diff options
Diffstat (limited to 'pack-write.c')
| -rw-r--r-- | pack-write.c | 282 |
1 files changed, 282 insertions, 0 deletions
diff --git a/pack-write.c b/pack-write.c new file mode 100644 index 0000000..a905ca4 --- /dev/null +++ b/pack-write.c @@ -0,0 +1,282 @@ +#include "cache.h" +#include "pack.h" +#include "csum-file.h" + +uint32_t pack_idx_default_version = 2; +uint32_t pack_idx_off32_limit = 0x7fffffff; + +static int sha1_compare(const void *_a, const void *_b) +{ + struct pack_idx_entry *a = *(struct pack_idx_entry **)_a; + struct pack_idx_entry *b = *(struct pack_idx_entry **)_b; + return hashcmp(a->sha1, b->sha1); +} + +/* + * On entry *sha1 contains the pack content SHA1 hash, on exit it is + * the SHA1 hash of sorted object names. The objects array passed in + * will be sorted by SHA1 on exit. + */ +const char *write_idx_file(const char *index_name, struct pack_idx_entry **objects, + int nr_objects, unsigned char *sha1) +{ + struct sha1file *f; + struct pack_idx_entry **sorted_by_sha, **list, **last; + off_t last_obj_offset = 0; + uint32_t array[256]; + int i, fd; + git_SHA_CTX ctx; + uint32_t index_version; + + if (nr_objects) { + sorted_by_sha = objects; + list = sorted_by_sha; + last = sorted_by_sha + nr_objects; + for (i = 0; i < nr_objects; ++i) { + if (objects[i]->offset > last_obj_offset) + last_obj_offset = objects[i]->offset; + } + qsort(sorted_by_sha, nr_objects, sizeof(sorted_by_sha[0]), + sha1_compare); + } + else + sorted_by_sha = list = last = NULL; + + if (!index_name) { + static char tmpfile[PATH_MAX]; + fd = odb_mkstemp(tmpfile, sizeof(tmpfile), "pack/tmp_idx_XXXXXX"); + index_name = xstrdup(tmpfile); + } else { + unlink(index_name); + fd = open(index_name, O_CREAT|O_EXCL|O_WRONLY, 0600); + } + if (fd < 0) + die_errno("unable to create '%s'", index_name); + f = sha1fd(fd, index_name); + + /* if last object's offset is >= 2^31 we should use index V2 */ + index_version = (last_obj_offset >> 31) ? 2 : pack_idx_default_version; + + /* index versions 2 and above need a header */ + if (index_version >= 2) { + struct pack_idx_header hdr; + hdr.idx_signature = htonl(PACK_IDX_SIGNATURE); + hdr.idx_version = htonl(index_version); + sha1write(f, &hdr, sizeof(hdr)); + } + + /* + * Write the first-level table (the list is sorted, + * but we use a 256-entry lookup to be able to avoid + * having to do eight extra binary search iterations). + */ + for (i = 0; i < 256; i++) { + struct pack_idx_entry **next = list; + while (next < last) { + struct pack_idx_entry *obj = *next; + if (obj->sha1[0] != i) + break; + next++; + } + array[i] = htonl(next - sorted_by_sha); + list = next; + } + sha1write(f, array, 256 * 4); + + /* compute the SHA1 hash of sorted object names. */ + git_SHA1_Init(&ctx); + + /* + * Write the actual SHA1 entries.. + */ + list = sorted_by_sha; + for (i = 0; i < nr_objects; i++) { + struct pack_idx_entry *obj = *list++; + if (index_version < 2) { + uint32_t offset = htonl(obj->offset); + sha1write(f, &offset, 4); + } + sha1write(f, obj->sha1, 20); + git_SHA1_Update(&ctx, obj->sha1, 20); + } + + if (index_version >= 2) { + unsigned int nr_large_offset = 0; + + /* write the crc32 table */ + list = sorted_by_sha; + for (i = 0; i < nr_objects; i++) { + struct pack_idx_entry *obj = *list++; + uint32_t crc32_val = htonl(obj->crc32); + sha1write(f, &crc32_val, 4); + } + + /* write the 32-bit offset table */ + list = sorted_by_sha; + for (i = 0; i < nr_objects; i++) { + struct pack_idx_entry *obj = *list++; + uint32_t offset = (obj->offset <= pack_idx_off32_limit) ? + obj->offset : (0x80000000 | nr_large_offset++); + offset = htonl(offset); + sha1write(f, &offset, 4); + } + + /* write the large offset table */ + list = sorted_by_sha; + while (nr_large_offset) { + struct pack_idx_entry *obj = *list++; + uint64_t offset = obj->offset; + if (offset > pack_idx_off32_limit) { + uint32_t split[2]; + split[0] = htonl(offset >> 32); + split[1] = htonl(offset & 0xffffffff); + sha1write(f, split, 8); + nr_large_offset--; + } + } + } + + sha1write(f, sha1, 20); + sha1close(f, NULL, CSUM_FSYNC); + git_SHA1_Final(sha1, &ctx); + return index_name; +} + +/* + * Update pack header with object_count and compute new SHA1 for pack data + * associated to