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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> |
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14 | #include <string.h> |
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15 | |
16 | #include "puzzles.h" |
17 | |
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18 | /* ---------------------------------------------------------------------- |
19 | * Core SHA algorithm: processes 16-word blocks into a message digest. |
20 | */ |
21 | |
22 | #define rol(x,y) ( ((x) << (y)) | (((uint32)x) >> (32-y)) ) |
23 | |
24 | static void SHA_Core_Init(uint32 h[5]) |
25 | { |
26 | h[0] = 0x67452301; |
27 | h[1] = 0xefcdab89; |
28 | h[2] = 0x98badcfe; |
29 | h[3] = 0x10325476; |
30 | h[4] = 0xc3d2e1f0; |
31 | } |
32 | |
33 | static void SHATransform(uint32 * digest, uint32 * block) |
34 | { |
35 | uint32 w[80]; |
36 | uint32 a, b, c, d, e; |
37 | int t; |
38 | |
39 | for (t = 0; t < 16; t++) |
40 | w[t] = block[t]; |
41 | |
42 | for (t = 16; t < 80; t++) { |
43 | uint32 tmp = w[t - 3] ^ w[t - 8] ^ w[t - 14] ^ w[t - 16]; |
44 | w[t] = rol(tmp, 1); |
45 | } |
46 | |
47 | a = digest[0]; |
48 | b = digest[1]; |
49 | c = digest[2]; |
50 | d = digest[3]; |
51 | e = digest[4]; |
52 | |
53 | for (t = 0; t < 20; t++) { |
54 | uint32 tmp = |
55 | rol(a, 5) + ((b & c) | (d & ~b)) + e + w[t] + 0x5a827999; |
56 | e = d; |
57 | d = c; |
58 | c = rol(b, 30); |
59 | b = a; |
60 | a = tmp; |
61 | } |
62 | for (t = 20; t < 40; t++) { |
63 | uint32 tmp = rol(a, 5) + (b ^ c ^ d) + e + w[t] + 0x6ed9eba1; |
64 | e = d; |
65 | d = c; |
66 | c = rol(b, 30); |
67 | b = a; |
68 | a = tmp; |
69 | } |
70 | for (t = 40; t < 60; t++) { |
71 | uint32 tmp = rol(a, |
72 | 5) + ((b & c) | (b & d) | (c & d)) + e + w[t] + |
73 | 0x8f1bbcdc; |
74 | e = d; |
75 | d = c; |
76 | c = rol(b, 30); |
77 | b = a; |
78 | a = tmp; |
79 | } |
80 | for (t = 60; t < 80; t++) { |
81 | uint32 tmp = rol(a, 5) + (b ^ c ^ d) + e + w[t] + 0xca62c1d6; |
82 | e = d; |
83 | d = c; |
84 | c = rol(b, 30); |
85 | b = a; |
86 | a = tmp; |
87 | } |
88 | |
89 | digest[0] += a; |
90 | digest[1] += b; |
91 | digest[2] += c; |
92 | digest[3] += d; |
93 | digest[4] += e; |
94 | } |
95 | |
96 | /* ---------------------------------------------------------------------- |
97 | * Outer SHA algorithm: take an arbitrary length byte string, |
98 | * convert it into 16-word blocks with the prescribed padding at |
99 | * the end, and pass those blocks to the core SHA algorithm. |
100 | */ |
101 | |
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102 | void SHA_Init(SHA_State * s) |
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103 | { |
104 | SHA_Core_Init(s->h); |
105 | s->blkused = 0; |
106 | s->lenhi = s->lenlo = 0; |
107 | } |
108 | |
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109 | void SHA_Bytes(SHA_State * s, void *p, int len) |
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110 | { |
111 | unsigned char *q = (unsigned char *) p; |
112 | uint32 wordblock[16]; |
113 | uint32 lenw = len; |
114 | int i; |
115 | |
116 | /* |
117 | * Update the length field. |
118 | */ |
119 | s->lenlo += lenw; |
120 | s->lenhi += (s->lenlo < lenw); |
121 | |
122 | if (s->blkused && s->blkused + len < 64) { |
123 | /* |
124 | * Trivial case: just add to the block. |
125 | */ |
126 | memcpy(s->block + s->blkused, q, len); |
127 | s->blkused += len; |
128 | } else { |
129 | /* |
130 | * We must complete and process at least one block. |
131 | */ |
132 | while (s->blkused + len >= 64) { |
133 | memcpy(s->block + s->blkused, q, 64 - s->blkused); |
134 | q += 64 - s->blkused; |
135 | len -= 64 - s->blkused; |
136 | /* Now process the block. Gather bytes big-endian into words */ |
137 | for (i = 0; i < 16; i++) { |
138 | wordblock[i] = |
139 | (((uint32) s->block[i * 4 + 0]) << 24) | |
140 | (((uint32) s->block[i * 4 + 1]) << 16) | |
141 | (((uint32) s->block[i * 4 + 2]) << 8) | |
142 | (((uint32) s->block[i * 4 + 3]) << 0); |
143 | } |
144 | SHATransform(s->h, wordblock); |
145 | s->blkused = 0; |
146 | } |
147 | memcpy(s->block, q, len); |
148 | s->blkused = len; |
149 | } |
150 | } |
151 | |
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152 | void SHA_Final(SHA_State * s, unsigned char *output) |
