find_unique_abbrev: move logic out of get_short_sha1()

The get_short_sha1() is only about reading short sha1s; we
do call it in a loop to check "is this long enough" for each
object, but otherwise it should not need to know about
things like our default_abbrev setting.

So instead of asking it to set default_automatic_abbrev as a
side-effect, let's just have find_unique_abbrev() pick the
right place to start its loop.  This requires a separate
approximate_object_count() function, but that naturally
belongs with the rest of sha1_file.c.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jeff King 2016-10-03 19:47:28 -04:00 коммит произвёл Junio C Hamano
Родитель e6c587c733
Коммит 8e3f52d778
3 изменённых файлов: 68 добавлений и 26 удалений

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@ -1204,7 +1204,6 @@ struct object_context {
#define GET_SHA1_TREEISH 020
#define GET_SHA1_BLOB 040
#define GET_SHA1_FOLLOW_SYMLINKS 0100
#define GET_SHA1_AUTOMATIC 0200
#define GET_SHA1_ONLY_TO_DIE 04000
#define GET_SHA1_DISAMBIGUATORS \
@ -1456,6 +1455,12 @@ extern void prepare_packed_git(void);
extern void reprepare_packed_git(void);
extern void install_packed_git(struct packed_git *pack);
/*
* Give a rough count of objects in the repository. This sacrifices accuracy
* for speed.
*/
unsigned long approximate_object_count(void);
extern struct packed_git *find_sha1_pack(const unsigned char *sha1,
struct packed_git *packs);

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@ -1381,6 +1381,32 @@ static void prepare_packed_git_one(char *objdir, int local)
strbuf_release(&path);
}
static int approximate_object_count_valid;
/*
* Give a fast, rough count of the number of objects in the repository. This
* ignores loose objects completely. If you have a lot of them, then either
* you should repack because your performance will be awful, or they are
* all unreachable objects about to be pruned, in which case they're not really
* interesting as a measure of repo size in the first place.
*/
unsigned long approximate_object_count(void)
{
static unsigned long count;
if (!approximate_object_count_valid) {
struct packed_git *p;
prepare_packed_git();
count = 0;
for (p = packed_git; p; p = p->next) {
if (open_pack_index(p))
continue;
count += p->num_objects;
}
}
return count;
}
static void *get_next_packed_git(const void *p)
{
return ((const struct packed_git *)p)->next;
@ -1455,6 +1481,7 @@ void prepare_packed_git(void)
void reprepare_packed_git(void)
{
approximate_object_count_valid = 0;
prepare_packed_git_run_once = 0;
prepare_packed_git();
}

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@ -15,7 +15,6 @@ typedef int (*disambiguate_hint_fn)(const unsigned char *, void *);
struct disambiguate_state {
int len; /* length of prefix in hex chars */
unsigned int nrobjects;
char hex_pfx[GIT_SHA1_HEXSZ + 1];
unsigned char bin_pfx[GIT_SHA1_RAWSZ];
@ -119,14 +118,6 @@ static void find_short_object_filename(struct disambiguate_state *ds)
if (strlen(de->d_name) != 38)
continue;
/*
* We only look at the one subdirectory, and we assume
* each subdirectory is roughly similar, so each
* object we find probably has 255 other objects in
* the other fan-out directories.
*/
ds->nrobjects += 256;
if (memcmp(de->d_name, ds->hex_pfx + 2, ds->len - 2))
continue;
memcpy(hex + 2, de->d_name, 38);
@ -160,7 +151,6 @@ static void unique_in_pack(struct packed_git *p,
open_pack_index(p);
num = p->num_objects;
ds->nrobjects += num;
last = num;
while (first < last) {
uint32_t mid = (first + last) / 2;
@ -390,9 +380,6 @@ static int show_ambiguous_object(const unsigned char *sha1, void *data)
return 0;
}
/* start from our historical default before the automatic abbreviation */
static int default_automatic_abbrev = FALLBACK_DEFAULT_ABBREV;
static int get_short_sha1(const char *name, int len, unsigned char *sha1,
unsigned flags)
{
@ -439,14 +426,6 @@ static int get_short_sha1(const char *name, int len, unsigned char *sha1,
for_each_abbrev(ds.hex_pfx, show_ambiguous_object, &ds);
}
if (len < 16 && !status && (flags & GET_SHA1_AUTOMATIC)) {
unsigned int expect_collision = 1 << (len * 2);
if (ds.nrobjects > expect_collision) {
default_automatic_abbrev = len+1;
return SHORT_NAME_AMBIGUOUS;
}
}
return status;
}
@ -476,22 +455,53 @@ int for_each_abbrev(const char *prefix, each_abbrev_fn fn, void *cb_data)
return ret;
}
/*
* Return the slot of the most-significant bit set in "val". There are various
* ways to do this quickly with fls() or __builtin_clzl(), but speed is
* probably not a big deal here.
*/
static unsigned msb(unsigned long val)
{
unsigned r = 0;
while (val >>= 1)
r++;
return r;
}
int find_unique_abbrev_r(char *hex, const unsigned char *sha1, int len)
{
int status, exists;
int flags = GET_SHA1_QUIETLY;
if (len < 0) {
flags |= GET_SHA1_AUTOMATIC;
len = default_automatic_abbrev;
unsigned long count = approximate_object_count();
/*
* Add one because the MSB only tells us the highest bit set,
* not including the value of all the _other_ bits (so "15"
* is only one off of 2^4, but the MSB is the 3rd bit.
*/
len = msb(count) + 1;
/*
* We now know we have on the order of 2^len objects, which
* expects a collision at 2^(len/2). But we also care about hex
* chars, not bits, and there are 4 bits per hex. So all
* together we need to divide by 2; but we also want to round
* odd numbers up, hence adding one before dividing.
*/
len = (len + 1) / 2;
/*
* For very small repos, we stick with our regular fallback.
*/
if (len < FALLBACK_DEFAULT_ABBREV)
len = FALLBACK_DEFAULT_ABBREV;
}
sha1_to_hex_r(hex, sha1);
if (len == 40 || !len)
return 40;
exists = has_sha1_file(sha1);
while (len < 40) {
unsigned char sha1_ret[20];
status = get_short_sha1(hex, len, sha1_ret, flags);
status = get_short_sha1(hex, len, sha1_ret, GET_SHA1_QUIETLY);
if (exists
? !status
: status == SHORT_NAME_NOT_FOUND) {