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- /*
- * 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)
- {
- const unsigned char *q = (const 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++];
- }
- /*
- * `(1UL << 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 &= (1UL << (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;
- }
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