                left -= 5;
                break;
            case '\"':
                dest[offset++] = '&';
                dest[offset++] = 'q';
                dest[offset++] = 'u';
                dest[offset++] = 'o';
                dest[offset++] = 't';
                dest[offset++] = ';';
                left -= 6;
                break;
            case '\'':
                dest[offset++] = '&';
                dest[offset++] = 'a';
                dest[offset++] = 'p';
                dest[offset++] = 'o';
                dest[offset++] = 's';
                dest[offset++] = ';';
                left -= 6;
                break;
            default:
                dest[offset++] = c;
                break;
        }
    }
    
    printf("\n");
    
    printf("dest=%s, left=%d\n", dest, left);
    
    if (dest) free(dest);
    
    return 0;
}