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153 | { |
154 | int i; |
155 | int pad; |
156 | unsigned char c[64]; |
157 | uint32 lenhi, lenlo; |
158 | |
159 | if (s->blkused >= 56) |
160 | pad = 56 + 64 - s->blkused; |
161 | else |
162 | pad = 56 - s->blkused; |
163 | |
164 | lenhi = (s->lenhi << 3) | (s->lenlo >> (32 - 3)); |
165 | lenlo = (s->lenlo << 3); |
166 | |
167 | memset(c, 0, pad); |
168 | c[0] = 0x80; |
169 | SHA_Bytes(s, &c, pad); |
170 | |
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171 | c[0] = (unsigned char)((lenhi >> 24) & 0xFF); |
172 | c[1] = (unsigned char)((lenhi >> 16) & 0xFF); |
173 | c[2] = (unsigned char)((lenhi >> 8) & 0xFF); |
174 | c[3] = (unsigned char)((lenhi >> 0) & 0xFF); |
175 | c[4] = (unsigned char)((lenlo >> 24) & 0xFF); |
176 | c[5] = (unsigned char)((lenlo >> 16) & 0xFF); |
177 | c[6] = (unsigned char)((lenlo >> 8) & 0xFF); |
178 | c[7] = (unsigned char)((lenlo >> 0) & 0xFF); |
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179 | |
180 | SHA_Bytes(s, &c, 8); |
181 | |
182 | for (i = 0; i < 5; i++) { |
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183 | output[i * 4] = (unsigned char)((s->h[i] >> 24) & 0xFF); |
184 | output[i * 4 + 1] = (unsigned char)((s->h[i] >> 16) & 0xFF); |
185 | output[i * 4 + 2] = (unsigned char)((s->h[i] >> 8) & 0xFF); |
186 | output[i * 4 + 3] = (unsigned char)((s->h[i]) & 0xFF); |
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187 | } |
188 | } |
189 | |
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190 | void SHA_Simple(void *p, int len, unsigned char *output) |
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191 | { |
192 | SHA_State s; |
193 | |
194 | SHA_Init(&s); |
195 | SHA_Bytes(&s, p, len); |
196 | SHA_Final(&s, output); |
197 | } |
198 | |
199 | /* ---------------------------------------------------------------------- |
200 | * The random number generator. |
201 | */ |
202 | |
203 | struct random_state { |
204 | unsigned char seedbuf[40]; |
205 | unsigned char databuf[20]; |
206 | int pos; |
207 | }; |
208 | |
209 | random_state *random_init(char *seed, int len) |
210 | { |
211 | random_state *state; |
212 | |
213 | state = snew(random_state); |
214 | |
215 | SHA_Simple(seed, len, state->seedbuf); |
216 | SHA_Simple(state->seedbuf, 20, state->seedbuf + 20); |
217 | SHA_Simple(state->seedbuf, 40, state->databuf); |
218 | state->pos = 0; |
219 | |
220 | return state; |
221 | } |
222 | |
223 | unsigned long random_bits(random_state *state, int bits) |
224 | { |
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225 | unsigned long ret = 0; |
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226 | int n; |
227 | |
228 | for (n = 0; n < bits; n += 8) { |
229 | if (state->pos >= 20) { |
230 | int i; |
231 | |
232 | for (i = 0; i < 20; i++) { |
233 | if (state->seedbuf[i] != 0xFF) { |
234 | state->seedbuf[i]++; |
235 | break; |
236 | } else |
237 | state->seedbuf[i] = 0; |
238 | } |
239 | SHA_Simple(state->seedbuf, 40, state->databuf); |
240 | state->pos = 0; |
241 | } |
242 | ret = (ret << 8) | state->databuf[state->pos++]; |
243 | } |
244 | |
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245 | /* |
246 | * `(1 << bits) - 1' is not good enough, since if bits==32 on a |
247 | * 32-bit machine, behaviour is undefined and Intel has a nasty |
248 | * habit of shifting left by zero instead. We'll shift by |
249 | * bits-1 and then separately shift by one. |
250 | */ |
251 | ret &= (1 << (bits-1)) * 2 - 1; |
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252 | return ret; |
253 | } |
254 | |
255 | unsigned long random_upto(random_state *state, unsigned long limit) |
256 | { |
257 | int bits = 0; |
258 | unsigned long max, divisor, data; |
259 | |
260 | while ((limit >> bits) != 0) |
261 | bits++; |
262 | |
263 | bits += 3; |
264 | assert(bits < 32); |
265 | |
266 | max = 1 << bits; |
267 | divisor = max / limit; |
268 | max = limit * divisor; |
269 | |
270 | do { |
271 | data = random_bits(state, bits); |
272 | } while (data >= max); |
273 | |
274 | return data / divisor; |
275 | } |
276 | |
277 | void random_free(random_state *state) |
278 | { |
279 | sfree(state); |
280 | } |