720a8fb7 |
1 | /* |
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 |
6 | * different platforms. |
7 | * |
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! |
11 | */ |
12 | |
13 | #include <assert.h> |
14 | |
15 | #include "puzzles.h" |
16 | |
17 | typedef unsigned long uint32; |
18 | |
19 | typedef struct { |
20 | uint32 h[5]; |
21 | unsigned char block[64]; |
22 | int blkused; |
23 | uint32 lenhi, lenlo; |
24 | } SHA_State; |
25 | |
26 | /* ---------------------------------------------------------------------- |
27 | * Core SHA algorithm: processes 16-word blocks into a message digest. |
28 | */ |
29 | |
30 | #define rol(x,y) ( ((x) << (y)) | (((uint32)x) >> (32-y)) ) |
31 | |
32 | static void SHA_Core_Init(uint32 h[5]) |
33 | { |
34 | h[0] = 0x67452301; |
35 | h[1] = 0xefcdab89; |
36 | h[2] = 0x98badcfe; |
37 | h[3] = 0x10325476; |
38 | h[4] = 0xc3d2e1f0; |
39 | } |
40 | |
41 | static void SHATransform(uint32 * digest, uint32 * block) |
42 | { |
43 | uint32 w[80]; |
44 | uint32 a, b, c, d, e; |
45 | int t; |
46 | |
47 | for (t = 0; t < 16; t++) |
48 | w[t] = block[t]; |
49 | |
50 | for (t = 16; t < 80; t++) { |
51 | uint32 tmp = w[t - 3] ^ w[t - 8] ^ w[t - 14] ^ w[t - 16]; |
52 | w[t] = rol(tmp, 1); |
53 | } |
54 | |
55 | a = digest[0]; |
56 | b = digest[1]; |
57 | c = digest[2]; |
58 | d = digest[3]; |
59 | e = digest[4]; |
60 | |
61 | for (t = 0; t < 20; t++) { |
62 | uint32 tmp = |
63 | rol(a, 5) + ((b & c) | (d & ~b)) + e + w[t] + 0x5a827999; |
64 | e = d; |
65 | d = c; |
66 | c = rol(b, 30); |
67 | b = a; |
68 | a = tmp; |
69 | } |
70 | for (t = 20; t < 40; t++) { |
71 | uint32 tmp = rol(a, 5) + (b ^ c ^ d) + e + w[t] + 0x6ed9eba1; |
72 | e = d; |
73 | d = c; |
74 | c = rol(b, 30); |
75 | b = a; |
76 | a = tmp; |
77 | } |
78 | for (t = 40; t < 60; t++) { |
79 | uint32 tmp = rol(a, |
80 | 5) + ((b & c) | (b & d) | (c & d)) + e + w[t] + |
81 | 0x8f1bbcdc; |
82 | e = d; |
83 | d = c; |
84 | c = rol(b, 30); |
85 | b = a; |
86 | a = tmp; |
87 | } |
88 | for (t = 60; t < 80; t++) { |
89 | uint32 tmp = rol(a, 5) + (b ^ c ^ d) + e + w[t] + 0xca62c1d6; |
90 | e = d; |
91 | d = c; |
92 | c = rol(b, 30); |
93 | b = a; |
94 | a = tmp; |
95 | } |
96 | |
97 | digest[0] += a; |
98 | digest[1] += b; |
99 | digest[2] += c; |
100 | digest[3] += d; |
101 | digest[4] += e; |
102 | } |
103 | |
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. |
108 | */ |
109 | |
110 | static void SHA_Init(SHA_State * s) |
111 | { |
112 | SHA_Core_Init(s->h); |
113 | s->blkused = 0; |
114 | s->lenhi = s->lenlo = 0; |
115 | } |
116 | |
117 | static void SHA_Bytes(SHA_State * s, void *p, int len) |
118 | { |
119 | unsigned char *q = (unsigned char *) p; |
120 | uint32 wordblock[16]; |
121 | uint32 lenw = len; |
122 | int i; |
123 | |
124 | /* |
125 | * Update the length field. |
126 | */ |
127 | s->lenlo += lenw; |
128 | s->lenhi += (s->lenlo < lenw); |
129 | |
130 | if (s->blkused && s->blkused + len < 64) { |
131 | /* |
132 | * Trivial case: just add to the block. |
133 | */ |
134 | memcpy(s->block + s->blkused, q, len); |
135 | s->blkused += len; |
136 | } else { |
137 | /* |
