summaryrefslogtreecommitdiff
path: root/tar-tree.c
blob: 8b0d75bd2cf12a531aee3d51e59a8ac8102ba6be (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
#include <time.h>
#include "cache.h"
 
#define RECORDSIZE	(512)
#define BLOCKSIZE	(RECORDSIZE * 20)
 
#define TYPEFLAG_AUTO		'\0'
#define TYPEFLAG_REG		'0'
#define TYPEFLAG_LNK		'2'
#define TYPEFLAG_DIR		'5'
#define TYPEFLAG_GLOBAL_HEADER	'g'
#define TYPEFLAG_EXT_HEADER	'x'
 
#define EXT_HEADER_PATH		1
#define EXT_HEADER_LINKPATH	2
 
static const char *tar_tree_usage = "tar-tree <key> [basedir]";
 
static char block[BLOCKSIZE];
static unsigned long offset;
 
static const char *basedir;
static time_t archive_time;
 
struct path_prefix {
	struct path_prefix *prev;
	const char *name;
};
 
/* tries hard to write, either succeeds or dies in the attempt */
static void reliable_write(void *buf, unsigned long size)
{
	while (size > 0) {
		long ret = write(1, buf, size);
		if (ret < 0) {
			if (errno == EAGAIN)
				continue;
			if (errno == EPIPE)
				exit(0);
			die("tar-tree: %s", strerror(errno));
		} else if (!ret) {
			die("tar-tree: disk full?");
		}
		size -= ret;
		buf += ret;
	}
}
 
/* writes out the whole block, but only if it is full */
static void write_if_needed(void)
{
	if (offset == BLOCKSIZE) {
		reliable_write(block, BLOCKSIZE);
		offset = 0;
	}
}
 
/* acquire the next record from the buffer; user must call write_if_needed() */
static char *get_record(void)
{
	char *p = block + offset;
	memset(p, 0, RECORDSIZE);
	offset += RECORDSIZE;
	return p;
}
 
/*
 * The end of tar archives is marked by 1024 nul bytes and after that
 * follows the rest of the block (if any).
 */
static void write_trailer(void)
{
	memset(block + offset, 0, RECORDSIZE);
	offset += RECORDSIZE;
	write_if_needed();
	memset(block + offset, 0, RECORDSIZE);
	offset += RECORDSIZE;
	write_if_needed();
	if (offset) {
		memset(block + offset, 0, BLOCKSIZE - offset);
		reliable_write(block, BLOCKSIZE);
		offset = 0;
	}
}
 
/*
 * queues up writes, so that all our write(2) calls write exactly one
 * full block; pads writes to RECORDSIZE
 */
static void write_blocked(void *buf, unsigned long size)
{
	unsigned long tail;
 
	if (offset) {
		unsigned long chunk = BLOCKSIZE - offset;
		if (size < chunk)
			chunk = size;
		memcpy(block + offset, buf, chunk);
		size -= chunk;
		offset += chunk;
		buf += chunk;
		write_if_needed();
	}
	while (size >= BLOCKSIZE) {
		reliable_write(buf, BLOCKSIZE);
		size -= BLOCKSIZE;
		buf += BLOCKSIZE;
	}
	if (size) {
		memcpy(block + offset, buf, size);
		buf += size;
		offset += size;
	}
	tail = offset % RECORDSIZE;
	if (tail)  {
		memset(block + offset, 0, RECORDSIZE - tail);
		offset += RECORDSIZE - tail;
	}
	write_if_needed();
}
 
static void append_string(char **p, const char *s)
{
	unsigned int len = strlen(s);
	memcpy(*p, s, len);
	*p += len;
}
 
static void append_char(char **p, char c)
{
	**p = c;
	*p += 1;
}
 
static void append_path_prefix(char **buffer, struct path_prefix *prefix)
{
	if (!prefix)
		return;
	append_path_prefix(buffer, prefix->prev);
	append_string(buffer, prefix->name);
	append_char(buffer, '/');
}
 
static unsigned int path_prefix_len(struct path_prefix *prefix)
{
	if (!prefix)
		return 0;
	return path_prefix_len(prefix->prev) + strlen(prefix->name) + 1;
}
 
static void append_path(char **p, int is_dir, const char *basepath,
                        struct path_prefix *prefix, const char *path)
{
	if (basepath) {
		append_string(p, basepath);
		append_char(p, '/');
	}
	append_path_prefix(p, prefix);
	append_string(p, path);
	if (is_dir)
		append_char(p, '/');
}
 
