Sixth batch
[git/git.git] / refs / iterator.c
1 /*
2 * Generic reference iterator infrastructure. See refs-internal.h for
3 * documentation about the design and use of reference iterators.
4 */
5
6 #include "cache.h"
7 #include "refs.h"
8 #include "refs/refs-internal.h"
9 #include "iterator.h"
10
11 int ref_iterator_advance(struct ref_iterator *ref_iterator)
12 {
13 return ref_iterator->vtable->advance(ref_iterator);
14 }
15
16 int ref_iterator_peel(struct ref_iterator *ref_iterator,
17 struct object_id *peeled)
18 {
19 return ref_iterator->vtable->peel(ref_iterator, peeled);
20 }
21
22 int ref_iterator_abort(struct ref_iterator *ref_iterator)
23 {
24 return ref_iterator->vtable->abort(ref_iterator);
25 }
26
27 void base_ref_iterator_init(struct ref_iterator *iter,
28 struct ref_iterator_vtable *vtable,
29 int ordered)
30 {
31 iter->vtable = vtable;
32 iter->ordered = !!ordered;
33 iter->refname = NULL;
34 iter->oid = NULL;
35 iter->flags = 0;
36 }
37
38 void base_ref_iterator_free(struct ref_iterator *iter)
39 {
40 /* Help make use-after-free bugs fail quickly: */
41 iter->vtable = NULL;
42 free(iter);
43 }
44
45 struct empty_ref_iterator {
46 struct ref_iterator base;
47 };
48
49 static int empty_ref_iterator_advance(struct ref_iterator *ref_iterator)
50 {
51 return ref_iterator_abort(ref_iterator);
52 }
53
54 static int empty_ref_iterator_peel(struct ref_iterator *ref_iterator,
55 struct object_id *peeled)
56 {
57 BUG("peel called for empty iterator");
58 }
59
60 static int empty_ref_iterator_abort(struct ref_iterator *ref_iterator)
61 {
62 base_ref_iterator_free(ref_iterator);
63 return ITER_DONE;
64 }
65
66 static struct ref_iterator_vtable empty_ref_iterator_vtable = {
67 empty_ref_iterator_advance,
68 empty_ref_iterator_peel,
69 empty_ref_iterator_abort
70 };
71
72 struct ref_iterator *empty_ref_iterator_begin(void)
73 {
74 struct empty_ref_iterator *iter = xcalloc(1, sizeof(*iter));
75 struct ref_iterator *ref_iterator = &iter->base;
76
77 base_ref_iterator_init(ref_iterator, &empty_ref_iterator_vtable, 1);
78 return ref_iterator;
79 }
80
81 int is_empty_ref_iterator(struct ref_iterator *ref_iterator)
82 {
83 return ref_iterator->vtable == &empty_ref_iterator_vtable;
84 }
85
86 struct merge_ref_iterator {
87 struct ref_iterator base;
88
89 struct ref_iterator *iter0, *iter1;
90
91 ref_iterator_select_fn *select;
92 void *cb_data;
93
94 /*
95 * A pointer to iter0 or iter1 (whichever is supplying the
96 * current value), or NULL if advance has not yet been called.
97 */
98 struct ref_iterator **current;
99 };
100
101 static int merge_ref_iterator_advance(struct ref_iterator *ref_iterator)
102 {
103 struct merge_ref_iterator *iter =
104 (struct merge_ref_iterator *)ref_iterator;
105 int ok;
106
107 if (!iter->current) {
108 /* Initialize: advance both iterators to their first entries */
109 if ((ok = ref_iterator_advance(iter->iter0)) != ITER_OK) {
110 iter->iter0 = NULL;
111 if (ok == ITER_ERROR)
112 goto error;
113 }
114 if ((ok = ref_iterator_advance(iter->iter1)) != ITER_OK) {
115 iter->iter1 = NULL;
116 if (ok == ITER_ERROR)
117 goto error;
118 }
119 } else {
120 /*
121 * Advance the current iterator past the just-used
122 * entry:
123 */
124 if ((ok = ref_iterator_advance(*iter->current)) != ITER_OK) {
125 *iter->current = NULL;
126 if (ok == ITER_ERROR)
127 goto error;
128 }
129 }
130
131 /* Loop until we find an entry that we can yield. */
132 while (1) {
133 struct ref_iterator **secondary;
134 enum iterator_selection selection =
135 iter->select(iter->iter0, iter->iter1, iter->cb_data);
136
137 if (selection == ITER_SELECT_DONE) {
138 return ref_iterator_abort(ref_iterator);
