]>
Commit | Line | Data |
---|---|---|
a310d434 NP |
1 | /* |
2 | * diff-delta.c: generate a delta between two buffers | |
3 | * | |
4 | * Many parts of this file have been lifted from LibXDiff version 0.10. | |
5 | * http://www.xmailserver.org/xdiff-lib.html | |
6 | * | |
7 | * LibXDiff was written by Davide Libenzi <davidel@xmailserver.org> | |
8 | * Copyright (C) 2003 Davide Libenzi | |
9 | * | |
10 | * Many mods for GIT usage by Nicolas Pitre <nico@cam.org>, (C) 2005. | |
11 | * | |
12 | * This file is free software; you can redistribute it and/or | |
13 | * modify it under the terms of the GNU Lesser General Public | |
14 | * License as published by the Free Software Foundation; either | |
15 | * version 2.1 of the License, or (at your option) any later version. | |
16 | * | |
17 | * Use of this within git automatically means that the LGPL | |
18 | * licensing gets turned into GPLv2 within this project. | |
19 | */ | |
20 | ||
21 | #include <stdlib.h> | |
22 | #include "delta.h" | |
23 | ||
24 | ||
25 | /* block size: min = 16, max = 64k, power of 2 */ | |
26 | #define BLK_SIZE 16 | |
27 | ||
28 | #define MIN(a, b) ((a) < (b) ? (a) : (b)) | |
29 | ||
30 | #define GR_PRIME 0x9e370001 | |
31 | #define HASH(v, b) (((unsigned int)(v) * GR_PRIME) >> (32 - (b))) | |
32 | ||
33 | /* largest prime smaller than 65536 */ | |
34 | #define BASE 65521 | |
35 | ||
36 | /* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */ | |
37 | #define NMAX 5552 | |
38 | ||
39 | #define DO1(buf, i) { s1 += buf[i]; s2 += s1; } | |
40 | #define DO2(buf, i) DO1(buf, i); DO1(buf, i + 1); | |
41 | #define DO4(buf, i) DO2(buf, i); DO2(buf, i + 2); | |
42 | #define DO8(buf, i) DO4(buf, i); DO4(buf, i + 4); | |
43 | #define DO16(buf) DO8(buf, 0); DO8(buf, 8); | |
44 | ||
45 | static unsigned int adler32(unsigned int adler, const unsigned char *buf, int len) | |
46 | { | |
47 | int k; | |
48 | unsigned int s1 = adler & 0xffff; | |
49 | unsigned int s2 = adler >> 16; | |
50 | ||
51 | while (len > 0) { | |
52 | k = MIN(len, NMAX); | |
53 | len -= k; | |
54 | while (k >= 16) { | |
55 | DO16(buf); | |
56 | buf += 16; | |
57 | k -= 16; | |
58 | } | |
59 | if (k != 0) | |
60 | do { | |
61 | s1 += *buf++; | |
62 | s2 += s1; | |
63 | } while (--k); | |
64 | s1 %= BASE; | |
65 | s2 %= BASE; | |
66 | } | |
67 | ||
68 | return (s2 << 16) | s1; | |
69 | } | |
70 | ||
71 | static unsigned int hashbits(unsigned int size) | |
72 | { | |
73 | unsigned int val = 1, bits = 0; | |
74 | while (val < size && bits < 32) { | |
75 | val <<= 1; | |
76 | bits++; | |
77 | } | |
78 | return bits ? bits: 1; | |
79 | } | |
80 | ||
81 | typedef struct s_chanode { | |
82 | struct s_chanode *next; | |
83 | int icurr; | |
84 | } chanode_t; | |
85 | ||
86 | typedef struct s_chastore { | |
87 | chanode_t *head, *tail; | |
88 | int isize, nsize; | |
89 | chanode_t *ancur; | |
90 | chanode_t *sncur; | |
91 | int scurr; | |
92 | } chastore_t; | |
93 | ||
94 | static void cha_init(chastore_t *cha, int isize, int icount) | |
95 | { | |
96 | cha->head = cha->tail = NULL; | |
97 | cha->isize = isize; | |
98 | cha->nsize = icount * isize; | |
99 | cha->ancur = cha->sncur = NULL; | |
100 | cha->scurr = 0; | |
101 | } | |
102 | ||
103 | static void *cha_alloc(chastore_t *cha) | |
104 | { | |
105 | chanode_t *ancur; | |
106 | void *data; | |
107 | ||
108 | ancur = cha->ancur; | |
