mirror of
https://github.com/git/git
synced 2024-08-25 02:35:46 +00:00
![Jeff King](/assets/img/avatar_default.png)
The point of this function is to drop an entry from the
"packed_git" cache that points to a file we might be
overwriting, because our contents may not be the same (and
hence the only caller was pack-objects as it moved a
temporary packfile into place).
In older versions of git, this could happen because the
names of packfiles were derived from the set of objects they
contained, not the actual bits on disk. But since 1190a1a
(pack-objects: name pack files after trailer hash,
2013-12-05), the name reflects the actual bits on disk, and
any two packfiles with the same name can be used
interchangeably.
Dropping this function not only saves a few lines of code,
it makes the lifetime of "struct packed_git" much easier to
reason about: namely, we now do not ever free these structs.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
371 lines
10 KiB
C
371 lines
10 KiB
C
#include "cache.h"
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#include "pack.h"
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#include "csum-file.h"
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void reset_pack_idx_option(struct pack_idx_option *opts)
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{
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memset(opts, 0, sizeof(*opts));
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opts->version = 2;
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opts->off32_limit = 0x7fffffff;
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}
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static int sha1_compare(const void *_a, const void *_b)
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{
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struct pack_idx_entry *a = *(struct pack_idx_entry **)_a;
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struct pack_idx_entry *b = *(struct pack_idx_entry **)_b;
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return hashcmp(a->sha1, b->sha1);
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}
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static int cmp_uint32(const void *a_, const void *b_)
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{
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uint32_t a = *((uint32_t *)a_);
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uint32_t b = *((uint32_t *)b_);
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return (a < b) ? -1 : (a != b);
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}
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static int need_large_offset(off_t offset, const struct pack_idx_option *opts)
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{
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uint32_t ofsval;
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if ((offset >> 31) || (opts->off32_limit < offset))
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return 1;
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if (!opts->anomaly_nr)
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return 0;
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ofsval = offset;
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return !!bsearch(&ofsval, opts->anomaly, opts->anomaly_nr,
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sizeof(ofsval), cmp_uint32);
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}
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/*
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* On entry *sha1 contains the pack content SHA1 hash, on exit it is
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* the SHA1 hash of sorted object names. The objects array passed in
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* will be sorted by SHA1 on exit.
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*/
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const char *write_idx_file(const char *index_name, struct pack_idx_entry **objects,
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int nr_objects, const struct pack_idx_option *opts,
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const unsigned char *sha1)
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{
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struct sha1file *f;
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struct pack_idx_entry **sorted_by_sha, **list, **last;
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off_t last_obj_offset = 0;
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uint32_t array[256];
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int i, fd;
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uint32_t index_version;
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if (nr_objects) {
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sorted_by_sha = objects;
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list = sorted_by_sha;
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last = sorted_by_sha + nr_objects;
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for (i = 0; i < nr_objects; ++i) {
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if (objects[i]->offset > last_obj_offset)
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last_obj_offset = objects[i]->offset;
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}
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qsort(sorted_by_sha, nr_objects, sizeof(sorted_by_sha[0]),
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sha1_compare);
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}
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else
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sorted_by_sha = list = last = NULL;
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if (opts->flags & WRITE_IDX_VERIFY) {
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assert(index_name);
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f = sha1fd_check(index_name);
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} else {
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if (!index_name) {
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static char tmp_file[PATH_MAX];
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fd = odb_mkstemp(tmp_file, sizeof(tmp_file), "pack/tmp_idx_XXXXXX");
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index_name = xstrdup(tmp_file);
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} else {
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unlink(index_name);
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fd = open(index_name, O_CREAT|O_EXCL|O_WRONLY, 0600);
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}
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if (fd < 0)
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die_errno("unable to create '%s'", index_name);
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f = sha1fd(fd, index_name);
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}
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/* if last object's offset is >= 2^31 we should use index V2 */
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index_version = need_large_offset(last_obj_offset, opts) ? 2 : opts->version;
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/* index versions 2 and above need a header */
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if (index_version >= 2) {
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struct pack_idx_header hdr;
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hdr.idx_signature = htonl(PACK_IDX_SIGNATURE);
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hdr.idx_version = htonl(index_version);
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sha1write(f, &hdr, sizeof(hdr));
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}
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/*
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* Write the first-level table (the list is sorted,
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* but we use a 256-entry lookup to be able to avoid
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* having to do eight extra binary search iterations).
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*/
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for (i = 0; i < 256; i++) {
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struct pack_idx_entry **next = list;
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while (next < last) {
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struct pack_idx_entry *obj = *next;
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if (obj->sha1[0] != i)
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break;
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next++;
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}
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array[i] = htonl(next - sorted_by_sha);
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list = next;
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}
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sha1write(f, array, 256 * 4);
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/*
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* Write the actual SHA1 entries..