139 } else if (selection == ITER_SELECT_ERROR) {
140 ref_iterator_abort(ref_iterator);
141 return ITER_ERROR;
142 }
143
144 if ((selection & ITER_CURRENT_SELECTION_MASK) == 0) {
145 iter->current = &iter->iter0;
146 secondary = &iter->iter1;
147 } else {
148 iter->current = &iter->iter1;
149 secondary = &iter->iter0;
150 }
151
152 if (selection & ITER_SKIP_SECONDARY) {
153 if ((ok = ref_iterator_advance(*secondary)) != ITER_OK) {
154 *secondary = NULL;
155 if (ok == ITER_ERROR)
156 goto error;
157 }
158 }
159
160 if (selection & ITER_YIELD_CURRENT) {
161 iter->base.refname = (*iter->current)->refname;
162 iter->base.oid = (*iter->current)->oid;
163 iter->base.flags = (*iter->current)->flags;
164 return ITER_OK;
165 }
166 }
167
168 error:
169 ref_iterator_abort(ref_iterator);
170 return ITER_ERROR;
171 }
172
173 static int merge_ref_iterator_peel(struct ref_iterator *ref_iterator,
174 struct object_id *peeled)
175 {
176 struct merge_ref_iterator *iter =
177 (struct merge_ref_iterator *)ref_iterator;
178
179 if (!iter->current) {
180 BUG("peel called before advance for merge iterator");
181 }
182 return ref_iterator_peel(*iter->current, peeled);
183 }
184
185 static int merge_ref_iterator_abort(struct ref_iterator *ref_iterator)
186 {
187 struct merge_ref_iterator *iter =
188 (struct merge_ref_iterator *)ref_iterator;
189 int ok = ITER_DONE;
190
191 if (iter->iter0) {
192 if (ref_iterator_abort(iter->iter0) != ITER_DONE)
193 ok = ITER_ERROR;
194 }
195 if (iter->iter1) {
196 if (ref_iterator_abort(iter->iter1) != ITER_DONE)
197 ok = ITER_ERROR;
198 }
199 base_ref_iterator_free(ref_iterator);
200 return ok;
201 }
202
203 static struct ref_iterator_vtable merge_ref_iterator_vtable = {
204 merge_ref_iterator_advance,
205 merge_ref_iterator_peel,
206 merge_ref_iterator_abort
207 };
208
209 struct ref_iterator *merge_ref_iterator_begin(
210 int ordered,
211 struct ref_iterator *iter0, struct ref_iterator *iter1,
212 ref_iterator_select_fn *select, void *cb_data)
213 {
214 struct merge_ref_iterator *iter = xcalloc(1, sizeof(*iter));
215 struct ref_iterator *ref_iterator = &iter->base;
216
217 /*
218 * We can't do the same kind of is_empty_ref_iterator()-style
219 * optimization here as overlay_ref_iterator_begin() does,
220 * because we don't know the semantics of the select function.
221 * It might, for example, implement "intersect" by passing
222 * references through only if they exist in both iterators.
223 */
224
225 base_ref_iterator_init(ref_iterator, &merge_ref_iterator_vtable, ordered);
226 iter->iter0 = iter0;
227 iter->iter1 = iter1;
228 iter->select = select;
229 iter->cb_data = cb_data;
230 iter->current = NULL;
231 return ref_iterator;
232 }
233
234 /*
235 * A ref_iterator_select_fn that overlays the items from front on top
236 * of those from back (like loose refs over packed refs). See
237 * overlay_ref_iterator_begin().
238 */
239 static enum iterator_selection overlay_iterator_select(
240 struct ref_iterator *front, struct ref_iterator *back,
241 void *cb_data)
242 {
243 int cmp;
244
245 if (!back)
246 return front ? ITER_SELECT_0 : ITER_SELECT_DONE;
247 else if (!front)
248 return ITER_SELECT_1;
249
250 cmp = strcmp(front->refname, back->refname);
251
252 if (cmp < 0)
253 return ITER_SELECT_0;
254 else if (cmp > 0)
255 return ITER_SELECT_1;
256 else
257 return ITER_SELECT_0_SKIP_1;
258 }
259
260 struct ref_iterator *overlay_ref_iterator_begin(
261 struct ref_iterator *front, struct ref_iterator *back)
262 {
263 /*
264 * Optimization: if one of the iterators is empty, return the
265 * other one rather than incurring the overhead of wrapping
266 * them.