138 | * We must complete and process at least one block. |
139 | */ |
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++) { |
146 | wordblock[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); |
151 | } |
152 | SHATransform(s->h, wordblock); |
153 | s->blkused = 0; |
154 | } |
155 | memcpy(s->block, q, len); |
156 | s->blkused = len; |
157 | } |
158 | } |
159 | |
160 | static void SHA_Final(SHA_State * s, unsigned char *output) |
161 | { |
162 | int i; |
163 | int pad; |
164 | unsigned char c[64]; |
165 | uint32 lenhi, lenlo; |
166 | |
167 | if (s->blkused >= 56) |
168 | pad = 56 + 64 - s->blkused; |
169 | else |
170 | pad = 56 - s->blkused; |
171 | |
172 | lenhi = (s->lenhi << 3) | (s->lenlo >> (32 - 3)); |
173 | lenlo = (s->lenlo << 3); |
174 | |
175 | memset(c, 0, pad); |
176 | c[0] = 0x80; |
177 | SHA_Bytes(s, &c, pad); |
178 | |
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; |
187 | |
188 | SHA_Bytes(s, &c, 8); |
189 | |
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; |
195 | } |
196 | } |
197 | |
198 | static void SHA_Simple(void *p, int len, unsigned char *output) |
199 | { |
200 | SHA_State s; |
201 | |
202 | SHA_Init(&s); |
203 | SHA_Bytes(&s, p, len); |
204 | SHA_Final(&s, output); |
205 | } |
206 | |
207 | /* ---------------------------------------------------------------------- |
208 | * The random number generator. |
209 | */ |
210 | |
211 | struct random_state { |
212 | unsigned char seedbuf[40]; |
213 | unsigned char databuf[20]; |
214 | int pos; |
215 | }; |
216 | |
217 | random_state *random_init(char *seed, int len) |
218 | { |
219 | random_state *state; |
220 | |
221 | state = snew(random_state); |
222 | |
223 | SHA_Simple(seed, len, state->seedbuf); |
224 | SHA_Simple(state->seedbuf, 20, state->seedbuf + 20); |
225 | SHA_Simple(state->seedbuf, 40, state->databuf); |
226 | state->pos = 0; |
227 | |
228 | return state; |
229 | } |
230 | |
231 | unsigned long random_bits(random_state *state, int bits) |
232 | { |
233 | int ret = 0; |
234 | int n; |
235 | |
236 | for (n = 0; n < bits; n += 8) { |
237 | if (state->pos >= 20) { |
238 | int i; |
239 | |
240 | for (i = 0; i < 20; i++) { |
241 | if (state->seedbuf[i] != 0xFF) { |
242 | state->seedbuf[i]++; |
243 | break; |
244 | } else |
245 | state->seedbuf[i] = 0; |
246 | } |
247 | SHA_Simple(state->seedbuf, 40, state->databuf); |
248 | state->pos = 0; |
249 | } |
250 | ret = (ret << 8) | state->databuf[state->pos++]; |
251 | } |
252 | |
253 | ret &= (1 << bits) - 1; |
254 | return ret; |
255 | } |
256 | |
257 | unsigned long random_upto(random_state *state, unsigned long limit) |
258 | { |
259 | int bits = 0; |
260 | unsigned long max, divisor, data; |
261 | |
262 | while ((limit >> bits) != 0) |
263 | bits++; |
264 | |
265 | bits += 3; |
266 | assert(bits < 32); |
267 | |
268 | max = 1 << bits; |
269 | divisor = max / limit; |
270 | max = limit * divisor; |
271 | |
272 | do { |
273 | data = random_bits(state, bits); |
274 | } while (data >= max); |
275 | |
276 | return data / divisor; |
277 | } |
278 | |
279 | void random_free(random_state *state) |
280 | { |
281 | sfree(state); |
282 | } |