tar-tree.c

   1 /*
   2  * Copyright (c) 2005, 2006 Rene Scharfe
   3  */
   4 #include <time.h>
   5 #include "cache.h"
   6 #include "tree-walk.h"
   7 #include "commit.h"
   8 #include "strbuf.h"
   9 #include "tar.h"
  10
  11 #define RECORDSIZE      (512)
  12 #define BLOCKSIZE       (RECORDSIZE * 20)
  13
  14 static const char tar_tree_usage[] = "git-tar-tree <key> [basedir]";
  15
  16 static char block[BLOCKSIZE];
  17 static unsigned long offset;
  18
  19 static time_t archive_time;
  20
  21 /* tries hard to write, either succeeds or dies in the attempt */
  22 static void reliable_write(void *buf, unsigned long size)
  23 {
  24         while (size > 0) {
  25                 long ret = xwrite(1, buf, size);
  26                 if (ret < 0) {
  27                         if (errno == EPIPE)
  28                                 exit(0);
  29                         die("git-tar-tree: %s", strerror(errno));
  30                 } else if (!ret) {
  31                         die("git-tar-tree: disk full?");
  32                 }
  33                 size -= ret;
  34                 buf += ret;
  35         }
  36 }
  37
  38 /* writes out the whole block, but only if it is full */
  39 static void write_if_needed(void)
  40 {
  41         if (offset == BLOCKSIZE) {
  42                 reliable_write(block, BLOCKSIZE);
  43                 offset = 0;
  44         }
  45 }
  46
  47 /* acquire the next record from the buffer; user must call write_if_needed() */
  48 static char *get_record(void)
  49 {
  50         char *p = block + offset;
  51         memset(p, 0, RECORDSIZE);
  52         offset += RECORDSIZE;
  53         return p;
  54 }
  55
  56 /*
  57  * The end of tar archives is marked by 1024 nul bytes and after that
  58  * follows the rest of the block (if any).
  59  */
  60 static void write_trailer(void)
  61 {
  62         get_record();
  63         write_if_needed();
  64         get_record();
  65         write_if_needed();
  66         while (offset) {
  67                 get_record();
  68                 write_if_needed();
  69         }
  70 }
  71
  72 /*
  73  * queues up writes, so that all our write(2) calls write exactly one
  74  * full block; pads writes to RECORDSIZE
  75  */
  76 static void write_blocked(void *buf, unsigned long size)
  77 {
  78         unsigned long tail;
  79
  80         if (offset) {
  81                 unsigned long chunk = BLOCKSIZE - offset;
  82                 if (size < chunk)
  83                         chunk = size;
  84                 memcpy(block + offset, buf, chunk);
  85                 size -= chunk;
  86                 offset += chunk;
  87                 buf += chunk;
  88                 write_if_needed();
  89         }
  90         while (size >= BLOCKSIZE) {
  91                 reliable_write(buf, BLOCKSIZE);
  92                 size -= BLOCKSIZE;
  93                 buf += BLOCKSIZE;
  94         }
  95         if (size) {
  96                 memcpy(block + offset, buf, size);
  97                 buf += size;
  98                 offset += size;
  99         }
 100         tail = offset % RECORDSIZE;
 101         if (tail)  {
 102                 memset(block + offset, 0, RECORDSIZE - tail);
 103                 offset += RECORDSIZE - tail;
 104         }
 105         write_if_needed();
 106 }
 107
 108 static void strbuf_append_string(struct strbuf *sb, const char *s)
 109 {
 110         int slen = strlen(s);
 111         int total = sb->len + slen;
 112         if (total > sb->alloc) {
 113                 sb->buf = xrealloc(sb->buf, total);
 114                 sb->alloc = total;
 115         }
 116         memcpy(sb->buf + sb->len, s, slen);
 117         sb->len = total;
 118 }
 119
 120 /*
 121  * pax extended header records have the format "%u %s=%s\n".  %u contains
 122  * the size of the whole string (including the %u), the first %s is the
 123  * keyword, the second one is the value.  This function constructs such a
 124  * string and appends it to a struct strbuf.