267 */
268 if (is_empty_ref_iterator(front)) {
269 ref_iterator_abort(front);
270 return back;
271 } else if (is_empty_ref_iterator(back)) {
272 ref_iterator_abort(back);
273 return front;
274 } else if (!front->ordered || !back->ordered) {
275 BUG("overlay_ref_iterator requires ordered inputs");
276 }
277
278 return merge_ref_iterator_begin(1, front, back,
279 overlay_iterator_select, NULL);
280 }
281
282 struct prefix_ref_iterator {
283 struct ref_iterator base;
284
285 struct ref_iterator *iter0;
286 char *prefix;
287 int trim;
288 };
289
290 /* Return -1, 0, 1 if refname is before, inside, or after the prefix. */
291 static int compare_prefix(const char *refname, const char *prefix)
292 {
293 while (*prefix) {
294 if (*refname != *prefix)
295 return ((unsigned char)*refname < (unsigned char)*prefix) ? -1 : +1;
296
297 refname++;
298 prefix++;
299 }
300
301 return 0;
302 }
303
304 static int prefix_ref_iterator_advance(struct ref_iterator *ref_iterator)
305 {
306 struct prefix_ref_iterator *iter =
307 (struct prefix_ref_iterator *)ref_iterator;
308 int ok;
309
310 while ((ok = ref_iterator_advance(iter->iter0)) == ITER_OK) {
311 int cmp = compare_prefix(iter->iter0->refname, iter->prefix);
312
313 if (cmp < 0)
314 continue;
315
316 if (cmp > 0) {
317 /*
318 * If the source iterator is ordered, then we
319 * can stop the iteration as soon as we see a
320 * refname that comes after the prefix:
321 */
322 if (iter->iter0->ordered) {
323 ok = ref_iterator_abort(iter->iter0);
324 break;
325 } else {
326 continue;
327 }
328 }
329
330 if (iter->trim) {
331 /*
332 * It is nonsense to trim off characters that
333 * you haven't already checked for via a
334 * prefix check, whether via this
335 * `prefix_ref_iterator` or upstream in
336 * `iter0`). So if there wouldn't be at least
337 * one character left in the refname after
338 * trimming, report it as a bug:
339 */
340 if (strlen(iter->iter0->refname) <= iter->trim)
341 BUG("attempt to trim too many characters");
342 iter->base.refname = iter->iter0->refname + iter->trim;
343 } else {
344 iter->base.refname = iter->iter0->refname;
345 }
346
347 iter->base.oid = iter->iter0->oid;
348 iter->base.flags = iter->iter0->flags;
349 return ITER_OK;
350 }
351
352 iter->iter0 = NULL;
353 if (ref_iterator_abort(ref_iterator) != ITER_DONE)
354 return ITER_ERROR;
355 return ok;
356 }
357
358 static int prefix_ref_iterator_peel(struct ref_iterator *ref_iterator,
359 struct object_id *peeled)
360 {
361 struct prefix_ref_iterator *iter =
362 (struct prefix_ref_iterator *)ref_iterator;
363
364 return ref_iterator_peel(iter->iter0, peeled);
365 }
366
367 static int prefix_ref_iterator_abort(struct ref_iterator *ref_iterator)
368 {
369 struct prefix_ref_iterator *iter =
370 (struct prefix_ref_iterator *)ref_iterator;
371 int ok = ITER_DONE;
372
373 if (iter->iter0)
374 ok = ref_iterator_abort(iter->iter0);
375 free(iter->prefix);
376 base_ref_iterator_free(ref_iterator);
377 return ok;
378 }
379
380 static struct ref_iterator_vtable prefix_ref_iterator_vtable = {
381 prefix_ref_iterator_advance,
382 prefix_ref_iterator_peel,
383 prefix_ref_iterator_abort
384 };
385
386 struct ref_iterator *prefix_ref_iterator_begin(struct ref_iterator *iter0,
387 const char *prefix,
388 int trim)
389 {
390 struct prefix_ref_iterator *iter;
391 struct ref_iterator *ref_iterator;
392
393 if (!*prefix && !trim)
394 return iter0; /* optimization: no need to wrap iterator */
395
396 iter = xcalloc(1, sizeof(*iter));
397 ref_iterator = &iter->base;
398
399 base_ref_iterator_init(ref_iterator, &prefix_ref_iterator_vtable, iter0->ordered);
400
401 iter->iter0 = iter0;
402 iter->prefix = xstrdup(prefix);
403 iter->trim = trim;
404
405 return ref_iterator;
406 }
407
408 struct ref_iterator *current_ref_iter = NULL;
409
410 int do_for_each_repo_ref_iterator(struct repository *r, struct ref_iterator *iter,
411 each_repo_ref_fn fn, void *cb_data)
412 {
413 int retval = 0, ok;
414 struct ref_iterator *old_ref_iter = current_ref_iter;
415
416 current_ref_iter = iter;
417 while ((ok = ref_iterator_advance(iter)) == ITER_OK) {
418 retval = fn(r, iter->refname, iter->oid, iter->flags, cb_data);
419 if (retval) {
420 /*
421 * If ref_iterator_abort() returns ITER_ERROR,
422 * we ignore that error in deference to the
423 * callback function's return value.
424 */
425 ref_iterator_abort(iter);
426 goto out;
427 }
428 }
429
430 out:
431 current_ref_iter = old_ref_iter;
432 if (ok == ITER_ERROR)
433 return -1;
434 return retval;
435 }