tar-tree.c

   1 #include <time.h>
   2 #include "cache.h"
   3
   4 #define RECORDSIZE      (512)
   5 #define BLOCKSIZE       (RECORDSIZE * 20)
   6
   7 static const char *tar_tree_usage = "tar-tree <key> [basedir]";
   8
   9 static char block[BLOCKSIZE];
  10 static unsigned long offset;
  11
  12 static const char *basedir;
  13 static time_t archive_time;
  14
  15 struct path_prefix {
  16         struct path_prefix *prev;
  17         const char *name;
  18 };
  19
  20 /* tries hard to write, either succeeds or dies in the attempt */
  21 static void reliable_write(void *buf, unsigned long size)
  22 {
  23         while (size > 0) {
  24                 long ret = write(1, buf, size);
  25                 if (ret < 0) {
  26                         if (errno == EAGAIN)
  27                                 continue;
  28                         if (errno == EPIPE)
  29                                 exit(0);
  30                         die("tar-tree: %s", strerror(errno));
  31                 } else if (!ret) {
  32                         die("tar-tree: disk full?");
  33                 }
  34                 size -= ret;
  35                 buf += ret;
  36         }
  37 }
  38
  39 /* writes out the whole block, but only if it is full */
  40 static void write_if_needed(void)
  41 {
  42         if (offset == BLOCKSIZE) {
  43                 reliable_write(block, BLOCKSIZE);
  44                 offset = 0;
  45         }
  46 }
  47
  48 /* acquire the next record from the buffer; user must call write_if_needed() */
  49 static char *get_record(void)
  50 {
  51         char *p = block + offset;
  52         memset(p, 0, RECORDSIZE);
  53         offset += RECORDSIZE;
  54         return p;
  55 }
  56
  57 /*
  58  * The end of tar archives is marked by 1024 nul bytes and after that
  59  * follows the rest of the block (if any).
  60  */
  61 static void write_trailer(void)
  62 {
  63         memset(block + offset, 0, RECORDSIZE);
  64         offset += RECORDSIZE;
  65         write_if_needed();
  66         memset(block + offset, 0, RECORDSIZE);
  67         offset += RECORDSIZE;
  68         write_if_needed();
  69         if (offset) {
  70                 memset(block + offset, 0, BLOCKSIZE - offset);
  71                 reliable_write(block, BLOCKSIZE);
  72                 offset = 0;
  73         }
  74 }
  75
  76 /*
  77  * queues up writes, so that all our write(2) calls write exactly one
  78  * full block; pads writes to RECORDSIZE
  79  */
  80 static void write_blocked(void *buf, unsigned long size)
  81 {
  82         unsigned long tail;
  83
  84         if (offset) {
  85                 unsigned long chunk = BLOCKSIZE - offset;
  86                 if (size < chunk)
  87                         chunk = size;
  88                 memcpy(block + offset, buf, chunk);
  89                 size -= chunk;
  90                 offset += chunk;
  91                 buf += chunk;
  92                 write_if_needed();
  93         }
  94         while (size >= BLOCKSIZE) {
  95                 reliable_write(buf, BLOCKSIZE);
  96                 size -= BLOCKSIZE;
  97                 buf += BLOCKSIZE;
  98         }
  99         if (size) {
 100                 memcpy(block + offset, buf, size);
 101                 buf += size;
 102                 offset += size;
 103         }
 104         tail = offset % RECORDSIZE;
 105         if (tail)  {
 106                 memset(block + offset, 0, RECORDSIZE - tail);
 107                 offset += RECORDSIZE - tail;
 108         }
 109         write_if_needed();
 110 }
 111
 112 static void append_string(char **p, const char *s)
 113 {
 114         unsigned int len = strlen(s);
 115         memcpy(*p, s, len);
 116         *p += len;
 117 }
 118
 119 static void append_char(char **p, char c)
 120 {
 121         **p = c;
 122         *p += 1;
 123 }
 124
 125 static void append_long(char **p, long n)
 126 {
 127         int len = sprintf(*p, "%ld", n);
 128         *p += len;
 129 }
 130
 131 static void append_path_prefix(char **buffer, struct path_prefix *prefix)
 132 {
 133         if (!prefix)
 134                 return;
 135         append_path_prefix(buffer, prefix->prev);
 136         append_string(buffer, prefix->name);
 137         append_char(buffer, '/');
 138 }
 139
 140 static unsigned int path_prefix_len(struct path_prefix *prefix)
 141 {
 142         if (!prefix)
 143                 return 0;
 144         return path_prefix_len(prefix->prev) + strlen(prefix->name) + 1;
