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         memset(block + offset, 0, RECORDSIZE);
  77         offset += RECORDSIZE;
  78         write_if_needed();
  79         memset(block + offset, 0, RECORDSIZE);
  80         offset += RECORDSIZE;
  81         write_if_needed();
  82         if (offset) {
  83                 memset(block + offset, 0, BLOCKSIZE - offset);
  84                 reliable_write(block, BLOCKSIZE);
  85                 offset = 0;
  86         }
  87 }
  88
  89 /*
  90  * queues up writes, so that all our write(2) calls write exactly one
  91  * full block; pads writes to RECORDSIZE
  92  */
  93 static void write_blocked(void *buf, unsigned long size)
  94 {
  95         unsigned long tail;
  96
  97         if (offset) {
  98                 unsigned long chunk = BLOCKSIZE - offset;
  99                 if (size < chunk)
 100                         chunk = size;
 101                 memcpy(block + offset, buf, chunk);
 102                 size -= chunk;
 103                 offset += chunk;
 104                 buf += chunk;
 105                 write_if_needed();
 106         }
 107         while (size >= BLOCKSIZE) {
 108                 reliable_write(buf, BLOCKSIZE);
 109                 size -= BLOCKSIZE;
 110                 buf += BLOCKSIZE;
 111         }
 112         if (size) {
 113                 memcpy(block + offset, buf, size);
 114                 buf += size;
 115                 offset += size;
 116         }
 117         tail = offset % RECORDSIZE;
 118         if (tail)  {
 119                 memset(block + offset, 0, RECORDSIZE - tail);
 120                 offset += RECORDSIZE - tail;
 121         }
 122         write_if_needed();
 123 }
 124
 125 static void append_string(char **p, const char *s)
 126 {
 127         unsigned int len = strlen(s);
 128         memcpy(*p, s, len);
 129         *p += len;
 130 }
 131
 132 static void append_char(char **p, char c)
 133 {
 134         **p = c;
 135         *p += 1;
 136 }
 137
 138 static void append_path_prefix(char **buffer, struct path_prefix *prefix)
 139 {
 140         if (!prefix)
 141                 return;
 142         append_path_prefix(buffer, prefix->prev);
 143         append_string(buffer, prefix->name);
 144         append_char(buffer, '/');
 145 }
 146
 147 static unsigned int path_prefix_len(struct path_prefix *prefix)
 148 {
 149         if (!prefix)
 150                 return 0;
 151         return path_prefix_len(prefix->prev) + strlen(prefix->name) + 1;
 152 }
 153
 154 static void append_path(char **p, int is_dir, const char *basepath,
 155                         struct path_prefix *prefix, const char *path)
 156 {
 157         if (basepath) {
 158                 append_string(p, basepath);
 159                 append_char(p, '/');
 160         }
 161         append_path_prefix(p, prefix);
 162         append_string(p, path);
 163         if (is_dir)
 164                 append_char(p, '/');
 165 }
 166
 167 static unsigned int path_len(int is_dir, const char *basepath,
 168                              struct path_prefix *prefix, const char *path)
 169 {
 170         unsigned int len = 0;
 171         if (basepath)
 172                 len += strlen(basepath) + 1;
 173         len += path_prefix_len(prefix) + strlen(path);
 174         if (is_dir)
 175                 len++;
 176         return len;
 177 }
 178
 179 static void append_extended_header_prefix(char **p, unsigned int size,
 180                                           const char *keyword)
 181 {
 182         int len = sprintf(*p, "%u %s=", size, keyword);
 183         *p += len;
 184 }
 185
 186 static unsigned int extended_header_len(const char *keyword,
 187                                         unsigned int valuelen)
 188 {
 189         /* "%u %s=%s\n" */
 190         unsigned int len = 1 + 1 + strlen(keyword) + 1 + valuelen + 1;
 191         if (len > 9)
 192                 len++;
 193         if (len > 99)
 194                 len++;
 195         return len;
 196 }
 197
 198 static void append_extended_header(char **p, const char *keyword,
 199                                    const char *value, unsigned int len)
 200 {
 201         unsigned int size = extended_header_len(keyword, len);
 202         append_extended_header_prefix(p, size, keyword);
 203         memcpy(*p, value, len);
 204         *p += len;
 205         append_char(p, '\n');
 206 }
 207
 208 static void write_header(const unsigned char *, char, const char *, struct path_prefix *,
 209                          const char *, unsigned int, void *, unsigned long);
 210
 211 /* stores a pax extended header directly in the block buffer */
