git/pack-redundant.c
Lukas Sandström 06a45c8cc9 Improve the readability of git-pack-redundant
Signed-off-by: Lukas Sandström <lukass@etek.chalmers.se>
Signed-off-by: Junio C Hamano <junkio@cox.net>
2005-11-18 15:34:17 -08:00

653 lines
13 KiB
C

/*
*
* Copyright 2005, Lukas Sandstrom <lukass@etek.chalmers.se>
*
* This file is licensed under the GPL v2.
*
*/
#include "cache.h"
static const char pack_redundant_usage[] =
"git-pack-redundant [ --verbose ] [ --alt-odb ] < --all | <.pack filename> ...>";
int load_all_packs = 0, verbose = 0, alt_odb = 0;
struct llist_item {
struct llist_item *next;
char *sha1;
};
struct llist {
struct llist_item *front;
struct llist_item *back;
size_t size;
} *all_objects; /* all objects which must be present in local packfiles */
struct pack_list {
struct pack_list *next;
struct packed_git *pack;
struct llist *unique_objects;
struct llist *all_objects;
} *local_packs = NULL, *altodb_packs = NULL;
struct pll {
struct pll *next;
struct pack_list *pl;
size_t pl_size;
};
inline void llist_free(struct llist *list)
{
while((list->back = list->front)) {
list->front = list->front->next;
free(list->back);
}
free(list);
}
inline void llist_init(struct llist **list)
{
*list = xmalloc(sizeof(struct llist));
(*list)->front = (*list)->back = NULL;
(*list)->size = 0;
}
struct llist * llist_copy(struct llist *list)
{
struct llist *ret;
struct llist_item *new, *old, *prev;
llist_init(&ret);
if ((ret->size = list->size) == 0)
return ret;
new = ret->front = xmalloc(sizeof(struct llist_item));
new->sha1 = list->front->sha1;
old = list->front->next;
while (old) {
prev = new;
new = xmalloc(sizeof(struct llist_item));
prev->next = new;
new->sha1 = old->sha1;
old = old->next;
}
new->next = NULL;
ret->back = new;
return ret;
}
inline struct llist_item * llist_insert(struct llist *list,
struct llist_item *after, char *sha1)
{
struct llist_item *new = xmalloc(sizeof(struct llist_item));
new->sha1 = sha1;
new->next = NULL;
if (after != NULL) {
new->next = after->next;
after->next = new;
if (after == list->back)
list->back = new;
} else {/* insert in front */
if (list->size == 0)
list->back = new;
else
new->next = list->front;
list->front = new;
}
list->size++;
return new;
}
inline struct llist_item * llist_insert_back(struct llist *list, char *sha1)
{
return llist_insert(list, list->back, sha1);
}
inline struct llist_item * llist_insert_sorted_unique(struct llist *list,
char *sha1, struct llist_item *hint)
{
struct llist_item *prev = NULL, *l;
l = (hint == NULL) ? list->front : hint;
while (l) {
int cmp = memcmp(l->sha1, sha1, 20);
if (cmp > 0) { /* we insert before this entry */
return llist_insert(list, prev, sha1);
}
if(!cmp) { /* already exists */
return l;
}
prev = l;
l = l->next;
}
/* insert at the end */
return llist_insert_back(list, sha1);
}
/* returns a pointer to an item in front of sha1 */
inline struct llist_item * llist_sorted_remove(struct llist *list, char *sha1,
struct llist_item *hint)
{
struct llist_item *prev, *l;
redo_from_start:
l = (hint == NULL) ? list->front : hint;
prev = NULL;
while (l) {
int cmp = memcmp(l->sha1, sha1, 20);
if (cmp > 0) /* not in list, since sorted */
return prev;
if(!cmp) { /* found */
if (prev == NULL) {
if (hint != NULL && hint != list->front) {
