зеркало из https://github.com/microsoft/git.git
Change pack file format. Hopefully for the last time.
This also adds a header with a signature, version info, and the number of objects to the pack file. It also encodes the file length and type more efficiently.
This commit is contained in:
Linus Torvalds
Родитель
d22b9290ab
Коммит
a733cb606f
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@ -2,25 +2,18 @@
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#include "cache.h"
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#include "object.h"
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#include "delta.h"
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#include "pack.h"
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#include "csum-file.h"
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static const char pack_usage[] = "git-pack-objects [--window=N] [--depth=N] {--stdout | base-name} < object-list";
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/*
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* The object type is a single-character shorthand:
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* - 'C' for "Commit"
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* - 'T' for "Tree"
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* - 'B' for "Blob"
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* - 'G' for "taG"
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* - 'D' for "Delta"
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*/
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struct object_entry {
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unsigned char sha1[20];
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unsigned long size;
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unsigned long offset;
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unsigned int depth;
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unsigned int hash;
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unsigned char type;
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enum object_type type;
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unsigned long delta_size;
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struct object_entry *delta;
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};
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@ -49,13 +42,54 @@ static void *delta_against(void *buf, unsigned long size, struct object_entry *e
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return delta_buf;
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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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static int encode_header(enum object_type type, unsigned long size, unsigned char *hdr)
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{
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int n = 1, i;
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unsigned char c;
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if (type < OBJ_COMMIT || type > OBJ_DELTA)
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die("bad type %d", type);
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/*
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* Shift the size up by 7 bits at a time,
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* until you get bits in the "high four".
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* That will be our beginning. We'll have
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* four size bits in 28..31, then groups
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* of seven in 21..27, 14..20, 7..13 and
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* finally 0..6.
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*/
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if (size) {
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n = 5;
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while (!(size & 0xfe000000)) {
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size <<= 7;
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n--;
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}
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}
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c = (type << 4) | (size >> 28);
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for (i = 1; i < n; i++) {
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*hdr++ = c | 0x80;
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c = (size >> 21) & 0x7f;
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size <<= 7;
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}
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*hdr = c;
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return n;
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}
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static unsigned long write_object(struct sha1file *f, struct object_entry *entry)
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{
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unsigned long size;
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char type[10];
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void *buf = read_sha1_file(entry->sha1, type, &size);
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char header[25];
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unsigned char header[10];
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unsigned hdrlen, datalen;
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enum object_type obj_type;
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if (!buf)
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die("unable to read %s", sha1_to_hex(entry->sha1));
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@ -67,18 +101,18 @@ static unsigned long write_object(struct sha1file *f, struct object_entry *entry
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* length, except for deltas that has the 20 bytes of delta sha
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* instead.
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*/
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header[0] = entry->type;
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hdrlen = 5;
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obj_type = entry->type;
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if (entry->delta) {
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header[0] = 'D';
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memcpy(header+5, entry->delta, 20);
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buf = delta_against(buf, size, entry);
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size = entry->delta_size;
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hdrlen = 25;
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obj_type = OBJ_DELTA;
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}
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datalen = htonl(size);
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memcpy(header+1, &datalen, 4);
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hdrlen = encode_header(obj_type, size, header);
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sha1write(f, header, hdrlen);
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if (entry->delta) {
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sha1write(f, entry->delta, 20);
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hdrlen += 20;
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}
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datalen = sha1write_compressed(f, buf, size);
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free(buf);
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return hdrlen + datalen;
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@ -88,13 +122,19 @@ static void write_pack_file(void)
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{
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int i;
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struct sha1file *f;
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unsigned long offset = 0;
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unsigned long offset;
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unsigned long mb;
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struct pack_header hdr;
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if (!base_name)
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f = sha1fd(1, "<stdout>");
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else
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f = sha1create("%s.%s", base_name, "pack");
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hdr.hdr_signature = htonl(PACK_SIGNATURE);
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hdr.hdr_version = htonl(1);
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hdr.hdr_entries = htonl(nr_objects);
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sha1write(f, &hdr, sizeof(hdr));
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offset = sizeof(hdr);
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for (i = 0; i < nr_objects; i++) {
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struct object_entry *entry = objects + i;
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entry->offset = offset;
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@ -168,13 +208,13 @@ static void check_object(struct object_entry *entry)
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if (!sha1_object_info(entry->sha1, type, &entry->size)) {
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if (!strcmp(type, "commit")) {
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entry->type = 'C';
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entry->type = OBJ_COMMIT;
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} else if (!strcmp(type, "tree")) {
