tar-tree.c

   1 /*
   2  * Copyright (c) 2005, 2006 Rene Scharfe
   3  */
   4 #include <time.h>
   5 #include "cache.h"
   6 #include "diff.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 void write_entry(const unsigned char *sha1, struct strbuf *path,
 165                         unsigned int mode, void *buffer, unsigned long size)
 166 {
 167         struct ustar_header header;
 168         struct strbuf ext_header;
 169
 170         memset(&header, 0, sizeof(header));
 171         ext_header.buf = NULL;
 172         ext_header.len = ext_header.alloc = 0;
 173
 174         if (!sha1) {
 175                 *header.typeflag = TYPEFLAG_GLOBAL_HEADER;
 176                 mode = 0100666;
 177                 strcpy(header.name, "pax_global_header");
 178         } else if (!path) {
 179                 *header.typeflag = TYPEFLAG_EXT_HEADER;
 180                 mode = 0100666;
 181                 sprintf(header.name, "%s.paxheader", sha1_to_hex(sha1));
 182         } else {
 183                 if (S_ISDIR(mode)) {
 184                         *header.typeflag = TYPEFLAG_DIR;
 185                         mode |= 0777;
 186                 } else if (S_ISLNK(mode)) {
 187                         *header.typeflag = TYPEFLAG_LNK;
 188                         mode |= 0777;
 189                 } else if (S_ISREG(mode)) {
 190                         *header.typeflag = TYPEFLAG_REG;
 191                         mode |= (mode & 0100) ? 0777 : 0666;
 192                 } else {
 193                         error("unsupported file mode: 0%o (SHA1: %s)",
 194                               mode, sha1_to_hex(sha1));
 195                         return;
 196                 }
 197                 if (path->len > sizeof(header.name)) {
 198                         sprintf(header.name, "%s.data", sha1_to_hex(sha1));
 199                         strbuf_append_ext_header(&ext_header, "path",
 200                                                  path->buf, path->len);
 201                 } else
 202                         memcpy(header.name, path->buf, path->len);
 203         }
 204
 205         if (S_ISLNK(mode) && buffer) {
 206                 if (size > sizeof(header.linkname)) {
 207                         sprintf(header.linkname, "see %s.paxheader",
 208                                 sha1_to_hex(sha1));
 209                         strbuf_append_ext_header(&ext_header, "linkpath",
 210                                                  buffer, size);
 211                 } else
 212                         memcpy(header.linkname, buffer, size);
 213         }
 214
 215         sprintf(header.mode, "%07o", mode & 07777);
 216         sprintf(header.size, "%011lo", S_ISREG(mode) ? size : 0);
 217         sprintf(header.mtime, "%011lo", archive_time);
 218
 219         /* XXX: should we provide more meaningful info here? */
 220         sprintf(header.uid, "%07o", 0);
 221         sprintf(header.gid, "%07o", 0);
 222         strncpy(header.uname, "git", 31);
 223         strncpy(header.gname, "git", 31);
 224         sprintf(header.devmajor, "%07o", 0);
 225         sprintf(header.devminor, "%07o", 0);
 226
 227         memcpy(header.magic, "ustar", 6);
 228         memcpy(header.version, "00", 2);
 229
 230         sprintf(header.chksum, "%07o", ustar_header_chksum(&header));
 231
 232         if (ext_header.len > 0) {
 233                 write_entry(sha1, NULL, 0, ext_header.buf, ext_header.len);
 234                 free(ext_header.buf);
 235         }
 236         write_blocked(&header, sizeof(header));
 237         if (S_ISREG(mode) && buffer && size > 0)
 238                 write_blocked(buffer, size);
 239 }
 240
 241 static void write_global_extended_header(const unsigned char *sha1)
 242 {
 243         struct strbuf ext_header;
 244         ext_header.buf = NULL;
 245         ext_header.len = ext_header.alloc = 0;
 246         strbuf_append_ext_header(&ext_header, "comment", sha1_to_hex(sha1), 40);
 247         write_entry(NULL, NULL, 0, ext_header.buf, ext_header.len);
 248         free(ext_header.buf);
 249 }
 250
 251 static void traverse_tree(struct tree_desc *tree, struct strbuf *path)
 252 {
 253         int pathlen = path->len;
 254
 255         while (tree->size) {
 256                 const char *name;
 257                 const unsigned char *sha1;
 258                 unsigned mode;
 259                 void *eltbuf;
 260                 char elttype[20];
 261                 unsigned long eltsize;
 262
 263                 sha1 = tree_entry_extract(tree, &name, &mode);
 264                 update_tree_entry(tree);
 265
 266                 eltbuf = read_sha1_file(sha1, elttype, &eltsize);
 267                 if (!eltbuf)
 268                         die("cannot read %s", sha1_to_hex(sha1));
 269
 270                 path->len = pathlen;
 271                 strbuf_append_string(path, name);
 272                 if (S_ISDIR(mode))
 273                         strbuf_append_string(path, "/");
 274
 275                 write_entry(sha1, path, mode, eltbuf, eltsize);
 276
 277                 if (S_ISDIR(mode)) {
 278                         struct tree_desc subtree;
 279                         subtree.buf = eltbuf;
 280                         subtree.size = eltsize;
 281                         traverse_tree(&subtree, path);
 282                 }
 283                 free(eltbuf);
 284         }
 285 }
 286
 287 int main(int argc, char **argv)
 288 {
 289         unsigned char sha1[20], tree_sha1[20];
 290         struct commit *commit;
 291         struct tree_desc tree;
 292         struct strbuf current_path;
 293
 294         current_path.buf = xmalloc(PATH_MAX);
 295         current_path.alloc = PATH_MAX;
 296         current_path.len = current_path.eof = 0;
 297
 298         setup_git_directory();
 299
 300         switch (argc) {
 301         case 3:
 302                 strbuf_append_string(&current_path, argv[2]);
 303                 strbuf_append_string(&current_path, "/");
 304                 /* FALLTHROUGH */
 305         case 2:
 306                 if (get_sha1(argv[1], sha1) < 0)
 307                         usage(tar_tree_usage);
 308                 break;
 309         default:
 310                 usage(tar_tree_usage);
 311         }
 312
 313         commit = lookup_commit_reference_gently(sha1, 1);
 314         if (commit) {
 315                 write_global_extended_header(commit->object.sha1);
 316                 archive_time = commit->date;
 317         } else
 318                 archive_time = time(NULL);
 319
 320         tree.buf = read_object_with_reference(sha1, "tree", &tree.size,
 321                                               tree_sha1);
 322         if (!tree.buf)
 323                 die("not a reference to a tag, commit or tree object: %s",
 324                     sha1_to_hex(sha1));
 325
 326         if (current_path.len > 0)
 327                 write_entry(tree_sha1, &current_path, 040777, NULL, 0);
 328         traverse_tree(&tree, &current_path);
 329         write_trailer();
 330         free(current_path.buf);
 331         return 0;
 332 }