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 = xwrite(1, buf, size);
  38                 if (ret < 0) {
  39                         if (errno == EPIPE)
  40                                 exit(0);
  41                         die("git-tar-tree: %s", strerror(errno));
  42                 } else if (!ret) {
  43                         die("git-tar-tree: disk full?");
  44                 }
  45                 size -= ret;
  46                 buf += ret;
  47         }
  48 }
  49
  50 /* writes out the whole block, but only if it is full */
  51 static void write_if_needed(void)
  52 {
  53         if (offset == BLOCKSIZE) {
  54                 reliable_write(block, BLOCKSIZE);
  55                 offset = 0;
  56         }
  57 }
  58
  59 /* acquire the next record from the buffer; user must call write_if_needed() */
  60 static char *get_record(void)
  61 {
  62         char *p = block + offset;
  63         memset(p, 0, RECORDSIZE);
  64         offset += RECORDSIZE;
  65         return p;
  66 }
  67
  68 /*
  69  * The end of tar archives is marked by 1024 nul bytes and after that
  70  * follows the rest of the block (if any).
  71  */
  72 static void write_trailer(void)
  73 {
  74         get_record();
  75         write_if_needed();
  76         get_record();
  77         write_if_needed();
  78         while (offset) {
  79                 get_record();
  80                 write_if_needed();
  81         }
  82 }
  83
  84 /*
  85  * queues up writes, so that all our write(2) calls write exactly one
  86  * full block; pads writes to RECORDSIZE
  87  */
  88 static void write_blocked(void *buf, unsigned long size)
  89 {
  90         unsigned long tail;
  91
  92         if (offset) {
  93                 unsigned long chunk = BLOCKSIZE - offset;
  94                 if (size < chunk)
  95                         chunk = size;
  96                 memcpy(block + offset, buf, chunk);
  97                 size -= chunk;
  98                 offset += chunk;
  99                 buf += chunk;
 100                 write_if_needed();
 101         }
 102         while (size >= BLOCKSIZE) {
 103                 reliable_write(buf, BLOCKSIZE);
 104                 size -= BLOCKSIZE;
 105                 buf += BLOCKSIZE;
 106         }
 107         if (size) {
 108                 memcpy(block + offset, buf, size);
 109                 buf += size;
 110                 offset += size;
 111         }
 112         tail = offset % RECORDSIZE;
 113         if (tail)  {
 114                 memset(block + offset, 0, RECORDSIZE - tail);
 115                 offset += RECORDSIZE - tail;
 116         }
 117         write_if_needed();
 118 }
 119
 120 static void append_string(char **p, const char *s)
 121 {
 122         unsigned int len = strlen(s);
 123         memcpy(*p, s, len);
 124         *p += len;
 125 }
 126
 127 static void append_char(char **p, char c)
 128 {
 129         **p = c;
 130         *p += 1;
 131 }
 132
 133 static void append_path_prefix(char **buffer, struct path_prefix *prefix)
 134 {
 135         if (!prefix)
 136                 return;
 137         append_path_prefix(buffer, prefix->prev);
 138         append_string(buffer, prefix->name);
 139         append_char(buffer, '/');
 140 }
 141
 142 static unsigned int path_prefix_len(struct path_prefix *prefix)
 143 {
 144         if (!prefix)
 145                 return 0;
 146         return path_prefix_len(prefix->prev) + strlen(prefix->name) + 1;
 147 }
 148
 149 static void append_path(char **p, int is_dir, const char *basepath,
 150                         struct path_prefix *prefix, const char *path)
 151 {
 152         if (basepath) {
 153                 append_string(p, basepath);
 154                 append_char(p, '/');
 155         }
 156         append_path_prefix(p, prefix);
 157         append_string(p, path);
 158         if (is_dir)
 159                 append_char(p, '/');
 160 }
 161
 162 static unsigned int path_len(int is_dir, const char *basepath,
 163                              struct path_prefix *prefix, const char *path)
 164 {
 165         unsigned int len = 0;
 166         if (basepath)
 167                 len += strlen(basepath) + 1;
 168         len += path_prefix_len(prefix) + strlen(path);
 169         if (is_dir)
 170                 len++;
 171         return len;
 172 }
 173
 174 static void append_extended_header_prefix(char **p, unsigned int size,
 175                                           const char *keyword)
 176 {
 177         int len = sprintf(*p, "%u %s=", size, keyword);
 178         *p += len;
 179 }
 180
 181 static unsigned int extended_header_len(const char *keyword,
 182                                         unsigned int valuelen)