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entry->type = 'T';
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entry->type = OBJ_TREE;
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} else if (!strcmp(type, "blob")) {
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entry->type = 'B';
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entry->type = OBJ_BLOB;
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} else if (!strcmp(type, "tag")) {
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entry->type = 'G';
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entry->type = OBJ_TAG;
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} else
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die("unable to pack object %s of type %s",
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sha1_to_hex(entry->sha1), type);
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@ -0,0 +1,23 @@
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#ifndef PACK_H
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#define PACK_H
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enum object_type {
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OBJ_NONE,
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OBJ_COMMIT,
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OBJ_TREE,
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OBJ_BLOB,
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OBJ_TAG,
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OBJ_DELTA,
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};
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/*
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* Packed object header
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*/
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#define PACK_SIGNATURE 0x5041434b /* "PACK" */
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struct pack_header {
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unsigned int hdr_signature;
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unsigned int hdr_version;
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unsigned int hdr_entries;
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};
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#endif
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75
sha1_file.c
75
sha1_file.c
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@ -10,6 +10,7 @@
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#include <dirent.h>
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#include "cache.h"
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#include "delta.h"
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#include "pack.h"
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#ifndef O_NOATIME
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#if defined(__linux__) && (defined(__i386__) || defined(__PPC__))
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@ -665,37 +666,60 @@ static int packed_delta_info(unsigned char *base_sha1,
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return 0;
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}
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static unsigned long unpack_object_header(struct packed_git *p, unsigned long offset,
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enum object_type *type, unsigned long *sizep)
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{
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unsigned char *pack, c;
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unsigned long size;
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if (offset >= p->pack_size)
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die("object offset outside of pack file");
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pack = p->pack_base + offset;
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c = *pack++;
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offset++;
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*type = (c >> 4) & 7;
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size = c & 15;
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while (c & 0x80) {
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if (offset >= p->pack_size)
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die("object offset outside of pack file");
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c = *pack++;
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offset++;
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size = (size << 7) | (c & 0x7f);
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}
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*sizep = size;
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return offset;
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}
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static int packed_object_info(struct pack_entry *entry,
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char *type, unsigned long *sizep)
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{
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struct packed_git *p = entry->p;
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unsigned long offset, size, left;
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unsigned char *pack;
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offset = entry->offset;
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if (p->pack_size - 5 < offset)
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die("object offset outside of pack file");
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enum object_type kind;
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if (use_packed_git(p))
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die("cannot map packed file");
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offset = unpack_object_header(p, entry->offset, &kind, &size);
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pack = p->pack_base + offset;
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size = (pack[1] << 24) + (pack[2] << 16) + (pack[3] << 8) + pack[4];
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left = p->pack_size - offset - 5;
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switch (*pack) {
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case 'D':
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return packed_delta_info(pack+5, size, left, type, sizep);
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left = p->pack_size - offset;
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switch (kind) {
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case OBJ_DELTA:
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return packed_delta_info(pack, size, left, type, sizep);
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break;
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case 'C':
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case OBJ_COMMIT:
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strcpy(type, "commit");
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break;
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case 'T':
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case OBJ_TREE:
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strcpy(type, "tree");
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break;
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case 'B':
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case OBJ_BLOB:
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strcpy(type, "blob");
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break;
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case 'G':
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case OBJ_TAG:
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strcpy(type, "tag");
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break;
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default:
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@ -787,37 +811,34 @@ static void *unpack_entry(struct pack_entry *entry,
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struct packed_git *p = entry->p;
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unsigned long offset, size, left;
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unsigned char *pack;
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offset = entry->offset;
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if (p->pack_size - 5 < offset)
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die("object offset outside of pack file");
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enum object_type kind;
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if (use_packed_git(p))
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die("cannot map packed file");
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offset = unpack_object_header(p, entry->offset, &kind, &size);
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pack = p->pack_base + offset;
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size = (pack[1] << 24) + (pack[2] << 16) + (pack[3] << 8) + pack[4];
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left = p->pack_size - offset - 5;
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switch (*pack) {
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case 'D':
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return unpack_delta_entry(pack+5, size, left, type, sizep);
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case 'C':
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left = p->pack_size - offset;
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switch (kind) {
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case OBJ_DELTA:
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return unpack_delta_entry(pack, size, left, type, sizep);
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case OBJ_COMMIT:
