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                 offset += size;
  98         }
  99         tail = offset % RECORDSIZE;
 100         if (tail)  {
 101                 memset(block + offset, 0, RECORDSIZE - tail);
 102                 offset += RECORDSIZE - tail;
 103         }
 104         write_if_needed();
 105 }
 106
 107 static void strbuf_append_string(struct strbuf *sb, const char *s)
 108 {
 109         int slen = strlen(s);
 110         int total = sb->len + slen;
 111         if (total > sb->alloc) {
 112                 sb->buf = xrealloc(sb->buf, total);
 113                 sb->alloc = total;
 114         }
 115         memcpy(sb->buf + sb->len, s, slen);
 116         sb->len = total;
 117 }
 118
 119 /*
 120  * pax extended header records have the format "%u %s=%s\n".  %u contains
 121  * the size of the whole string (including the %u), the first %s is the
 122  * keyword, the second one is the value.  This function constructs such a
 123  * string and appends it to a struct strbuf.
 124  */
 125 static void strbuf_append_ext_header(struct strbuf *sb, const char *keyword,
 126                                      const char *value, unsigned int valuelen)
 127 {
 128         char *p;
 129         int len, total, tmp;
 130
 131         /* "%u %s=%s\n" */
 132         len = 1 + 1 + strlen(keyword) + 1 + valuelen + 1;
 133         for (tmp = len; tmp > 9; tmp /= 10)
 134                 len++;
 135
 136         total = sb->len + len;
 137         if (total > sb->alloc) {
 138                 sb->buf = xrealloc(sb->buf, total);
 139                 sb->alloc = total;
 140         }
 141
 142         p = sb->buf;
 143         p += sprintf(p, "%u %s=", len, keyword);
 144         memcpy(p, value, valuelen);
 145         p += valuelen;
 146         *p = '\n';
 147         sb->len = total;
 148 }
 149
 150 static unsigned int ustar_header_chksum(const struct ustar_header *header)
 151 {
 152         char *p = (char *)header;
 153         unsigned int chksum = 0;
 154         while (p < header->chksum)
 155                 chksum += *p++;
 156         chksum += sizeof(header->chksum) * ' ';
 157         p += sizeof(header->chksum);
 158         while (p < (char *)header + sizeof(struct ustar_header))
 159                 chksum += *p++;
 160         return chksum;
 161 }
 162
 163 static int get_path_prefix(const struct strbuf *path, int maxlen)
 164 {
 165         int i = path->len;
 166         if (i > maxlen)
 167                 i = maxlen;
 168         while (i > 0 && path->buf[i] != '/')
 169                 i--;
 170         return i;
 171 }
 172
 173 static void write_entry(const unsigned char *sha1, struct strbuf *path,
 174                         unsigned int mode, void *buffer, unsigned long size)
 175 {
 176         struct ustar_header header;
 177         struct strbuf ext_header;
 178
 179         memset(&header, 0, sizeof(header));
 180         ext_header.buf = NULL;
 181         ext_header.len = ext_header.alloc = 0;
 182
 183         if (!sha1) {
 184                 *header.typeflag = TYPEFLAG_GLOBAL_HEADER;
 185                 mode = 0100666;
 186                 strcpy(header.name, "pax_global_header");
 187         } else if (!path) {
 188                 *header.typeflag = TYPEFLAG_EXT_HEADER;
 189                 mode = 0100666;
 190                 sprintf(header.name, "%s.paxheader", sha1_to_hex(sha1));
 191         } else {
 192                 if (S_ISDIR(mode)) {
 193                         *header.typeflag = TYPEFLAG_DIR;
 194                         mode |= 0777;
 195                 } else if (S_ISLNK(mode)) {
 196                         *header.typeflag = TYPEFLAG_LNK;
 197                         mode |= 0777;
 198                 } else if (S_ISREG(mode)) {
 199                         *header.typeflag = TYPEFLAG_REG;
 200                         mode |= (mode & 0100) ? 0777 : 0666;
 201                 } else {
 202                         error("unsupported file mode: 0%o (SHA1: %s)",
 203                               mode, sha1_to_hex(sha1));
 204                         return;
 205                 }
 206                 if (path->len > sizeof(header.name)) {
 207                         int plen = get_path_prefix(path, sizeof(header.prefix));
 208                         int rest = path->len - plen - 1;
 209                         if (plen > 0 && rest <= sizeof(header.name)) {
 210                                 memcpy(header.prefix, path->buf, plen);
 211                                 memcpy(header.name, path->buf + plen + 1, rest);
 212                         } else {
 213                                 sprintf(header.name, "%s.data",
 214                                         sha1_to_hex(sha1));
 215                                 strbuf_append_ext_header(&ext_header, "path",
 216                                                          path->buf, path->len);
 217                         }
 218                 } else
 219                         memcpy(header.name, path->buf, path->len);
 220         }
 221
