main ()
{
short len, rc;
len = sizeof verbuf;
/* first, read the version message object file */
if ((FILE *) NULL == (fp = fopenb (VERFILE, "r")))
{
printf ("ERROR -- Unable to open \"%s\" for reading (errno = %d)\n",
VERFILE, errno);
exit (1);
}
rewind (fp);
if (1 != (rc = fread (&verbuf, len, 1, fp)))
{
printf ("ERROR -- Unable to read \"%s\" (rc = %d, errno = %d)\n",
VERFILE, rc, errno);
if (ferror (fp))
printf (" File system ERROR.\n");
else if (feof (fp))
printf (" Premature EOF.\n");
else
printf (" Neither ERROR or EOF set -- very odd\n");
fclose (fp);
exit (1);
}
/* close the file, print the version message, and exit */
fclose (fp);
printf ("Current version: %s\n", verbuf.ver);
exit (0);
}
int prime_test(const char *store, long num) {
long shift = num >> 2;
if (!shift)
{
if (num == 2)
{
puts("p(1) = 2");
}
else if (num == 3)
{
puts("p(2) = 3");
}
else
{
puts("composite");
}
return 0;
}
FILEb * file = fopenb(store, "r");
if (!file) {
fprintf(stderr, "could not open file for reading: %s\n", store);
return 2;
}
int bits = 1;
long cnum = fgetb(file, 2);
long primeAt = 3;
shift >>= 1;
while (shift)
{
fseekb(file, cnum * bits, SEEK_CUR);
primeAt += cnum;
bits++;
shift >>= 1;
cnum = fgetb(file, bits + 1);
if (cnum <= 0)
{
fprintf(stderr, "the store doesn't go that high\n");
fcloseb(file);
return 3;
}
}
// get the base from which to seek
long base = ftellb(file);
long lOffset = 0;
long lVal = (2L << bits) + (fgetb(file, bits) << 1) + 1L;
if (num <= lVal)
{
if (num == lVal)
{
printf("p(%ld) = %ld\n", primeAt, num);
}
else
{
puts("composite");
}
fcloseb(file);
return 0;
}
fseekb(file, (cnum - 2) * bits, SEEK_CUR);
long rOffset = cnum - 1;
long rVal = (2L << bits) + (fgetb(file, bits) << 1) + 1L;
long cOffset, cVal;
// see if we have all the primes of this bit length
if (rVal <= num)
{
if (rVal == num)
{
printf("p(%ld) = %ld\n", primeAt + rOffset, num);
fcloseb(file);
return 0;
}
cnum = fgetb(file, bits + 2);
if (cnum <= 0)
{
fprintf(stderr, "the store doesn't go that high\n");
fcloseb(file);
return 1;
}
else
{
puts("composite");
fcloseb(file);
return 0;
}
}
while (lOffset + 1 < rOffset)
{
cOffset = (lOffset + rOffset) / 2;
fseekb(file, base + cOffset * bits, SEEK_SET);
cVal = (2L << bits) + (fgetb(file, bits) << 1) + 1L;
if (cVal == num)
{
printf("p(%ld) = %ld\n", primeAt + cOffset, num);
fcloseb(file);
return 0;
}
else if (cVal < num)
{
lOffset = cOffset;
lVal = cVal;
}
else
{
rOffset = cOffset;
rVal = cVal;
}
}
puts("composite");
fcloseb(file);
return 0;
}
