aboutsummaryrefslogtreecommitdiff
path: root/tree-walk.c
blob: 67a9a0c5a5bf7d7125765679318cfcd68c160da7 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
#include "cache.h"
#include "tree-walk.h"
#include "tree.h"

static const char *get_mode(const char *str, unsigned int *modep)
{
	unsigned char c;
	unsigned int mode = 0;

	if (*str == ' ')
		return NULL;

	while ((c = *str++) != ' ') {
		if (c < '0' || c > '7')
			return NULL;
		mode = (mode << 3) + (c - '0');
	}
	*modep = mode;
	return str;
}

static void decode_tree_entry(struct tree_desc *desc, const char *buf, unsigned long size)
{
	const char *path;
	unsigned int mode, len;

	if (size < 24 || buf[size - 21])
		die("corrupt tree file");

	path = get_mode(buf, &mode);
	if (!path || !*path)
		die("corrupt tree file");
	len = strlen(path) + 1;

	/* Initialize the descriptor entry */
	desc->entry.path = path;
	desc->entry.mode = mode;
	desc->entry.sha1 = (const unsigned char *)(path + len);
}

void init_tree_desc(struct tree_desc *desc, const void *buffer, unsigned long size)
{
	desc->buffer = buffer;
	desc->size = size;
	if (size)
		decode_tree_entry(desc, buffer, size);
}

void *fill_tree_descriptor(struct tree_desc *desc, const unsigned char *sha1)
{
	unsigned long size = 0;
	void *buf = NULL;

	if (sha1) {
		buf = read_object_with_reference(sha1, tree_type, &size, NULL);
		if (!buf)
			die("unable to read tree %s", sha1_to_hex(sha1));
	}
	init_tree_desc(desc, buf, size);
	return buf;
}

static void entry_clear(struct name_entry *a)
{
	memset(a, 0, sizeof(*a));
}

static void entry_extract(struct tree_desc *t, struct name_entry *a)
{
	*a = t->entry;
}

void update_tree_entry(struct tree_desc *desc)
{
	const void *buf = desc->buffer;
	const unsigned char *end = desc->entry.sha1 + 20;
	unsigned long size = desc->size;
	unsigned long len = end - (const unsigned char *)buf;

	if (size < len)
		die("corrupt tree file");
	buf = end;
	size -= len;
	desc->buffer = buf;
	desc->size = size;
	if (size)
		decode_tree_entry(desc, buf, size);
}

int tree_entry(struct tree_desc *desc, struct name_entry *entry)
{
	if (!desc->size)
		return 0;

	*entry = desc->entry;
	update_tree_entry(desc);
	return 1;
}

void setup_traverse_info(struct traverse_info *info, const char *base)
{
	int pathlen = strlen(base);
	static struct traverse_info dummy;

	memset(info, 0, sizeof(*info));
	if (pathlen && base[pathlen-1] == '/')
		pathlen--;
	info->pathlen = pathlen ? pathlen + 1 : 0;
	info->name.path = base;
	info->name.sha1 = (void *)(base + pathlen + 1);
	if (pathlen)
		info->prev = &dummy;
}

char *make_traverse_path(char *path, const struct traverse_info *info, const struct name_entry *n)
{
	int len = tree_entry_len(n->path, n->sha1);
	int pathlen = info->pathlen;

	path[pathlen + len] = 0;
	for (;;) {
		memcpy(path + pathlen, n->path, len);
		if (!pathlen)
			break;
		path[--pathlen] = '/';
		n = &info->name;
		len = tree_entry_len(n->path, n->sha1);
		info = info->prev;
		pathlen -= len;
	}
	return path;
}

struct tree_desc_skip {
	struct tree_desc_skip *prev;
	const void *ptr;
};

struct tree_desc_x {
	struct tree_desc d;
	struct tree_desc_skip *skip;
};

static int name_compare(const char *a, int a_len,
			const char *b, int b_len)
{
	int len = (a_len < b_len) ? a_len : b_len;
	int cmp = memcmp(a, b, len);
	if (cmp)
		return cmp;
	return (a_len - b_len);
}

