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git/rev-cache.c

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#include "refs.h"
#include "cache.h"
#include "rev-cache.h"
struct rev_cache **rev_cache;
int nr_revs, alloc_revs;
struct rev_list_elem *rle_free;
#define BATCH_SIZE 512
int find_rev_cache(const unsigned char *sha1)
{
int lo = 0, hi = nr_revs;
while (lo < hi) {
int mi = (lo + hi) / 2;
struct rev_cache *ri = rev_cache[mi];
int cmp = memcmp(sha1, ri->sha1, 20);
if (!cmp)
return mi;
if (cmp < 0)
hi = mi;
else
lo = mi + 1;
}
return -lo - 1;
}
static struct rev_list_elem *alloc_list_elem(void)
{
struct rev_list_elem *rle;
if (!rle_free) {
int i;
rle = xmalloc(sizeof(*rle) * BATCH_SIZE);
for (i = 0; i < BATCH_SIZE - 1; i++) {
rle[i].ri = NULL;
rle[i].next = &rle[i + 1];
}
rle[BATCH_SIZE - 1].ri = NULL;
rle[BATCH_SIZE - 1].next = NULL;
rle_free = rle;
}
rle = rle_free;
rle_free = rle->next;
return rle;
}
static struct rev_cache *create_rev_cache(const unsigned char *sha1)
{
struct rev_cache *ri;
int pos = find_rev_cache(sha1);
if (0 <= pos)
return rev_cache[pos];
pos = -pos - 1;
if (alloc_revs <= ++nr_revs) {
alloc_revs = alloc_nr(alloc_revs);
rev_cache = xrealloc(rev_cache, sizeof(ri) * alloc_revs);
}
if (pos < nr_revs)
memmove(rev_cache + pos + 1, rev_cache + pos,
(nr_revs - pos - 1) * sizeof(ri));
ri = xcalloc(1, sizeof(*ri));
memcpy(ri->sha1, sha1, 20);
rev_cache[pos] = ri;
return ri;
}
static unsigned char last_sha1[20];
static void write_one_rev_cache(FILE *rev_cache_file, struct rev_cache *ri)
{
unsigned char flag;
struct rev_list_elem *rle;
if (ri->written)
return;
if (ri->parsed) {
/* We use last_sha1 compression only for the first parent;
* otherwise the resulting rev-cache would lose the parent
* order information.
*/
if (ri->parents &&
!memcmp(ri->parents->ri->sha1, last_sha1, 20))
flag = (ri->num_parents - 1) | 0x80;
else
flag = ri->num_parents;
fwrite(ri->sha1, 20, 1, rev_cache_file);
fwrite(&flag, 1, 1, rev_cache_file);
for (rle = ri->parents; rle; rle = rle->next) {
if (flag & 0x80 && rle == ri->parents)
continue;
fwrite(rle->ri->sha1, 20, 1, rev_cache_file);
}
memcpy(last_sha1, ri->sha1, 20);
ri->written = 1;
}
/* recursively write children depth first */
for (rle = ri->children; rle; rle = rle->next)
write_one_rev_cache(rev_cache_file, rle->ri);
}
void write_rev_cache(const char *newpath, const char *oldpath)
{
/* write the following commit ancestry information in
* $GIT_DIR/info/rev-cache.
*
* The format is:
* 20-byte SHA1 (commit ID)
* 1-byte flag:
* - bit 0-6 records "number of parent commit SHA1s to
* follow" (i.e. up to 127 children can be listed).
* - when the bit 7 is on, then "the entry immediately
* before this entry is one of the parents of this
* commit".
* N x 20-byte SHA1 (parent commit IDs)
*/
FILE *rev_cache_file;
int i;
struct rev_cache *ri;
if (!strcmp(newpath, oldpath)) {
/* If we are doing it in place */
rev_cache_file = fopen(newpath, "a");
}
else {
char buf[8096];
size_t sz;
FILE *oldfp = fopen(oldpath, "r");
rev_cache_file = fopen(newpath, "w");
if (oldfp) {
while (1) {
sz = fread(buf, 1, sizeof(buf), oldfp);
if (sz == 0)
break;
fwrite(buf, 1, sz, rev_cache_file);
}
fclose(oldfp);
}
}
memset(last_sha1, 0, 20);
/* Go through available rev_cache structures, starting from
* parentless ones first, so that we would get most out of
* last_sha1 optimization by the depth first behaviour of
* write_one_rev_cache().