109 | if (!ancur || ancur->icurr == cha->nsize) { | |
110 | ancur = malloc(sizeof(chanode_t) + cha->nsize); | |
111 | if (!ancur) | |
112 | return NULL; | |
113 | ancur->icurr = 0; | |
114 | ancur->next = NULL; | |
115 | if (cha->tail) | |
116 | cha->tail->next = ancur; | |
117 | if (!cha->head) | |
118 | cha->head = ancur; | |
119 | cha->tail = ancur; | |
120 | cha->ancur = ancur; | |
121 | } | |
122 | ||
123 | data = (void *)ancur + sizeof(chanode_t) + ancur->icurr; | |
124 | ancur->icurr += cha->isize; | |
125 | return data; | |
126 | } | |
127 | ||
128 | static void cha_free(chastore_t *cha) | |
129 | { | |
130 | chanode_t *cur = cha->head; | |
131 | while (cur) { | |
132 | chanode_t *tmp = cur; | |
133 | cur = cur->next; | |
134 | free(tmp); | |
135 | } | |
136 | } | |
137 | ||
138 | typedef struct s_bdrecord { | |
139 | struct s_bdrecord *next; | |
140 | unsigned int fp; | |
141 | const unsigned char *ptr; | |
142 | } bdrecord_t; | |
143 | ||
144 | typedef struct s_bdfile { | |
145 | const unsigned char *data, *top; | |
146 | chastore_t cha; | |
147 | unsigned int fphbits; | |
148 | bdrecord_t **fphash; | |
149 | } bdfile_t; | |
150 | ||
151 | static int delta_prepare(const unsigned char *buf, int bufsize, bdfile_t *bdf) | |
152 | { | |
153 | unsigned int fphbits; | |
154 | int i, hsize; | |
155 | const unsigned char *base, *data, *top; | |
156 | bdrecord_t *brec; | |
157 | bdrecord_t **fphash; | |
158 | ||
159 | fphbits = hashbits(bufsize / BLK_SIZE + 1); | |
160 | hsize = 1 << fphbits; | |
161 | fphash = malloc(hsize * sizeof(bdrecord_t *)); | |
162 | if (!fphash) | |
163 | return -1; | |
164 | for (i = 0; i < hsize; i++) | |
165 | fphash[i] = NULL; | |
166 | cha_init(&bdf->cha, sizeof(bdrecord_t), hsize / 4 + 1); | |
167 | ||
168 | bdf->data = data = base = buf; | |
169 | bdf->top = top = buf + bufsize; | |
170 | data += (bufsize / BLK_SIZE) * BLK_SIZE; | |
171 | if (data == top) | |
172 | data -= BLK_SIZE; | |
173 | ||
174 | for ( ; data >= base; data -= BLK_SIZE) { | |
175 | brec = cha_alloc(&bdf->cha); | |
176 | if (!brec) { | |
177 | cha_free(&bdf->cha); | |
178 | free(fphash); | |
179 | return -1; | |
180 | } | |
181 | brec->fp = adler32(0, data, MIN(BLK_SIZE, top - data)); | |
182 | brec->ptr = data; | |
183 | i = HASH(brec->fp, fphbits); | |
184 | brec->next = fphash[i]; | |
185 | fphash[i] = brec; | |
186 | } | |
187 | ||
188 | bdf->fphbits = fphbits; | |
189 | bdf->fphash = fphash; | |
190 | ||
191 | return 0; | |
192 | } | |
193 | ||
194 | static void delta_cleanup(bdfile_t *bdf) | |
195 | { | |
196 | free(bdf->fphash); | |
197 | cha_free(&bdf->cha); | |
198 | } | |
199 | ||
200 | #define COPYOP_SIZE(o, s) \ | |
201 | (!!(o & 0xff) + !!(o & 0xff00) + !!(o & 0xff0000) + !!(o & 0xff000000) + \ | |
202 | !!(s & 0xff) + !!(s & 0xff00) + 1) | |
203 | ||
204 | void *diff_delta(void *from_buf, unsigned long from_size, | |
205 | void *to_buf, unsigned long to_size, | |
75c42d8c LT |
206 | unsigned long *delta_size, |
207 | unsigned long max_size) | |
a310d434 NP |
208 | { |
209 | int i, outpos, outsize, inscnt, csize, msize, moff; | |
210 | unsigned int fp; | |
211 | const unsigned char *data, *top, *ptr1, *ptr2; | |
212 | unsigned char *out, *orig; | |
213 | bdrecord_t *brec; | |
214 | bdfile_t bdf; | |
215 | ||
216 | if (!from_size || !to_size || delta_prepare(from_buf, from_size, &bdf)) | |
