Mercurial > hg
annotate mercurial/mpatch.c @ 35892:00a56c83ab64
revset: drop deprecated evolution predicates
author | Matt Harbison <matt_harbison@yahoo.com> |
---|---|
date | Fri, 02 Feb 2018 23:48:25 -0500 |
parents | 1f4249c764f1 |
children | 90a274965de7 |
rev | line source |
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72 | 1 /* |
2 mpatch.c - efficient binary patching for Mercurial | |
3 | |
4 This implements a patch algorithm that's O(m + nlog n) where m is the | |
5 size of the output and n is the number of patches. | |
6 | |
7 Given a list of binary patches, it unpacks each into a hunk list, | |
8 then combines the hunk lists with a treewise recursion to form a | |
9 single hunk list. This hunk list is then applied to the original | |
10 text. | |
11 | |
12 The text (or binary) fragments are copied directly from their source | |
13 Python objects into a preallocated output string to avoid the | |
14 allocation of intermediate Python objects. Working memory is about 2x | |
15 the total number of hunks. | |
16 | |
2859 | 17 Copyright 2005, 2006 Matt Mackall <mpm@selenic.com> |
72 | 18 |
19 This software may be used and distributed according to the terms | |
20 of the GNU General Public License, incorporated herein by reference. | |
21 */ | |
22 | |
23 #include <stdlib.h> | |
24 #include <string.h> | |
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25 |
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26 #include "bitmanipulation.h" |
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27 #include "compat.h" |
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28 #include "mpatch.h" |
72 | 29 |
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30 static struct mpatch_flist *lalloc(ssize_t size) |
72 | 31 { |
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32 struct mpatch_flist *a = NULL; |
72 | 33 |
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34 if (size < 1) |
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35 size = 1; |
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36 |
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37 a = (struct mpatch_flist *)malloc(sizeof(struct mpatch_flist)); |
128 | 38 if (a) { |
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39 a->base = (struct mpatch_frag *)malloc( |
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40 sizeof(struct mpatch_frag) * size); |
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41 if (a->base) { |
128 | 42 a->head = a->tail = a->base; |
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43 return a; |
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44 } |
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45 free(a); |
128 | 46 } |
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47 return NULL; |
72 | 48 } |
49 | |
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50 void mpatch_lfree(struct mpatch_flist *a) |
72 | 51 { |
128 | 52 if (a) { |
53 free(a->base); | |
54 free(a); | |
55 } | |
72 | 56 } |
57 | |
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58 static ssize_t lsize(struct mpatch_flist *a) |
72 | 59 { |
60 return a->tail - a->head; | |
61 } | |
62 | |
63 /* move hunks in source that are less cut to dest, compensating | |
64 for changes in offset. the last hunk may be split if necessary. | |
65 */ | |
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66 static int gather(struct mpatch_flist *dest, struct mpatch_flist *src, int cut, |
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67 int offset) |
72 | 68 { |
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69 struct mpatch_frag *d = dest->tail, *s = src->head; |
72 | 70 int postend, c, l; |
71 | |
72 while (s != src->tail) { | |
73 if (s->start + offset >= cut) | |
82 | 74 break; /* we've gone far enough */ |
72 | 75 |
76 postend = offset + s->start + s->len; | |
77 if (postend <= cut) { | |
78 /* save this hunk */ | |
79 offset += s->start + s->len - s->end; | |
80 *d++ = *s++; | |
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81 } else { |
72 | 82 /* break up this hunk */ |
83 c = cut - offset; | |
84 if (s->end < c) | |
85 c = s->end; | |
86 l = cut - offset - s->start; | |
87 if (s->len < l) | |
88 l = s->len; | |
89 | |
90 offset += s->start + l - c; | |
91 | |
92 d->start = s->start; | |
93 d->end = c; | |
94 d->len = l; | |
95 d->data = s->data; | |
96 d++; | |
97 s->start = c; | |
98 s->len = s->len - l; | |
99 s->data = s->data + l; | |
100 | |
82 | 101 break; |
72 | 102 } |
103 } | |
104 | |
105 dest->tail = d; | |
106 src->head = s; | |
107 return offset; | |
108 } | |
109 | |
110 /* like gather, but with no output list */ | |
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111 static int discard(struct mpatch_flist *src, int cut, int offset) |
72 | 112 { |
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113 struct mpatch_frag *s = src->head; |
72 | 114 int postend, c, l; |
115 | |
116 while (s != src->tail) { | |
117 if (s->start + offset >= cut) | |
82 | 118 break; |
72 | 119 |
120 postend = offset + s->start + s->len; | |
121 if (postend <= cut) { | |
122 offset += s->start + s->len - s->end; | |
123 s++; | |
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124 } else { |
72 | 125 c = cut - offset; |
126 if (s->end < c) | |
127 c = s->end; | |
128 l = cut - offset - s->start; | |
129 if (s->len < l) | |
130 l = s->len; | |
131 | |
132 offset += s->start + l - c; | |
133 s->start = c; | |
134 s->len = s->len - l; | |
135 s->data = s->data + l; | |
136 | |
82 | 137 break; |
72 | 138 } |
139 } | |
140 | |
141 src->head = s; | |
142 return offset; | |
143 } | |
144 | |
145 /* combine hunk lists a and b, while adjusting b for offset changes in a/ | |
146 this deletes a and b and returns the resultant list. */ | |
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147 static struct mpatch_flist *combine(struct mpatch_flist *a, |
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148 struct mpatch_flist *b) |
72 | 149 { |
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150 struct mpatch_flist *c = NULL; |