 125  */
 126 static void strbuf_append_ext_header(struct strbuf *sb, const char *keyword,
 127                                      const char *value, unsigned int valuelen)
 128 {
 129         char *p;
 130         int len, total, tmp;
 131
 132         /* "%u %s=%s\n" */
 133         len = 1 + 1 + strlen(keyword) + 1 + valuelen + 1;
 134         for (tmp = len; tmp > 9; tmp /= 10)
 135                 len++;
 136
 137         total = sb->len + len;
 138         if (total > sb->alloc) {
 139                 sb->buf = xrealloc(sb->buf, total);
 140                 sb->alloc = total;
 141         }
 142
 143         p = sb->buf;
 144         p += sprintf(p, "%u %s=", len, keyword);
 145         memcpy(p, value, valuelen);
 146         p += valuelen;
 147         *p = '\n';
 148         sb->len = total;
 149 }
 150
 151 static unsigned int ustar_header_chksum(const struct ustar_header *header)
 152 {
 153         char *p = (char *)header;
 154         unsigned int chksum = 0;
 155         while (p < header->chksum)
 156                 chksum += *p++;
 157         chksum += sizeof(header->chksum) * ' ';
 158         p += sizeof(header->chksum);
 159         while (p < (char *)header + sizeof(struct ustar_header))
 160                 chksum += *p++;
 161         return chksum;
 162 }
 163
 164 static int get_path_prefix(const struct strbuf *path, int maxlen)
 165 {
 166         int i = path->len;
 167         if (i > maxlen)
 168                 i = maxlen;
 169         while (i > 0 && path->buf[i] != '/')
 170                 i--;
 171         return i;
 172 }
 173
 174 static void write_entry(const unsigned char *sha1, struct strbuf *path,
 175                         unsigned int mode, void *buffer, unsigned long size)
 176 {
 177         struct ustar_header header;
 178         struct strbuf ext_header;
 179
 180         memset(&header, 0, sizeof(header));
 181         ext_header.buf = NULL;
 182         ext_header.len = ext_header.alloc = 0;
 183
 184         if (!sha1) {
 185                 *header.typeflag = TYPEFLAG_GLOBAL_HEADER;
 186                 mode = 0100666;
 187                 strcpy(header.name, "pax_global_header");
 188         } else if (!path) {
 189                 *header.typeflag = TYPEFLAG_EXT_HEADER;
 190                 mode = 0100666;
 191                 sprintf(header.name, "%s.paxheader", sha1_to_hex(sha1));
 192         } else {
 193                 if (S_ISDIR(mode)) {
 194                         *header.typeflag = TYPEFLAG_DIR;
 195                         mode |= 0777;
 196                 } else if (S_ISLNK(mode)) {
 197                         *header.typeflag = TYPEFLAG_LNK;
 198                         mode |= 0777;
 199                 } else if (S_ISREG(mode)) {
 200                         *header.typeflag = TYPEFLAG_REG;
 201                         mode |= (mode & 0100) ? 0777 : 0666;
 202                 } else {
 203                         error("unsupported file mode: 0%o (SHA1: %s)",
 204                               mode, sha1_to_hex(sha1));
 205                         return;
 206                 }
 207                 if (path->len > sizeof(header.name)) {
 208                         int plen = get_path_prefix(path, sizeof(header.prefix));
 209                         int rest = path->len - plen - 1;
 210                         if (plen > 0 && rest <= sizeof(header.name)) {
 211                                 memcpy(header.prefix, path->buf, plen);
 212                                 memcpy(header.name, path->buf + plen + 1, rest);
 213                         } else {
 214                                 sprintf(header.name, "%s.data",
 215                                         sha1_to_hex(sha1));
 216                                 strbuf_append_ext_header(&ext_header, "path",
 217                                                          path->buf, path->len);
 218                         }
 219                 } else
 220                         memcpy(header.name, path->buf, path->len);
 221         }
 222
 223         if (S_ISLNK(mode) && buffer) {
 224                 if (size > sizeof(header.linkname)) {
 225                         sprintf(header.linkname, "see %s.paxheader",
 226                                 sha1_to_hex(sha1));
 227                         strbuf_append_ext_header(&ext_header, "linkpath",
 228                                                  buffer, size);
 229                 } else
 230                         memcpy(header.linkname, buffer, size);
 231         }
 232