217 | return NULL; | |
218 | ||
219 | outpos = 0; | |
220 | outsize = 8192; | |
221 | out = malloc(outsize); | |
222 | if (!out) { | |
223 | delta_cleanup(&bdf); | |
224 | return NULL; | |
225 | } | |
226 | ||
227 | data = to_buf; | |
228 | top = to_buf + to_size; | |
229 | ||
230 | /* store reference buffer size */ | |
69a2d426 NP |
231 | out[outpos++] = from_size; |
232 | from_size >>= 7; | |
233 | while (from_size) { | |
234 | out[outpos - 1] |= 0x80; | |
235 | out[outpos++] = from_size; | |
236 | from_size >>= 7; | |
237 | } | |
a310d434 NP |
238 | |
239 | /* store target buffer size */ | |
69a2d426 NP |
240 | out[outpos++] = to_size; |
241 | to_size >>= 7; | |
242 | while (to_size) { | |
243 | out[outpos - 1] |= 0x80; | |
244 | out[outpos++] = to_size; | |
245 | to_size >>= 7; | |
246 | } | |
a310d434 NP |
247 | |
248 | inscnt = 0; | |
249 | moff = 0; | |
250 | while (data < top) { | |
251 | msize = 0; | |
252 | fp = adler32(0, data, MIN(top - data, BLK_SIZE)); | |
253 | i = HASH(fp, bdf.fphbits); | |
254 | for (brec = bdf.fphash[i]; brec; brec = brec->next) { | |
255 | if (brec->fp == fp) { | |
256 | csize = bdf.top - brec->ptr; | |
257 | if (csize > top - data) | |
258 | csize = top - data; | |
259 | for (ptr1 = brec->ptr, ptr2 = data; | |
260 | csize && *ptr1 == *ptr2; | |
261 | csize--, ptr1++, ptr2++); | |
262 | ||
263 | csize = ptr1 - brec->ptr; | |
264 | if (csize > msize) { | |
265 | moff = brec->ptr - bdf.data; | |
266 | msize = csize; | |
267 | if (msize >= 0x10000) { | |
268 | msize = 0x10000; | |
269 | break; | |
270 | } | |
271 | } | |
272 | } | |
273 | } | |
274 | ||
275 | if (!msize || msize < COPYOP_SIZE(moff, msize)) { | |
276 | if (!inscnt) | |
277 | outpos++; | |
278 | out[outpos++] = *data++; | |
279 | inscnt++; | |
280 | if (inscnt == 0x7f) { | |
281 | out[outpos - inscnt - 1] = inscnt; | |
282 | inscnt = 0; | |
283 | } | |
284 | } else { | |
285 | if (inscnt) { | |
286 | out[outpos - inscnt - 1] = inscnt; | |
287 | inscnt = 0; | |
288 | } | |
289 | ||
290 | data += msize; | |
291 | orig = out + outpos++; | |
292 | i = 0x80; | |
293 | ||
294 | if (moff & 0xff) { out[outpos++] = moff; i |= 0x01; } | |
295 | moff >>= 8; | |
296 | if (moff & 0xff) { out[outpos++] = moff; i |= 0x02; } | |
297 | moff >>= 8; | |
298 | if (moff & 0xff) { out[outpos++] = moff; i |= 0x04; } | |
299 | moff >>= 8; | |
300 | if (moff & 0xff) { out[outpos++] = moff; i |= 0x08; } | |
301 | ||
302 | if (msize & 0xff) { out[outpos++] = msize; i |= 0x10; } | |
303 | msize >>= 8; | |
304 | if (msize & 0xff) { out[outpos++] = msize; i |= 0x20; } | |
305 | ||
306 | *orig = i; | |
307 | } | |
308 | ||
75c42d8c LT |
309 | if (max_size && outpos > max_size) { |
310 | free(out); | |
311 | delta_cleanup(&bdf); | |
312 | return NULL; | |
313 | } | |
dcde55bc NP |
314 | |
315 | /* next time around the largest possible output is 1 + 4 + 3 */ | |
a310d434 NP |
316 | if (outpos > outsize - 8) { |
317 | void *tmp = out; | |
318 | outsize = outsize * 3 / 2; | |
319 | out = realloc(out, outsize); | |
320 | if (!out) { | |
321 | free(tmp); | |
322 | delta_cleanup(&bdf); | |
323 | return NULL; | |
324 | } | |
325 | } | |
326 | } | |
327 | ||
328 | if (inscnt) | |
329 | out[outpos - inscnt - 1] = inscnt; | |
330 | ||
331 | delta_cleanup(&bdf); | |
332 | *delta_size = outpos; | |
333 | return out; | |
334 | } |