 222         if (S_ISLNK(mode) && buffer) {
 223                 if (size > sizeof(header.linkname)) {
 224                         sprintf(header.linkname, "see %s.paxheader",
 225                                 sha1_to_hex(sha1));
 226                         strbuf_append_ext_header(&ext_header, "linkpath",
 227                                                  buffer, size);
 228                 } else
 229                         memcpy(header.linkname, buffer, size);
 230         }
 231
 232         sprintf(header.mode, "%07o", mode & 07777);
 233         sprintf(header.size, "%011lo", S_ISREG(mode) ? size : 0);
 234         sprintf(header.mtime, "%011lo", archive_time);
 235
 236         /* XXX: should we provide more meaningful info here? */
 237         sprintf(header.uid, "%07o", 0);
 238         sprintf(header.gid, "%07o", 0);
 239         strncpy(header.uname, "git", 31);
 240         strncpy(header.gname, "git", 31);
 241         sprintf(header.devmajor, "%07o", 0);
 242         sprintf(header.devminor, "%07o", 0);
 243
 244         memcpy(header.magic, "ustar", 6);
 245         memcpy(header.version, "00", 2);
 246
 247         sprintf(header.chksum, "%07o", ustar_header_chksum(&header));
 248
 249         if (ext_header.len > 0) {
 250                 write_entry(sha1, NULL, 0, ext_header.buf, ext_header.len);
 251                 free(ext_header.buf);
 252         }
 253         write_blocked(&header, sizeof(header));
 254         if (S_ISREG(mode) && buffer && size > 0)
 255                 write_blocked(buffer, size);
 256 }
 257
 258 static void write_global_extended_header(const unsigned char *sha1)
 259 {
 260         struct strbuf ext_header;
 261         ext_header.buf = NULL;
 262         ext_header.len = ext_header.alloc = 0;
 263         strbuf_append_ext_header(&ext_header, "comment", sha1_to_hex(sha1), 40);
 264         write_entry(NULL, NULL, 0, ext_header.buf, ext_header.len);
 265         free(ext_header.buf);
 266 }
 267
 268 static void traverse_tree(struct tree_desc *tree, struct strbuf *path)
 269 {
 270         int pathlen = path->len;
 271
 272         while (tree->size) {
 273                 const char *name;
 274                 const unsigned char *sha1;
 275                 unsigned mode;
 276                 void *eltbuf;
 277                 char elttype[20];
 278                 unsigned long eltsize;
 279
 280                 sha1 = tree_entry_extract(tree, &name, &mode);
 281                 update_tree_entry(tree);
 282
 283                 eltbuf = read_sha1_file(sha1, elttype, &eltsize);
 284                 if (!eltbuf)
 285                         die("cannot read %s", sha1_to_hex(sha1));
 286
 287                 path->len = pathlen;
 288                 strbuf_append_string(path, name);
 289                 if (S_ISDIR(mode))
 290                         strbuf_append_string(path, "/");
 291
 292                 write_entry(sha1, path, mode, eltbuf, eltsize);
 293
 294                 if (S_ISDIR(mode)) {
 295                         struct tree_desc subtree;
 296                         subtree.buf = eltbuf;
 297                         subtree.size = eltsize;
 298                         traverse_tree(&subtree, path);
 299                 }
 300                 free(eltbuf);
 301         }
 302 }
 303
 304 int main(int argc, char **argv)
 305 {
 306         unsigned char sha1[20], tree_sha1[20];
 307         struct commit *commit;
 308         struct tree_desc tree;
 309         struct strbuf current_path;
 310
 311         current_path.buf = xmalloc(PATH_MAX);
 312         current_path.alloc = PATH_MAX;
 313         current_path.len = current_path.eof = 0;
 314
 315         setup_git_directory();
 316         git_config(git_default_config);
 317
 318         switch (argc) {
 319         case 3:
 320                 strbuf_append_string(&current_path, argv[2]);
 321                 strbuf_append_string(&current_path, "/");
 322                 /* FALLTHROUGH */
 323         case 2:
 324                 if (get_sha1(argv[1], sha1) < 0)
 325                         usage(tar_tree_usage);
 326                 break;
 327         default:
 328                 usage(tar_tree_usage);
 329         }
 330
 331         commit = lookup_commit_reference_gently(sha1, 1);
 332         if (commit) {
 333                 write_global_extended_header(commit->object.sha1);
 334                 archive_time = commit->date;
 335         } else
 336                 archive_time = time(NULL);
 337
 338         tree.buf = read_object_with_reference(sha1, tree_type, &tree.size,
 339                                               tree_sha1);
 340         if (!tree.buf)
 341                 die("not a reference to a tag, commit or tree object: %s",
 342                     sha1_to_hex(sha1));
 343
 344         if (current_path.len > 0)
 345                 write_entry(tree_sha1, &current_path, 040777, NULL, 0);
 346         traverse_tree(&tree, &current_path);
 347         write_trailer();
 348         free(current_path.buf);
 349         return 0;
 350 }