/* we don't know the previous element */
hint = NULL;
goto redo_from_start;
}
list->front = l->next;
} else
prev->next = l->next;
if (l == list->back)
list->back = prev;
free(l);
list->size--;
return prev;
}
prev = l;
l = l->next;
}
return prev;
}
/* computes A\B */
void llist_sorted_difference_inplace(struct llist *A,
struct llist *B)
{
struct llist_item *hint, *b;
hint = NULL;
b = B->front;
while (b) {
hint = llist_sorted_remove(A, b->sha1, hint);
b = b->next;
}
}
inline struct pack_list * pack_list_insert(struct pack_list **pl,
struct pack_list *entry)
{
struct pack_list *p = xmalloc(sizeof(struct pack_list));
memcpy(p, entry, sizeof(struct pack_list));
p->next = *pl;
*pl = p;
return p;
}
inline size_t pack_list_size(struct pack_list *pl)
{
size_t ret = 0;
while(pl) {
ret++;
pl = pl->next;
}
return ret;
}
struct pack_list * pack_list_difference(struct pack_list *A,
struct pack_list *B)
{
struct pack_list *ret, *pl;
if (A == NULL)
return NULL;
pl = B;
while (pl != NULL) {
if (A->pack == pl->pack)
return pack_list_difference(A->next, B);
pl = pl->next;
}
ret = xmalloc(sizeof(struct pack_list));
memcpy(ret, A, sizeof(struct pack_list));
ret->next = pack_list_difference(A->next, B);
return ret;
}
void cmp_two_packs(struct pack_list *p1, struct pack_list *p2)
{
int p1_off, p2_off;
void *p1_base, *p2_base;
struct llist_item *p1_hint = NULL, *p2_hint = NULL;
p1_off = p2_off = 256 * 4 + 4;
p1_base = (void *)p1->pack->index_base;
p2_base = (void *)p2->pack->index_base;
while (p1_off <= p1->pack->index_size - 3 * 20 &&
p2_off <= p2->pack->index_size - 3 * 20)
{
int cmp = memcmp(p1_base + p1_off, p2_base + p2_off, 20);
/* cmp ~ p1 - p2 */
if (cmp == 0) {
p1_hint = llist_sorted_remove(p1->unique_objects,
p1_base + p1_off, p1_hint);
p2_hint = llist_sorted_remove(p2->unique_objects,
p1_base + p1_off, p2_hint);
p1_off+=24;
p2_off+=24;
continue;
}
if (cmp < 0) { /* p1 has the object, p2 doesn't */
p1_off+=24;
} else { /* p2 has the object, p1 doesn't */
p2_off+=24;
}
}
}
void pll_insert(struct pll **pll, struct pll **hint_table)
{
struct pll *prev;
int i = (*pll)->pl_size - 1;
if (hint_table[i] == NULL) {
hint_table[i--] = *pll;
for (; i >= 0; --i) {
if (hint_table[i] != NULL)
break;
}
if (hint_table[i] == NULL) /* no elements in list */
die("Why did this happen?");
}
prev = hint_table[i];
while (prev->next && prev->next->pl_size < (*pll)->pl_size)
prev = prev->next;
(*pll)->next = prev->next;
prev->next = *pll;
}
/* all the permutations have to be free()d at the same time,
* since they refer to each other
*/
struct pll * get_all_permutations(struct pack_list *list)
{
struct pll *subset, *pll, *new_pll = NULL; /*silence warning*/
static struct pll **hint = NULL;
if (hint == NULL)
hint = xcalloc(pack_list_size(list), sizeof(struct pll *));
if (list == NULL)
return NULL;
if (list->next == NULL) {
new_pll = xmalloc(sizeof(struct pll));
hint[0] = new_pll;
new_pll->next = NULL;
new_pll->pl = list;
new_pll->pl_size = 1;
return new_pll;
}
pll = subset = get_all_permutations(list->next);
while (pll) {
if (pll->pl->pack == list->pack) {
pll = pll->next;
continue;
}
new_pll = xmalloc(sizeof(struct pll));
new_pll->pl = xmalloc(sizeof(struct pack_list));
memcpy(new_pll->pl, list, sizeof(struct pack_list));
new_pll->pl->next = pll->pl;
