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Sweden-Number/ipc/generic_hash.c

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/***************************************************************************
* Copyright 1995 Michael Veksler. mveksler@vnet.ibm.com
***************************************************************************
* File: generic_hash.c
* Purpose : dynamically growing hash, may use shared or local memory.
***************************************************************************
*/
#ifdef CONFIG_IPC
#include <sys/types.h>
#include <stdlib.h>
#include <assert.h>
#include "generic_hash.h"
#define ROUND_UP4(num) (( (num)+3) & ~3)
#define FREE_ENTRY 0
#define DELETED_ENTRY ((DWORD)-1)
#define NO_OF_PRIMES 512
#define GET_ITEM(items,size,i)\
(*(HASH_ITEM*) \
( ((char *)(items))+ \
(i)*(size)) )
static HASH_ITEM *locate_entry(HASH_CONTAINER* hash, DWORD key,
HASH_VAL *seeked_data, BOOL skip_deleted);
static void copy_hash_items(HASH_CONTAINER *hash, HASH_ITEM *old_items,
int old_n_items);
static BOOL arrays_initialized = FALSE;
static int primes[NO_OF_PRIMES];
static int best_primes[NO_OF_PRIMES];
static int no_of_primes;
static int no_of_best_primes;
static int max_num;
/* binary search for `num' in the `primes' array */
static BOOL prime_binary_search_found(int num)
{
int min_idx, max_idx, idx;
min_idx=0;
max_idx=no_of_primes-1;
while (min_idx <= max_idx) {
idx = (max_idx + min_idx) >> 1;
if (num == primes[idx])
return TRUE;
if (num < primes[idx])
max_idx = idx-1;
else
min_idx = idx+1;
}
return FALSE;
}
static BOOL is_prime(int num)
{
int i;
if ((num & 0x1) == 0) /* can be divided by 2 */
if (num == 2)
return TRUE;
else
return FALSE;
if (num <= primes[no_of_primes-1])
return prime_binary_search_found(num);
for (i=0 ; i < no_of_primes ; i++) {
if (num % primes[i] == 0)
return FALSE;
if (num < primes[i] * primes[i])
return TRUE;
}
return TRUE;
}
static void setup_primes()
{
int num;
primes[0]=2;
primes[1]=3;
no_of_primes=2;
/* count in modulo 6 to avoid numbers that divide by 2 or 3 */
for (num=5 ; ; num+=6) {
if (is_prime(num)) {
primes[no_of_primes++]=num;
if (no_of_primes >= NO_OF_PRIMES)
break;
}
if (is_prime(num+2)) {
primes[no_of_primes++]=num+2;
if (no_of_primes >= NO_OF_PRIMES)
break;
}
}
max_num= primes[no_of_primes-1] * primes[no_of_primes-1];
}
/* Find primes which are far "enough" from powers of two */
void setup_best_primes()
{
int i;
int num;
int pow2before, pow2after;
int min_range, max_range;
min_range=3;
max_range=3;
pow2before= 2;
pow2after= 4;
no_of_best_primes= 0;
for (i=0 ; i < no_of_primes ; i++){
num= primes[i];
if (num > pow2after) {
pow2before= pow2after;
pow2after <<=1;
min_range= pow2before+ (pow2before >> 3);
max_range= pow2after- (pow2before >> 2);
}
if (num > min_range && num < max_range)
best_primes[no_of_best_primes++]=num;
}
}
/* binary search for `num' in the `best_primes' array,
* Return smallest best_prime >= num.
*/
static int best_prime_binary_search(int num)
{
int min_idx, max_idx, idx;
min_idx=0;
max_idx=no_of_best_primes-1;
while (1) {
idx = (max_idx + min_idx) >> 1;
if (num == best_primes[idx])
return num;
if (num < best_primes[idx]) {
max_idx = idx-1;
if (max_idx <= min_idx)
return best_primes[idx];
}
else {
min_idx = idx+1;
if (min_idx >= max_idx)
return best_primes[max_idx];
}
}
}
/* Find the best prime, near `num' (which can be any number) */
static int best_prime(int num)
{
int log2;
int pow2less, pow2more;
int min_range, max_range;
if (num < 11)
return 11;
if (num <= best_primes[no_of_best_primes-1])
return best_prime_binary_search(num);
assert( num < max_num );
for (log2=0 ; num >> log2 ; log2++)
;
pow2less= 1 << log2;
pow2more= 1 << (log2+1);
min_range= pow2less + (pow2less >> 3);
max_range= pow2more - (pow2more >> 3);
if (num < min_range)
num= min_range;
num |= 1; /* make sure num can't be divided by 2 */
while (1) {
if (num >= max_range) {
pow2less<<= 1;
pow2more<<= 1;
min_range= pow2less + (pow2less >> 3);
max_range= pow2more - (pow2more >> 3);
num= min_range | 1; /* make sure num can't be divided by 2 */
}
/* num should be here in the range: (min_range, max_range) */
if (is_prime(num))
return num;
num+=2;
}
}
/* FIXME: This can be done before compiling. (uning a script)*/
static void setup_arrays()
{
setup_primes();
setup_best_primes();
}
/* Discard all DELETED_ENTRYs moving the data to it's correct location.