 212 static void write_extended_header(const char *headerfilename, int is_dir,
 213                                   unsigned int flags, const char *basepath,
 214                                   struct path_prefix *prefix,
 215                                   const char *path, unsigned int namelen,
 216                                   void *content, unsigned int contentsize)
 217 {
 218         char *buffer, *p;
 219         unsigned int pathlen, size, linkpathlen = 0;
 220
 221         size = pathlen = extended_header_len("path", namelen);
 222         if (flags & EXT_HEADER_LINKPATH) {
 223                 linkpathlen = extended_header_len("linkpath", contentsize);
 224                 size += linkpathlen;
 225         }
 226         write_header(NULL, TYPEFLAG_EXT_HEADER, NULL, NULL, headerfilename,
 227                      0100600, NULL, size);
 228
 229         buffer = p = malloc(size);
 230         if (!buffer)
 231                 die("git-tar-tree: %s", strerror(errno));
 232         append_extended_header_prefix(&p, pathlen, "path");
 233         append_path(&p, is_dir, basepath, prefix, path);
 234         append_char(&p, '\n');
 235         if (flags & EXT_HEADER_LINKPATH)
 236                 append_extended_header(&p, "linkpath", content, contentsize);
 237         write_blocked(buffer, size);
 238         free(buffer);
 239 }
 240
 241 static void write_global_extended_header(const unsigned char *sha1)
 242 {
 243         char *p;
 244         unsigned int size;
 245
 246         size = extended_header_len("comment", 40);
 247         write_header(NULL, TYPEFLAG_GLOBAL_HEADER, NULL, NULL,
 248                      "pax_global_header", 0100600, NULL, size);
 249
 250         p = get_record();
 251         append_extended_header(&p, "comment", sha1_to_hex(sha1), 40);
 252         write_if_needed();
 253 }
 254
 255 /* stores a ustar header directly in the block buffer */
 256 static void write_header(const unsigned char *sha1, char typeflag, const char *basepath,
 257                          struct path_prefix *prefix, const char *path,
 258                          unsigned int mode, void *buffer, unsigned long size)
 259 {
 260         unsigned int namelen;
 261         char *header = NULL;
 262         unsigned int checksum = 0;
 263         int i;
 264         unsigned int ext_header = 0;
 265
 266         if (typeflag == TYPEFLAG_AUTO) {
 267                 if (S_ISDIR(mode))
 268                         typeflag = TYPEFLAG_DIR;
 269                 else if (S_ISLNK(mode))
 270                         typeflag = TYPEFLAG_LNK;
 271                 else
 272                         typeflag = TYPEFLAG_REG;
 273         }
 274
 275         namelen = path_len(S_ISDIR(mode), basepath, prefix, path);
 276         if (namelen > 100)
 277                 ext_header |= EXT_HEADER_PATH;
 278         if (typeflag == TYPEFLAG_LNK && size > 100)
 279                 ext_header |= EXT_HEADER_LINKPATH;
 280
 281         /* the extended header must be written before the normal one */
 282         if (ext_header) {
 283                 char headerfilename[51];
 284                 sprintf(headerfilename, "%s.paxheader", sha1_to_hex(sha1));
 285                 write_extended_header(headerfilename, S_ISDIR(mode),
 286                                       ext_header, basepath, prefix, path,
 287                                       namelen, buffer, size);
 288         }
 289
 290         header = get_record();
 291
 292         if (ext_header) {
 293                 sprintf(header, "%s.data", sha1_to_hex(sha1));
 294         } else {
 295                 char *p = header;
 296                 append_path(&p, S_ISDIR(mode), basepath, prefix, path);
 297         }
 298
 299         if (typeflag == TYPEFLAG_LNK) {
 300                 if (ext_header & EXT_HEADER_LINKPATH) {
 301                         sprintf(&header[157], "see %s.paxheader",
 302                                 sha1_to_hex(sha1));
 303                 } else {
 304                         if (buffer)
 305                                 strncpy(&header[157], buffer, size);
 306                 }
 307         }
 308
 309         if (S_ISDIR(mode))
 310                 mode |= 0755;   /* GIT doesn't store permissions of dirs */
 311         if (S_ISLNK(mode))
 312                 mode |= 0777;   /* ... nor of symlinks */
 313         sprintf(&header[100], "%07o", mode & 07777);
 314
 315         /* XXX: should we provide more meaningful info here? */
 316         sprintf(&header[108], "%07o", 0);       /* uid */
 317         sprintf(&header[116], "%07o", 0);       /* gid */
 318         strncpy(&header[265], "git", 31);       /* uname */
 319         strncpy(&header[297], "git", 31);       /* gname */