static unsigned int path_len(int is_dir, const char *basepath,
                             struct path_prefix *prefix, const char *path)
{
	unsigned int len = 0;
	if (basepath)
		len += strlen(basepath) + 1;
	len += path_prefix_len(prefix) + strlen(path);
	if (is_dir)
		len++;
	return len;
}
 
static void append_extended_header_prefix(char **p, unsigned int size,
                                          const char *keyword)
{
	int len = sprintf(*p, "%u %s=", size, keyword);
	*p += len;
}
 
static unsigned int extended_header_len(const char *keyword,
                                        unsigned int valuelen)
{
	/* "%u %s=%s\n" */
	unsigned int len = 1 + 1 + strlen(keyword) + 1 + valuelen + 1;
	if (len > 9)
		len++;
	if (len > 99)
		len++;
	return len;
}
 
static void append_extended_header(char **p, const char *keyword,
                                   const char *value, unsigned int len)
{
	unsigned int size = extended_header_len(keyword, len);
	append_extended_header_prefix(p, size, keyword);
	memcpy(*p, value, len);
	*p += len;
	append_char(p, '\n');
}
 
static void write_header(const char *, char, const char *, struct path_prefix *,
                         const char *, unsigned int, void *, unsigned long);
 
/* stores a pax extended header directly in the block buffer */
static void write_extended_header(const char *headerfilename, int is_dir,
                                  unsigned int flags, const char *basepath,
                                  struct path_prefix *prefix,
                                  const char *path, unsigned int namelen,
                                  void *content, unsigned int contentsize)
{
	char *buffer, *p;
	unsigned int pathlen, size, linkpathlen = 0;
 
	size = pathlen = extended_header_len("path", namelen);
	if (flags & EXT_HEADER_LINKPATH) {
		linkpathlen = extended_header_len("linkpath", contentsize);
		size += linkpathlen;
	}
	write_header(NULL, TYPEFLAG_EXT_HEADER, NULL, NULL, headerfilename,
	             0100600, NULL, size);
 
	buffer = p = malloc(size);
	if (!buffer)
		die("git-tar-tree: %s", strerror(errno));
	append_extended_header_prefix(&p, pathlen, "path");
	append_path(&p, is_dir, basepath, prefix, path);
	append_char(&p, '\n');
	if (flags & EXT_HEADER_LINKPATH)
		append_extended_header(&p, "linkpath", content, contentsize);
	write_blocked(buffer, size);
	free(buffer);
}
 
static void write_global_extended_header(const char *sha1)
{
	char *p;
	unsigned int size;
 
	size = extended_header_len("comment", 40);
	write_header(NULL, TYPEFLAG_GLOBAL_HEADER, NULL, NULL,
	             "pax_global_header", 0100600, NULL, size);
 
	p = get_record();
	append_extended_header(&p, "comment", sha1_to_hex(sha1), 40);
	write_if_needed();
}
 
/* stores a ustar header directly in the block buffer */
static void write_header(const char *sha1, char typeflag, const char *basepath,
                         struct path_prefix *prefix, const char *path,
                         unsigned int mode, void *buffer, unsigned long size)
{
	unsigned int namelen; 
	char *header = NULL;
	unsigned int checksum = 0;
	int i;
	unsigned int ext_header = 0;
 
	if (typeflag == TYPEFLAG_AUTO) {
		if (S_ISDIR(mode))
			typeflag = TYPEFLAG_DIR;
		else if (S_ISLNK(mode))
			typeflag = TYPEFLAG_LNK;
		else
			typeflag = TYPEFLAG_REG;
	}
 
	namelen = path_len(S_ISDIR(mode), basepath, prefix, path);
	if (namelen > 100)
		ext_header |= EXT_HEADER_PATH;
	if (typeflag == TYPEFLAG_LNK && size > 100)
		ext_header |= EXT_HEADER_LINKPATH;
 
	/* the extended header must be written before the normal one */
	if (ext_header) {
		char headerfilename[51];
		sprintf(headerfilename, "%s.paxheader", sha1_to_hex(sha1));
		write_extended_header(headerfilename, S_ISDIR(mode),
		                      ext_header, basepath, prefix, path,
		                      namelen, buffer, size);
	}
 
	header = get_record();
 
	if (ext_header) {
		sprintf(header, "%s.data", sha1_to_hex(sha1));
	} else {
		char *p = header;
		append_path(&p, S_ISDIR(mode), basepath, prefix, path);
	}
 
	if (typeflag == TYPEFLAG_LNK) {
		if (ext_header & EXT_HEADER_LINKPATH) {
			sprintf(&header[157], "see %s.paxheader",
			        sha1_to_hex(sha1));
		} else {
			if (buffer)
				strncpy(&header[157], buffer, size);
		}
	}
 
	if (S_ISDIR(mode))
		mode |= 0755;	/* GIT doesn't store permissions of dirs */
	if (S_ISLNK(mode))
		mode |= 0777;   /* ... nor of symlinks */
	sprintf(&header[100], "%07o", mode & 07777);
 
