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Hash: iterable now per partes by an iterator

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It's now possible to pause iteration through hash. This requires
struct hash_iterator to be allocated somewhere handy.

The iteration itself is surrounded by HASH_WALK_ITER and
HASH_WALK_ITER_END. Call HASH_WALK_ITER_PUT to ask for pausing; it may
still do some more iterations until it comes to a suitable pausing
point. The iterator must be initalized to an empty structure. No cleanup
is needed if iteration is abandoned inbetween.
This commit is contained in:
Maria Matejka
2022-06-29 13:22:40 +02:00
parent b06911f6ef
commit d5e3272f3d
2 changed files with 71 additions and 10 deletions
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40
lib/hash.h
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@@ -10,7 +10,7 @@
#ifndef _BIRD_HASH_H_
#define _BIRD_HASH_H_
#define HASH(type) struct { type **data; uint count, order; }
#define HASH(type) struct { type **data; uint count; u16 iterators; u8 order; u8 down_requested:1; }
#define HASH_TYPE(v) typeof(** (v).data)
#define HASH_SIZE(v) (1U << (v).order)
@@ -125,20 +125,26 @@
#define HASH_MAY_STEP_DOWN_(v,pool,rehash_fn,args) \
({ \
if (((v).count < (HASH_SIZE(v) REHASH_LO_MARK(args))) && \
((v).order > (REHASH_LO_BOUND(args)))) \
if ((v).iterators) \
(v).down_requested = 1; \
else if (((v).count < (HASH_SIZE(v) REHASH_LO_MARK(args))) && \
((v).order > (REHASH_LO_BOUND(args)))) \
rehash_fn(&(v), pool, -(REHASH_LO_STEP(args))); \
})
#define HASH_MAY_RESIZE_DOWN_(v,pool,rehash_fn,args) \
({ \
uint _o = (v).order; \
while (((v).count < ((1U << _o) REHASH_LO_MARK(args))) && \
(_o > (REHASH_LO_BOUND(args)))) \
_o -= (REHASH_LO_STEP(args)); \
if (_o < (v).order) \
rehash_fn(&(v), pool, _o - (v).order); \
})
if ((v).iterators) \
(v).down_requested = 1; \
else { \
uint _o = (v).order; \
while (((v).count < ((1U << _o) REHASH_LO_MARK(args))) && \
(_o > (REHASH_LO_BOUND(args)))) \
_o -= (REHASH_LO_STEP(args)); \
if (_o < (v).order) \
rehash_fn(&(v), pool, _o - (v).order); \
} \
})
#define HASH_INSERT2(v,id,pool,node) \
@@ -195,6 +201,20 @@
#define HASH_WALK_FILTER_END } while (0)
#define HASH_WALK_ITER(v, id, n, iter) \
do { \
uint _hash_walk_iter_put = 0; \
uint _shift = 32 - (v).order; \
for ( ; !_hash_walk_iter_put; (iter) += (1U << _shift)) { \
_hash_walk_iter_put = ((iter) + (1U << _shift) == 0); \
for (HASH_TYPE(v) *n = (v).data[(iter) >> _shift]; n; n = id##_NEXT((n)))\
if (HASH_FN(v, id, id##_KEY(n)) >= ((iter) >> _shift)) \
#define HASH_WALK_ITER_PUT (_hash_walk_iter_put = 1)
#define HASH_WALK_ITER_END } } while (0)
static inline void
mem_hash_init(u64 *h)
{