16529c39a9fc7a3245c6bca8f1df5f8920c31201
   1#include "cache.h"
   2#include "pack.h"
   3#include "csum-file.h"
   4
   5void reset_pack_idx_option(struct pack_idx_option *opts)
   6{
   7        memset(opts, 0, sizeof(*opts));
   8        opts->version = 2;
   9        opts->off32_limit = 0x7fffffff;
  10}
  11
  12static int sha1_compare(const void *_a, const void *_b)
  13{
  14        struct pack_idx_entry *a = *(struct pack_idx_entry **)_a;
  15        struct pack_idx_entry *b = *(struct pack_idx_entry **)_b;
  16        return hashcmp(a->sha1, b->sha1);
  17}
  18
  19/*
  20 * On entry *sha1 contains the pack content SHA1 hash, on exit it is
  21 * the SHA1 hash of sorted object names. The objects array passed in
  22 * will be sorted by SHA1 on exit.
  23 */
  24const char *write_idx_file(const char *index_name, struct pack_idx_entry **objects,
  25                           int nr_objects, const struct pack_idx_option *opts,
  26                           unsigned char *sha1)
  27{
  28        struct sha1file *f;
  29        struct pack_idx_entry **sorted_by_sha, **list, **last;
  30        off_t last_obj_offset = 0;
  31        uint32_t array[256];
  32        int i, fd;
  33        git_SHA_CTX ctx;
  34        uint32_t index_version;
  35
  36        if (nr_objects) {
  37                sorted_by_sha = objects;
  38                list = sorted_by_sha;
  39                last = sorted_by_sha + nr_objects;
  40                for (i = 0; i < nr_objects; ++i) {
  41                        if (objects[i]->offset > last_obj_offset)
  42                                last_obj_offset = objects[i]->offset;
  43                }
  44                qsort(sorted_by_sha, nr_objects, sizeof(sorted_by_sha[0]),
  45                      sha1_compare);
  46        }
  47        else
  48                sorted_by_sha = list = last = NULL;
  49
  50        if (opts->flags & WRITE_IDX_VERIFY) {
  51                assert(index_name);
  52                f = sha1fd_check(index_name);
  53        } else {
  54                if (!index_name) {
  55                        static char tmpfile[PATH_MAX];
  56                        fd = odb_mkstemp(tmpfile, sizeof(tmpfile), "pack/tmp_idx_XXXXXX");
  57                        index_name = xstrdup(tmpfile);
  58                } else {
  59                        unlink(index_name);
  60                        fd = open(index_name, O_CREAT|O_EXCL|O_WRONLY, 0600);
  61                }
  62                if (fd < 0)
  63                        die_errno("unable to create '%s'", index_name);
  64                f = sha1fd(fd, index_name);
  65        }
  66
  67        /* if last object's offset is >= 2^31 we should use index V2 */
  68        index_version = (last_obj_offset >> 31) ? 2 : opts->version;
  69
  70        /* index versions 2 and above need a header */
  71        if (index_version >= 2) {
  72                struct pack_idx_header hdr;
  73                hdr.idx_signature = htonl(PACK_IDX_SIGNATURE);
  74                hdr.idx_version = htonl(index_version);
  75                sha1write(f, &hdr, sizeof(hdr));
  76        }
  77
  78        /*
  79         * Write the first-level table (the list is sorted,
  80         * but we use a 256-entry lookup to be able to avoid
  81         * having to do eight extra binary search iterations).
  82         */
  83        for (i = 0; i < 256; i++) {
  84                struct pack_idx_entry **next = list;
  85                while (next < last) {
  86                        struct pack_idx_entry *obj = *next;
  87                        if (obj->sha1[0] != i)
  88                                break;
  89                        next++;
  90                }
  91                array[i] = htonl(next - sorted_by_sha);
  92                list = next;
  93        }
  94        sha1write(f, array, 256 * 4);
  95
  96        /* compute the SHA1 hash of sorted object names. */
  97        git_SHA1_Init(&ctx);
  98
  99        /*
 100         * Write the actual SHA1 entries..