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*/
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list = sorted_by_sha;
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for (i = 0; i < nr_objects; i++) {
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struct pack_idx_entry *obj = *list++;
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if (index_version < 2) {
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uint32_t offset = htonl(obj->offset);
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sha1write(f, &offset, 4);
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}
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sha1write(f, obj->sha1, 20);
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if ((opts->flags & WRITE_IDX_STRICT) &&
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(i && !hashcmp(list[-2]->sha1, obj->sha1)))
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die("The same object %s appears twice in the pack",
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sha1_to_hex(obj->sha1));
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}
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if (index_version >= 2) {
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unsigned int nr_large_offset = 0;
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/* write the crc32 table */
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list = sorted_by_sha;
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for (i = 0; i < nr_objects; i++) {
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struct pack_idx_entry *obj = *list++;
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uint32_t crc32_val = htonl(obj->crc32);
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sha1write(f, &crc32_val, 4);
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}
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/* write the 32-bit offset table */
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list = sorted_by_sha;
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for (i = 0; i < nr_objects; i++) {
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struct pack_idx_entry *obj = *list++;
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uint32_t offset;
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offset = (need_large_offset(obj->offset, opts)
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? (0x80000000 | nr_large_offset++)
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: obj->offset);
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offset = htonl(offset);
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sha1write(f, &offset, 4);
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}
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/* write the large offset table */
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list = sorted_by_sha;
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while (nr_large_offset) {
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struct pack_idx_entry *obj = *list++;
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uint64_t offset = obj->offset;
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uint32_t split[2];
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if (!need_large_offset(offset, opts))
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continue;
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split[0] = htonl(offset >> 32);
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split[1] = htonl(offset & 0xffffffff);
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sha1write(f, split, 8);
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nr_large_offset--;
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}
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}
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sha1write(f, sha1, 20);
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sha1close(f, NULL, ((opts->flags & WRITE_IDX_VERIFY)
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? CSUM_CLOSE : CSUM_FSYNC));
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return index_name;
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}
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off_t write_pack_header(struct sha1file *f, uint32_t nr_entries)
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{
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struct pack_header hdr;
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hdr.hdr_signature = htonl(PACK_SIGNATURE);
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hdr.hdr_version = htonl(PACK_VERSION);
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hdr.hdr_entries = htonl(nr_entries);
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sha1write(f, &hdr, sizeof(hdr));
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return sizeof(hdr);
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}
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/*
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* Update pack header with object_count and compute new SHA1 for pack data
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* associated to pack_fd, and write that SHA1 at the end. That new SHA1
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* is also returned in new_pack_sha1.
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*
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* If partial_pack_sha1 is non null, then the SHA1 of the existing pack
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* (without the header update) is computed and validated against the
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* one provided in partial_pack_sha1. The validation is performed at
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* partial_pack_offset bytes in the pack file. The SHA1 of the remaining
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* data (i.e. from partial_pack_offset to the end) is then computed and
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* returned in partial_pack_sha1.
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*
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* Note that new_pack_sha1 is updated last, so both new_pack_sha1 and
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* partial_pack_sha1 can refer to the same buffer if the caller is not
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* interested in the resulting SHA1 of pack data above partial_pack_offset.
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*/
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void fixup_pack_header_footer(int pack_fd,
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unsigned char *new_pack_sha1,
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const char *pack_name,
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uint32_t object_count,
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unsigned char *partial_pack_sha1,
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off_t partial_pack_offset)
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{
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int aligned_sz, buf_sz = 8 * 1024;
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git_SHA_CTX old_sha1_ctx, new_sha1_ctx;
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struct pack_header hdr;
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char *buf;
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git_SHA1_Init(&old_sha1_ctx);
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git_SHA1_Init(&new_sha1_ctx);
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if (lseek(pack_fd, 0, SEEK_SET) != 0)
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die_errno("Failed seeking to start of '%s'", pack_name);
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if (read_in_full(pack_fd, &hdr, sizeof(hdr)) != sizeof(hdr))
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die_errno("Unable to reread header of '%s'", pack_name);
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if (lseek(pack_fd, 0, SEEK_SET) != 0)
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die_errno("Failed seeking to start of '%s'", pack_name);
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git_SHA1_Update(&old_sha1_ctx, &hdr, sizeof(hdr));
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hdr.hdr_entries = htonl(object_count);
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git_SHA1_Update(&new_sha1_ctx, &hdr, sizeof(hdr));
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write_or_die(pack_fd, &hdr, sizeof(hdr));
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partial_pack_offset -= sizeof(hdr);
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buf = xmalloc(buf_sz);
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aligned_sz = buf_sz - sizeof(hdr);
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for (;;) {
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ssize_t m, n;
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m = (partial_pack_sha1 && partial_pack_offset < aligned_sz) ?
