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 char *write_idx_file(char *index_name, struct pack_idx_entry **objects,
  21                      int nr_objects, unsigned char *sha1)
  22 {
  23         struct sha1file *f;
  24         struct pack_idx_entry **sorted_by_sha, **list, **last;
  25         off_t last_obj_offset = 0;
  26         uint32_t array[256];
  27         int i, fd;
  28         SHA_CTX ctx;
  29         uint32_t index_version;
  30
  31         if (nr_objects) {
  32                 sorted_by_sha = objects;
  33                 list = sorted_by_sha;
  34                 last = sorted_by_sha + nr_objects;
  35                 for (i = 0; i < nr_objects; ++i) {
  36                         if (objects[i]->offset > last_obj_offset)
  37                                 last_obj_offset = objects[i]->offset;
  38                 }
  39                 qsort(sorted_by_sha, nr_objects, sizeof(sorted_by_sha[0]),
  40                       sha1_compare);
  41         }
  42         else
  43                 sorted_by_sha = list = last = NULL;
  44
  45         if (!index_name) {
  46                 static char tmpfile[PATH_MAX];
  47                 snprintf(tmpfile, sizeof(tmpfile),
  48                          "%s/tmp_idx_XXXXXX", get_object_directory());
  49                 fd = xmkstemp(tmpfile);
  50                 index_name = xstrdup(tmpfile);
  51         } else {
  52                 unlink(index_name);
  53                 fd = open(index_name, O_CREAT|O_EXCL|O_WRONLY, 0600);
  54         }
  55         if (fd < 0)
  56                 die("unable to create %s: %s", index_name, strerror(errno));
  57         f = sha1fd(fd, index_name);
  58
  59         /* if last object's offset is >= 2^31 we should use index V2 */
  60         index_version = (last_obj_offset >> 31) ? 2 : pack_idx_default_version;
  61
  62         /* index versions 2 and above need a header */
  63         if (index_version >= 2) {
  64                 struct pack_idx_header hdr;
  65                 hdr.idx_signature = htonl(PACK_IDX_SIGNATURE);
  66                 hdr.idx_version = htonl(index_version);
  67                 sha1write(f, &hdr, sizeof(hdr));
  68         }
  69
  70         /*
  71          * Write the first-level table (the list is sorted,
  72          * but we use a 256-entry lookup to be able to avoid
  73          * having to do eight extra binary search iterations).
  74          */
  75         for (i = 0; i < 256; i++) {
  76                 struct pack_idx_entry **next = list;
  77                 while (next < last) {
  78                         struct pack_idx_entry *obj = *next;
  79                         if (obj->sha1[0] != i)
  80                                 break;
  81                         next++;
  82                 }
  83                 array[i] = htonl(next - sorted_by_sha);
  84                 list = next;
  85         }
  86         sha1write(f, array, 256 * 4);
  87
  88         /* compute the SHA1 hash of sorted object names. */
  89         SHA1_Init(&ctx);
  90
  91         /*
  92          * Write the actual SHA1 entries..
  93          */
  94         list = sorted_by_sha;
  95         for (i = 0; i < nr_objects; i++) {
  96                 struct pack_idx_entry *obj = *list++;
  97                 if (index_version < 2) {
  98                         uint32_t offset = htonl(obj->offset);
  99                         sha1write(f, &offset, 4);
 100                 }
 101                 sha1write(f, obj->sha1, 20);
 102                 SHA1_Update(&ctx, obj->sha1, 20);
 103         }
 104
 105         if (index_version >= 2) {
 106                 unsigned int nr_large_offset = 0;
 107
 108                 /* write the crc32 table */
 109                 list = sorted_by_sha;
 110                 for (i = 0; i < nr_objects; i++) {
 111                         struct pack_idx_entry *obj = *list++;
 112                         uint32_t crc32_val = htonl(obj->crc32);
 113                         sha1write(f, &crc32_val, 4);
 114                 }
 115
 116                 /* write the 32-bit offset table */
 117                 list = sorted_by_sha;
 118                 for (i = 0; i < nr_objects; i++) {
 119                         struct pack_idx_entry *obj = *list++;
 120                         uint32_t offset = (obj->offset <= pack_idx_off32_limit) ?
 121                                 obj->offset : (0x80000000 | nr_large_offset++);
 122                         offset = htonl(offset);
 123                         sha1write(f, &offset, 4);
 124                 }
 125
 126                 /* write the large offset table */
 127                 list = sorted_by_sha;
 128                 while (nr_large_offset) {
 129                         struct pack_idx_entry *obj = *list++;
 130                         uint64_t offset = obj->offset;
 131                         if (offset > pack_idx_off32_limit) {
 132                                 uint32_t split[2];
 133                                 split[0] = htonl(offset >> 32);
 134                                 split[1] = htonl(offset & 0xffffffff);
 135                                 sha1write(f, split, 8);
 136                                 nr_large_offset--;
 137                         }
 138                 }
 139         }
 140
 141         sha1write(f, sha1, 20);
 142         sha1close(f, NULL, 1);
 143         SHA1_Final(sha1, &ctx);
 144         return index_name;
 145 }
 146
 147 void fixup_pack_header_footer(int pack_fd,
 148                          unsigned char *pack_file_sha1,
 149                          const char *pack_name,
 150                          uint32_t object_count)
 151 {
 152         static const int buf_sz = 128 * 1024;
 153         SHA_CTX c;
 154         struct pack_header hdr;
 155         char *buf;
 156
 157         if (lseek(pack_fd, 0, SEEK_SET) != 0)
 158                 die("Failed seeking to start: %s", strerror(errno));
 159         if (read_in_full(pack_fd, &hdr, sizeof(hdr)) != sizeof(hdr))
 160                 die("Unable to reread header of %s: %s", pack_name, strerror(errno));
 161         if (lseek(pack_fd, 0, SEEK_SET) != 0)
 162                 die("Failed seeking to start: %s", strerror(errno));
 163         hdr.hdr_entries = htonl(object_count);
 164         write_or_die(pack_fd, &hdr, sizeof(hdr));
 165
 166         SHA1_Init(&c);
 167         SHA1_Update(&c, &hdr, sizeof(hdr));
 168
 169         buf = xmalloc(buf_sz);
 170         for (;;) {
 171                 ssize_t n = xread(pack_fd, buf, buf_sz);
 172                 if (!n)
 173                         break;
 174                 if (n < 0)
 175                         die("Failed to checksum %s: %s", pack_name, strerror(errno));
 176                 SHA1_Update(&c, buf, n);
 177         }
 178         free(buf);
 179
 180         SHA1_Final(pack_file_sha1, &c);
 181         write_or_die(pack_fd, pack_file_sha1, 20);
 182 }