pack-write.c

   1 #include "cache.h"
   2 #include "pack.h"
   3 #include "csum-file.h"
   4
   5 uint32_t pack_idx_default_version = 1;
   6 uint32_t pack_idx_off32_limit = 0x7fffffff;
   7
   8 static int sha1_compare(const void *_a, const void *_b)
   9 {
  10         struct pack_idx_entry *a = *(struct pack_idx_entry **)_a;
  11         struct pack_idx_entry *b = *(struct pack_idx_entry **)_b;
  12         return hashcmp(a->sha1, b->sha1);
  13 }
  14
  15 /*
  16  * On entry *sha1 contains the pack content SHA1 hash, on exit it is
  17  * the SHA1 hash of sorted object names. The objects array passed in
  18  * will be sorted by SHA1 on exit.
  19  */
  20 const char *write_idx_file(const char *index_name, struct pack_idx_entry **objects, int nr_objects, unsigned char *sha1)
  21 {
  22         struct sha1file *f;
  23         struct pack_idx_entry **sorted_by_sha, **list, **last;
  24         off_t last_obj_offset = 0;
  25         uint32_t array[256];
  26         int i, fd;
  27         SHA_CTX ctx;
  28         uint32_t index_version;
  29
  30         if (nr_objects) {
  31                 sorted_by_sha = objects;
  32                 list = sorted_by_sha;
  33                 last = sorted_by_sha + nr_objects;
  34                 for (i = 0; i < nr_objects; ++i) {
  35                         if (objects[i]->offset > last_obj_offset)
  36                                 last_obj_offset = objects[i]->offset;
  37                 }
  38                 qsort(sorted_by_sha, nr_objects, sizeof(sorted_by_sha[0]),
  39                       sha1_compare);
  40         }
  41         else
  42                 sorted_by_sha = list = last = NULL;
  43
  44         if (!index_name) {
  45                 static char tmpfile[PATH_MAX];
  46                 snprintf(tmpfile, sizeof(tmpfile),
  47                          "%s/tmp_idx_XXXXXX", get_object_directory());
  48                 fd = mkstemp(tmpfile);
  49                 index_name = xstrdup(tmpfile);
  50         } else {
  51                 unlink(index_name);
  52                 fd = open(index_name, O_CREAT|O_EXCL|O_WRONLY, 0600);
  53         }
  54         if (fd < 0)
  55                 die("unable to create %s: %s", index_name, strerror(errno));
  56         f = sha1fd(fd, index_name);
  57
  58         /* if last object's offset is >= 2^31 we should use index V2 */
  59         index_version = (last_obj_offset >> 31) ? 2 : pack_idx_default_version;
  60
  61         /* index versions 2 and above need a header */
  62         if (index_version >= 2) {
  63                 struct pack_idx_header hdr;
  64                 hdr.idx_signature = htonl(PACK_IDX_SIGNATURE);
  65                 hdr.idx_version = htonl(index_version);
  66                 sha1write(f, &hdr, sizeof(hdr));
  67         }
  68
  69         /*
  70          * Write the first-level table (the list is sorted,
  71          * but we use a 256-entry lookup to be able to avoid
  72          * having to do eight extra binary search iterations).
  73          */
  74         for (i = 0; i < 256; i++) {
  75                 struct pack_idx_entry **next = list;
  76                 while (next < last) {
  77                         struct pack_idx_entry *obj = *next;
  78                         if (obj->sha1[0] != i)
  79                                 break;
  80                         next++;
  81                 }
  82                 array[i] = htonl(next - sorted_by_sha);
  83                 list = next;
  84         }
  85         sha1write(f, array, 256 * 4);
  86
  87         /* compute the SHA1 hash of sorted object names. */
  88         SHA1_Init(&ctx);
  89
  90         /*
  91          * Write the actual SHA1 entries..
  92          */
  93         list = sorted_by_sha;
  94         for (i = 0; i < nr_objects; i++) {
  95                 struct pack_idx_entry *obj = *list++;
  96                 if (index_version < 2) {
  97                         uint32_t offset = htonl(obj->offset);
  98                         sha1write(f, &offset, 4);
  99                 }
 100                 sha1write(f, obj->sha1, 20);
 101                 SHA1_Update(&ctx, obj->sha1, 20);
 102         }
 103
 104         if (index_version >= 2) {
 105                 unsigned int nr_large_offset = 0;
 106
 107                 /* write the crc32 table */
 108                 list = sorted_by_sha;
 109                 for (i = 0; i < nr_objects; i++) {
 110                         struct pack_idx_entry *obj = *list++;
 111                         uint32_t crc32_val = htonl(obj->crc32);
 112                         sha1write(f, &crc32_val, 4);
 113                 }
 114
 115                 /* write the 32-bit offset table */
 116                 list = sorted_by_sha;
 117                 for (i = 0; i < nr_objects; i++) {
 118                         struct pack_idx_entry *obj = *list++;
 119                         uint32_t offset = (obj->offset <= pack_idx_off32_limit) ?
 120                                 obj->offset : (0x80000000 | nr_large_offset++);
 121                         offset = htonl(offset);
 122                         sha1write(f, &offset, 4);
 123                 }
 124
 125                 /* write the large offset table */
 126                 list = sorted_by_sha;
 127                 while (nr_large_offset) {
 128                         struct pack_idx_entry *obj = *list++;
 129                         uint64_t offset = obj->offset;
 130                         if (offset > pack_idx_off32_limit) {
 131                                 uint32_t split[2];
 132                                 split[0] = htonl(offset >> 32);
 133                                 split[1] = htonl(offset & 0xffffffff);
 134                                 sha1write(f, split, 8);
 135                                 nr_large_offset--;
 136                         }
 137                 }
 138         }
 139
 140         sha1write(f, sha1, 20);
 141         sha1close(f, NULL, 1);
 142         SHA1_Final(sha1, &ctx);
 143         return index_name;
 144 }
 145
 146 void fixup_pack_header_footer(int pack_fd,
 147                          unsigned char *pack_file_sha1,
 148                          const char *pack_name,
 149                          uint32_t object_count)
 150 {
 151         static const int buf_sz = 128 * 1024;
 152         SHA_CTX c;
 153         struct pack_header hdr;
 154         char *buf;
 155
 156         if (lseek(pack_fd, 0, SEEK_SET) != 0)
 157                 die("Failed seeking to start: %s", strerror(errno));
 158         if (read_in_full(pack_fd, &hdr, sizeof(hdr)) != sizeof(hdr))
 159                 die("Unable to reread header of %s: %s", pack_name, strerror(errno));
 160         if (lseek(pack_fd, 0, SEEK_SET) != 0)
 161                 die("Failed seeking to start: %s", strerror(errno));
 162         hdr.hdr_entries = htonl(object_count);
 163         write_or_die(pack_fd, &hdr, sizeof(hdr));
 164
 165         SHA1_Init(&c);
 166         SHA1_Update(&c, &hdr, sizeof(hdr));
 167
 168         buf = xmalloc(buf_sz);
 169         for (;;) {
 170                 ssize_t n = xread(pack_fd, buf, buf_sz);
 171                 if (!n)
 172                         break;
 173                 if (n < 0)
 174                         die("Failed to checksum %s: %s", pack_name, strerror(errno));
 175                 SHA1_Update(&c, buf, n);
 176         }
 177         free(buf);
 178
 179         SHA1_Final(pack_file_sha1, &c);
 180         write_or_die(pack_fd, pack_file_sha1, 20);
 181 }