 101         */
 102        list = sorted_by_sha;
 103        for (i = 0; i < nr_objects; i++) {
 104                struct pack_idx_entry *obj = *list++;
 105                if (index_version < 2) {
 106                        uint32_t offset = htonl(obj->offset);
 107                        sha1write(f, &offset, 4);
 108                }
 109                sha1write(f, obj->sha1, 20);
 110                git_SHA1_Update(&ctx, obj->sha1, 20);
 111        }
 112
 113        if (index_version >= 2) {
 114                unsigned int nr_large_offset = 0;
 115
 116                /* write the crc32 table */
 117                list = sorted_by_sha;
 118                for (i = 0; i < nr_objects; i++) {
 119                        struct pack_idx_entry *obj = *list++;
 120                        uint32_t crc32_val = htonl(obj->crc32);
 121                        sha1write(f, &crc32_val, 4);
 122                }
 123
 124                /* write the 32-bit offset table */
 125                list = sorted_by_sha;
 126                for (i = 0; i < nr_objects; i++) {
 127                        struct pack_idx_entry *obj = *list++;
 128                        uint32_t offset = (obj->offset <= opts->off32_limit) ?
 129                                obj->offset : (0x80000000 | nr_large_offset++);
 130                        offset = htonl(offset);
 131                        sha1write(f, &offset, 4);
 132                }
 133
 134                /* write the large offset table */
 135                list = sorted_by_sha;
 136                while (nr_large_offset) {
 137                        struct pack_idx_entry *obj = *list++;
 138                        uint64_t offset = obj->offset;
 139                        if (offset > opts->off32_limit) {
 140                                uint32_t split[2];
 141                                split[0] = htonl(offset >> 32);
 142                                split[1] = htonl(offset & 0xffffffff);
 143                                sha1write(f, split, 8);
 144                                nr_large_offset--;
 145                        }
 146                }
 147        }
 148
 149        sha1write(f, sha1, 20);
 150        sha1close(f, NULL, ((opts->flags & WRITE_IDX_VERIFY)
 151                            ? CSUM_CLOSE : CSUM_FSYNC));
 152        git_SHA1_Final(sha1, &ctx);
 153        return index_name;
 154}
 155
 156/*
 157 * Update pack header with object_count and compute new SHA1 for pack data
 158 * associated to pack_fd, and write that SHA1 at the end.  That new SHA1
 159 * is also returned in new_pack_sha1.
 160 *
 161 * If partial_pack_sha1 is non null, then the SHA1 of the existing pack
 162 * (without the header update) is computed and validated against the
 163 * one provided in partial_pack_sha1.  The validation is performed at
 164 * partial_pack_offset bytes in the pack file.  The SHA1 of the remaining
 165 * data (i.e. from partial_pack_offset to the end) is then computed and
 166 * returned in partial_pack_sha1.
 167 *
 168 * Note that new_pack_sha1 is updated last, so both new_pack_sha1 and
 169 * partial_pack_sha1 can refer to the same buffer if the caller is not
 170 * interested in the resulting SHA1 of pack data above partial_pack_offset.
 171 */
 172void fixup_pack_header_footer(int pack_fd,
 173                         unsigned char *new_pack_sha1,
 174                         const char *pack_name,
 175                         uint32_t object_count,
 176                         unsigned char *partial_pack_sha1,
 177                         off_t partial_pack_offset)
 178{
 179        int aligned_sz, buf_sz = 8 * 1024;
 180        git_SHA_CTX old_sha1_ctx, new_sha1_ctx;
 181        struct pack_header hdr;
 182        char *buf;
 183
 184        git_SHA1_Init(&old_sha1_ctx);
 185        git_SHA1_Init(&new_sha1_ctx);
 186
 187        if (lseek(pack_fd, 0, SEEK_SET) != 0)
 188                die_errno("Failed seeking to start of '%s'", pack_name);
 189        if (read_in_full(pack_fd, &hdr, sizeof(hdr)) != sizeof(hdr))
 190                die_errno("Unable to reread header of '%s'", pack_name);
 191        if (lseek(pack_fd, 0, SEEK_SET) != 0)
 192                die_errno("Failed seeking to start of '%s'", pack_name);
 193        git_SHA1_Update(&old_sha1_ctx, &hdr, sizeof(hdr));
 194        hdr.hdr_entries = htonl(object_count);
 195        git_SHA1_Update(&new_sha1_ctx, &hdr, sizeof(hdr));
 196        write_or_die(pack_fd, &hdr, sizeof(hdr));
 197        partial_pack_offset -= sizeof(hdr);
 198
 199        buf = xmalloc(buf_sz);
 200        aligned_sz = buf_sz - sizeof(hdr);
 201        for (;;) {
 202                ssize_t m, n;
 203                m = (partial_pack_sha1 && partial_pack_offset < aligned_sz) ?