static int check_entry_match(const char *a, int a_len, const char *b, int b_len)
{
	/*
	 * The caller wants to pick *a* from a tree or nothing.
	 * We are looking at *b* in a tree.
	 *
	 * (0) If a and b are the same name, we are trivially happy.
	 *
	 * There are three possibilities where *a* could be hiding
	 * behind *b*.
	 *
	 * (1) *a* == "t",   *b* == "ab"  i.e. *b* sorts earlier than *a* no
	 *                                matter what.
	 * (2) *a* == "t",   *b* == "t-2" and "t" is a subtree in the tree;
	 * (3) *a* == "t-2", *b* == "t"   and "t-2" is a blob in the tree.
	 *
	 * Otherwise we know *a* won't appear in the tree without
	 * scanning further.
	 */

	int cmp = name_compare(a, a_len, b, b_len);

	/* Most common case first -- reading sync'd trees */
	if (!cmp)
		return cmp;

	if (0 < cmp) {
		/* a comes after b; it does not matter if it is case (3)
		if (b_len < a_len && !memcmp(a, b, b_len) && a[b_len] < '/')
			return 1;
		*/
		return 1; /* keep looking */
	}

	/* b comes after a; are we looking at case (2)? */
	if (a_len < b_len && !memcmp(a, b, a_len) && b[a_len] < '/')
		return 1; /* keep looking */

	return -1; /* a cannot appear in the tree */
}

/*
 * From the extended tree_desc, extract the first name entry, while
 * paying attention to the candidate "first" name.  Most importantly,
 * when looking for an entry, if there are entries that sorts earlier
 * in the tree object representation than that name, skip them and
 * process the named entry first.  We will remember that we haven't
 * processed the first entry yet, and in the later call skip the
 * entry we processed early when update_extended_entry() is called.
 *
 * E.g. if the underlying tree object has these entries:
 *
 *    blob    "t-1"
 *    blob    "t-2"
 *    tree    "t"
 *    blob    "t=1"
 *
 * and the "first" asks for "t", remember that we still need to
 * process "t-1" and "t-2" but extract "t".  After processing the
 * entry "t" from this call, the caller will let us know by calling
 * update_extended_entry() that we can remember "t" has been processed
 * already.
 */

static void extended_entry_extract(struct tree_desc_x *t,
				   struct name_entry *a,
				   const char *first,
				   int first_len)
{
	const char *path;
	int len;
	struct tree_desc probe;
	struct tree_desc_skip *skip;

	/*
	 * Extract the first entry from the tree_desc, but skip the
	 * ones that we already returned in earlier rounds.
	 */
	while (1) {
		if (!t->d.size) {
			entry_clear(a);
			break; /* not found */
		}
		entry_extract(&t->d, a);
		for (skip = t->skip; skip; skip = skip->prev)
			if (a->path == skip->ptr)
				break; /* found */
		if (!skip)
			break;
		/* We have processed this entry already. */
		update_tree_entry(&t->d);
	}

	if (!first || !a->path)
		return;

	/*
	 * The caller wants "first" from this tree, or nothing.
	 */
	path = a->path;
	len = tree_entry_len(a->path, a->sha1);
	switch (check_entry_match(first, first_len, path, len)) {
	case -1:
		entry_clear(a);
	case 0:
		return;
	default:
		break;
	}

	/*
	 * We need to look-ahead -- we suspect that a subtree whose
	 * name is "first" may be hiding behind the current entry "path".
	 */
	probe = t->d;
	while (probe.size) {
		entry_extract(&probe, a);
		path = a->path;
		len = tree_entry_len(a->path, a->sha1);
		switch (check_entry_match(first, first_len, path, len)) {
		case -1:
			entry_clear(a);
		case 0:
			return;
		default:
			update_tree_entry(&probe);
			break;
		}
		/* keep looking */
	}
	entry_clear(a);
}

static void update_extended_entry(struct tree_desc_x *t, struct name_entry *a)
{
	if (t->d.entry.path == a->path) {
		update_tree_entry(&t->d);
	} else {
		/* we have returned this entry early */
		struct tree_desc_skip *skip = xmalloc(sizeof(*skip));
		skip->ptr = a->path;
		skip->prev = t->skip;
		t->skip = skip;
	}
}

