Mercurial > hg > mercurial-crew-with-dirclash
annotate mercurial/mpatch.c @ 520:12b4b5612fe4
Add some TODO items
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Add some TODO items
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author | mpm@selenic.com |
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date | Wed, 29 Jun 2005 11:12:50 -0800 |
parents | 7f3fc8fd427e |
children | b460a2fd8bb7 f2442a6a5893 |
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 | |
17 Copyright 2005 Matt Mackall <mpm@selenic.com> | |
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 <Python.h> | |
24 #include <stdlib.h> | |
25 #include <string.h> | |
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26 #ifdef _WIN32 |
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27 #include <stdint.h> |
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28 static uint32_t ntohl(uint32_t x) |
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29 { |
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30 return ((x & 0x000000ffUL) << 24) | |
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31 ((x & 0x0000ff00UL) << 8) | |
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32 ((x & 0x00ff0000UL) >> 8) | |
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33 ((x & 0xff000000UL) >> 24); |
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34 } |
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35 #else |
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36 #include <sys/types.h> |
472 | 37 #include <netinet/in.h> |
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38 #endif |
72 | 39 |
40 static char mpatch_doc[] = "Efficient binary patching."; | |
41 | |
42 struct frag { | |
43 int start, end, len; | |
44 char *data; | |
45 }; | |
46 | |
47 struct flist { | |
48 struct frag *base, *head, *tail; | |
49 }; | |
50 | |
51 static struct flist *lalloc(int size) | |
52 { | |
128 | 53 struct flist *a = NULL; |
72 | 54 |
55 a = malloc(sizeof(struct flist)); | |
128 | 56 if (a) { |
57 a->base = malloc(sizeof(struct frag) * size); | |
282 | 58 if (!a->base) { |
128 | 59 free(a); |
282 | 60 a = NULL; |
61 } else | |
128 | 62 a->head = a->tail = a->base; |
63 } | |
72 | 64 return a; |
65 } | |
66 | |
67 static void lfree(struct flist *a) | |
68 { | |
128 | 69 if (a) { |
70 free(a->base); | |
71 free(a); | |
72 } | |
72 | 73 } |
74 | |
75 static int lsize(struct flist *a) | |
76 { | |
77 return a->tail - a->head; | |
78 } | |
79 | |
80 /* move hunks in source that are less cut to dest, compensating | |
81 for changes in offset. the last hunk may be split if necessary. | |
82 */ | |
83 static int gather(struct flist *dest, struct flist *src, int cut, int offset) | |
84 { | |
85 struct frag *d = dest->tail, *s = src->head; | |
86 int postend, c, l; | |
87 | |
88 while (s != src->tail) { | |
89 if (s->start + offset >= cut) | |
82 | 90 break; /* we've gone far enough */ |
72 | 91 |
92 postend = offset + s->start + s->len; | |
93 if (postend <= cut) { | |
94 /* save this hunk */ | |
95 offset += s->start + s->len - s->end; | |
96 *d++ = *s++; | |
97 } | |
98 else { | |
99 /* break up this hunk */ | |
100 c = cut - offset; | |
101 if (s->end < c) | |
102 c = s->end; | |
103 l = cut - offset - s->start; | |
104 if (s->len < l) | |
105 l = s->len; | |
106 | |
107 offset += s->start + l - c; | |
108 | |
109 d->start = s->start; | |
110 d->end = c; | |
111 d->len = l; | |
112 d->data = s->data; | |
113 d++; | |
114 s->start = c; | |
115 s->len = s->len - l; | |
116 s->data = s->data + l; | |
117 | |
82 | 118 break; |
72 | 119 } |
120 } | |
121 | |
122 dest->tail = d; | |
123 src->head = s; | |
124 return offset; | |
125 } | |
126 | |
127 /* like gather, but with no output list */ | |
128 static int discard(struct flist *src, int cut, int offset) | |
129 { | |
130 struct frag *s = src->head; | |
131 int postend, c, l; | |
132 | |
133 while (s != src->tail) { | |
134 if (s->start + offset >= cut) | |
82 | 135 break; |
72 | 136 |
137 postend = offset + s->start + s->len; | |
138 if (postend <= cut) { | |
139 offset += s->start + s->len - s->end; | |
140 s++; | |
141 } | |
142 else { | |
143 c = cut - offset; | |
144 if (s->end < c) | |
145 c = s->end; | |
146 l = cut - offset - s->start; | |
147 if (s->len < l) | |
148 l = s->len; | |
149 | |
150 offset += s->start + l - c; | |
151 s->start = c; | |
152 s->len = s->len - l; | |
153 s->data = s->data + l; | |
154 | |
82 | 155 break; |
72 | 156 } |
157 } | |
158 | |
159 src->head = s; | |
160 return offset; | |
161 } | |
162 | |
163 /* combine hunk lists a and b, while adjusting b for offset changes in a/ | |
164 this deletes a and b and returns the resultant list. */ | |