pack_fd, and write that SHA1 at the end. That new SHA1 + * is also returned in new_pack_sha1. + * + * If partial_pack_sha1 is non null, then the SHA1 of the existing pack + * (without the header update) is computed and validated against the + * one provided in partial_pack_sha1. The validation is performed at + * partial_pack_offset bytes in the pack file. The SHA1 of the remaining + * data (i.e. from partial_pack_offset to the end) is then computed and + * returned in partial_pack_sha1. + * + * Note that new_pack_sha1 is updated last, so both new_pack_sha1 and + * partial_pack_sha1 can refer to the same buffer if the caller is not + * interested in the resulting SHA1 of pack data above partial_pack_offset. + */ +void fixup_pack_header_footer(int pack_fd, + unsigned char *new_pack_sha1, + const char *pack_name, + uint32_t object_count, + unsigned char *partial_pack_sha1, + off_t partial_pack_offset) +{ + int aligned_sz, buf_sz = 8 * 1024; + git_SHA_CTX old_sha1_ctx, new_sha1_ctx; + struct pack_header hdr; + char *buf; + + git_SHA1_Init(&old_sha1_ctx); + git_SHA1_Init(&new_sha1_ctx); + + if (lseek(pack_fd, 0, SEEK_SET) != 0) + die_errno("Failed seeking to start of '%s'", pack_name); + if (read_in_full(pack_fd, &hdr, sizeof(hdr)) != sizeof(hdr)) + die_errno("Unable to reread header of '%s'", pack_name); + if (lseek(pack_fd, 0, SEEK_SET) != 0) + die_errno("Failed seeking to start of '%s'", pack_name); + git_SHA1_Update(&old_sha1_ctx, &hdr, sizeof(hdr)); + hdr.hdr_entries = htonl(object_count); + git_SHA1_Update(&new_sha1_ctx, &hdr, sizeof(hdr)); + write_or_die(pack_fd, &hdr, sizeof(hdr)); + partial_pack_offset -= sizeof(hdr); + + buf = xmalloc(buf_sz); + aligned_sz = buf_sz - sizeof(hdr); + for (;;) { + ssize_t m, n; + m = (partial_pack_sha1 && partial_pack_offset < aligned_sz) ? + partial_pack_offset : aligned_sz; + n = xread(pack_fd, buf, m); + if (!n) + break; + if (n < 0) + die_errno("Failed to checksum '%s'", pack_name); + git_SHA1_Update(&new_sha1_ctx, buf, n); + + aligned_sz -= n; + if (!aligned_sz) + aligned_sz = buf_sz; + + if (!partial_pack_sha1) + continue; + + git_SHA1_Update(&old_sha1_ctx, buf, n); + partial_pack_offset -= n; + if (partial_pack_offset == 0) { + unsigned char sha1[20]; + git_SHA1_Final(sha1, &old_sha1_ctx); + if (hashcmp(sha1, partial_pack_sha1) != 0) + die("Unexpected checksum for %s " + "(disk corruption?)", pack_name); + /* + * Now let's compute the SHA1 of the remainder of the + * pack, which also means making partial_pack_offset + * big enough not to matter anymore. + */ + git_SHA1_Init(&old_sha1_ctx); + partial_pack_offset = ~partial_pack_offset; + partial_pack_offset -= MSB(partial_pack_offset, 1); + } + } + free(buf); + + if (partial_pack_sha1) + git_SHA1_Final(partial_pack_sha1, &old_sha1_ctx); + git_SHA1_Final(new_pack_sha1, &new_sha1_ctx); + write_or_die(pack_fd, new_pack_sha1, 20); + fsync_or_die(pack_fd, pack_name); +} + +char *index_pack_lockfile(int ip_out) +{ + char packname[46]; + + /* + * The first thing we expect from index-pack's output + * is "pack\t%40s\n" or "keep\t%40s\n" (46 bytes) where + * %40s is the newly created pack SHA1 name. In the "keep" + * case, we need it to remove the corresponding .keep file + * later on. If we don't get that then tough luck with it. + */ + if (read_in_full(ip_out, packname, 46) == 46 && packname[45] == '\n' && + memcmp(packname, "keep\t", 5) == 0) { + char path[PATH_MAX]; + packname[45] = 0; + snprintf(path, sizeof(path), "%s/pack/pack-%s.keep", + get_object_directory(), packname + 5); + return xstrdup(path); + } + return NULL; +} + +/* + * The per-object header is a pretty dense thing, which is + * - first byte: low four bits are "size", then three bits of "type", + * and the high bit is "size continues". + * - each byte afterwards: low seven bits are size continuation, + * with the high bit being "size continues" + */ +int encode_in_pack_object_header(enum object_type type, uintmax_t size, unsigned char *hdr) +{ + int n = 1; + unsigned char c; + + if (type < OBJ_COMMIT || type > OBJ_REF_DELTA) + die("bad type %d", type); + + c = (type << 4) | (size & 15); + size >>= 4; + while (size) { + *hdr++ = c | 0x80; + c = size & 0x7f; + size >>= 7; + n++; + } + *hdr = c; + return n; +} |