git-tag: update usage string and documentation.
[git.git] / tar-tree.c
1 /*
2  * Copyright (c) 2005 Rene Scharfe
3  */
4 #include <time.h>
5 #include "cache.h"
6
7 #define RECORDSIZE      (512)
8 #define BLOCKSIZE       (RECORDSIZE * 20)
9
10 #define TYPEFLAG_AUTO           '\0'
11 #define TYPEFLAG_REG            '0'
12 #define TYPEFLAG_LNK            '2'
13 #define TYPEFLAG_DIR            '5'
14 #define TYPEFLAG_GLOBAL_HEADER  'g'
15 #define TYPEFLAG_EXT_HEADER     'x'
16
17 #define EXT_HEADER_PATH         1
18 #define EXT_HEADER_LINKPATH     2
19
20 static const char tar_tree_usage[] = "git-tar-tree <key> [basedir]";
21
22 static char block[BLOCKSIZE];
23 static unsigned long offset;
24
25 static const char *basedir;
26 static time_t archive_time;
27
28 struct path_prefix {
29         struct path_prefix *prev;
30         const char *name;
31 };
32
33 /* tries hard to write, either succeeds or dies in the attempt */
34 static void reliable_write(void *buf, unsigned long size)
35 {
36         while (size > 0) {
37                 long ret = write(1, buf, size);
38                 if (ret < 0) {
39                         if (errno == EAGAIN)
40                                 continue;
41                         if (errno == EPIPE)
42                                 exit(0);
43                         die("git-tar-tree: %s", strerror(errno));
44                 } else if (!ret) {
45                         die("git-tar-tree: disk full?");
46                 }
47                 size -= ret;
48                 buf += ret;
49         }
50 }
51
52 /* writes out the whole block, but only if it is full */
53 static void write_if_needed(void)
54 {
55         if (offset == BLOCKSIZE) {
56                 reliable_write(block, BLOCKSIZE);
57                 offset = 0;
58         }
59 }
60
61 /* acquire the next record from the buffer; user must call write_if_needed() */
62 static char *get_record(void)
63 {
64         char *p = block + offset;
65         memset(p, 0, RECORDSIZE);
66         offset += RECORDSIZE;
67         return p;
68 }
69
70 /*
71  * The end of tar archives is marked by 1024 nul bytes and after that
72  * follows the rest of the block (if any).
73  */
74 static void write_trailer(void)
75 {
76         get_record();
77         write_if_needed();
78         get_record();
79         write_if_needed();
80         while (offset) {
81                 get_record();
82                 write_if_needed();
83         }
84 }
85
86 /*
87  * queues up writes, so that all our write(2) calls write exactly one
88  * full block; pads writes to RECORDSIZE
89  */
90 static void write_blocked(void *buf, unsigned long size)
91 {
92         unsigned long tail;
93
94         if (offset) {
95                 unsigned long chunk = BLOCKSIZE - offset;
96                 if (size < chunk)
97                         chunk = size;
98                 memcpy(block + offset, buf, chunk);
99                 size -= chunk;
100                 offset += chunk;
101                 buf += chunk;
102                 write_if_needed();
103         }
104         while (size >= BLOCKSIZE) {
105                 reliable_write(buf, BLOCKSIZE);
106                 size -= BLOCKSIZE;
107                 buf += BLOCKSIZE;
108         }
109         if (size) {
110                 memcpy(block + offset, buf, size);
111                 buf += size;
112                 offset += size;
113         }
114         tail = offset % RECORDSIZE;
115         if (tail)  {
116                 memset(block + offset, 0, RECORDSIZE - tail);
117                 offset += RECORDSIZE - tail;
118         }
119         write_if_needed();
120 }
121
122 static void append_string(char **p, const char *s)
123 {
124         unsigned int len = strlen(s);
125         memcpy(*p, s, len);
126         *p += len;
127 }
128
129 static void append_char(char **p, char c)
130 {
131         **p = c;
132         *p += 1;
133 }
134
135 static void append_path_prefix(char **buffer, struct path_prefix *prefix)
136 {
137         if (!prefix)
138                 return;
139         append_path_prefix(buffer, prefix->prev);
140         append_string(buffer, prefix->name);
141         append_char(buffer, '/');
142 }
143
144 static unsigned int path_prefix_len(struct path_prefix *prefix)
145 {
146         if (!prefix)
147                 return 0;
148         return path_prefix_len(prefix->prev) + strlen(prefix->name) + 1;
149 }
150
151 static void append_path(char **p, int is_dir, const char *basepath,
152                         struct path_prefix *prefix, const char *path)
153 {
154         if (basepath) {
155                 append_string(p, basepath);
156                 append_char(p, '/');
157         }
158         append_path_prefix(p, prefix);
159         append_string(p, path);
160         if (is_dir)
161                 append_char(p, '/');
162 }
163
164 static unsigned int path_len(int is_dir, const char *basepath,
165                              struct path_prefix *prefix, const char *path)
166 {
167         unsigned int len = 0;
168         if (basepath)
169                 len += strlen(basepath) + 1;
170         len += path_prefix_len(prefix) + strlen(path);
171         if (is_dir)
172                 len++;
173         return len;
174 }
175
