v4k-git-backup/engine/split/v4k_id.c

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// -----------------------------------------------------------------------------
// factory of handle ids, based on code by randy gaul (PD/Zlib licensed)
// - rlyeh, public domain
//
// [src] http://www.randygaul.net/wp-content/uploads/2021/04/handle_table.cpp
// [ref] http://bitsquid.blogspot.com.es/2011/09/managing-decoupling-part-4-id-lookup.html
// [ref] http://glampert.com/2016/05-04/dissecting-idhashindex/
// [ref] https://github.com/nlguillemot/dof/blob/master/viewer/packed_freelist.h
// [ref] https://gist.github.com/pervognsen/ffd89e45b5750e9ce4c6c8589fc7f253
typedef union id64 {
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uint64_t h;
struct {
#if (ID_INDEX_BITS+ID_COUNT_BITS) != 64
uint64_t padding : 64-ID_INDEX_BITS-ID_COUNT_BITS;
#endif
uint64_t index : ID_INDEX_BITS;
uint64_t count : ID_COUNT_BITS;
};
} id64;
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typedef struct id_factory id_factory;
id_factory id_factory_create(uint64_t capacity /*= 256*/);
id64 id_factory_insert(id_factory *f, uint64_t data);
uint64_t id_factory_getvalue(id_factory *f, id64 handle);
void id_factory_setvalue(id_factory *f, id64 handle, uint64_t data);
void id_factory_erase(id_factory *f, id64 handle);
bool id_factory_isvalid(id_factory *f, id64 handle);
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void id_factory_destroy(id_factory *f);
// ---
typedef struct id_factory {
uint64_t freelist;
uint64_t capacity;
uint64_t canary;
union entry* entries;
} id_factory;
typedef union entry {
struct {
uint64_t data : ID_DATA_BITS;
uint64_t count : ID_COUNT_BITS;
};
uint64_t h;
} entry;
id_factory id_factory_create(uint64_t capacity) {
if(!capacity) capacity = 1ULL << ID_INDEX_BITS;
id_factory f = {0};
f.entries = CALLOC(1, sizeof(entry) * capacity);
f.capacity = capacity;
for (int i = 0; i < capacity - 1; ++i) {
f.entries[i].data = i + 1;
f.entries[i].count = 0;
}
f.entries[capacity - 1].h = 0;
f.entries[capacity - 1].data = ~0;
f.entries[capacity - 1].count = ~0;
f.canary = f.entries[capacity - 1].data;
return f;
}
void id_factory_destroy(id_factory *f) {
FREE(f->entries);
}
id64 id_factory_insert(id_factory *f, uint64_t data) {
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// pop element off the free list
assert(f->freelist != f->canary && "max alive capacity reached");
uint64_t index = f->freelist;
f->freelist = f->entries[f->freelist].data;
// create new id64
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f->entries[index].data = data;
id64 handle = {0};
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handle.index = index;
handle.count = f->entries[index].count;
return handle;
}
void id_factory_erase(id_factory *f, id64 handle) {
// push id64 onto the freelist
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uint64_t index = handle.index;
f->entries[index].data = f->freelist;
f->freelist = index;
// increment the count. this signifies a change in lifetime (this particular id64 is now dead)
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// the next time this particular index is used in alloc, a new `count` will be used to uniquely identify
f->entries[index].count++;
}
uint64_t id_factory_getvalue(id_factory *f, id64 handle) {
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uint64_t index = handle.index;
uint64_t count = handle.count;
assert(f->entries[index].count == count);
return f->entries[index].data;
}
void id_factory_setvalue(id_factory *f, id64 handle, uint64_t data) {
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uint64_t index = handle.index;
uint64_t count = handle.count;
assert(f->entries[index].count == count);
f->entries[index].data = data;
}
bool id_factory_isvalid(id_factory *f, id64 handle) {
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uint64_t index = handle.index;
uint64_t count = handle.count;
if (index >= f->capacity) return false;
return f->entries[index].count == count;
}
#if 0
// monitor history of a single entity by running `id_factory | find " 123."`
AUTORUN {
trap_install();
id_factory f = id_factory_create(optioni("--NUM",256));
array(id64) ids = 0;
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for( int i = 0 ; ; ++i, i &= ((1ULL << ID_INDEX_BITS) - 1) ) { // infinite wrap
printf("count_ids(%d) ", array_count(ids));
bool insert = randf() < 0.49; // biased against deletion
if( insert ) {
id64 h = id_factory_insert(&f, i);
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array_push(ids, h);
printf("add %llu.%llu\n", h.index, h.count);
} else {
int count = array_count(ids);
if( count ) {
int chosen = randi(0,count);
printf("del %d.\n", chosen);
id64 h = ids[chosen];
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id_factory_erase(&f, h);
array_erase(ids, chosen);
}
}
}
}
#endif
// ----------------------------------------------------------------------
// public api
static id_factory fid; // @fixme: threadsafe
uintptr_t id_make(void *ptr) {
do_once fid = id_factory_create(0), id_factory_insert(&fid, 0); // init and reserve id(0)
id64 newid = id_factory_insert(&fid, (uint64_t)(uintptr_t)ptr ); // 48-bit effective addr
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return newid.h;
}
void *id_handle(uintptr_t id) {
return (void *)(uintptr_t)id_factory_getvalue(&fid, ((id64){ (uint64_t)id }) );
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}
void id_dispose(uintptr_t id) {
id_factory_erase(&fid, ((id64){ (uint64_t)id }) );
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}
bool id_valid(uintptr_t id) {
return id_factory_isvalid(&fid, ((id64){ (uint64_t)id }) );
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}