mirrors/ecl
1
Fork 0
mirror of https://gitlab.com/embeddable-common-lisp/ecl.git synced 2026-01-20 11:32:35 -08:00
Code Issues Projects Releases Packages Wiki Activity

random: correct Mersenne-Twister RNG initializer

Browse source 
Previous code had some deviations from the original algorithm and a
bug preventing the use of the value acquired from /dev/urandom. This
is the corrected version.

Signed-off-by: Daniel Kochmański <daniel@turtleware.eu>
This commit is contained in:
Daniel Kochmański 2015-09-20 13:04:42 +02:00
parent ba758250da
commit f1d256f2ea
1 changed files with 8 additions and 14 deletions
Download patch file Download diff file Expand all files Collapse all files

22
src/c/num_rand.d
View file

@ -54,27 +54,21 @@ init_random_state()
#if !defined(ECL_MS_WINDOWS_HOST)
/* fopen() might read full 4kB blocks and discard
* a lot of entropy, so use open() */
int fh = open("/dev/urandom", O_RDONLY);
char buffer[16];
if (fh != -1) {
j = read(fh, buffer, sizeof(buffer));
for (; j < sizeof(buffer) && j < MT_N; j++){
mt[j] = buffer[j];
}
int file_handler = open("/dev/urandom", O_RDONLY);
if (file_handler != -1) {
read(file_handler, mt, sizeof(ulong));
close(fh);
} else
#endif
{
/* cant get urandom, use crappy source */
/* and/or fill rest of area */
mt[j++] = (rand() + time(0)) & 0xffffffffUL;
for (; j < MT_N; j++){
mt[j] = (1812433253UL * (mt[j-1] ^ (mt[j-1] >> 30)) + j);
if (j >= 16)
mt[j] ^= mt[j-16];
mt[j] &= 0xffffffffUL;
}
mt[0] = (rand() + time(0));
}
mt[0] &= 0xffffffffUL;
for (j=1; j < MT_N; j++)
mt[j] = (1812433253UL * (mt[j-1] ^ (mt[j-1] >> 30)) + j) & 0xffffffffUL;
mt[MT_N] = MT_N+1;
return a;
}