midx.c

   1 #include "cache.h"
   2 #include "csum-file.h"
   3 #include "lockfile.h"
   4 #include "midx.h"
   5
   6 #define MIDX_SIGNATURE 0x4d494458 /* "MIDX" */
   7 #define MIDX_VERSION 1
   8 #define MIDX_HASH_VERSION 1
   9 #define MIDX_HEADER_SIZE 12
  10
  11 static char *get_midx_filename(const char *object_dir)
  12 {
  13         return xstrfmt("%s/pack/multi-pack-index", object_dir);
  14 }
  15
  16 static size_t write_midx_header(struct hashfile *f,
  17                                 unsigned char num_chunks,
  18                                 uint32_t num_packs)
  19 {
  20         unsigned char byte_values[4];
  21
  22         hashwrite_be32(f, MIDX_SIGNATURE);
  23         byte_values[0] = MIDX_VERSION;
  24         byte_values[1] = MIDX_HASH_VERSION;
  25         byte_values[2] = num_chunks;
  26         byte_values[3] = 0; /* unused */
  27         hashwrite(f, byte_values, sizeof(byte_values));
  28         hashwrite_be32(f, num_packs);
  29
  30         return MIDX_HEADER_SIZE;
  31 }
  32
  33 int write_midx_file(const char *object_dir)
  34 {
  35         unsigned char num_chunks = 0;
  36         char *midx_name;
  37         struct hashfile *f = NULL;
  38         struct lock_file lk;
  39
  40         midx_name = get_midx_filename(object_dir);
  41         if (safe_create_leading_directories(midx_name)) {
  42                 UNLEAK(midx_name);
  43                 die_errno(_("unable to create leading directories of %s"),
  44                           midx_name);
  45         }
  46
  47         hold_lock_file_for_update(&lk, midx_name, LOCK_DIE_ON_ERROR);
  48         f = hashfd(lk.tempfile->fd, lk.tempfile->filename.buf);
  49         FREE_AND_NULL(midx_name);
  50
  51         write_midx_header(f, num_chunks, 0);
  52
  53         finalize_hashfile(f, NULL, CSUM_FSYNC | CSUM_HASH_IN_STREAM);
  54         commit_lock_file(&lk);
  55
  56         return 0;
  57 }