archive-tar.c

   1 /*
   2  * Copyright (c) 2005, 2006 Rene Scharfe
   3  */
   4 #include "cache.h"
   5 #include "tar.h"
   6 #include "archive.h"
   7
   8 #define RECORDSIZE      (512)
   9 #define BLOCKSIZE       (RECORDSIZE * 20)
  10
  11 static char block[BLOCKSIZE];
  12 static unsigned long offset;
  13
  14 static int tar_umask = 002;
  15
  16 /* writes out the whole block, but only if it is full */
  17 static void write_if_needed(void)
  18 {
  19         if (offset == BLOCKSIZE) {
  20                 write_or_die(1, block, BLOCKSIZE);
  21                 offset = 0;
  22         }
  23 }
  24
  25 /*
  26  * queues up writes, so that all our write(2) calls write exactly one
  27  * full block; pads writes to RECORDSIZE
  28  */
  29 static void write_blocked(const void *data, unsigned long size)
  30 {
  31         const char *buf = data;
  32         unsigned long tail;
  33
  34         if (offset) {
  35                 unsigned long chunk = BLOCKSIZE - offset;
  36                 if (size < chunk)
  37                         chunk = size;
  38                 memcpy(block + offset, buf, chunk);
  39                 size -= chunk;
  40                 offset += chunk;
  41                 buf += chunk;
  42                 write_if_needed();
  43         }
  44         while (size >= BLOCKSIZE) {
  45                 write_or_die(1, buf, BLOCKSIZE);
  46                 size -= BLOCKSIZE;
  47                 buf += BLOCKSIZE;
  48         }
  49         if (size) {
  50                 memcpy(block + offset, buf, size);
  51                 offset += size;
  52         }
  53         tail = offset % RECORDSIZE;
  54         if (tail)  {
  55                 memset(block + offset, 0, RECORDSIZE - tail);
  56                 offset += RECORDSIZE - tail;
  57         }
  58         write_if_needed();
  59 }
  60
  61 /*
  62  * The end of tar archives is marked by 2*512 nul bytes and after that
  63  * follows the rest of the block (if any).
  64  */
  65 static void write_trailer(void)
  66 {
  67         int tail = BLOCKSIZE - offset;
  68         memset(block + offset, 0, tail);
  69         write_or_die(1, block, BLOCKSIZE);
  70         if (tail < 2 * RECORDSIZE) {
  71                 memset(block, 0, offset);
  72                 write_or_die(1, block, BLOCKSIZE);
  73         }
  74 }
  75
  76 /*
  77  * pax extended header records have the format "%u %s=%s\n".  %u contains
  78  * the size of the whole string (including the %u), the first %s is the
  79  * keyword, the second one is the value.  This function constructs such a
  80  * string and appends it to a struct strbuf.
  81  */
  82 static void strbuf_append_ext_header(struct strbuf *sb, const char *keyword,
  83                                      const char *value, unsigned int valuelen)
  84 {
  85         int len, tmp;
  86
  87         /* "%u %s=%s\n" */
  88         len = 1 + 1 + strlen(keyword) + 1 + valuelen + 1;
  89         for (tmp = len; tmp > 9; tmp /= 10)
  90                 len++;
  91
  92         strbuf_grow(sb, len);
  93         strbuf_addf(sb, "%u %s=", len, keyword);
  94         strbuf_add(sb, value, valuelen);
  95         strbuf_addch(sb, '\n');
  96 }
  97
  98 static unsigned int ustar_header_chksum(const struct ustar_header *header)
  99 {
 100         char *p = (char *)header;
 101         unsigned int chksum = 0;
 102         while (p < header->chksum)
 103                 chksum += *p++;
 104         chksum += sizeof(header->chksum) * ' ';
 105         p += sizeof(header->chksum);
 106         while (p < (char *)header + sizeof(struct ustar_header))
 107                 chksum += *p++;
 108         return chksum;
 109 }
 110
 111 static size_t get_path_prefix(const char *path, size_t pathlen, size_t maxlen)
 112 {
 113         size_t i = pathlen;
 114         if (i > maxlen)
 115                 i = maxlen;
 116         do {
 117                 i--;
 118         } while (i > 0 && path[i] != '/');
 119         return i;
 120 }
 121
 122 static int write_tar_entry(struct archiver_args *args,
 123                 const unsigned char *sha1, const char *path, size_t pathlen,
 124                 unsigned int mode, void *buffer, unsigned long size)
 125 {
 126         struct ustar_header header;
 127         struct strbuf ext_header = STRBUF_INIT;
 128         int err = 0;
 129
 130         memset(&header, 0, sizeof(header));
 131
 132         if (!sha1) {
 133                 *header.typeflag = TYPEFLAG_GLOBAL_HEADER;
 134                 mode = 0100666;
 135                 strcpy(header.name, "pax_global_header");
 136         } else if (!path) {
 137                 *header.typeflag = TYPEFLAG_EXT_HEADER;
 138                 mode = 0100666;
 139                 sprintf(header.name, "%s.paxheader", sha1_to_hex(sha1));
 140         } else {
