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static char rcsid[] = "$Header: /home/sater/bridge/bigdeal/RCS/dos.c,v 1.9 2000/08/26 14:15:22 sater Exp $";
#include <conio.h>
#include <time.h>
#include <ctype.h>
#include <stdio.h>
#include "types.h"
#include "bigdeal.h"
#include "collect.h"
extern FILE *flog;
/*
* Find the best clock to use in this environment
* We prefer uclock, since it generates more bits
* But it is not ansi, so use clock as an alternative
*/
#ifdef UCLOCKS_PER_SEC
int
bestclock()
{
return (int) uclock();
}
#else
#ifdef CLOCKS_PER_SEC
int
bestclock()
{
return (int) clock();
}
#else
There is no clock, this program needs it, so do not compile
#endif
#endif
#define MAX_INTERVAL_ENTROPY 6
int
getchtm(int *nbits)
/*
* Read one character from standard input
* Time the wait, and use bits for random
* MUST be in cbreak mode for this to work
*/
{
int t1, t2;
int tdiff;
int c;
int shift;
int b;
/*
* First get the best clock we have
*/
t1 = bestclock();
/*
* Now get one character
*/
c = getch();
/*
* If it is zero, which can happen with getch() under DOS
* we have a two character sequence(function key probably)
* and we make one character out of it by appending the next
*/
if (c == 0)
c = getch() + 256;
/*
* and get the clock after the keypress
*/
t2 = bestclock();
/*
* Number of ticks we waited goes to tdiff
*/
tdiff = t2 - t1;
/*
* Now we are going to believe half the bits we get
*/
for (shift = tdiff, b = 0; shift>2 ; shift >>= 2, b++)
;
if (b < MAX_INTERVAL_ENTROPY)
*nbits = b;
else
*nbits = MAX_INTERVAL_ENTROPY;
/*
* We send all the bits to the collect pool
* but do not count the bits yet (parameter 0)
* because higher layers might decide not to believe this
* character, and its associated timing
*/
collect_more((byte *) &t1, sizeof(t1), 0);
collect_more((byte *) &t2, sizeof(t2), 0);
if (flog)
fprintf(flog, "Collected character %d, timediff %d, timebits %d\n",
c, tdiff, *nbits);
return c;
}
void
os_collect() {
time_t t;
(void) time(&t);
/* Trust 6 bits of seconds */
collect_more((byte *) &t, sizeof(t), 6);
}
void
cbreak()
{
}
void
cooked()
{
}
void
os_start()
{
/*
* Start the clock running
*/
(void) bestclock();
}
void
os_finish()
{
}
int
legal_filename_prefix(char *s)
/*
* Legal prefix to make legal name when three letter suffix added
*/
{
if (*s == 0) /* Too short */
return 0;
if (strlen(s) > 8)
return 0;
while (*s) {
if (!isalnum(*s) && *s != '-' && *s != '_')
return 0;
s++;
}
return 1;
}
char *os_init_file_name()
{
return "bigdeal.ini";
}
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