 233         sprintf(header.mode, "%07o", mode & 07777);
 234         sprintf(header.size, "%011lo", S_ISREG(mode) ? size : 0);
 235         sprintf(header.mtime, "%011lo", archive_time);
 236
 237         /* XXX: should we provide more meaningful info here? */
 238         sprintf(header.uid, "%07o", 0);
 239         sprintf(header.gid, "%07o", 0);
 240         strncpy(header.uname, "git", 31);
 241         strncpy(header.gname, "git", 31);
 242         sprintf(header.devmajor, "%07o", 0);
 243         sprintf(header.devminor, "%07o", 0);
 244
 245         memcpy(header.magic, "ustar", 6);
 246         memcpy(header.version, "00", 2);
 247
 248         sprintf(header.chksum, "%07o", ustar_header_chksum(&header));
 249
 250         if (ext_header.len > 0) {
 251                 write_entry(sha1, NULL, 0, ext_header.buf, ext_header.len);
 252                 free(ext_header.buf);
 253         }
 254         write_blocked(&header, sizeof(header));
 255         if (S_ISREG(mode) && buffer && size > 0)
 256                 write_blocked(buffer, size);
 257 }
 258
 259 static void write_global_extended_header(const unsigned char *sha1)
 260 {
 261         struct strbuf ext_header;
 262         ext_header.buf = NULL;
 263         ext_header.len = ext_header.alloc = 0;
 264         strbuf_append_ext_header(&ext_header, "comment", sha1_to_hex(sha1), 40);
 265         write_entry(NULL, NULL, 0, ext_header.buf, ext_header.len);
 266         free(ext_header.buf);
 267 }
 268
 269 static void traverse_tree(struct tree_desc *tree, struct strbuf *path)
 270 {
 271         int pathlen = path->len;
 272
 273         while (tree->size) {
 274                 const char *name;
 275                 const unsigned char *sha1;
 276                 unsigned mode;
 277                 void *eltbuf;
 278                 char elttype[20];
 279                 unsigned long eltsize;
 280
 281                 sha1 = tree_entry_extract(tree, &name, &mode);
 282                 update_tree_entry(tree);
 283
 284                 eltbuf = read_sha1_file(sha1, elttype, &eltsize);
 285                 if (!eltbuf)
 286                         die("cannot read %s", sha1_to_hex(sha1));
 287
 288                 path->len = pathlen;
 289                 strbuf_append_string(path, name);
 290                 if (S_ISDIR(mode))
 291                         strbuf_append_string(path, "/");
 292
 293                 write_entry(sha1, path, mode, eltbuf, eltsize);
 294
 295                 if (S_ISDIR(mode)) {
 296                         struct tree_desc subtree;
 297                         subtree.buf = eltbuf;
 298                         subtree.size = eltsize;
 299                         traverse_tree(&subtree, path);
 300                 }
 301                 free(eltbuf);
 302         }
 303 }
 304
 305 int main(int argc, char **argv)
 306 {
 307         unsigned char sha1[20], tree_sha1[20];
 308         struct commit *commit;
 309         struct tree_desc tree;
 310         struct strbuf current_path;
 311
 312         current_path.buf = xmalloc(PATH_MAX);
 313         current_path.alloc = PATH_MAX;
 314         current_path.len = current_path.eof = 0;
 315
 316         setup_git_directory();
 317         git_config(git_default_config);
 318
 319         switch (argc) {
 320         case 3:
 321                 strbuf_append_string(&current_path, argv[2]);
 322                 strbuf_append_string(&current_path, "/");
 323                 /* FALLTHROUGH */
 324         case 2:
 325                 if (get_sha1(argv[1], sha1) < 0)
 326                         usage(tar_tree_usage);
 327                 break;
 328         default:
 329                 usage(tar_tree_usage);
 330         }
 331
 332         commit = lookup_commit_reference_gently(sha1, 1);
 333         if (commit) {
 334                 write_global_extended_header(commit->object.sha1);
 335                 archive_time = commit->date;
 336         } else
 337                 archive_time = time(NULL);
 338
 339         tree.buf = read_object_with_reference(sha1, "tree", &tree.size,
 340                                               tree_sha1);
 341         if (!tree.buf)
 342                 die("not a reference to a tag, commit or tree object: %s",
 343                     sha1_to_hex(sha1));
 344
 345         if (current_path.len > 0)
 346                 write_entry(tree_sha1, &current_path, 040777, NULL, 0);
 347         traverse_tree(&tree, &current_path);
 348         write_trailer();
 349         free(current_path.buf);
 350         return 0;
 351 }