static void free_extended_entry(struct tree_desc_x *t)
{
	struct tree_desc_skip *p, *s;

	for (s = t->skip; s; s = p) {
		p = s->prev;
		free(s);
	}
}

int traverse_trees(int n, struct tree_desc *t, struct traverse_info *info)
{
	int ret = 0;
	struct name_entry *entry = xmalloc(n*sizeof(*entry));
	int i;
	struct tree_desc_x *tx = xcalloc(n, sizeof(*tx));

	for (i = 0; i < n; i++)
		tx[i].d = t[i];

	for (;;) {
		unsigned long mask, dirmask;
		const char *first = NULL;
		int first_len = 0;
		struct name_entry *e;
		int len;

		for (i = 0; i < n; i++) {
			e = entry + i;
			extended_entry_extract(tx + i, e, NULL, 0);
		}

		/*
		 * A tree may have "t-2" at the current location even
		 * though it may have "t" that is a subtree behind it,
		 * and another tree may return "t".  We want to grab
		 * all "t" from all trees to match in such a case.
		 */
		for (i = 0; i < n; i++) {
			e = entry + i;
			if (!e->path)
				continue;
			len = tree_entry_len(e->path, e->sha1);
			if (!first) {
				first = e->path;
				first_len = len;
				continue;
			}
			if (name_compare(e->path, len, first, first_len) < 0) {
				first = e->path;
				first_len = len;
			}
		}

		if (first) {
			for (i = 0; i < n; i++) {
				e = entry + i;
				extended_entry_extract(tx + i, e, first, first_len);
				/* Cull the ones that are not the earliest */
				if (!e->path)
					continue;
				len = tree_entry_len(e->path, e->sha1);
				if (name_compare(e->path, len, first, first_len))
					entry_clear(e);
			}
		}

		/* Now we have in entry[i] the earliest name from the trees */
		mask = 0;
		dirmask = 0;
		for (i = 0; i < n; i++) {
			if (!entry[i].path)
				continue;
			mask |= 1ul << i;
			if (S_ISDIR(entry[i].mode))
				dirmask |= 1ul << i;
		}
		if (!mask)
			break;
		ret = info->fn(n, mask, dirmask, entry, info);
		if (ret < 0)
			break;
		mask &= ret;
		ret = 0;
		for (i = 0; i < n; i++)
			if (mask & (1ul << i))
				update_extended_entry(tx + i, entry + i);
	}
	free(entry);
	for (i = 0; i < n; i++)
		free_extended_entry(tx + i);
	free(tx);
	return ret;
}

static int find_tree_entry(struct tree_desc *t, const char *name, unsigned char *result, unsigned *mode)
{
	int namelen = strlen(name);
	while (t->size) {
		const char *entry;
		const unsigned char *sha1;
		int entrylen, cmp;

		sha1 = tree_entry_extract(t, &entry, mode);
		update_tree_entry(t);
		entrylen = tree_entry_len(entry, sha1);
		if (entrylen > namelen)
			continue;
		cmp = memcmp(name, entry, entrylen);
		if (cmp > 0)
			continue;
		if (cmp < 0)
			break;
		if (entrylen == namelen) {
			hashcpy(result, sha1);
			return 0;
		}
		if (name[entrylen] != '/')
			continue;
		if (!S_ISDIR(*mode))
			break;
		if (++entrylen == namelen) {
			hashcpy(result, sha1);
			return 0;
		}
		return get_tree_entry(sha1, name + entrylen, result, mode);
	}
	return -1;
}

int get_tree_entry(const unsigned char *tree_sha1, const char *name, unsigned char *sha1, unsigned *mode)
{
	int retval;
	void *tree;
	unsigned long size;
	struct tree_desc t;
	unsigned char root[20];

	tree = read_object_with_reference(tree_sha1, tree_type, &size, root);
	if (!tree)
		return -1;

	if (name[0] == '\0') {
		hashcpy(sha1, root);
		free(tree);
		return 0;
	}

	init_tree_desc(&t, tree, size);
	retval = find_tree_entry(&t, name, sha1, mode);
	free(tree);
	return retval;
}