new_pll->pl_size = pll->pl_size + 1;
pll_insert(&new_pll, hint);
pll = pll->next;
}
/* add ourself */
new_pll = xmalloc(sizeof(struct pll));
new_pll->pl = xmalloc(sizeof(struct pack_list));
memcpy(new_pll->pl, list, sizeof(struct pack_list));
new_pll->pl->next = NULL;
new_pll->pl_size = 1;
pll_insert(&new_pll, hint);
return hint[0];
}
int is_superset(struct pack_list *pl, struct llist *list)
{
struct llist *diff;
diff = llist_copy(list);
while (pl) {
llist_sorted_difference_inplace(diff,
pl->all_objects);
if (diff->size == 0) { /* we're done */
llist_free(diff);
return 1;
}
pl = pl->next;
}
llist_free(diff);
return 0;
}
size_t sizeof_union(struct packed_git *p1, struct packed_git *p2)
{
size_t ret = 0;
int p1_off, p2_off;
void *p1_base, *p2_base;
p1_off = p2_off = 256 * 4 + 4;
p1_base = (void *)p1->index_base;
p2_base = (void *)p2->index_base;
while (p1_off <= p1->index_size - 3 * 20 &&
p2_off <= p2->index_size - 3 * 20)
{
int cmp = memcmp(p1_base + p1_off, p2_base + p2_off, 20);
/* cmp ~ p1 - p2 */
if (cmp == 0) {
ret++;
p1_off+=24;
p2_off+=24;
continue;
}
if (cmp < 0) { /* p1 has the object, p2 doesn't */
p1_off+=24;
} else { /* p2 has the object, p1 doesn't */
p2_off+=24;
}
}
return ret;
}
/* another O(n^2) function ... */
size_t get_pack_redundancy(struct pack_list *pl)
{
struct pack_list *subset;
if (pl == NULL)
return 0;
size_t ret = 0;
while ((subset = pl->next)) {
while(subset) {
ret += sizeof_union(pl->pack, subset->pack);
subset = subset->next;
}
pl = pl->next;
}
return ret;
}
inline size_t pack_set_bytecount(struct pack_list *pl)
{
size_t ret = 0;
while (pl) {
ret += pl->pack->pack_size;
ret += pl->pack->index_size;
pl = pl->next;
}
return ret;
}
void minimize(struct pack_list **min)
{
struct pack_list *pl, *unique = NULL,
*non_unique = NULL, *min_perm = NULL;
struct pll *perm, *perm_all, *perm_ok = NULL, *new_perm;
struct llist *missing;
size_t min_perm_size = (size_t)-1, perm_size;
pl = local_packs;
while (pl) {
if(pl->unique_objects->size)
pack_list_insert(&unique, pl);
else
pack_list_insert(&non_unique, pl);
pl = pl->next;
}
/* find out which objects are missing from the set of unique packs */
missing = llist_copy(all_objects);
pl = unique;
while (pl) {
llist_sorted_difference_inplace(missing,
pl->all_objects);
pl = pl->next;
}
/* return if there are no objects missing from the unique set */
if (missing->size == 0) {
*min = unique;
return;
}
/* find the permutations which contain all missing objects */
perm_all = perm = get_all_permutations(non_unique);
while (perm) {
if (perm_ok && perm->pl_size > perm_ok->pl_size)
break; /* ignore all larger permutations */
if (is_superset(perm->pl, missing)) {
new_perm = xmalloc(sizeof(struct pll));
memcpy(new_perm, perm, sizeof(struct pll));
new_perm->next = perm_ok;
perm_ok = new_perm;
}
perm = perm->next;
}
if (perm_ok == NULL)
die("Internal error: No complete sets found!\n");
/* find the permutation with the smallest size */
perm = perm_ok;
while (perm) {
perm_size = pack_set_bytecount(perm->pl);
if (min_perm_size > perm_size) {
min_perm_size = perm_size;
min_perm = perm->pl;
}
perm = perm->next;
}
*min = min_perm;
/* add the unique packs to the list */
pl = unique;
while(pl) {
pack_list_insert(min, pl);
pl = pl->next;
}
}
void load_all_objects()
{