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strcpy(type, "commit");
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break;
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case 'T':
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case OBJ_TREE:
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strcpy(type, "tree");
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break;
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case 'B':
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case OBJ_BLOB:
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strcpy(type, "blob");
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break;
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case 'G':
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case OBJ_TAG:
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strcpy(type, "tag");
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break;
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default:
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die("corrupted pack file");
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}
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*sizep = size;
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return unpack_non_delta_entry(pack+5, size, left);
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return unpack_non_delta_entry(pack, size, left);
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}
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static int find_pack_entry_1(const unsigned char *sha1,
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@ -1,6 +1,7 @@
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#include "cache.h"
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#include "object.h"
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#include "delta.h"
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#include "pack.h"
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static int dry_run;
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static int nr_entries;
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@ -92,7 +93,7 @@ static int check_index(void)
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}
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static int unpack_non_delta_entry(struct pack_entry *entry,
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int kind,
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enum object_type kind,
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unsigned char *data,
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unsigned long size,
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unsigned long left)
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@ -101,9 +102,9 @@ static int unpack_non_delta_entry(struct pack_entry *entry,
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z_stream stream;
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char *buffer;
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unsigned char sha1[20];
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char *type_s;
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char *type;
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printf("%s %c %lu\n", sha1_to_hex(entry->sha1), kind, size);
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printf("%s %c %lu\n", sha1_to_hex(entry->sha1), ".CTBGD"[kind], size);
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if (dry_run)
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return 0;
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@ -121,18 +122,18 @@ static int unpack_non_delta_entry(struct pack_entry *entry,
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if ((st != Z_STREAM_END) || stream.total_out != size)
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goto err_finish;
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switch (kind) {
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case 'C': type_s = "commit"; break;
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case 'T': type_s = "tree"; break;
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case 'B': type_s = "blob"; break;
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case 'G': type_s = "tag"; break;
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case OBJ_COMMIT: type = "commit"; break;
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case OBJ_TREE: type = "tree"; break;
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case OBJ_BLOB: type = "blob"; break;
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case OBJ_TAG: type = "tag"; break;
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default: goto err_finish;
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}
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if (write_sha1_file(buffer, size, type_s, sha1) < 0)
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if (write_sha1_file(buffer, size, type, sha1) < 0)
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die("failed to write %s (%s)",
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sha1_to_hex(entry->sha1), type_s);
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printf("%s %s\n", sha1_to_hex(sha1), type_s);
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sha1_to_hex(entry->sha1), type);
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printf("%s %s\n", sha1_to_hex(sha1), type);
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if (memcmp(sha1, entry->sha1, 20))
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die("resulting %s have wrong SHA1", type_s);
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die("resulting %s have wrong SHA1", type);
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finish:
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st = 0;
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@ -237,28 +238,44 @@ static int unpack_delta_entry(struct pack_entry *entry,
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static void unpack_entry(struct pack_entry *entry)
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{
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unsigned long offset, size, left;
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unsigned char *pack;
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unsigned char *pack, c;
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int type;
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/* Have we done this one already due to deltas based on it? */
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if (lookup_object(entry->sha1))
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return;
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offset = ntohl(entry->offset);
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if (offset > pack_size - 5)
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die("object offset outside of pack file");
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if (offset >= pack_size)
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goto bad;
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pack = pack_base + offset;
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size = (pack[1] << 24) + (pack[2] << 16) + (pack[3] << 8) + pack[4];
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left = pack_size - offset - 5;
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switch (*pack) {
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case 'C': case 'T': case 'B': case 'G':
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unpack_non_delta_entry(entry, *pack, pack+5, size, left);
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break;
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case 'D':
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unpack_delta_entry(entry, pack+5, size, left);
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break;
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default:
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die("corrupted pack file");
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c = *pack++;
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offset++;
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type = (c >> 4) & 7;
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size = (c & 15);
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while (c & 0x80) {
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if (offset >= pack_size)
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goto bad;
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offset++;
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c = *pack++;
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size = (size << 7) + (c & 0x7f);
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}
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left = pack_size - offset;
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switch (type) {
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case OBJ_COMMIT:
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case OBJ_TREE:
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case OBJ_BLOB:
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case OBJ_TAG:
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unpack_non_delta_entry(entry, type, pack, size, left);
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return;
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case OBJ_DELTA:
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unpack_delta_entry(entry, pack+5, size, left);
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return;
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}
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bad:
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die("corrupted pack file");
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}
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/*
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