 145 }
 146
 147 static void append_path(char **p, int is_dir, const char *basepath,
 148                         struct path_prefix *prefix, const char *path)
 149 {
 150         if (basepath) {
 151                 append_string(p, basepath);
 152                 append_char(p, '/');
 153         }
 154         append_path_prefix(p, prefix);
 155         append_string(p, path);
 156         if (is_dir)
 157                 append_char(p, '/');
 158 }
 159
 160 static unsigned int path_len(int is_dir, const char *basepath,
 161                              struct path_prefix *prefix, const char *path)
 162 {
 163         unsigned int len = 0;
 164         if (basepath)
 165                 len += strlen(basepath) + 1;
 166         len += path_prefix_len(prefix) + strlen(path);
 167         if (is_dir)
 168                 len++;
 169         return len;
 170 }
 171
 172 static void write_header(const char *, char, const char *, struct path_prefix *,
 173                          const char *, unsigned int, unsigned long);
 174
 175 /* stores a pax extended header directly in the block buffer */
 176 static void write_extended_header(const char *headerfilename, int is_dir,
 177                                   const char *basepath,
 178                                   struct path_prefix *prefix,
 179                                   const char *path, unsigned int namelen)
 180 {
 181         char *p;
 182         unsigned int size = 1 + 6 + namelen + 1;
 183         if (size > 9)
 184                 size++;
 185         if (size > 99)
 186                 size++;
 187         if (size > RECORDSIZE)
 188                 die("tar-tree: extended header too big, wtf?");
 189         write_header(NULL, 'x', NULL, NULL, headerfilename, 0100600, size);
 190         p = get_record();
 191         append_long(&p, size);
 192         append_string(&p, " path=");
 193         append_path(&p, is_dir, basepath, prefix, path);
 194         append_char(&p, '\n');
 195         write_if_needed();
 196 }
 197
 198 static void write_global_extended_header(const char *sha1)
 199 {
 200         char *p;
 201         write_header(NULL, 'g', NULL, NULL, "pax_global_header", 0, 52);
 202         p = get_record();
 203         append_long(&p, 52);    /* 2 + 9 + 40 + 1 */
 204         append_string(&p, " comment=");
 205         append_string(&p, sha1_to_hex(sha1));
 206         append_char(&p, '\n');
 207         write_if_needed();
 208 }
 209
 210 /* stores a ustar header directly in the block buffer */
 211 static void write_header(const char *sha1, char typeflag, const char *basepath,
 212                          struct path_prefix *prefix, const char *path,
 213                          unsigned int mode, unsigned long size)
 214 {
 215         unsigned int namelen;
 216         char *p, *header = NULL;
 217         unsigned int checksum = 0;
 218         int i;
 219
 220         namelen = path_len(S_ISDIR(mode), basepath, prefix, path);
 221         if (namelen > 500) {
 222                 die("tar-tree: name too log of object %s\n", sha1_to_hex(sha1));
 223         } else if (namelen > 100) {
 224                 char *sha1_hex = sha1_to_hex(sha1);
 225                 char headerfilename[51];
 226                 sprintf(headerfilename, "%s.paxheader", sha1_hex);
 227                 /* the extended header must be written before the normal one */
 228                 write_extended_header(headerfilename, S_ISDIR(mode), basepath,
 229                                       prefix, path, namelen);
 230
 231                 header = get_record();
 232                 sprintf(header, "%s.data", sha1_hex);
 233         } else {
 234                 p = header = get_record();
 235                 append_path(&p, S_ISDIR(mode), basepath, prefix, path);
 236         }
 237
 238         if (S_ISDIR(mode))
 239                 mode |= 0755;   /* GIT doesn't store permissions of dirs */
 240         sprintf(&header[100], "%07o", mode & 07777);
 241
 242         /* XXX: should we provide more meaningful info here? */
 243         sprintf(&header[108], "%07o", 0);       /* uid */
 244         sprintf(&header[116], "%07o", 0);       /* gid */
 245         strncpy(&header[265], "git", 31);       /* uname */
 246         strncpy(&header[297], "git", 31);       /* gname */
 247
 248         sprintf(&header[124], "%011lo", S_ISDIR(mode) ? 0 : size);
 249         sprintf(&header[136], "%011lo", archive_time);
 250
 251         header[156] = typeflag;
 252
 253         memcpy(&header[257], "ustar", 6);