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151 struct mpatch_frag *bh, *ct; |
72 | 152 int offset = 0, post; |
153 | |
128 | 154 if (a && b) |
155 c = lalloc((lsize(a) + lsize(b)) * 2); | |
156 | |
157 if (c) { | |
72 | 158 |
128 | 159 for (bh = b->head; bh != b->tail; bh++) { |
160 /* save old hunks */ | |
161 offset = gather(c, a, bh->start, offset); | |
72 | 162 |
128 | 163 /* discard replaced hunks */ |
164 post = discard(a, bh->end, offset); | |
72 | 165 |
128 | 166 /* insert new hunk */ |
167 ct = c->tail; | |
168 ct->start = bh->start - offset; | |
169 ct->end = bh->end - post; | |
170 ct->len = bh->len; | |
171 ct->data = bh->data; | |
172 c->tail++; | |
173 offset = post; | |
174 } | |
175 | |
176 /* hold on to tail from a */ | |
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177 memcpy(c->tail, a->head, sizeof(struct mpatch_frag) * lsize(a)); |
128 | 178 c->tail += lsize(a); |
72 | 179 } |
180 | |
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181 mpatch_lfree(a); |
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182 mpatch_lfree(b); |
72 | 183 return c; |
184 } | |
185 | |
186 /* decode a binary patch into a hunk list */ | |
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187 int mpatch_decode(const char *bin, ssize_t len, struct mpatch_flist **res) |
72 | 188 { |
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189 struct mpatch_flist *l; |
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190 struct mpatch_frag *lt; |
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191 int pos = 0; |
72 | 192 |
193 /* assume worst case size, we won't have many of these lists */ | |
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194 l = lalloc(len / 12 + 1); |
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195 if (!l) |
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196 return MPATCH_ERR_NO_MEM; |
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197 |
72 | 198 lt = l->tail; |
199 | |
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200 while (pos >= 0 && pos < len) { |
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201 lt->start = getbe32(bin + pos); |
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202 lt->end = getbe32(bin + pos + 4); |
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203 lt->len = getbe32(bin + pos + 8); |
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204 lt->data = bin + pos + 12; |
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205 pos += 12 + lt->len; |
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206 if (lt->start > lt->end || lt->len < 0) |
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207 break; /* sanity check */ |
72 | 208 lt++; |
209 } | |
210 | |
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211 if (pos != len) { |
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212 mpatch_lfree(l); |
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213 return MPATCH_ERR_CANNOT_BE_DECODED; |
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214 } |
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215 |
72 | 216 l->tail = lt; |
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217 *res = l; |
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218 return 0; |
72 | 219 } |
220 | |
221 /* calculate the size of resultant text */ | |
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222 ssize_t mpatch_calcsize(ssize_t len, struct mpatch_flist *l) |
72 | 223 { |
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224 ssize_t outlen = 0, last = 0; |
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225 struct mpatch_frag *f = l->head; |
72 | 226 |
227 while (f != l->tail) { | |
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228 if (f->start < last || f->end > len) { |
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229 return MPATCH_ERR_INVALID_PATCH; |
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230 } |
72 | 231 outlen += f->start - last; |
232 last = f->end; | |
233 outlen += f->len; | |
234 f++; | |
235 } | |
236 | |
237 outlen += len - last; | |
238 return outlen; | |
239 } | |
240 | |
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241 int mpatch_apply(char *buf, const char *orig, ssize_t len, |
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242 struct mpatch_flist *l) |
72 | 243 { |
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244 struct mpatch_frag *f = l->head; |
72 | 245 int last = 0; |
246 char *p = buf; | |
247 | |
248 while (f != l->tail) { | |
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249 if (f->start < last || f->end > len) { |
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250 return MPATCH_ERR_INVALID_PATCH; |
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251 } |
72 | 252 memcpy(p, orig + last, f->start - last); |
253 p += f->start - last; | |
254 memcpy(p, f->data, f->len); | |
255 last = f->end; | |
256 p += f->len; | |
257 f++; | |
258 } | |
259 memcpy(p, orig + last, len - last); | |
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260 return 0; |
72 | 261 } |
262 | |
263 /* recursively generate a patch of all bins between start and end */ | |
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264 struct mpatch_flist * |
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265 mpatch_fold(void *bins, struct mpatch_flist *(*get_next_item)(void *, ssize_t), |
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266 ssize_t start, ssize_t end) |
72 | 267 { |
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268 ssize_t len; |
72 | 269 |
270 if (start + 1 == end) { | |
271 /* trivial case, output a decoded list */ | |
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272 return get_next_item(bins, start); |
72 | 273 } |
274 | |
275 /* divide and conquer, memory management is elsewhere */ | |
276 len = (end - start) / 2; | |
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277 return combine(mpatch_fold(bins, get_next_item, start, start + len), |
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278 mpatch_fold(bins, get_next_item, start + len, end)); |
72 | 279 } |