	/* XXX: should we provide more meaningful info here? */
	sprintf(&header[108], "%07o", 0);	/* uid */
	sprintf(&header[116], "%07o", 0);	/* gid */
	strncpy(&header[265], "git", 31);	/* uname */
	strncpy(&header[297], "git", 31);	/* gname */
 
	if (S_ISDIR(mode) || S_ISLNK(mode))
		size = 0;
	sprintf(&header[124], "%011lo", size);
	sprintf(&header[136], "%011lo", archive_time);
 
	header[156] = typeflag;
 
	memcpy(&header[257], "ustar", 6);
	memcpy(&header[263], "00", 2);
 
	printf(&header[329], "%07o", 0);	/* devmajor */
	printf(&header[337], "%07o", 0);	/* devminor */
 
	memset(&header[148], ' ', 8);
	for (i = 0; i < RECORDSIZE; i++)
		checksum += header[i];
	sprintf(&header[148], "%07o", checksum & 0x1fffff);
 
	write_if_needed();
}
 
static void traverse_tree(void *buffer, unsigned long size,
			  struct path_prefix *prefix)
{
	struct path_prefix this_prefix;
	this_prefix.prev = prefix;
 
	while (size) {
		int namelen = strlen(buffer)+1;
		void *eltbuf;
		char elttype[20];
		unsigned long eltsize;
		unsigned char *sha1 = buffer + namelen;
		char *path = strchr(buffer, ' ') + 1;
		unsigned int mode;
 
		if (size < namelen + 20 || sscanf(buffer, "%o", &mode) != 1)
			die("corrupt 'tree' file");
		buffer = sha1 + 20;
		size -= namelen + 20;
 
		eltbuf = read_sha1_file(sha1, elttype, &eltsize);
		if (!eltbuf)
			die("cannot read %s", sha1_to_hex(sha1));
		write_header(sha1, TYPEFLAG_AUTO, basedir, prefix, path,
		             mode, eltbuf, eltsize);
		if (!strcmp(elttype, "tree")) {
			this_prefix.name = path;
			traverse_tree(eltbuf, eltsize, &this_prefix);
		} else if (!strcmp(elttype, "blob") && !S_ISLNK(mode)) {
			write_blocked(eltbuf, eltsize);
		}
		free(eltbuf);
	}
}
 
/* get commit time from committer line of commit object */
time_t commit_time(void * buffer, unsigned long size)
{
	time_t result = 0;
	char *p = buffer;
 
	while (size > 0) {
		char *endp = memchr(p, '\n', size);
		if (!endp || endp == p)
			break;
		*endp = '\0';
		if (endp - p > 10 && !memcmp(p, "committer ", 10)) {
			char *nump = strrchr(p, '>');
			if (!nump)
				break;
			nump++;
			result = strtoul(nump, &endp, 10);
			if (*endp != ' ')
				result = 0;
			break;
		}
		size -= endp - p - 1;
		p = endp + 1;
	}
	return result;
}
 
int main(int argc, char **argv)
{
	unsigned char sha1[20];
	unsigned char commit_sha1[20];
	void *buffer;
	unsigned long size;
 
	switch (argc) {
	case 3:
		basedir = argv[2];
		/* FALLTHROUGH */
	case 2:
		if (get_sha1(argv[1], sha1) < 0)
			usage(tar_tree_usage);
		break;
	default:
		usage(tar_tree_usage);
	}
 
	buffer = read_object_with_reference(sha1, "commit", &size, commit_sha1);
	if (buffer) {
		write_global_extended_header(commit_sha1);
		archive_time = commit_time(buffer, size);
		free(buffer);
	}
	buffer = read_object_with_reference(sha1, "tree", &size, NULL);
	if (!buffer)
		die("not a reference to a tag, commit or tree object: %s",
		    sha1_to_hex(sha1));
	if (!archive_time)
		archive_time = time(NULL);
	if (basedir)
		write_header("0", TYPEFLAG_DIR, NULL, NULL, basedir, 040755,
		             NULL, 0);
	traverse_tree(buffer, size, NULL);
	free(buffer);
	write_trailer();
	return 0;
}