mirror of
https://github.com/golang/go
synced 2024-11-21 09:24:42 -07:00
runtime: random offset for map iteration
R=golang-dev, r CC=golang-dev https://golang.org/cl/5285042
This commit is contained in:
parent
304cf4dc9b
commit
e40d6e066a
@ -4085,7 +4085,8 @@ a single byte in the string.
|
||||
</li>
|
||||
|
||||
<li>
|
||||
The iteration order over maps is not specified.
|
||||
The iteration order over maps is not specified
|
||||
and is not guaranteed to be the same from one iteration to the next.
|
||||
If map entries that have not yet been reached are deleted during iteration,
|
||||
the corresponding iteration values will not be produced. If map entries are
|
||||
inserted during iteration, the behavior is implementation-dependent, but the
|
||||
|
@ -80,16 +80,18 @@ typedef struct Hiter Hiter;
|
||||
struct Hiter
|
||||
{
|
||||
uchar data[8]; // return val from next
|
||||
int32 elemsize; // size of elements in table */
|
||||
int32 changes; // number of changes observed last time */
|
||||
int32 i; // stack pointer in subtable_state */
|
||||
uchar last[8]; // last hash value returned */
|
||||
uchar h[8]; // the hash table */
|
||||
int32 elemsize; // size of elements in table
|
||||
int32 changes; // number of changes observed last time
|
||||
int32 i; // stack pointer in subtable_state
|
||||
int32 cycled; // actually a bool but pad for next field, a pointer
|
||||
uchar last[8]; // last hash value returned
|
||||
uchar cycle[8]; // the value where we started and will stop
|
||||
uchar h[8]; // the hash table
|
||||
struct
|
||||
{
|
||||
uchar sub[8]; // pointer into subtable */
|
||||
uchar start[8]; // pointer into start of subtable */
|
||||
uchar end[8]; // pointer into end of subtable */
|
||||
uchar sub[8]; // pointer into subtable
|
||||
uchar start[8]; // pointer into start of subtable
|
||||
uchar end[8]; // pointer into end of subtable
|
||||
uchar pad[8];
|
||||
} sub[4];
|
||||
};
|
||||
|
@ -506,20 +506,27 @@ iter_restart (struct hash_iter *it, struct hash_subtable *st, int32 used)
|
||||
static void *
|
||||
hash_next (struct hash_iter *it)
|
||||
{
|
||||
int32 elemsize = it->elemsize;
|
||||
struct hash_iter_sub *sub = &it->subtable_state[it->i];
|
||||
struct hash_entry *e = sub->e;
|
||||
struct hash_entry *last = sub->last;
|
||||
hash_hash_t e_hash = 0;
|
||||
int32 elemsize;
|
||||
struct hash_iter_sub *sub;
|
||||
struct hash_entry *e;
|
||||
struct hash_entry *last;
|
||||
hash_hash_t e_hash;
|
||||
|
||||
if (it->changes != it->h->changes) { /* hash table's structure changed; recompute */
|
||||
if (~it->last_hash == 0)
|
||||
return (0);
|
||||
it->changes = it->h->changes;
|
||||
it->i = 0;
|
||||
iter_restart (it, it->h->st, 0);
|
||||
sub = &it->subtable_state[it->i];
|
||||
e = sub->e;
|
||||
last = sub->last;
|
||||
}
|
||||
elemsize = it->elemsize;
|
||||
|
||||
Again:
|
||||
e_hash = 0;
|
||||
sub = &it->subtable_state[it->i];
|
||||
e = sub->e;
|
||||
last = sub->last;
|
||||
|
||||
if (e != sub->start && it->last_hash != HASH_OFFSET (e, -elemsize)->hash) {
|
||||
struct hash_entry *start = HASH_OFFSET (e, -(elemsize * it->h->max_probes));
|
||||
struct hash_entry *pe = HASH_OFFSET (e, -elemsize);
|
||||
@ -542,8 +549,20 @@ hash_next (struct hash_iter *it)
|
||||
}
|
||||
if (e > last) {
|
||||
if (it->i == 0) {
|
||||
it->last_hash = HASH_OFFSET (e, -elemsize)->hash;
|
||||
sub->e = e;
|
||||
if(!it->cycled) {
|
||||
// Wrap to zero and iterate up until it->cycle.
|
||||
it->cycled = true;
|
||||
it->last_hash = 0;
|
||||
it->subtable_state[0].e = it->h->st->entry;
|
||||
it->subtable_state[0].start = it->h->st->entry;
|
||||
it->subtable_state[0].last = it->h->st->last;
|
||||
goto Again;
|
||||
}
|
||||
// Set last_hash to impossible value and
|
||||
// break it->changes, so that check at top of
|
||||
// hash_next will be used if we get called again.
|
||||
it->last_hash = ~(uintptr_t)0;
|
||||
it->changes--;
|
||||
return (0);
|
||||
} else {
|
||||
it->i--;
|
||||
@ -552,6 +571,15 @@ hash_next (struct hash_iter *it)
|
||||
last = sub->last;
|
||||
}
|
||||
} else if ((e_hash & HASH_MASK) != HASH_SUBHASH) {
|
||||
if(it->cycled && e->hash > it->cycle) {
|
||||
// Already returned this.
|
||||
// Set last_hash to impossible value and
|
||||
// break it->changes, so that check at top of
|
||||
// hash_next will be used if we get called again.
|
||||
it->last_hash = ~(uintptr_t)0;
|
||||
it->changes--;
|
||||
return (0);
|
||||
}
|
||||
it->last_hash = e->hash;
|
||||
sub->e = HASH_OFFSET (e, elemsize);
|
||||
return (e->data);
|
||||
@ -581,6 +609,17 @@ hash_iter_init (Hmap *h, struct hash_iter *it)
|
||||
it->subtable_state[0].e = h->st->entry;
|
||||
it->subtable_state[0].start = h->st->entry;
|
||||
it->subtable_state[0].last = h->st->last;
|
||||
|
||||
// fastrand1 returns 31 useful bits.
|
||||
// We don't care about not having a bottom bit but we
|
||||
// do want top bits.
|
||||
if(sizeof(void*) == 8)
|
||||
it->cycle = (uint64)runtime·fastrand1()<<33 | (uint64)runtime·fastrand1()<<2;
|
||||
else
|
||||
it->cycle = runtime·fastrand1()<<1;
|
||||
it->cycled = false;
|
||||
it->last_hash = it->cycle;
|
||||
iter_restart(it, it->h->st, 0);
|
||||
}
|
||||
|
||||
static void
|
||||
|
@ -82,7 +82,9 @@ struct hash_iter {
|
||||
int32 elemsize; /* size of elements in table */
|
||||
int32 changes; /* number of changes observed last time */
|
||||
int32 i; /* stack pointer in subtable_state */
|
||||
bool cycled; /* have reached the end and wrapped to 0 */
|
||||
hash_hash_t last_hash; /* last hash value returned */
|
||||
hash_hash_t cycle; /* hash value where we started */
|
||||
struct Hmap *h; /* the hash table */
|
||||
struct hash_iter_sub {
|
||||
struct hash_entry *e; /* pointer into subtable */
|
||||
|
Loading…
Reference in New Issue
Block a user