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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 | |
18 | typedef unsigned long uint32; |
19 | |
20 | typedef struct { |
21 | uint32 h[5]; |
22 | unsigned char block[64]; |
23 | int blkused; |
24 | uint32 lenhi, lenlo; |
25 | } SHA_State; |
26 | |
27 | /* ---------------------------------------------------------------------- |
28 | * Core SHA algorithm: processes 16-word blocks into a message digest. |
29 | */ |
30 | |
31 | #define rol(x,y) ( ((x) << (y)) | (((uint32)x) >> (32-y)) ) |
32 | |
33 | static void SHA_Core_Init(uint32 h[5]) |
34 | { |
35 | h[0] = 0x67452301; |
36 | h[1] = 0xefcdab89; |
37 | h[2] = 0x98badcfe; |
38 | h[3] = 0x10325476; |
39 | h[4] = 0xc3d2e1f0; |
40 | } |
41 | |
42 | static void SHATransform(uint32 * digest, uint32 * block) |
43 | { |
44 | uint32 w[80]; |
45 | uint32 a, b, c, d, e; |
46 | int t; |
47 | |
48 | for (t = 0; t < 16; t++) |
49 | w[t] = block[t]; |
50 | |
51 | for (t = 16; t < 80; t++) { |
52 | uint32 tmp = w[t - 3] ^ w[t - 8] ^ w[t - 14] ^ w[t - 16]; |
53 | w[t] = rol(tmp, 1); |
54 | } |
55 | |
56 | a = digest[0]; |
57 | b = digest[1]; |
58 | c = digest[2]; |
59 | d = digest[3]; |
60 | e = digest[4]; |
61 | |
62 | for (t = 0; t < 20; t++) { |
63 | uint32 tmp = |
64 | rol(a, 5) + ((b & c) | (d & ~b)) + e + w[t] + 0x5a827999; |
65 | e = d; |
66 | d = c; |
67 | c = rol(b, 30); |
68 | b = a; |
69 | a = tmp; |
70 | } |
71 | for (t = 20; t < 40; t++) { |
72 | uint32 tmp = rol(a, 5) + (b ^ c ^ d) + e + w[t] + 0x6ed9eba1; |
73 | e = d; |
74 | d = c; |
75 | c = rol(b, 30); |
76 | b = a; |
77 | a = tmp; |
78 | } |
79 | for (t = 40; t < 60; t++) { |
80 | uint32 tmp = rol(a, |
81 | 5) + ((b & c) | (b & d) | (c & d)) + e + w[t] + |
82 | 0x8f1bbcdc; |
83 | e = d; |
84 | d = c; |
85 | c = rol(b, 30); |
86 | b = a; |
87 | a = tmp; |
88 | } |
89 | for (t = 60; t < 80; t++) { |
90 | uint32 tmp = rol(a, 5) + (b ^ c ^ d) + e + w[t] + 0xca62c1d6; |
91 | e = d; |
92 | d = c; |
93 | c = rol(b, 30); |
94 | b = a; |
95 | a = tmp; |
96 | } |
97 | |
98 | digest[0] += a; |
99 | digest[1] += b; |
100 | digest[2] += c; |
101 | digest[3] += d; |
102 | digest[4] += e; |
103 | } |
104 | |
105 | /* ---------------------------------------------------------------------- |
106 | * Outer SHA algorithm: take an arbitrary length byte string, |
107 | * convert it into 16-word blocks with the prescribed padding at |
108 | * the end, and pass those blocks to the core SHA algorithm. |
109 | */ |
110 | |
111 | static void SHA_Init(SHA_State * s) |
112 | { |
113 | SHA_Core_Init(s->h); |
114 | s->blkused = 0; |
115 | s->lenhi = s->lenlo = 0; |
116 | } |
117 | |
118 | static void SHA_Bytes(SHA_State * s, void *p, int len) |
119 | { |
120 | unsigned char *q = (unsigned char *) p; |
121 | uint32 wordblock[16]; |
122 | uint32 lenw = len; |
123 | int i; |
124 | |
125 | /* |
126 | * Update the length field. |
127 | */ |
128 | s->lenlo += lenw; |
129 | s->lenhi += (s->lenlo < lenw); |
130 | |
131 | if (s->blkused && s->blkused + len < 64) { |
132 | /* |
133 | * Trivial case: just add to the block. |
134 | */ |
135 | memcpy(s->block + s->blkused, q, len); |
136 | s->blkused += len; |
137 | } else { |
138 | /* |
139 | * We must complete and process at least one block. |
140 | */ |
141 | while (s->blkused + len >= 64) { |
142 | memcpy(s->block + s->blkused, q, 64 - s->blkused); |
143 | q += 64 - s->blkused; |
144 | len -= 64 - s->blkused; |
145 | /* Now process the block. Gather bytes big-endian into words */ |
146 | for (i = 0; i < 16; i++) { |
147 | wordblock[i] = |
148 | (((uint32) s->block[i * 4 + 0]) << 24) | |
149 | (((uint32) s->block[i * 4 + 1]) << 16) | |
150 | (((uint32) s->block[i * 4 + 2]) << 8) | |
151 | (((uint32) s->block[i * 4 + 3]) << 0); |