 320
 321         if (S_ISDIR(mode) || S_ISLNK(mode))
 322                 size = 0;
 323         sprintf(&header[124], "%011lo", size);
 324         sprintf(&header[136], "%011lo", archive_time);
 325
 326         header[156] = typeflag;
 327
 328         memcpy(&header[257], "ustar", 6);
 329         memcpy(&header[263], "00", 2);
 330
 331         printf(&header[329], "%07o", 0);        /* devmajor */
 332         printf(&header[337], "%07o", 0);        /* devminor */
 333
 334         memset(&header[148], ' ', 8);
 335         for (i = 0; i < RECORDSIZE; i++)
 336                 checksum += header[i];
 337         sprintf(&header[148], "%07o", checksum & 0x1fffff);
 338
 339         write_if_needed();
 340 }
 341
 342 static void traverse_tree(void *buffer, unsigned long size,
 343                           struct path_prefix *prefix)
 344 {
 345         struct path_prefix this_prefix;
 346         this_prefix.prev = prefix;
 347
 348         while (size) {
 349                 int namelen = strlen(buffer)+1;
 350                 void *eltbuf;
 351                 char elttype[20];
 352                 unsigned long eltsize;
 353                 unsigned char *sha1 = buffer + namelen;
 354                 char *path = strchr(buffer, ' ') + 1;
 355                 unsigned int mode;
 356
 357                 if (size < namelen + 20 || sscanf(buffer, "%o", &mode) != 1)
 358                         die("corrupt 'tree' file");
 359                 buffer = sha1 + 20;
 360                 size -= namelen + 20;
 361
 362                 eltbuf = read_sha1_file(sha1, elttype, &eltsize);
 363                 if (!eltbuf)
 364                         die("cannot read %s", sha1_to_hex(sha1));
 365                 write_header(sha1, TYPEFLAG_AUTO, basedir, prefix, path,
 366                              mode, eltbuf, eltsize);
 367                 if (!strcmp(elttype, "tree")) {
 368                         this_prefix.name = path;
 369                         traverse_tree(eltbuf, eltsize, &this_prefix);
 370                 } else if (!strcmp(elttype, "blob") && !S_ISLNK(mode)) {
 371                         write_blocked(eltbuf, eltsize);
 372                 }
 373                 free(eltbuf);
 374         }
 375 }
 376
 377 /* get commit time from committer line of commit object */
 378 static time_t commit_time(void * buffer, unsigned long size)
 379 {
 380         time_t result = 0;
 381         char *p = buffer;
 382
 383         while (size > 0) {
 384                 char *endp = memchr(p, '\n', size);
 385                 if (!endp || endp == p)
 386                         break;
 387                 *endp = '\0';
 388                 if (endp - p > 10 && !memcmp(p, "committer ", 10)) {
 389                         char *nump = strrchr(p, '>');
 390                         if (!nump)
 391                                 break;
 392                         nump++;
 393                         result = strtoul(nump, &endp, 10);
 394                         if (*endp != ' ')
 395                                 result = 0;
 396                         break;
 397                 }
 398                 size -= endp - p - 1;
 399                 p = endp + 1;
 400         }
 401         return result;
 402 }
 403
 404 int main(int argc, char **argv)
 405 {
 406         unsigned char sha1[20];
 407         unsigned char commit_sha1[20];
 408         void *buffer;
 409         unsigned long size;
 410
 411         switch (argc) {
 412         case 3:
 413                 basedir = argv[2];
 414                 /* FALLTHROUGH */
 415         case 2:
 416                 if (get_sha1(argv[1], sha1) < 0)
 417                         usage(tar_tree_usage);
 418                 break;
 419         default:
 420                 usage(tar_tree_usage);
 421         }
 422
 423         buffer = read_object_with_reference(sha1, "commit", &size, commit_sha1);
 424         if (buffer) {
 425                 write_global_extended_header(commit_sha1);
 426                 archive_time = commit_time(buffer, size);
 427                 free(buffer);
 428         }
 429         buffer = read_object_with_reference(sha1, "tree", &size, NULL);
 430         if (!buffer)
 431                 die("not a reference to a tag, commit or tree object: %s",
 432                     sha1_to_hex(sha1));
 433         if (!archive_time)
 434                 archive_time = time(NULL);
 435         if (basedir)
 436                 write_header("0", TYPEFLAG_DIR, NULL, NULL, basedir, 040755,
 437                              NULL, 0);
 438         traverse_tree(buffer, size, NULL);
 439         free(buffer);
 440         write_trailer();
 441         return 0;
 442 }