ref: b780b073da9a038347066d4ba65d9c28cc9eedce
dir: /random.c/
/*
* random.c: Internal random number generator, guaranteed to work
* the same way on all platforms. Used when generating an initial
* game state from a random game seed; required to ensure that game
* seeds can be exchanged between versions of a puzzle compiled for
* different platforms.
*
* The generator is based on SHA-1. This is almost certainly
* overkill, but I had the SHA-1 code kicking around and it was
* easier to reuse it than to do anything else!
*/
#include <assert.h>
#include <string.h>
#include <stdio.h>
#include "puzzles.h"
/* ----------------------------------------------------------------------
* Core SHA algorithm: processes 16-word blocks into a message digest.
*/
#define rol(x,y) ( ((x) << (y)) | (((uint32)x) >> (32-y)) )
static void SHA_Core_Init(uint32 h[5])
{
h[0] = 0x67452301;
h[1] = 0xefcdab89;
h[2] = 0x98badcfe;
h[3] = 0x10325476;
h[4] = 0xc3d2e1f0;
}
static void SHATransform(uint32 * digest, uint32 * block)
{
uint32 w[80];
uint32 a, b, c, d, e;
int t;
for (t = 0; t < 16; t++)
w[t] = block[t];
for (t = 16; t < 80; t++) {
uint32 tmp = w[t - 3] ^ w[t - 8] ^ w[t - 14] ^ w[t - 16];
w[t] = rol(tmp, 1);
}
a = digest[0];
b = digest[1];
c = digest[2];
d = digest[3];
e = digest[4];
for (t = 0; t < 20; t++) {
uint32 tmp =
rol(a, 5) + ((b & c) | (d & ~b)) + e + w[t] + 0x5a827999;
e = d;
d = c;
c = rol(b, 30);
b = a;
a = tmp;
}
for (t = 20; t < 40; t++) {
uint32 tmp = rol(a, 5) + (b ^ c ^ d) + e + w[t] + 0x6ed9eba1;
e = d;
d = c;
c = rol(b, 30);
b = a;
a = tmp;
}
for (t = 40; t < 60; t++) {
uint32 tmp = rol(a,
5) + ((b & c) | (b & d) | (c & d)) + e + w[t] +
0x8f1bbcdc;
e = d;
d = c;
c = rol(b, 30);
b = a;
a = tmp;
}
for (t = 60; t < 80; t++) {
uint32 tmp = rol(a, 5) + (b ^ c ^ d) + e + w[t] + 0xca62c1d6;
e = d;
d = c;
c = rol(b, 30);
b = a;
a = tmp;
}
digest[0] += a;
digest[1] += b;
digest[2] += c;
digest[3] += d;
digest[4] += e;
}
/* ----------------------------------------------------------------------
* Outer SHA algorithm: take an arbitrary length byte string,
* convert it into 16-word blocks with the prescribed padding at
* the end, and pass those blocks to the core SHA algorithm.
*/
void SHA_Init(SHA_State * s)
{
SHA_Core_Init(s->h);
s->blkused = 0;
s->lenhi = s->lenlo = 0;
}
void SHA_Bytes(SHA_State * s, const void *p, int len)
{
unsigned char *q = (unsigned char *) p;
uint32 wordblock[16];
uint32 lenw = len;
int i;
/*
* Update the length field.
*/
s->lenlo += lenw;
s->lenhi += (s->lenlo < lenw);
if (s->blkused && s->blkused + len < 64) {
/*
* Trivial case: just add to the block.
*/
memcpy(s->block + s->blkused, q, len);
s->blkused += len;
} else {
/*
* We must complete and process at least one block.
*/
while (s->blkused + len >= 64) {
memcpy(s->block + s->blkused, q, 64 - s->blkused);
q += 64 - s->blkused;
len -= 64 - s->blkused;
/* Now process the block. Gather bytes big-endian into words */
for (i = 0; i < 16; i++) {
wordblock[i] =
(((uint32) s->block[i * 4 + 0]) << 24) |
(((uint32) s->block[i * 4 + 1]) << 16) |
(((uint32) s->block[i * 4 + 2]) << 8) |
(((uint32) s->block[i * 4 + 3]) << 0);
}
SHATransform(s->h, wordblock);
s->blkused = 0;
}
memcpy(s->block, q, len);
s->blkused = len;
}
}
void SHA_Final(SHA_State * s, unsigned char *output)
{
int i;
int pad;
unsigned char c[64];
uint32 lenhi, lenlo;
if (s->blkused >= 56)
pad = 56 + 64 - s->blkused;
else
pad = 56 - s->blkused;
lenhi = (s->lenhi << 3) | (s->lenlo >> (32 - 3));
lenlo = (s->lenlo << 3);
memset(c, 0, pad);
c[0] = 0x80;
SHA_Bytes(s, &c, pad);
c[0] = (unsigned char)((lenhi >> 24) & 0xFF);
c[1] = (unsigned char)((lenhi >> 16) & 0xFF);
c[2] = (unsigned char)((lenhi >> 8) & 0xFF);
c[3] = (unsigned char)((lenhi >> 0) & 0xFF);
c[4] = (unsigned char)((lenlo >> 24) & 0xFF);
c[5] = (unsigned char)((lenlo >> 16) & 0xFF);
c[6] = (unsigned char)((lenlo >> 8) & 0xFF);
c[7] = (unsigned char)((lenlo >> 0) & 0xFF);
SHA_Bytes(s, &c, 8);
for (i = 0; i < 5; i++) {
output[i * 4] = (unsigned char)((s->h[i] >> 24) & 0xFF);
output[i * 4 + 1] = (unsigned char)((s->h[i] >> 16) & 0xFF);
output[i * 4 + 2] = (unsigned char)((s->h[i] >> 8) & 0xFF);
output[i * 4 + 3] = (unsigned char)((s->h[i]) & 0xFF);
}
}
void SHA_Simple(const void *p, int len, unsigned char *output)
{
SHA_State s;
SHA_Init(&s);
SHA_Bytes(&s, p, len);
SHA_Final(&s, output);
}
/* ----------------------------------------------------------------------
* The random number generator.
