pack-write.con commit Merge git://git.kernel.org/pub/scm/gitk/gitk (39a76bd)
   1#include "cache.h"
   2#include "pack.h"
   3#include "csum-file.h"
   4
   5uint32_t pack_idx_default_version = 2;
   6uint32_t pack_idx_off32_limit = 0x7fffffff;
   7
   8static 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 */
  20char *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        git_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/pack/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        git_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                git_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, CSUM_FSYNC);
 143        git_SHA1_Final(sha1, &ctx);
 144        return index_name;
 145}
 146
 147/*
 148 * Update pack header with object_count and compute new SHA1 for pack data
 149 * associated to pack_fd, and write that SHA1 at the end.  That new SHA1
 150 * is also returned in new_pack_sha1.
 151 *
 152 * If partial_pack_sha1 is non null, then the SHA1 of the existing pack
 153 * (without the header update) is computed and validated against the
 154 * one provided in partial_pack_sha1.  The validation is performed at
 155 * partial_pack_offset bytes in the pack file.  The SHA1 of the remaining
 156 * data (i.e. from partial_pack_offset to the end) is then computed and
 157 * returned in partial_pack_sha1.
 158 *
 159 * Note that new_pack_sha1 is updated last, so both new_pack_sha1 and
 160 * partial_pack_sha1 can refer to the same buffer if the caller is not
 161 * interested in the resulting SHA1 of pack data above partial_pack_offset.
 162 */
 163void fixup_pack_header_footer(int pack_fd,
 164                         unsigned char *new_pack_sha1,
 165                         const char *pack_name,
 166                         uint32_t object_count,
 167                         unsigned char *partial_pack_sha1,
 168                         off_t partial_pack_offset)
 169{
 170        int aligned_sz, buf_sz = 8 * 1024;
 171        git_SHA_CTX old_sha1_ctx, new_sha1_ctx;
 172        struct pack_header hdr;
 173        char *buf;
 174
 175        git_SHA1_Init(&old_sha1_ctx);
 176        git_SHA1_Init(&new_sha1_ctx);
 177
 178        if (lseek(pack_fd, 0, SEEK_SET) != 0)
 179                die("Failed seeking to start of %s: %s", pack_name, strerror(errno));
 180        if (read_in_full(pack_fd, &hdr, sizeof(hdr)) != sizeof(hdr))
 181                die("Unable to reread header of %s: %s", pack_name, strerror(errno));
 182        if (lseek(pack_fd, 0, SEEK_SET) != 0)
 183                die("Failed seeking to start of %s: %s", pack_name, strerror(errno));
 184        git_SHA1_Update(&old_sha1_ctx, &hdr, sizeof(hdr));
 185        hdr.hdr_entries = htonl(object_count);
 186        git_SHA1_Update(&new_sha1_ctx, &hdr, sizeof(hdr));
 187        write_or_die(pack_fd, &hdr, sizeof(hdr));
 188        partial_pack_offset -= sizeof(hdr);
 189
 190        buf = xmalloc(buf_sz);
 191        aligned_sz = buf_sz - sizeof(hdr);
 192        for (;;) {
 193                ssize_t m, n;
 194                m = (partial_pack_sha1 && partial_pack_offset < aligned_sz) ?
 195                        partial_pack_offset : aligned_sz;
 196                n = xread(pack_fd, buf, m);
 197                if (!n)
 198                        break;
 199                if (n < 0)
 200                        die("Failed to checksum %s: %s", pack_name, strerror(errno));
 201                git_SHA1_Update(&new_sha1_ctx, buf, n);
 202
 203                aligned_sz -= n;
 204                if (!aligned_sz)
 205                        aligned_sz = buf_sz;
 206
 207                if (!partial_pack_sha1)
 208                        continue;
 209
 210                git_SHA1_Update(&old_sha1_ctx, buf, n);
 211                partial_pack_offset -= n;
 212                if (partial_pack_offset == 0) {
 213                        unsigned char sha1[20];
 214                        git_SHA1_Final(sha1, &old_sha1_ctx);
 215                        if (hashcmp(sha1, partial_pack_sha1) != 0)
 216                                die("Unexpected checksum for %s "
 217                                    "(disk corruption?)", pack_name);
 218                        /*
 219                         * Now let's compute the SHA1 of the remainder of the
 220                         * pack, which also means making partial_pack_offset
 221                         * big enough not to matter anymore.
 222                         */
 223                        git_SHA1_Init(&old_sha1_ctx);
 224                        partial_pack_offset = ~partial_pack_offset;
 225                        partial_pack_offset -= MSB(partial_pack_offset, 1);
 226                }
 227        }
 228        free(buf);
 229
 230        if (partial_pack_sha1)
 231                git_SHA1_Final(partial_pack_sha1, &old_sha1_ctx);
 232        git_SHA1_Final(new_pack_sha1, &new_sha1_ctx);
 233        write_or_die(pack_fd, new_pack_sha1, 20);
 234        fsync_or_die(pack_fd, pack_name);
 235}
 236
 237char *index_pack_lockfile(int ip_out)
 238{
 239        char packname[46];
 240
 241        /*
 242         * The first thing we expects from index-pack's output
 243         * is "pack\t%40s\n" or "keep\t%40s\n" (46 bytes) where
 244         * %40s is the newly created pack SHA1 name.  In the "keep"
 245         * case, we need it to remove the corresponding .keep file
 246         * later on.  If we don't get that then tough luck with it.
 247         */
 248        if (read_in_full(ip_out, packname, 46) == 46 && packname[45] == '\n' &&
 249            memcmp(packname, "keep\t", 5) == 0) {
 250                char path[PATH_MAX];
 251                packname[45] = 0;
 252                snprintf(path, sizeof(path), "%s/pack/pack-%s.keep",
 253                         get_object_directory(), packname + 5);
 254                return xstrdup(path);
 255        }
 256        return NULL;
 257}