176 static void append_extended_header_prefix(char **p, unsigned int size,
177                                           const char *keyword)
178 {
179         int len = sprintf(*p, "%u %s=", size, keyword);
180         *p += len;
181 }
182
183 static unsigned int extended_header_len(const char *keyword,
184                                         unsigned int valuelen)
185 {
186         /* "%u %s=%s\n" */
187         unsigned int len = 1 + 1 + strlen(keyword) + 1 + valuelen + 1;
188         if (len > 9)
189                 len++;
190         if (len > 99)
191                 len++;
192         return len;
193 }
194
195 static void append_extended_header(char **p, const char *keyword,
196                                    const char *value, unsigned int len)
197 {
198         unsigned int size = extended_header_len(keyword, len);
199         append_extended_header_prefix(p, size, keyword);
200         memcpy(*p, value, len);
201         *p += len;
202         append_char(p, '\n');
203 }
204
205 static void write_header(const unsigned char *, char, const char *, struct path_prefix *,
206                          const char *, unsigned int, void *, unsigned long);
207
208 /* stores a pax extended header directly in the block buffer */
209 static void write_extended_header(const char *headerfilename, int is_dir,
210                                   unsigned int flags, const char *basepath,
211                                   struct path_prefix *prefix,
212                                   const char *path, unsigned int namelen,
213                                   void *content, unsigned int contentsize)
214 {
215         char *buffer, *p;
216         unsigned int pathlen, size, linkpathlen = 0;
217
218         size = pathlen = extended_header_len("path", namelen);
219         if (flags & EXT_HEADER_LINKPATH) {
220                 linkpathlen = extended_header_len("linkpath", contentsize);
221                 size += linkpathlen;
222         }
223         write_header(NULL, TYPEFLAG_EXT_HEADER, NULL, NULL, headerfilename,
224                      0100600, NULL, size);
225
226         buffer = p = malloc(size);
227         if (!buffer)
228                 die("git-tar-tree: %s", strerror(errno));
229         append_extended_header_prefix(&p, pathlen, "path");
230         append_path(&p, is_dir, basepath, prefix, path);
231         append_char(&p, '\n');
232         if (flags & EXT_HEADER_LINKPATH)
233                 append_extended_header(&p, "linkpath", content, contentsize);
234         write_blocked(buffer, size);
235         free(buffer);
236 }
237
238 static void write_global_extended_header(const unsigned char *sha1)
239 {
240         char *p;
241         unsigned int size;
242
243         size = extended_header_len("comment", 40);
244         write_header(NULL, TYPEFLAG_GLOBAL_HEADER, NULL, NULL,
245                      "pax_global_header", 0100600, NULL, size);
246
247         p = get_record();
248         append_extended_header(&p, "comment", sha1_to_hex(sha1), 40);
249         write_if_needed();
250 }
251
252 /* stores a ustar header directly in the block buffer */
253 static void write_header(const unsigned char *sha1, char typeflag, const char *basepath,
254                          struct path_prefix *prefix, const char *path,
255                          unsigned int mode, void *buffer, unsigned long size)
256 {
257         unsigned int namelen; 
258         char *header = NULL;
259         unsigned int checksum = 0;
260         int i;
261         unsigned int ext_header = 0;
262
263         if (typeflag == TYPEFLAG_AUTO) {
264                 if (S_ISDIR(mode))
265                         typeflag = TYPEFLAG_DIR;
266                 else if (S_ISLNK(mode))
267                         typeflag = TYPEFLAG_LNK;
268                 else
269                         typeflag = TYPEFLAG_REG;
270         }
271
272         namelen = path_len(S_ISDIR(mode), basepath, prefix, path);
273         if (namelen > 100)
274                 ext_header |= EXT_HEADER_PATH;
275         if (typeflag == TYPEFLAG_LNK && size > 100)
276                 ext_header |= EXT_HEADER_LINKPATH;
277
278         /* the extended header must be written before the normal one */
279         if (ext_header) {
280                 char headerfilename[51];
281                 sprintf(headerfilename, "%s.paxheader", sha1_to_hex(sha1));
282                 write_extended_header(headerfilename, S_ISDIR(mode),
283                                       ext_header, basepath, prefix, path,
284                                       namelen, buffer, size);
285         }
286
287         header = get_record();
288
289         if (ext_header) {
290                 sprintf(header, "%s.data", sha1_to_hex(sha1));
291         } else {
292                 char *p = header;
293                 append_path(&p, S_ISDIR(mode), basepath, prefix, path);
294         }
295
296         if (typeflag == TYPEFLAG_LNK) {
297                 if (ext_header & EXT_HEADER_LINKPATH) {
298                         sprintf(&header[157], "see %s.paxheader",
299                                 sha1_to_hex(sha1));
300                 } else {
301                         if (buffer)
302                                 strncpy(&header[157], buffer, size);
303                 }
304         }
305