 204                        partial_pack_offset : aligned_sz;
 205                n = xread(pack_fd, buf, m);
 206                if (!n)
 207                        break;
 208                if (n < 0)
 209                        die_errno("Failed to checksum '%s'", pack_name);
 210                git_SHA1_Update(&new_sha1_ctx, buf, n);
 211
 212                aligned_sz -= n;
 213                if (!aligned_sz)
 214                        aligned_sz = buf_sz;
 215
 216                if (!partial_pack_sha1)
 217                        continue;
 218
 219                git_SHA1_Update(&old_sha1_ctx, buf, n);
 220                partial_pack_offset -= n;
 221                if (partial_pack_offset == 0) {
 222                        unsigned char sha1[20];
 223                        git_SHA1_Final(sha1, &old_sha1_ctx);
 224                        if (hashcmp(sha1, partial_pack_sha1) != 0)
 225                                die("Unexpected checksum for %s "
 226                                    "(disk corruption?)", pack_name);
 227                        /*
 228                         * Now let's compute the SHA1 of the remainder of the
 229                         * pack, which also means making partial_pack_offset
 230                         * big enough not to matter anymore.
 231                         */
 232                        git_SHA1_Init(&old_sha1_ctx);
 233                        partial_pack_offset = ~partial_pack_offset;
 234                        partial_pack_offset -= MSB(partial_pack_offset, 1);
 235                }
 236        }
 237        free(buf);
 238
 239        if (partial_pack_sha1)
 240                git_SHA1_Final(partial_pack_sha1, &old_sha1_ctx);
 241        git_SHA1_Final(new_pack_sha1, &new_sha1_ctx);
 242        write_or_die(pack_fd, new_pack_sha1, 20);
 243        fsync_or_die(pack_fd, pack_name);
 244}
 245
 246char *index_pack_lockfile(int ip_out)
 247{
 248        char packname[46];
 249
 250        /*
 251         * The first thing we expect from index-pack's output
 252         * is "pack\t%40s\n" or "keep\t%40s\n" (46 bytes) where
 253         * %40s is the newly created pack SHA1 name.  In the "keep"
 254         * case, we need it to remove the corresponding .keep file
 255         * later on.  If we don't get that then tough luck with it.
 256         */
 257        if (read_in_full(ip_out, packname, 46) == 46 && packname[45] == '\n' &&
 258            memcmp(packname, "keep\t", 5) == 0) {
 259                char path[PATH_MAX];
 260                packname[45] = 0;
 261                snprintf(path, sizeof(path), "%s/pack/pack-%s.keep",
 262                         get_object_directory(), packname + 5);
 263                return xstrdup(path);
 264        }
 265        return NULL;
 266}
 267
 268/*
 269 * The per-object header is a pretty dense thing, which is
 270 *  - first byte: low four bits are "size", then three bits of "type",
 271 *    and the high bit is "size continues".
 272 *  - each byte afterwards: low seven bits are size continuation,
 273 *    with the high bit being "size continues"
 274 */
 275int encode_in_pack_object_header(enum object_type type, uintmax_t size, unsigned char *hdr)
 276{
 277        int n = 1;
 278        unsigned char c;
 279
 280        if (type < OBJ_COMMIT || type > OBJ_REF_DELTA)
 281                die("bad type %d", type);
 282
 283        c = (type << 4) | (size & 15);
 284        size >>= 4;
 285        while (size) {
 286                *hdr++ = c | 0x80;
 287                c = size & 0x7f;
 288                size >>= 7;
 289                n++;
 290        }
 291        *hdr = c;
 292        return n;
 293}