74 }

    75 

    76 void fpcrtl_insert__vars(string255 *src, string255 *dst, SizeInt index) {

    77     int num_insert;

    78     int num_shift;

    79     int num_preshift;

    80 

    81     // nothing to do if empty string is inserted or index invalid

    82     if ((src->len == 0) || (index < 1) || (index > 255)) {

    83         return;

    84     }

    85 

    86     num_insert = src->len;

    87     // number of chars from start of destination string to end of insertion

    88     num_preshift = index - 1 + num_insert;

    89 

    90     // don't overflow on insert

    91     if (num_preshift > 255) {

    92         num_insert = 255 - (index - 1);

    93         num_shift = 0;

    94     }

    95     // shift trailing chars

    96     else {

    97         // number of bytes to be shifted

    98         num_shift = dst->len - (index - 1);

    99 

   100         if (num_shift > 0) {

   101             // don't overflow when shifting

   102             if (num_shift + num_preshift > 255)

   103                 num_shift = 255 - num_preshift;

   104 

   105             // time to move some bytes!

   106             memmove(dst->str + num_preshift, dst->str + index - 1, num_shift);

   107         }

   108     }

   109 

   110     // actual byte insertion

   111     memmove(dst->str + index - 1, src->str, num_insert);

   112     // store new length

   113     dst->len = num_shift + num_preshift;