* Done without a temporary buffer.
* May require some efficiency improvements ( currently it's o(N^2)
* or is it o(N^3) in the worst case ? In the avarege it seems to be
* something like o(N log (N)))
*/
static void static_collect_garbge(HASH_CONTAINER *hash)
{
int i;
BOOL change;
HASH_ITEM *items;
HASH_ITEM *located;
HASH_ITEM *item;
int key;
items= hash->items;
do {
change= FALSE;
for (i=hash->shared->total_items-1 ; i >= 0 ; i--) {
item= &GET_ITEM(items,hash->bytes_per_item,i);
key= item->key;
if (key != DELETED_ENTRY && key != FREE_ENTRY) {
/* try to place the entry in a deleted location */
located= locate_entry(hash, key, &item->data,
0 /* no skip_deleted */);
if (located->key == DELETED_ENTRY) {
change= TRUE;
memcpy(&located, &item,
hash->bytes_per_item);
item->key= DELETED_ENTRY;
}
}
}
} while (change);
/* No change means that there is no need to go through a DELETED_ENTRY
* in order to reach an item, so DELETED_ENTRY looses it's special
* meaning, and it is the same as FREE_ENTRY.
*/
for (i=hash->shared->total_items-1 ; i >= 0 ; i--)
if (GET_ITEM(items,hash->bytes_per_item,i).key == DELETED_ENTRY)
GET_ITEM(items,hash->bytes_per_item,i).key = FREE_ENTRY;
hash->shared->deleted_items=0;
}
static void collect_garbge(HASH_CONTAINER *hash)
{
HASH_SHARED *shared= hash->shared;
HASH_ITEM *temp_items;
int size;
size= shared->total_items * hash->bytes_per_item;
temp_items= (HASH_ITEM*)malloc(size);
if (temp_items==NULL) {
static_collect_garbge(hash);
} else {
memcpy(temp_items, hash->items, size);
copy_hash_items(hash, temp_items, shared->total_items);
}
}
static void copy_hash_items(HASH_CONTAINER *hash, HASH_ITEM *old_items,
int old_n_items)
{
HASH_SHARED *shared= hash->shared;
HASH_ITEM *item;
int i;
shared->deleted_items = 0;
shared->free_items= shared->total_items;
/* make all items free */
for (i= shared->total_items-1 ; i>=0 ; i--)
GET_ITEM(hash->items, hash->bytes_per_item, i).key = FREE_ENTRY;
/* copy items */
for (i=0 ; i <= old_n_items; i++) {
item= &GET_ITEM(old_items, hash->bytes_per_item,i);
if (item->key != FREE_ENTRY && item->key != DELETED_ENTRY)
hash_add_item(hash, item->key, &item->data);
}
}
static void reorder_hash(HASH_CONTAINER *hash)
{
HASH_SHARED *shared= hash->shared;
HASH_ITEM *items, *old_items;
HASH_PTR shared_items, old_shared_items;
int n_items, old_n_items;
int size;
if (shared->deleted_items > hash->min_free_items) {
collect_garbge(hash);
return;
}
n_items= best_prime(shared->total_items * HASH_REALLOC_JUMPS);
size= n_items *
(sizeof(items[0]) - sizeof(items[0].data) + hash->bytes_per_item);
shared_items= hash->allocate_mem(size);
items= hash->access_mem(shared_items);
if (items == NULL) {
collect_garbge(hash);
return;
}
old_shared_items = shared->items;
old_n_items= shared->total_items;
old_items= hash->items;
/* setup a new clean hash based on the parameters of the original one */
hash->items= items;
shared->total_items = n_items;
shared->items= shared_items;
set_hash_parameters(hash, hash->maximum_load);
copy_hash_items(hash, old_items, old_n_items);
hash->free_mem(old_shared_items);
hash->last_ptr_update= ++shared->ptr_updates;
}
/* low level: attach hash existing hash items, no checks are performed
* No complex calculations done.