 183 {
 184         /* "%u %s=%s\n" */
 185         unsigned int len = 1 + 1 + strlen(keyword) + 1 + valuelen + 1;
 186         if (len > 9)
 187                 len++;
 188         if (len > 99)
 189                 len++;
 190         return len;
 191 }
 192
 193 static void append_extended_header(char **p, const char *keyword,
 194                                    const char *value, unsigned int len)
 195 {
 196         unsigned int size = extended_header_len(keyword, len);
 197         append_extended_header_prefix(p, size, keyword);
 198         memcpy(*p, value, len);
 199         *p += len;
 200         append_char(p, '\n');
 201 }
 202
 203 static void write_header(const unsigned char *, char, const char *, struct path_prefix *,
 204                          const char *, unsigned int, void *, unsigned long);
 205
 206 /* stores a pax extended header directly in the block buffer */
 207 static void write_extended_header(const char *headerfilename, int is_dir,
 208                                   unsigned int flags, const char *basepath,
 209                                   struct path_prefix *prefix,
 210                                   const char *path, unsigned int namelen,
 211                                   void *content, unsigned int contentsize)
 212 {
 213         char *buffer, *p;
 214         unsigned int pathlen, size, linkpathlen = 0;
 215
 216         size = pathlen = extended_header_len("path", namelen);
 217         if (flags & EXT_HEADER_LINKPATH) {
 218                 linkpathlen = extended_header_len("linkpath", contentsize);
 219                 size += linkpathlen;
 220         }
 221         write_header(NULL, TYPEFLAG_EXT_HEADER, NULL, NULL, headerfilename,
 222                      0100600, NULL, size);
 223
 224         buffer = p = malloc(size);
 225         if (!buffer)
 226                 die("git-tar-tree: %s", strerror(errno));
 227         append_extended_header_prefix(&p, pathlen, "path");
 228         append_path(&p, is_dir, basepath, prefix, path);
 229         append_char(&p, '\n');
 230         if (flags & EXT_HEADER_LINKPATH)
 231                 append_extended_header(&p, "linkpath", content, contentsize);
 232         write_blocked(buffer, size);
 233         free(buffer);
 234 }
 235
 236 static void write_global_extended_header(const unsigned char *sha1)
 237 {
 238         char *p;
 239         unsigned int size;
 240
 241         size = extended_header_len("comment", 40);
 242         write_header(NULL, TYPEFLAG_GLOBAL_HEADER, NULL, NULL,
 243                      "pax_global_header", 0100600, NULL, size);
 244
 245         p = get_record();
 246         append_extended_header(&p, "comment", sha1_to_hex(sha1), 40);
 247         write_if_needed();
 248 }
 249
 250 /* stores a ustar header directly in the block buffer */
 251 static void write_header(const unsigned char *sha1, char typeflag, const char *basepath,
 252                          struct path_prefix *prefix, const char *path,
 253                          unsigned int mode, void *buffer, unsigned long size)
 254 {
 255         unsigned int namelen;
 256         char *header = NULL;
 257         unsigned int checksum = 0;
 258         int i;
 259         unsigned int ext_header = 0;
 260
 261         if (typeflag == TYPEFLAG_AUTO) {
 262                 if (S_ISDIR(mode))
 263                         typeflag = TYPEFLAG_DIR;
 264                 else if (S_ISLNK(mode))
 265                         typeflag = TYPEFLAG_LNK;
 266                 else
 267                         typeflag = TYPEFLAG_REG;
 268         }
 269
 270         namelen = path_len(S_ISDIR(mode), basepath, prefix, path);
 271         if (namelen > 100)
 272                 ext_header |= EXT_HEADER_PATH;
 273         if (typeflag == TYPEFLAG_LNK && size > 100)
 274                 ext_header |= EXT_HEADER_LINKPATH;
 275
 276         /* the extended header must be written before the normal one */
 277         if (ext_header) {
 278                 char headerfilename[51];
 279                 sprintf(headerfilename, "%s.paxheader", sha1_to_hex(sha1));
 280                 write_extended_header(headerfilename, S_ISDIR(mode),
 281                                       ext_header, basepath, prefix, path,
 282                                       namelen, buffer, size);
 283         }
 284
 285         header = get_record();
 286
 287         if (ext_header) {
 288                 sprintf(header, "%s.data", sha1_to_hex(sha1));
 289         } else {
 290                 char *p = header;
 291                 append_path(&p, S_ISDIR(mode), basepath, prefix, path);
 292         }
 293
 294         if (typeflag == TYPEFLAG_LNK) {
 295                 if (ext_header & EXT_HEADER_LINKPATH) {
