mirror of
https://github.com/git/git.git
synced 2024-09-28 16:13:01 +02:00
01247d8742
This makes it match the new delta encoding, and admittedly makes the code easier to follow. This also updates the PACK file version to 2, since this (and the delta encoding change in the previous commit) are incompatible with the old format.
449 lines
11 KiB
C
449 lines
11 KiB
C
#include <ctype.h>
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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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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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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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static struct object_entry **sorted_by_sha, **sorted_by_type;
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static struct object_entry *objects = NULL;
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static int nr_objects = 0, nr_alloc = 0;
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static const char *base_name;
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static unsigned char pack_file_sha1[20];
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static void *delta_against(void *buf, unsigned long size, struct object_entry *entry)
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{
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unsigned long othersize, delta_size;
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char type[10];
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void *otherbuf = read_sha1_file(entry->delta->sha1, type, &othersize);
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void *delta_buf;
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if (!otherbuf)
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die("unable to read %s", sha1_to_hex(entry->delta->sha1));
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delta_buf = diff_delta(otherbuf, othersize,
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buf, size, &delta_size, ~0UL);
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if (!delta_buf || delta_size != entry->delta_size)
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die("delta size changed");
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free(buf);
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free(otherbuf);
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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;
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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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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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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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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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if (size != entry->size)
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die("object %s size inconsistency (%lu vs %lu)", sha1_to_hex(entry->sha1), size, entry->size);
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/*
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* The object header is a byte of 'type' followed by zero or
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* more bytes of length. For deltas, the 20 bytes of delta sha1
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* follows that.
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*/
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obj_type = entry->type;
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if (entry->delta) {
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buf = delta_against(buf, size, entry);
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size = entry->delta_size;
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obj_type = OBJ_DELTA;
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}
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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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}
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static unsigned long write_one(struct sha1file *f,
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struct object_entry *e,
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unsigned long offset)
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{
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if (e->offset)
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/* offset starts from header size and cannot be zero
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* if it is written already.
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*/
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return offset;
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e->offset = offset;
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offset += write_object(f, e);
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/* if we are delitified, write out its base object. */
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if (e->delta)
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offset = write_one(f, e->delta, offset);
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return offset;
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}
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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;
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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(PACK_VERSION);
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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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offset = write_one(f, objects + i, offset);
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sha1close(f, pack_file_sha1, 1);
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mb = offset >> 20;
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offset &= 0xfffff;
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}
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static void write_index_file(void)
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{
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int i;
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struct sha1file *f = sha1create("%s.%s", base_name, "idx");
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struct object_entry **list = sorted_by_sha;
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struct object_entry **last = list + nr_objects;
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unsigned int array[256];
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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 object_entry **next = list;
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while (next < last) {
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struct object_entry *entry = *next;
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if (entry->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 * sizeof(int));
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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 object_entry *entry = *list++;
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unsigned int offset = htonl(entry->offset);
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sha1write(f, &offset, 4);
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sha1write(f, entry->sha1, 20);
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}
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sha1write(f, pack_file_sha1, 20);
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sha1close(f, NULL, 1);
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}
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static void add_object_entry(unsigned char *sha1, unsigned int hash)
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{
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unsigned int idx = nr_objects;
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struct object_entry *entry;
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if (idx >= nr_alloc) {
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unsigned int needed = (idx + 1024) * 3 / 2;
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objects = xrealloc(objects, needed * sizeof(*entry));
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nr_alloc = needed;
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}
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entry = objects + idx;
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memset(entry, 0, sizeof(*entry));
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memcpy(entry->sha1, sha1, 20);
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entry->hash = hash;
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nr_objects = idx+1;
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}
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static void check_object(struct object_entry *entry)
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{
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char type[20];
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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 = OBJ_COMMIT;
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} else if (!strcmp(type, "tree")) {
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entry->type = OBJ_TREE;
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} else if (!strcmp(type, "blob")) {
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entry->type = OBJ_BLOB;
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} else if (!strcmp(type, "tag")) {
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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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}
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else
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die("unable to get type of object %s",
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sha1_to_hex(entry->sha1));
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}
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static void get_object_details(void)
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{
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int i;
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struct object_entry *entry = objects;
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for (i = 0; i < nr_objects; i++)
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check_object(entry++);
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}
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typedef int (*entry_sort_t)(const struct object_entry *, const struct object_entry *);
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static entry_sort_t current_sort;
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static int sort_comparator(const void *_a, const void *_b)
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{
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struct object_entry *a = *(struct object_entry **)_a;
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struct object_entry *b = *(struct object_entry **)_b;
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return current_sort(a,b);
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}
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static struct object_entry **create_sorted_list(entry_sort_t sort)
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{
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struct object_entry **list = xmalloc(nr_objects * sizeof(struct object_entry *));
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int i;
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for (i = 0; i < nr_objects; i++)
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list[i] = objects + i;
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current_sort = sort;
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qsort(list, nr_objects, sizeof(struct object_entry *), sort_comparator);
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return list;
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}
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static int sha1_sort(const struct object_entry *a, const struct object_entry *b)
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{
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return memcmp(a->sha1, b->sha1, 20);
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}
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static int type_size_sort(const struct object_entry *a, const struct object_entry *b)
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{
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if (a->type < b->type)
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return -1;
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if (a->type > b->type)
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return 1;
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if (a->hash < b->hash)
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return -1;
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if (a->hash > b->hash)
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return 1;
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if (a->size < b->size)
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return -1;
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if (a->size > b->size)
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return 1;
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return a < b ? -1 : (a > b);
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}
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struct unpacked {
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struct object_entry *entry;
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void *data;
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};
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/*
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* We search for deltas _backwards_ in a list sorted by type and
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* by size, so that we see progressively smaller and smaller files.