*/
static HASH_CONTAINER *attach_no_check(HASH_ITEM *items, int bytes_per_datum)
{
HASH_CONTAINER *hash;
int bytes_per_item;
HASH_ITEM dummy_item;
hash= (HASH_CONTAINER*) malloc(sizeof(HASH_CONTAINER) );
if (hash == NULL)
return NULL;
bytes_per_item= bytes_per_datum+
sizeof(dummy_item)-sizeof(dummy_item.data);
hash->bytes_per_item= ROUND_UP4(bytes_per_item);
hash->items= items;
hash->is_correct_item= NULL;
hash->allocate_mem= HASH_MEM_ALLOC;
hash->access_mem= HASH_MEM_ACCESS;
hash->free_mem= HASH_MEM_FREE;
set_hash_parameters(hash, HASH_LOAD);
return hash;
}
/* Attach existing & running remote (i.e. shared) hash.
* Attach the items using the data stored in "shared"
*/
HASH_CONTAINER *attach_remote_hash(HASH_SHARED *shared, int bytes_per_datum,
HASH_ITEM *(*access_mem)(HASH_PTR))
{
HASH_CONTAINER *hash;
HASH_ITEM *items;
assert(access_mem != NULL);
if (! arrays_initialized)
setup_arrays();
items=access_mem(shared->items);
hash= attach_no_check(items, bytes_per_datum);
if (hash == NULL)
return NULL;
hash->shared_was_malloced = FALSE;
hash->shared= shared;
return (hash);
}
HASH_CONTAINER *create_remote_hash(HASH_SHARED *shared,
int bytes_per_datum,
int total_items,
HASH_PTR (*allocate_mem)(int size),
HASH_ITEM *(*access_mem)(HASH_PTR))
{
HASH_CONTAINER *hash;
int size;
int i;
assert(total_items >= 1);
assert(bytes_per_datum >=1);
assert(access_mem != NULL);
assert(allocate_mem != NULL);
assert(shared != NULL);
if (! arrays_initialized)
setup_arrays();
if (total_items < MIN_HASH)
total_items= MIN_HASH;
else
total_items= best_prime(total_items);
hash= attach_no_check(NULL, bytes_per_datum);
if (hash==NULL) {
free(hash);
return NULL;
}
shared->total_items= total_items;
hash->shared= shared;
hash->shared_was_malloced = FALSE;
size= total_items * hash->bytes_per_item;
shared->items = allocate_mem(size);
hash->items= access_mem(shared->items);
if (hash->items == NULL ) {
free(hash);
return NULL;
}
shared->items.ptr= hash->items;
/* make all items free */
for (i=0 ; i < total_items ; i++)
GET_ITEM(hash->items,hash->bytes_per_item,i).key = FREE_ENTRY;
shared->deleted_items= 0;
shared->free_items= total_items;
shared->ptr_updates= 0;
return hash;
}
/* hash constructor: create brand new hash */
HASH_CONTAINER *create_hash(int bytes_per_datum, int total_items)
{
HASH_CONTAINER *hash;
HASH_SHARED *shared;
shared= (HASH_SHARED*)malloc(sizeof(HASH_SHARED));
if (shared == NULL)
return NULL;
hash= create_remote_hash(shared, bytes_per_datum, total_items,
HASH_MEM_ALLOC, HASH_MEM_ACCESS);
if (hash == NULL) {
free(shared);
return NULL;
}
hash->shared_was_malloced = TRUE;
return hash;
}
/* set the extra handlers to non default values */
void set_hash_handlers(HASH_CONTAINER *hash,
HASH_ITEM_TEST *is_correct_item,
HASH_PTR (*allocate_mem)(int size),
void (*free_mem)(HASH_PTR),
HASH_ITEM *(*access_mem)(HASH_PTR))
{
assert(hash);
assert(allocate_mem);
assert(free_mem);
hash->free_mem = free_mem;
hash->allocate_mem = allocate_mem;
hash->access_mem = access_mem;
hash->is_correct_item = is_correct_item;
}
/* set extra parameters */
void set_hash_parameters(HASH_CONTAINER *hash, int load)
{
assert(hash);
assert(load>30); /* no sence to realloc with less than */
/* 50% load, limiting to 30% to be on */
/* the safe size */
assert(load<=100);
hash->maximum_load= load;
hash->min_free_items= (1.0 - load/100.0) * hash->shared->total_items + 1 ;
}
/* hash destructor: destroy anything related to the hash */
void destroy_hash(HASH_CONTAINER *hash)
{
assert(hash);
hash->free_mem(hash->shared->items);
if (hash->shared_was_malloced)
free(hash->shared);
free(hash);
}
/* hash destructor: just detach hash, without destroing it (makes */
/* sence in shared memory environment) */
void detach_hash(HASH_CONTAINER *hash)
{
assert(hash);
free(hash);
}
/********** Hash usage *************/
static inline BOOL
correct_entry(HASH_ITEM *item, int key, HASH_VAL *seeked_data,
HASH_ITEM_TEST *is_correct_item, BOOL skip_deleted)
{
switch(item->key) {
case FREE_ENTRY:
return TRUE;
case DELETED_ENTRY:
return skip_deleted ? FALSE : TRUE;
default:
if (item->key != key)
return FALSE;
if (is_correct_item != NULL)
return is_correct_item(&item->data, seeked_data);
else
return TRUE;
}
}
/* The algorithm of the hash (one of the 2 standard hash implementations):
* Iterate through the hash table until
* 1. The entry has been found.