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partial_pack_offset : aligned_sz;
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n = xread(pack_fd, buf, m);
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if (!n)
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break;
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if (n < 0)
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die_errno("Failed to checksum '%s'", pack_name);
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git_SHA1_Update(&new_sha1_ctx, buf, n);
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aligned_sz -= n;
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if (!aligned_sz)
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aligned_sz = buf_sz;
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if (!partial_pack_sha1)
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continue;
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git_SHA1_Update(&old_sha1_ctx, buf, n);
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partial_pack_offset -= n;
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if (partial_pack_offset == 0) {
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unsigned char sha1[20];
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git_SHA1_Final(sha1, &old_sha1_ctx);
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if (hashcmp(sha1, partial_pack_sha1) != 0)
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die("Unexpected checksum for %s "
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"(disk corruption?)", pack_name);
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/*
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* Now let's compute the SHA1 of the remainder of the
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* pack, which also means making partial_pack_offset
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* big enough not to matter anymore.
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*/
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git_SHA1_Init(&old_sha1_ctx);
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partial_pack_offset = ~partial_pack_offset;
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partial_pack_offset -= MSB(partial_pack_offset, 1);
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}
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}
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free(buf);
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if (partial_pack_sha1)
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git_SHA1_Final(partial_pack_sha1, &old_sha1_ctx);
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git_SHA1_Final(new_pack_sha1, &new_sha1_ctx);
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write_or_die(pack_fd, new_pack_sha1, 20);
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fsync_or_die(pack_fd, pack_name);
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}
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char *index_pack_lockfile(int ip_out)
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{
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char packname[46];
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/*
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* The first thing we expect from index-pack's output
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* is "pack\t%40s\n" or "keep\t%40s\n" (46 bytes) where
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* %40s is the newly created pack SHA1 name. In the "keep"
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* case, we need it to remove the corresponding .keep file
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* later on. If we don't get that then tough luck with it.
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*/
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if (read_in_full(ip_out, packname, 46) == 46 && packname[45] == '\n') {
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const char *name;
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packname[45] = 0;
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if (skip_prefix(packname, "keep\t", &name))
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return xstrfmt("%s/pack/pack-%s.keep",
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get_object_directory(), name);
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}
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return NULL;
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}
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/*
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* The per-object header is a pretty dense thing, which is
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* - first byte: low four bits are "size", then three bits of "type",
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* and the high bit is "size continues".
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* - each byte afterwards: low seven bits are size continuation,
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* with the high bit being "size continues"
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*/
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int encode_in_pack_object_header(enum object_type type, uintmax_t size, unsigned char *hdr)
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{
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int n = 1;
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unsigned char c;
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if (type < OBJ_COMMIT || type > OBJ_REF_DELTA)
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die("bad type %d", type);
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c = (type << 4) | (size & 15);
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size >>= 4;
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while (size) {
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*hdr++ = c | 0x80;
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c = size & 0x7f;
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size >>= 7;
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n++;
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}
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*hdr = c;
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return n;
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}
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struct sha1file *create_tmp_packfile(char **pack_tmp_name)
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{
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char tmpname[PATH_MAX];
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int fd;
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fd = odb_mkstemp(tmpname, sizeof(tmpname), "pack/tmp_pack_XXXXXX");
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*pack_tmp_name = xstrdup(tmpname);
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return sha1fd(fd, *pack_tmp_name);
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}
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void finish_tmp_packfile(struct strbuf *name_buffer,
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const char *pack_tmp_name,
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struct pack_idx_entry **written_list,
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uint32_t nr_written,
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struct pack_idx_option *pack_idx_opts,
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unsigned char sha1[])
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{
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const char *idx_tmp_name;
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int basename_len = name_buffer->len;
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if (adjust_shared_perm(pack_tmp_name))
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die_errno("unable to make temporary pack file readable");
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idx_tmp_name = write_idx_file(NULL, written_list, nr_written,
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pack_idx_opts, sha1);
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if (adjust_shared_perm(idx_tmp_name))
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die_errno("unable to make temporary index file readable");
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strbuf_addf(name_buffer, "%s.pack", sha1_to_hex(sha1));
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if (rename(pack_tmp_name, name_buffer->buf))
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die_errno("unable to rename temporary pack file");
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strbuf_setlen(name_buffer, basename_len);
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strbuf_addf(name_buffer, "%s.idx", sha1_to_hex(sha1));
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if (rename(idx_tmp_name, name_buffer->buf))
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die_errno("unable to rename temporary index file");
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strbuf_setlen(name_buffer, basename_len);
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free((void *)idx_tmp_name);
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}
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