2 * random.c: Internal random number generator, guaranteed to work
3 * the same way on all platforms. Used when generating an initial
4 * game state from a random game seed; required to ensure that game
5 * seeds can be exchanged between versions of a puzzle compiled for
8 * The generator is based on SHA-1. This is almost certainly
9 * overkill, but I had the SHA-1 code kicking around and it was
10 * easier to reuse it than to do anything else!
17 typedef unsigned long uint32;
21 unsigned char block[64];
26 /* ----------------------------------------------------------------------
27 * Core SHA algorithm: processes 16-word blocks into a message digest.
30 #define rol(x,y) ( ((x) << (y)) | (((uint32)x) >> (32-y)) )
32 static void SHA_Core_Init(uint32 h[5])
41 static void SHATransform(uint32 * digest, uint32 * block)
47 for (t = 0; t < 16; t++)
50 for (t = 16; t < 80; t++) {
51 uint32 tmp = w[t - 3] ^ w[t - 8] ^ w[t - 14] ^ w[t - 16];
61 for (t = 0; t < 20; t++) {
63 rol(a, 5) + ((b & c) | (d & ~b)) + e + w[t] + 0x5a827999;
70 for (t = 20; t < 40; t++) {
71 uint32 tmp = rol(a, 5) + (b ^ c ^ d) + e + w[t] + 0x6ed9eba1;
78 for (t = 40; t < 60; t++) {
80 5) + ((b & c) | (b & d) | (c & d)) + e + w[t] +
88 for (t = 60; t < 80; t++) {
89 uint32 tmp = rol(a, 5) + (b ^ c ^ d) + e + w[t] + 0xca62c1d6;
104 /* ----------------------------------------------------------------------
105 * Outer SHA algorithm: take an arbitrary length byte string,
106 * convert it into 16-word blocks with the prescribed padding at
107 * the end, and pass those blocks to the core SHA algorithm.
110 static void SHA_Init(SHA_State * s)
114 s->lenhi = s->lenlo = 0;
117 static void SHA_Bytes(SHA_State * s, void *p, int len)
119 unsigned char *q = (unsigned char *) p;
120 uint32 wordblock[16];
125 * Update the length field.
128 s->lenhi += (s->lenlo < lenw);
130 if (s->blkused && s->blkused + len < 64) {
132 * Trivial case: just add to the block.
134 memcpy(s->block + s->blkused, q, len);
138 * We must complete and process at least one block.
140 while (s->blkused + len >= 64) {
141 memcpy(s->block + s->blkused, q, 64 - s->blkused);
142 q += 64 - s->blkused;
143 len -= 64 - s->blkused;
144 /* Now process the block. Gather bytes big-endian into words */
145 for (i = 0; i < 16; i++) {
147 (((uint32) s->block[i * 4 + 0]) << 24) |
148 (((uint32) s->block[i * 4 + 1]) << 16) |
149 (((uint32) s->block[i * 4 + 2]) << 8) |
150 (((uint32) s->block[i * 4 + 3]) << 0);
152 SHATransform(s->h, wordblock);
155 memcpy(s->block, q, len);
160 static void SHA_Final(SHA_State * s, unsigned char *output)
167 if (s->blkused >= 56)
168 pad = 56 + 64 - s->blkused;
170 pad = 56 - s->blkused;
172 lenhi = (s->lenhi << 3) | (s->lenlo >> (32 - 3));
173 lenlo = (s->lenlo << 3);
177 SHA_Bytes(s, &c, pad);
179 c[0] = (lenhi >> 24) & 0xFF;
180 c[1] = (lenhi >> 16) & 0xFF;
181 c[2] = (lenhi >> 8) & 0xFF;
182 c[3] = (lenhi >> 0) & 0xFF;
183 c[4] = (lenlo >> 24) & 0xFF;
184 c[5] = (lenlo >> 16) & 0xFF;
185 c[6] = (lenlo >> 8) & 0xFF;
186 c[7] = (lenlo >> 0) & 0xFF;
190 for (i = 0; i < 5; i++) {
191 output[i * 4] = (s->h[i] >> 24) & 0xFF;
192 output[i * 4 + 1] = (s->h[i] >> 16) & 0xFF;
193 output[i * 4 + 2] = (s->h[i] >> 8) & 0xFF;
194 output[i * 4 + 3] = (s->h[i]) & 0xFF;
198 static void SHA_Simple(void *p, int len, unsigned char *output)
203 SHA_Bytes(&s, p, len);
204 SHA_Final(&s, output);
207 /* ----------------------------------------------------------------------
208 * The random number generator.
211 struct random_state {
212 unsigned char seedbuf[40];
213 unsigned char databuf[20];
217 random_state *random_init(char *seed, int len)
221 state = snew(random_state);
223 SHA_Simple(seed, len, state->seedbuf);
224 SHA_Simple(state->seedbuf, 20, state->seedbuf + 20);
225 SHA_Simple(state->seedbuf, 40, state->databuf);
231 unsigned long random_bits(random_state *state, int bits)
236 for (n = 0; n < bits; n += 8) {
237 if (state->pos >= 20) {
240 for (i = 0; i < 20; i++) {
241 if (state->seedbuf[i] != 0xFF) {
245 state->seedbuf[i] = 0;
247 SHA_Simple(state->seedbuf, 40, state->databuf);
250 ret = (ret << 8) | state->databuf[state->pos++];
253 ret &= (1 << bits) - 1;
257 unsigned long random_upto(random_state *state, unsigned long limit)
260 unsigned long max, divisor, data;
262 while ((limit >> bits) != 0)
269 divisor = max / limit;
270 max = limit * divisor;
273 data = random_bits(state, bits);
274 } while (data >= max);
276 return data / divisor;
279 void random_free(random_state *state)