*/
struct random_state {
unsigned char seedbuf[40];
unsigned char databuf[20];
int pos;
};
random_state *random_new(const char *seed, int len)
{
random_state *state;
state = snew(random_state);
SHA_Simple(seed, len, state->seedbuf);
SHA_Simple(state->seedbuf, 20, state->seedbuf + 20);
SHA_Simple(state->seedbuf, 40, state->databuf);
state->pos = 0;
return state;
}
random_state *random_copy(random_state *tocopy)
{
random_state *result;
result = snew(random_state);
memcpy(result->seedbuf, tocopy->seedbuf, sizeof(result->seedbuf));
memcpy(result->databuf, tocopy->databuf, sizeof(result->databuf));
result->pos = tocopy->pos;
return result;
}
unsigned long random_bits(random_state *state, int bits)
{
unsigned long ret = 0;
int n;
for (n = 0; n < bits; n += 8) {
if (state->pos >= 20) {
int i;
for (i = 0; i < 20; i++) {
if (state->seedbuf[i] != 0xFF) {
state->seedbuf[i]++;
break;
} else
state->seedbuf[i] = 0;
}
SHA_Simple(state->seedbuf, 40, state->databuf);
state->pos = 0;
}
ret = (ret << 8) | state->databuf[state->pos++];
}
/*
* `(1 << bits) - 1' is not good enough, since if bits==32 on a
* 32-bit machine, behaviour is undefined and Intel has a nasty
* habit of shifting left by zero instead. We'll shift by
* bits-1 and then separately shift by one.
*/
ret &= (1 << (bits-1)) * 2 - 1;
return ret;
}
unsigned long random_upto(random_state *state, unsigned long limit)
{
int bits = 0;
unsigned long max, divisor, data;
while ((limit >> bits) != 0)
bits++;
bits += 3;
assert(bits < 32);
max = 1L << bits;
divisor = max / limit;
max = limit * divisor;
do {
data = random_bits(state, bits);
} while (data >= max);
return data / divisor;
}
void random_free(random_state *state)
{
sfree(state);
}
char *random_state_encode(random_state *state)
{
char retbuf[256];
int len = 0, i;
for (i = 0; i < lenof(state->seedbuf); i++)
len += sprintf(retbuf+len, "%02x", state->seedbuf[i]);
for (i = 0; i < lenof(state->databuf); i++)
len += sprintf(retbuf+len, "%02x", state->databuf[i]);
len += sprintf(retbuf+len, "%02x", state->pos);
return dupstr(retbuf);
}
random_state *random_state_decode(const char *input)
{
random_state *state;
int pos, byte, digits;
state = snew(random_state);
memset(state->seedbuf, 0, sizeof(state->seedbuf));
memset(state->databuf, 0, sizeof(state->databuf));
state->pos = 0;
byte = digits = 0;
pos = 0;
while (*input) {
int v = *input++;
if (v >= '0' && v <= '9')
v = v - '0';
else if (v >= 'A' && v <= 'F')
v = v - 'A' + 10;
else if (v >= 'a' && v <= 'f')
v = v - 'a' + 10;
else
v = 0;
byte = (byte << 4) | v;
digits++;
if (digits == 2) {
/*
* We have a byte. Put it somewhere.
*/
if (pos < lenof(state->seedbuf))
state->seedbuf[pos++] = byte;
else if (pos < lenof(state->seedbuf) + lenof(state->databuf))
state->databuf[pos++ - lenof(state->seedbuf)] = byte;
else if (pos == lenof(state->seedbuf) + lenof(state->databuf) &&
byte <= lenof(state->databuf))
state->pos = byte;
byte = digits = 0;
}
}
return state;
}