demo of string handling

sn_make_path.c

/* This functions takes a path to a directory (C:/blah) and a file name (foobar.txt) then returns the full path of the file (C:/blah/foobar.txt) */

size_t sn_make_path(char *buffer, size_t bsize, const char *dir_path, const char *file_name, char dir_sep) {
  size_t dir_len = strlen(dir_path);
  size_t file_len = strlen(file_name);
  int add_slash = dir_len > 0 && dir_path[dir_len - 1] != dir_sep;

  size_t file_path_len = dir_len + file_len + add_slash;

  if (bsize > 0) {

    if (dir_len+1>bsize)
      dir_len = bsize-1;
    if (add_slash+1>bsize-dir_len)
      add_slash = 0;
    if (file_len+1>bsize-dir_len-add_slash)
      file_len = bsize-dir_len-add_slash-1;

    memcpy(buffer, dir_path, dir_len);
    if (add_slash)
      buffer[dir_len] = dir_sep;
    memcpy(buffer+dir_len+add_slash, file_path, file_len);
    buffer[dir_len+add_slash+file_len] = 0;
  }
  return file_path_len;
}