 254         memcpy(&header[263], "00", 2);
 255
 256         printf(&header[329], "%07o", 0);        /* devmajor */
 257         printf(&header[337], "%07o", 0);        /* devminor */
 258
 259         memset(&header[148], ' ', 8);
 260         for (i = 0; i < RECORDSIZE; i++)
 261                 checksum += header[i];
 262         sprintf(&header[148], "%07o", checksum & 0x1fffff);
 263
 264         write_if_needed();
 265 }
 266
 267 static void traverse_tree(void *buffer, unsigned long size,
 268                           struct path_prefix *prefix)
 269 {
 270         struct path_prefix this_prefix;
 271         this_prefix.prev = prefix;
 272
 273         while (size) {
 274                 int namelen = strlen(buffer)+1;
 275                 void *eltbuf;
 276                 char elttype[20];
 277                 unsigned long eltsize;
 278                 unsigned char *sha1 = buffer + namelen;
 279                 char *path = strchr(buffer, ' ') + 1;
 280                 unsigned int mode;
 281
 282                 if (size < namelen + 20 || sscanf(buffer, "%o", &mode) != 1)
 283                         die("corrupt 'tree' file");
 284                 buffer = sha1 + 20;
 285                 size -= namelen + 20;
 286
 287                 eltbuf = read_sha1_file(sha1, elttype, &eltsize);
 288                 if (!eltbuf)
 289                         die("cannot read %s", sha1_to_hex(sha1));
 290                 write_header(sha1, S_ISDIR(mode) ? '5' : '0', basedir,
 291                              prefix, path, mode, eltsize);
 292                 if (!strcmp(elttype, "tree")) {
 293                         this_prefix.name = path;
 294                         traverse_tree(eltbuf, eltsize, &this_prefix);
 295                 } else if (!strcmp(elttype, "blob")) {
 296                         write_blocked(eltbuf, eltsize);
 297                 }
 298                 free(eltbuf);
 299         }
 300 }
 301
 302 /* get commit time from committer line of commit object */
 303 time_t commit_time(void * buffer, unsigned long size)
 304 {
 305         time_t result = 0;
 306         char *p = buffer;
 307
 308         while (size > 0) {
 309                 char *endp = memchr(p, '\n', size);
 310                 if (!endp || endp == p)
 311                         break;
 312                 *endp = '\0';
 313                 if (endp - p > 10 && !memcmp(p, "committer ", 10)) {
 314                         char *nump = strrchr(p, '>');
 315                         if (!nump)
 316                                 break;
 317                         nump++;
 318                         result = strtoul(nump, &endp, 10);
 319                         if (*endp != ' ')
 320                                 result = 0;
 321                         break;
 322                 }
 323                 size -= endp - p - 1;
 324                 p = endp + 1;
 325         }
 326         return result;
 327 }
 328
 329 int main(int argc, char **argv)
 330 {
 331         unsigned char sha1[20];
 332         unsigned char commit_sha1[20];
 333         void *buffer;
 334         unsigned long size;
 335
 336         switch (argc) {
 337         case 3:
 338                 basedir = argv[2];
 339                 /* FALLTHROUGH */
 340         case 2:
 341                 if (get_sha1(argv[1], sha1) < 0)
 342                         usage(tar_tree_usage);
 343                 break;
 344         default:
 345                 usage(tar_tree_usage);
 346         }
 347
 348         sha1_file_directory = getenv(DB_ENVIRONMENT);
 349         if (!sha1_file_directory)
 350                 sha1_file_directory = DEFAULT_DB_ENVIRONMENT;
 351
 352         buffer = read_object_with_reference(sha1, "commit", &size, commit_sha1);
 353         if (buffer) {
 354                 write_global_extended_header(commit_sha1);
 355                 archive_time = commit_time(buffer, size);
 356                 free(buffer);
 357         }
 358         buffer = read_object_with_reference(sha1, "tree", &size, NULL);
 359         if (!buffer)
 360                 die("not a reference to a tag, commit or tree object: %s",
 361                     sha1_to_hex(sha1));
 362         if (!archive_time)
 363                 archive_time = time(NULL);
 364         if (basedir)
 365                 write_header("0", '5', NULL, NULL, basedir, 040755, 0);
 366         traverse_tree(buffer, size, NULL);
 367         free(buffer);
 368         write_trailer();
 369         return 0;
 370 }