 296                         sprintf(&header[157], "see %s.paxheader",
 297                                 sha1_to_hex(sha1));
 298                 } else {
 299                         if (buffer)
 300                                 strncpy(&header[157], buffer, size);
 301                 }
 302         }
 303
 304         if (S_ISDIR(mode))
 305                 mode |= 0755;   /* GIT doesn't store permissions of dirs */
 306         if (S_ISLNK(mode))
 307                 mode |= 0777;   /* ... nor of symlinks */
 308         sprintf(&header[100], "%07o", mode & 07777);
 309
 310         /* XXX: should we provide more meaningful info here? */
 311         sprintf(&header[108], "%07o", 0);       /* uid */
 312         sprintf(&header[116], "%07o", 0);       /* gid */
 313         strncpy(&header[265], "git", 31);       /* uname */
 314         strncpy(&header[297], "git", 31);       /* gname */
 315
 316         if (S_ISDIR(mode) || S_ISLNK(mode))
 317                 size = 0;
 318         sprintf(&header[124], "%011lo", size);
 319         sprintf(&header[136], "%011lo", archive_time);
 320
 321         header[156] = typeflag;
 322
 323         memcpy(&header[257], "ustar", 6);
 324         memcpy(&header[263], "00", 2);
 325
 326         sprintf(&header[329], "%07o", 0);       /* devmajor */
 327         sprintf(&header[337], "%07o", 0);       /* devminor */
 328
 329         memset(&header[148], ' ', 8);
 330         for (i = 0; i < RECORDSIZE; i++)
 331                 checksum += header[i];
 332         sprintf(&header[148], "%07o", checksum & 0x1fffff);
 333
 334         write_if_needed();
 335 }
 336
 337 static void traverse_tree(void *buffer, unsigned long size,
 338                           struct path_prefix *prefix)
 339 {
 340         struct path_prefix this_prefix;
 341         this_prefix.prev = prefix;
 342
 343         while (size) {
 344                 int namelen = strlen(buffer)+1;
 345                 void *eltbuf;
 346                 char elttype[20];
 347                 unsigned long eltsize;
 348                 unsigned char *sha1 = buffer + namelen;
 349                 char *path = strchr(buffer, ' ') + 1;
 350                 unsigned int mode;
 351
 352                 if (size < namelen + 20 || sscanf(buffer, "%o", &mode) != 1)
 353                         die("corrupt 'tree' file");
 354                 if (S_ISDIR(mode) || S_ISREG(mode))
 355                         mode |= (mode & 0100) ? 0777 : 0666;
 356                 buffer = sha1 + 20;
 357                 size -= namelen + 20;
 358
 359                 eltbuf = read_sha1_file(sha1, elttype, &eltsize);
 360                 if (!eltbuf)
 361                         die("cannot read %s", sha1_to_hex(sha1));
 362                 write_header(sha1, TYPEFLAG_AUTO, basedir, prefix, path,
 363                              mode, eltbuf, eltsize);
 364                 if (!strcmp(elttype, "tree")) {
 365                         this_prefix.name = path;
 366                         traverse_tree(eltbuf, eltsize, &this_prefix);
 367                 } else if (!strcmp(elttype, "blob") && !S_ISLNK(mode)) {
 368                         write_blocked(eltbuf, eltsize);
 369                 }
 370                 free(eltbuf);
 371         }
 372 }
 373
 374 /* get commit time from committer line of commit object */
 375 static time_t commit_time(void * buffer, unsigned long size)
 376 {
 377         time_t result = 0;
 378         char *p = buffer;
 379
 380         while (size > 0) {
 381                 char *endp = memchr(p, '\n', size);
 382                 if (!endp || endp == p)
 383                         break;
 384                 *endp = '\0';
 385                 if (endp - p > 10 && !memcmp(p, "committer ", 10)) {
 386                         char *nump = strrchr(p, '>');
 387                         if (!nump)
 388                                 break;
 389                         nump++;
 390                         result = strtoul(nump, &endp, 10);
 391                         if (*endp != ' ')
 392                                 result = 0;
 393                         break;
 394                 }
 395                 size -= endp - p - 1;
 396                 p = endp + 1;
 397         }
 398         return result;
 399 }
 400
 401 int main(int argc, char **argv)
 402 {
 403         unsigned char sha1[20];
 404         unsigned char commit_sha1[20];
 405         void *buffer;
 406         unsigned long size;
 407
 408         setup_git_directory();
 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, 040777, NULL, 0);
 437         traverse_tree(buffer, size, NULL);
 438         free(buffer);
 439         write_trailer();
 440         return 0;
 441 }