 141                 if (S_ISDIR(mode) || S_ISGITLINK(mode)) {
 142                         *header.typeflag = TYPEFLAG_DIR;
 143                         mode = (mode | 0777) & ~tar_umask;
 144                 } else if (S_ISLNK(mode)) {
 145                         *header.typeflag = TYPEFLAG_LNK;
 146                         mode |= 0777;
 147                 } else if (S_ISREG(mode)) {
 148                         *header.typeflag = TYPEFLAG_REG;
 149                         mode = (mode | ((mode & 0100) ? 0777 : 0666)) & ~tar_umask;
 150                 } else {
 151                         return error("unsupported file mode: 0%o (SHA1: %s)",
 152                                         mode, sha1_to_hex(sha1));
 153                 }
 154                 if (pathlen > sizeof(header.name)) {
 155                         size_t plen = get_path_prefix(path, pathlen,
 156                                         sizeof(header.prefix));
 157                         size_t rest = pathlen - plen - 1;
 158                         if (plen > 0 && rest <= sizeof(header.name)) {
 159                                 memcpy(header.prefix, path, plen);
 160                                 memcpy(header.name, path + plen + 1, rest);
 161                         } else {
 162                                 sprintf(header.name, "%s.data",
 163                                         sha1_to_hex(sha1));
 164                                 strbuf_append_ext_header(&ext_header, "path",
 165                                                 path, pathlen);
 166                         }
 167                 } else
 168                         memcpy(header.name, path, pathlen);
 169         }
 170
 171         if (S_ISLNK(mode) && buffer) {
 172                 if (size > sizeof(header.linkname)) {
 173                         sprintf(header.linkname, "see %s.paxheader",
 174                                 sha1_to_hex(sha1));
 175                         strbuf_append_ext_header(&ext_header, "linkpath",
 176                                                  buffer, size);
 177                 } else
 178                         memcpy(header.linkname, buffer, size);
 179         }
 180
 181         sprintf(header.mode, "%07o", mode & 07777);
 182         sprintf(header.size, "%011lo", S_ISREG(mode) ? size : 0);
 183         sprintf(header.mtime, "%011lo", (unsigned long) args->time);
 184
 185         sprintf(header.uid, "%07o", 0);
 186         sprintf(header.gid, "%07o", 0);
 187         strlcpy(header.uname, "root", sizeof(header.uname));
 188         strlcpy(header.gname, "root", sizeof(header.gname));
 189         sprintf(header.devmajor, "%07o", 0);
 190         sprintf(header.devminor, "%07o", 0);
 191
 192         memcpy(header.magic, "ustar", 6);
 193         memcpy(header.version, "00", 2);
 194
 195         sprintf(header.chksum, "%07o", ustar_header_chksum(&header));
 196
 197         if (ext_header.len > 0) {
 198                 err = write_tar_entry(args, sha1, NULL, 0, 0, ext_header.buf,
 199                                 ext_header.len);
 200                 if (err)
 201                         return err;
 202         }
 203         strbuf_release(&ext_header);
 204         write_blocked(&header, sizeof(header));
 205         if (S_ISREG(mode) && buffer && size > 0)
 206                 write_blocked(buffer, size);
 207         return err;
 208 }
 209
 210 static int write_global_extended_header(struct archiver_args *args)
 211 {
 212         const unsigned char *sha1 = args->commit_sha1;
 213         struct strbuf ext_header = STRBUF_INIT;
 214         int err;
 215
 216         strbuf_append_ext_header(&ext_header, "comment", sha1_to_hex(sha1), 40);
 217         err = write_tar_entry(args, NULL, NULL, 0, 0, ext_header.buf,
 218                         ext_header.len);
 219         strbuf_release(&ext_header);
 220         return err;
 221 }
 222
 223 static int git_tar_config(const char *var, const char *value, void *cb)
 224 {
 225         if (!strcmp(var, "tar.umask")) {
 226                 if (value && !strcmp(value, "user")) {
 227                         tar_umask = umask(0);
 228                         umask(tar_umask);
 229                 } else {
 230                         tar_umask = git_config_int(var, value);
 231                 }
 232                 return 0;
 233         }
 234         return git_default_config(var, value, cb);
 235 }
 236
 237 int write_tar_archive(struct archiver_args *args)
 238 {
 239         int err = 0;
 240
 241         git_config(git_tar_config, NULL);
 242
 243         if (args->commit_sha1)
 244                 err = write_global_extended_header(args);
 245         if (!err)
 246                 err = write_archive_entries(args, write_tar_entry);
 247         if (!err)
 248                 write_trailer();
 249         return err;
 250 }