152 | } |
153 | SHATransform(s->h, wordblock); |
154 | s->blkused = 0; |
155 | } |
156 | memcpy(s->block, q, len); |
157 | s->blkused = len; |
158 | } |
159 | } |
160 | |
161 | static void SHA_Final(SHA_State * s, unsigned char *output) |
162 | { |
163 | int i; |
164 | int pad; |
165 | unsigned char c[64]; |
166 | uint32 lenhi, lenlo; |
167 | |
168 | if (s->blkused >= 56) |
169 | pad = 56 + 64 - s->blkused; |
170 | else |
171 | pad = 56 - s->blkused; |
172 | |
173 | lenhi = (s->lenhi << 3) | (s->lenlo >> (32 - 3)); |
174 | lenlo = (s->lenlo << 3); |
175 | |
176 | memset(c, 0, pad); |
177 | c[0] = 0x80; |
178 | SHA_Bytes(s, &c, pad); |
179 | |
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180 | c[0] = (unsigned char)((lenhi >> 24) & 0xFF); |
181 | c[1] = (unsigned char)((lenhi >> 16) & 0xFF); |
182 | c[2] = (unsigned char)((lenhi >> 8) & 0xFF); |
183 | c[3] = (unsigned char)((lenhi >> 0) & 0xFF); |
184 | c[4] = (unsigned char)((lenlo >> 24) & 0xFF); |
185 | c[5] = (unsigned char)((lenlo >> 16) & 0xFF); |
186 | c[6] = (unsigned char)((lenlo >> 8) & 0xFF); |
187 | c[7] = (unsigned char)((lenlo >> 0) & 0xFF); |
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188 | |
189 | SHA_Bytes(s, &c, 8); |
190 | |
191 | for (i = 0; i < 5; i++) { |
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192 | output[i * 4] = (unsigned char)((s->h[i] >> 24) & 0xFF); |
193 | output[i * 4 + 1] = (unsigned char)((s->h[i] >> 16) & 0xFF); |
194 | output[i * 4 + 2] = (unsigned char)((s->h[i] >> 8) & 0xFF); |
195 | output[i * 4 + 3] = (unsigned char)((s->h[i]) & 0xFF); |
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196 | } |
197 | } |
198 | |
199 | static void SHA_Simple(void *p, int len, unsigned char *output) |
200 | { |
201 | SHA_State s; |
202 | |
203 | SHA_Init(&s); |
204 | SHA_Bytes(&s, p, len); |
205 | SHA_Final(&s, output); |
206 | } |
207 | |
208 | /* ---------------------------------------------------------------------- |
209 | * The random number generator. |
210 | */ |
211 | |
212 | struct random_state { |
213 | unsigned char seedbuf[40]; |
214 | unsigned char databuf[20]; |
215 | int pos; |
216 | }; |
217 | |
218 | random_state *random_init(char *seed, int len) |
219 | { |
220 | random_state *state; |
221 | |
222 | state = snew(random_state); |
223 | |
224 | SHA_Simple(seed, len, state->seedbuf); |
225 | SHA_Simple(state->seedbuf, 20, state->seedbuf + 20); |
226 | SHA_Simple(state->seedbuf, 40, state->databuf); |
227 | state->pos = 0; |
228 | |
229 | return state; |
230 | } |
231 | |
232 | unsigned long random_bits(random_state *state, int bits) |
233 | { |
234 | int ret = 0; |
235 | int n; |
236 | |
237 | for (n = 0; n < bits; n += 8) { |
238 | if (state->pos >= 20) { |
239 | int i; |
240 | |
241 | for (i = 0; i < 20; i++) { |
242 | if (state->seedbuf[i] != 0xFF) { |
243 | state->seedbuf[i]++; |
244 | break; |
245 | } else |
246 | state->seedbuf[i] = 0; |
247 | } |
248 | SHA_Simple(state->seedbuf, 40, state->databuf); |
249 | state->pos = 0; |
250 | } |
251 | ret = (ret << 8) | state->databuf[state->pos++]; |
252 | } |
253 | |
254 | ret &= (1 << bits) - 1; |
255 | return ret; |
256 | } |
257 | |
258 | unsigned long random_upto(random_state *state, unsigned long limit) |
259 | { |
260 | int bits = 0; |
261 | unsigned long max, divisor, data; |
262 | |
263 | while ((limit >> bits) != 0) |
264 | bits++; |
265 | |
266 | bits += 3; |
267 | assert(bits < 32); |
268 | |
269 | max = 1 << bits; |
270 | divisor = max / limit; |
271 | max = limit * divisor; |
272 | |
273 | do { |
274 | data = random_bits(state, bits); |
275 | } while (data >= max); |
276 | |
277 | return data / divisor; |
278 | } |
279 | |
280 | void random_free(random_state *state) |
281 | { |
282 | sfree(state); |
283 | } |