struct pack_list *pl = local_packs;
struct llist_item *hint, *l;
int i;
llist_init(&all_objects);
while (pl) {
i = 0;
hint = NULL;
l = pl->all_objects->front;
while (l) {
hint = llist_insert_sorted_unique(all_objects,
l->sha1, hint);
l = l->next;
}
pl = pl->next;
}
/* remove objects present in remote packs */
pl = altodb_packs;
while (pl) {
llist_sorted_difference_inplace(all_objects, pl->all_objects);
pl = pl->next;
}
}
/* this scales like O(n^2) */
void cmp_local_packs()
{
struct pack_list *subset, *pl = local_packs;
while ((subset = pl)) {
while((subset = subset->next))
cmp_two_packs(pl, subset);
pl = pl->next;
}
}
void scan_alt_odb_packs()
{
struct pack_list *local, *alt;
alt = altodb_packs;
while (alt) {
local = local_packs;
while (local) {
llist_sorted_difference_inplace(local->unique_objects,
alt->all_objects);
local = local->next;
}
alt = alt->next;
}
}
struct pack_list * add_pack(struct packed_git *p)
{
struct pack_list l;
size_t off;
void *base;
if (!p->pack_local && !(alt_odb || verbose))
return NULL;
l.pack = p;
llist_init(&l.all_objects);
off = 256 * 4 + 4;
base = (void *)p->index_base;
while (off <= p->index_size - 3 * 20) {
llist_insert_back(l.all_objects, base + off);
off += 24;
}
/* this list will be pruned in cmp_two_packs later */
l.unique_objects = llist_copy(l.all_objects);
if (p->pack_local)
return pack_list_insert(&local_packs, &l);
else
return pack_list_insert(&altodb_packs, &l);
}
struct pack_list * add_pack_file(char *filename)
{
struct packed_git *p = packed_git;
if (strlen(filename) < 40)
die("Bad pack filename: %s\n", filename);
while (p) {
if (strstr(p->pack_name, filename))
return add_pack(p);
p = p->next;
}
die("Filename %s not found in packed_git\n", filename);
}
void load_all()
{
struct packed_git *p = packed_git;
while (p) {
add_pack(p);
p = p->next;
}
}
int main(int argc, char **argv)
{
int i;
struct pack_list *min, *red, *pl;
for (i = 1; i < argc; i++) {
const char *arg = argv[i];
if(!strcmp(arg, "--")) {
i++;
break;
}
if(!strcmp(arg, "--all")) {
load_all_packs = 1;
continue;
}
if(!strcmp(arg, "--verbose")) {
verbose = 1;
continue;
}
if(!strcmp(arg, "--alt-odb")) {
alt_odb = 1;
continue;
}
if(*arg == '-')
usage(pack_redundant_usage);
else
break;
}
prepare_packed_git();
if (load_all_packs)
load_all();
else
while (*(argv + i) != NULL)
add_pack_file(*(argv + i++));
if (local_packs == NULL)
die("Zero packs found!\n");
load_all_objects();
cmp_local_packs();
if (alt_odb)
scan_alt_odb_packs();
minimize(&min);
if (verbose) {
fprintf(stderr, "There are %lu packs available in alt-odbs.\n",
(unsigned long)pack_list_size(altodb_packs));
fprintf(stderr, "The smallest (bytewise) set of packs is:\n");
pl = min;
while (pl) {
fprintf(stderr, "\t%s\n", pl->pack->pack_name);
pl = pl->next;
}
fprintf(stderr, "containing %lu duplicate objects "
"with a total size of %lukb.\n",
(unsigned long)get_pack_redundancy(min),
(unsigned long)pack_set_bytecount(min)/1024);
fprintf(stderr, "A total of %lu unique objects were considered.\n",
(unsigned long)all_objects->size);
fprintf(stderr, "Redundant packs (with indexes):\n");
}
pl = red = pack_list_difference(local_packs, min);
while (pl) {
printf("%s\n%s\n",
sha1_pack_index_name(pl->pack->sha1),
pl->pack->pack_name);
pl = pl->next;
}
return 0;
}