306         if (S_ISDIR(mode))
307                 mode |= 0755;   /* GIT doesn't store permissions of dirs */
308         if (S_ISLNK(mode))
309                 mode |= 0777;   /* ... nor of symlinks */
310         sprintf(&header[100], "%07o", mode & 07777);
311
312         /* XXX: should we provide more meaningful info here? */
313         sprintf(&header[108], "%07o", 0);       /* uid */
314         sprintf(&header[116], "%07o", 0);       /* gid */
315         strncpy(&header[265], "git", 31);       /* uname */
316         strncpy(&header[297], "git", 31);       /* gname */
317
318         if (S_ISDIR(mode) || S_ISLNK(mode))
319                 size = 0;
320         sprintf(&header[124], "%011lo", size);
321         sprintf(&header[136], "%011lo", archive_time);
322
323         header[156] = typeflag;
324
325         memcpy(&header[257], "ustar", 6);
326         memcpy(&header[263], "00", 2);
327
328         sprintf(&header[329], "%07o", 0);       /* devmajor */
329         sprintf(&header[337], "%07o", 0);       /* devminor */
330
331         memset(&header[148], ' ', 8);
332         for (i = 0; i < RECORDSIZE; i++)
333                 checksum += header[i];
334         sprintf(&header[148], "%07o", checksum & 0x1fffff);
335
336         write_if_needed();
337 }
338
339 static void traverse_tree(void *buffer, unsigned long size,
340                           struct path_prefix *prefix)
341 {
342         struct path_prefix this_prefix;
343         this_prefix.prev = prefix;
344
345         while (size) {
346                 int namelen = strlen(buffer)+1;
347                 void *eltbuf;
348                 char elttype[20];
349                 unsigned long eltsize;
350                 unsigned char *sha1 = buffer + namelen;
351                 char *path = strchr(buffer, ' ') + 1;
352                 unsigned int mode;
353
354                 if (size < namelen + 20 || sscanf(buffer, "%o", &mode) != 1)
355                         die("corrupt 'tree' file");
356                 if (S_ISDIR(mode) || S_ISREG(mode))
357                         mode |= (mode & 0100) ? 0777 : 0666;
358                 buffer = sha1 + 20;
359                 size -= namelen + 20;
360
361                 eltbuf = read_sha1_file(sha1, elttype, &eltsize);
362                 if (!eltbuf)
363                         die("cannot read %s", sha1_to_hex(sha1));
364                 write_header(sha1, TYPEFLAG_AUTO, basedir, prefix, path,
365                              mode, eltbuf, eltsize);
366                 if (!strcmp(elttype, "tree")) {
367                         this_prefix.name = path;
368                         traverse_tree(eltbuf, eltsize, &this_prefix);
369                 } else if (!strcmp(elttype, "blob") && !S_ISLNK(mode)) {
370                         write_blocked(eltbuf, eltsize);
371                 }
372                 free(eltbuf);
373         }
374 }
375
376 /* get commit time from committer line of commit object */
377 static time_t commit_time(void * buffer, unsigned long size)
378 {
379         time_t result = 0;
380         char *p = buffer;
381
382         while (size > 0) {
383                 char *endp = memchr(p, '\n', size);
384                 if (!endp || endp == p)
385                         break;
386                 *endp = '\0';
387                 if (endp - p > 10 && !memcmp(p, "committer ", 10)) {
388                         char *nump = strrchr(p, '>');
389                         if (!nump)
390                                 break;
391                         nump++;
392                         result = strtoul(nump, &endp, 10);
393                         if (*endp != ' ')
394                                 result = 0;
395                         break;
396                 }
397                 size -= endp - p - 1;
398                 p = endp + 1;
399         }
400         return result;
401 }
402
403 int main(int argc, char **argv)
404 {
405         unsigned char sha1[20];
406         unsigned char commit_sha1[20];
407         void *buffer;
408         unsigned long size;
409
410         switch (argc) {
411         case 3:
412                 basedir = argv[2];
413                 /* FALLTHROUGH */
414         case 2:
415                 if (get_sha1(argv[1], sha1) < 0)
416                         usage(tar_tree_usage);
417                 break;
418         default:
419                 usage(tar_tree_usage);
420         }
421
422         buffer = read_object_with_reference(sha1, "commit", &size, commit_sha1);
423         if (buffer) {
424                 write_global_extended_header(commit_sha1);
425                 archive_time = commit_time(buffer, size);
426                 free(buffer);
427         }
428         buffer = read_object_with_reference(sha1, "tree", &size, NULL);
429         if (!buffer)
430                 die("not a reference to a tag, commit or tree object: %s",
431                     sha1_to_hex(sha1));
432         if (!archive_time)
433                 archive_time = time(NULL);
434         if (basedir)
435                 write_header((unsigned char *)"0", TYPEFLAG_DIR, NULL, NULL,
436                         basedir, 040755, NULL, 0);
437         traverse_tree(buffer, size, NULL);
438         free(buffer);
439         write_trailer();
440         return 0;
441 }