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* That's because we prefer deltas to be from the bigger file
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* to the smaller - deletes are potentially cheaper, but perhaps
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* more importantly, the bigger file is likely the more recent
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* one.
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*/
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static int try_delta(struct unpacked *cur, struct unpacked *old, unsigned max_depth)
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{
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struct object_entry *cur_entry = cur->entry;
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struct object_entry *old_entry = old->entry;
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unsigned long size, oldsize, delta_size, sizediff;
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long max_size;
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void *delta_buf;
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/* Don't bother doing diffs between different types */
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if (cur_entry->type != old_entry->type)
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return -1;
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size = cur_entry->size;
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if (size < 50)
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return -1;
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oldsize = old_entry->size;
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sizediff = oldsize > size ? oldsize - size : size - oldsize;
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if (sizediff > size / 8)
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return -1;
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if (old_entry->depth >= max_depth)
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return 0;
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/*
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* NOTE!
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*
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* We always delta from the bigger to the smaller, since that's
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* more space-efficient (deletes don't have to say _what_ they
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* delete).
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*/
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max_size = size / 2 - 20;
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if (cur_entry->delta)
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max_size = cur_entry->delta_size-1;
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if (sizediff >= max_size)
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return -1;
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delta_buf = diff_delta(old->data, oldsize,
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cur->data, size, &delta_size, max_size);
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if (!delta_buf)
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return 0;
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cur_entry->delta = old_entry;
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cur_entry->delta_size = delta_size;
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cur_entry->depth = old_entry->depth + 1;
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free(delta_buf);
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return 0;
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}
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static void find_deltas(struct object_entry **list, int window, int depth)
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{
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int i, idx;
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unsigned int array_size = window * sizeof(struct unpacked);
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struct unpacked *array = xmalloc(array_size);
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memset(array, 0, array_size);
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i = nr_objects;
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idx = 0;
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while (--i >= 0) {
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struct object_entry *entry = list[i];
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struct unpacked *n = array + idx;
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unsigned long size;
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char type[10];
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int j;
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free(n->data);
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n->entry = entry;
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n->data = read_sha1_file(entry->sha1, type, &size);
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if (size != entry->size)
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die("object %s inconsistent object length (%lu vs %lu)", sha1_to_hex(entry->sha1), size, entry->size);
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j = window;
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while (--j > 0) {
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unsigned int other_idx = idx + j;
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struct unpacked *m;
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if (other_idx >= window)
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other_idx -= window;
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m = array + other_idx;
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if (!m->entry)
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break;
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if (try_delta(n, m, depth) < 0)
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break;
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}
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idx++;
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if (idx >= window)
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idx = 0;
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}
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}
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int main(int argc, char **argv)
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{
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char line[PATH_MAX + 20];
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int window = 10, depth = 10, pack_to_stdout = 0;
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int i;
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for (i = 1; i < argc; i++) {
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const char *arg = argv[i];
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if (*arg == '-') {
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if (!strncmp("--window=", arg, 9)) {
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char *end;
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window = strtoul(arg+9, &end, 0);
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if (!arg[9] || *end)
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usage(pack_usage);
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continue;
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}
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if (!strncmp("--depth=", arg, 8)) {
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char *end;
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depth = strtoul(arg+8, &end, 0);
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if (!arg[8] || *end)
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usage(pack_usage);
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continue;
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}
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if (!strcmp("--stdout", arg)) {
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pack_to_stdout = 1;
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continue;
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}
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usage(pack_usage);
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}
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if (base_name)
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usage(pack_usage);
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base_name = arg;
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}
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if (pack_to_stdout != !base_name)
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usage(pack_usage);
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while (fgets(line, sizeof(line), stdin) != NULL) {
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unsigned int hash;
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char *p;
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unsigned char sha1[20];
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if (get_sha1_hex(line, sha1))
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die("expected sha1, got garbage");
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hash = 0;
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p = line+40;
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while (*p) {
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unsigned char c = *p++;
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if (isspace(c))
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continue;
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hash = hash * 11 + c;
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}
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add_object_entry(sha1, hash);
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}
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get_object_details();
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fprintf(stderr, "Packing %d objects\n", nr_objects);
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sorted_by_sha = create_sorted_list(sha1_sort);
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sorted_by_type = create_sorted_list(type_size_sort);
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if (window && depth)
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find_deltas(sorted_by_type, window+1, depth);
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write_pack_file();
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if (!pack_to_stdout)
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write_index_file();
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return 0;
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}
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