*/
for (i = 0; i < nr_revs; i++) {
ri = rev_cache[i];
if (ri->num_parents)
continue;
write_one_rev_cache(rev_cache_file, ri);
}
/* Then the rest */
for (i = 0; i < nr_revs; i++) {
ri = rev_cache[i];
write_one_rev_cache(rev_cache_file, ri);
}
fclose(rev_cache_file);
}
static void add_parent(struct rev_cache *child,
const unsigned char *parent_sha1)
{
struct rev_cache *parent = create_rev_cache(parent_sha1);
struct rev_list_elem *e = alloc_list_elem();
/* Keep the parent list ordered in the same way the commit
* object records them.
*/
e->ri = parent;
e->next = NULL;
if (!child->parents_tail)
child->parents = e;
else
child->parents_tail->next = e;
child->parents_tail = e;
child->num_parents++;
/* There is no inherent order of the children so we just
* LIFO them together.
*/
e = alloc_list_elem();
e->next = parent->children;
parent->children = e;
e->ri = child;
parent->num_children++;
}
int read_rev_cache(const char *path, FILE *dumpfile, int dry_run)
{
unsigned char *map;
int fd;
struct stat st;
unsigned long ofs, len;
struct rev_cache *ri = NULL;
fd = open(path, O_RDONLY);
if (fd < 0) {
if (dry_run)
return error("cannot open %s", path);
if (errno == ENOENT)
return 0;
return -1;
}
if (fstat(fd, &st)) {
close(fd);
return -1;
}
map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
close(fd);
if (map == MAP_FAILED)
return -1;
memset(last_sha1, 0, 20);
ofs = 0;
len = st.st_size;
while (ofs < len) {
unsigned char sha1[20];
int flag, cnt, i;
if (len < ofs + 21)
die("rev-cache too short");
memcpy(sha1, map + ofs, 20);
flag = map[ofs + 20];
ofs += 21;
cnt = (flag & 0x7f) + ((flag & 0x80) != 0);
if (len < ofs + (flag & 0x7f) * 20)
die("rev-cache too short to have %d more parents",
(flag & 0x7f));
if (dumpfile)
fprintf(dumpfile, "%s", sha1_to_hex(sha1));
if (!dry_run) {
ri = create_rev_cache(sha1);
if (!ri)
die("cannot create rev-cache for %s",
sha1_to_hex(sha1));
ri->written = ri->parsed = 1;
}
i = 0;
if (flag & 0x80) {
if (!dry_run)
add_parent(ri, last_sha1);
if (dumpfile)
fprintf(dumpfile, " %s",
sha1_to_hex(last_sha1));
i++;
}
while (i++ < cnt) {
if (!dry_run)
add_parent(ri, map + ofs);
if (dumpfile)
fprintf(dumpfile, " %s",
sha1_to_hex(last_sha1));
ofs += 20;
}
if (dumpfile)
fprintf(dumpfile, "\n");
memcpy(last_sha1, sha1, 20);
}
if (ofs != len)
die("rev-cache truncated?");
munmap(map, len);
return 0;
}
int record_rev_cache(const unsigned char *sha1, FILE *dumpfile)
{
unsigned char parent[20];
char type[20];
unsigned long size, ofs;
unsigned int cnt, i;
void *buf;
struct rev_cache *ri;
buf = read_sha1_file(sha1, type, &size);
if (!buf)
return error("%s: not found", sha1_to_hex(sha1));
if (strcmp(type, "commit")) {
free(buf);
return error("%s: not a commit but a %s",
sha1_to_hex(sha1), type);
}
ri = create_rev_cache(sha1);
if (ri->parsed)
return 0;
if (dumpfile)
fprintf(dumpfile, "commit %s\n", sha1_to_hex(sha1));
cnt = 0;
ofs = 46; /* "tree " + hex-sha1 + "\n" */
while (!memcmp(buf + ofs, "parent ", 7) &&
!get_sha1_hex(buf + ofs + 7, parent)) {
ofs += 48;
cnt++;
}
if (cnt * 48 + 46 != ofs) {
free(buf);
die("internal error in record_rev_cache");
}
ri = create_rev_cache(sha1);
ri->parsed = 1;
for (i = 0; i < cnt; i++) {
unsigned char parent_sha1[20];
ofs = 46 + i * 48 + 7;
get_sha1_hex(buf + ofs, parent_sha1);
add_parent(ri, parent_sha1);
record_rev_cache(parent_sha1, dumpfile);
}
free(buf);
return 0;
}