* 2. A FREE entry has been found.
* 3. For insert operations only- A DELETED entry has been found.
* The difference between DELETED and FREE entires is that
* DELETED entry was one occupied, while FREE was never allocated.
* The idea behind this structure to keep other entries reachable.
*/
static HASH_ITEM *locate_entry(HASH_CONTAINER* hash, DWORD key,
HASH_VAL *seeked_data, BOOL skip_deleted)
{
DWORD hash_idx, hash_leaps;
HASH_ITEM *item;
int i;
int total_items;
assert(hash);
total_items= hash->shared->total_items;
hash_idx= key % total_items;
item= &GET_ITEM(hash->items, hash->bytes_per_item, hash_idx);
if ( correct_entry( item, key, seeked_data,
hash->is_correct_item, skip_deleted) )
return item;
/* get the WORDs in different order in this DWORD to avoid clustering */
hash_leaps=((DWORD)MAKELONG(HIWORD(key), LOWORD(key))
% (total_items-1)) +1;
/* interate through the hash table using hash_leaps */
for (i= total_items ; i ; i--) {
hash_idx+= hash_leaps;
if (hash_idx > total_items)
hash_idx -= total_items;
item= &GET_ITEM(hash->items,hash->bytes_per_item, hash_idx);
if ( correct_entry( item, key, seeked_data,
hash->is_correct_item, skip_deleted) )
return item;
}
return NULL;
}
static inline void sync_shared_hash(HASH_CONTAINER *hash)
{
HASH_SHARED *shared= hash->shared;
if (shared->ptr_updates == hash->last_ptr_update)
return;
assert(shared->ptr_updates >= hash->last_ptr_update);
hash->last_ptr_update= shared->ptr_updates;
hash->min_free_items= (1.0 - hash->maximum_load/100.0) *
shared->total_items + 1 ;
hash->items= hash->access_mem(shared->items);
}
HASH_VAL *hash_locate_item(HASH_CONTAINER* hash,
int key, HASH_VAL *seeked_data)
{
HASH_ITEM *item;
assert(hash != NULL);
sync_shared_hash(hash);
item= locate_entry(hash, key, seeked_data, 1 /* skip_deleted */);
if (item == NULL)
return NULL;
if (item->key == FREE_ENTRY )
return NULL;
return &item->data;
}
BOOL hash_add_item(HASH_CONTAINER* hash, int key, HASH_VAL *data)
{
HASH_SHARED *shared;
HASH_ITEM *item;
assert(hash != NULL);
sync_shared_hash(hash);
shared= hash->shared;
item=locate_entry(hash, key, data, 0 /* no skip_deleted */);
assert(item != NULL);
if (item->key == key)
return FALSE;
if (item->key == FREE_ENTRY)
shared->free_items--;
else
shared->deleted_items--;
item->key= key;
memcpy(&item->data, data, hash->bytes_per_item-sizeof(key));
if (shared->free_items < hash->min_free_items ||
shared->deleted_items > hash->min_free_items)
reorder_hash(hash);
return TRUE;
}
BOOL hash_delete_item(HASH_CONTAINER* hash, int key, HASH_VAL *seeked_data)
{
HASH_ITEM *item;
assert(hash != NULL);
sync_shared_hash(hash);
item=locate_entry(hash, key, seeked_data, 1 /* skip_deleted */);
if (item == NULL)
return FALSE;
if (item->key == FREE_ENTRY)
return FALSE;
item->key = DELETED_ENTRY;
hash->shared->deleted_items++;
return TRUE;
}
void *ret_null()
{
return NULL;
}
HASH_ITEM *access_local_hash(HASH_PTR ptr)
{
return ptr.ptr;
}
#endif /* CONFIG_IPC */
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