165 static struct flist *combine(struct flist *a, struct flist *b) | |
166 { | |
128 | 167 struct flist *c = NULL; |
168 struct frag *bh, *ct; | |
72 | 169 int offset = 0, post; |
170 | |
128 | 171 if (a && b) |
172 c = lalloc((lsize(a) + lsize(b)) * 2); | |
173 | |
174 if (c) { | |
72 | 175 |
128 | 176 for (bh = b->head; bh != b->tail; bh++) { |
177 /* save old hunks */ | |
178 offset = gather(c, a, bh->start, offset); | |
72 | 179 |
128 | 180 /* discard replaced hunks */ |
181 post = discard(a, bh->end, offset); | |
72 | 182 |
128 | 183 /* insert new hunk */ |
184 ct = c->tail; | |
185 ct->start = bh->start - offset; | |
186 ct->end = bh->end - post; | |
187 ct->len = bh->len; | |
188 ct->data = bh->data; | |
189 c->tail++; | |
190 offset = post; | |
191 } | |
192 | |
193 /* hold on to tail from a */ | |
194 memcpy(c->tail, a->head, sizeof(struct frag) * lsize(a)); | |
195 c->tail += lsize(a); | |
72 | 196 } |
197 | |
198 lfree(a); | |
199 lfree(b); | |
200 return c; | |
201 } | |
202 | |
203 /* decode a binary patch into a hunk list */ | |
204 static struct flist *decode(char *bin, int len) | |
205 { | |
206 struct flist *l; | |
207 struct frag *lt; | |
208 char *end = bin + len; | |
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209 char decode[12]; /* for dealing with alignment issues */ |
72 | 210 |
211 /* assume worst case size, we won't have many of these lists */ | |
212 l = lalloc(len / 12); | |
213 lt = l->tail; | |
214 | |
215 while (bin < end) { | |
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216 memcpy(decode, bin, 12); |
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217 lt->start = ntohl(*(uint32_t *)decode); |
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218 lt->end = ntohl(*(uint32_t *)(decode + 4)); |
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219 lt->len = ntohl(*(uint32_t *)(decode + 8)); |
72 | 220 lt->data = bin + 12; |
221 bin += 12 + lt->len; | |
222 lt++; | |
223 } | |
224 | |
225 l->tail = lt; | |
226 return l; | |
227 } | |
228 | |
229 /* calculate the size of resultant text */ | |
230 static int calcsize(int len, struct flist *l) | |
231 { | |
232 int outlen = 0, last = 0; | |
233 struct frag *f = l->head; | |
234 | |
235 while (f != l->tail) { | |
236 outlen += f->start - last; | |
237 last = f->end; | |
238 outlen += f->len; | |
239 f++; | |
240 } | |
241 | |
242 outlen += len - last; | |
243 return outlen; | |
244 } | |
245 | |
246 static void apply(char *buf, char *orig, int len, struct flist *l) | |
247 { | |
248 struct frag *f = l->head; | |
249 int last = 0; | |
250 char *p = buf; | |
251 | |
252 while (f != l->tail) { | |
253 memcpy(p, orig + last, f->start - last); | |
254 p += f->start - last; | |
255 memcpy(p, f->data, f->len); | |
256 last = f->end; | |
257 p += f->len; | |
258 f++; | |
259 } | |
260 memcpy(p, orig + last, len - last); | |
261 } | |
262 | |
263 /* recursively generate a patch of all bins between start and end */ | |
264 static struct flist *fold(PyObject *bins, int start, int end) | |
265 { | |
266 int len; | |
267 | |
268 if (start + 1 == end) { | |
269 /* trivial case, output a decoded list */ | |
270 PyObject *tmp = PyList_GetItem(bins, start); | |
128 | 271 if (!tmp) |
272 return NULL; | |
72 | 273 return decode(PyString_AsString(tmp), PyString_Size(tmp)); |
274 } | |
275 | |
276 /* divide and conquer, memory management is elsewhere */ | |
277 len = (end - start) / 2; | |
278 return combine(fold(bins, start, start + len), | |
279 fold(bins, start + len, end)); | |
280 } | |
281 | |
282 static PyObject * | |
283 patches(PyObject *self, PyObject *args) | |
284 { | |
285 PyObject *text, *bins, *result; | |
286 struct flist *patch; | |
287 char *in, *out; | |
288 int len, outlen; | |
289 | |
128 | 290 if (!PyArg_ParseTuple(args, "SO:mpatch", &text, &bins)) |
72 | 291 return NULL; |
292 | |
293 len = PyList_Size(bins); | |
294 if (!len) { | |
295 /* nothing to do */ | |
296 Py_INCREF(text); | |
297 return text; | |
298 } | |
299 | |
300 patch = fold(bins, 0, len); | |
128 | 301 if (!patch) |
302 return PyErr_NoMemory(); | |
303 | |
72 | 304 outlen = calcsize(PyString_Size(text), patch); |
305 result = PyString_FromStringAndSize(NULL, outlen); | |
128 | 306 if (result) { |
307 in = PyString_AsString(text); | |
308 out = PyString_AsString(result); | |
309 apply(out, in, PyString_Size(text), patch); | |
310 } | |
311 | |
72 | 312 lfree(patch); |
313 return result; | |
314 } | |
315 | |
316 static PyMethodDef methods[] = { | |
317 {"patches", patches, METH_VARARGS, "apply a series of patches\n"}, | |
318 {NULL, NULL} | |
319 }; | |
320 | |
321 PyMODINIT_FUNC | |
322 initmpatch(void) | |
323 { | |
324 Py_InitModule3("mpatch", methods, mpatch_doc); | |
325 } | |
326 |