a85b5759f3
These files were pulled from the 1.6.3 release tarball. This new version builds against OpenSSL version 1.1 which will be the default in the new Debian Stable which is due to be released RealSoonNow (tm).
447 lines
16 KiB
C
447 lines
16 KiB
C
/*
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* util/storage/lruhash.h - hashtable, hash function, LRU keeping.
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*
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* Copyright (c) 2007, NLnet Labs. All rights reserved.
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*
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* This software is open source.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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*
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* Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* Neither the name of the NLNET LABS nor the names of its contributors may
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* be used to endorse or promote products derived from this software without
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* specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
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* TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/**
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* \file
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*
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* This file contains a hashtable with LRU keeping of entries.
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*
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* The hash table keeps a maximum memory size. Old entries are removed
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* to make space for new entries.
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*
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* The locking strategy is as follows:
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* o since (almost) every read also implies a LRU update, the
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* hashtable lock is a spinlock, not rwlock.
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* o the idea is to move every thread through the hash lock quickly,
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* so that the next thread can access the lookup table.
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* o User performs hash function.
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*
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* For read:
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* o lock hashtable.
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* o lookup hash bin.
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* o lock hash bin.
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* o find entry (if failed, unlock hash, unl bin, exit).
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* o swizzle pointers for LRU update.
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* o unlock hashtable.
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* o lock entry (rwlock).
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* o unlock hash bin.
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* o work on entry.
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* o unlock entry.
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*
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* To update an entry, gain writelock and change the entry.
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* (the entry must keep the same hashvalue, so a data update.)
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* (you cannot upgrade a readlock to a writelock, because the item may
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* be deleted, it would cause race conditions. So instead, unlock and
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* relookup it in the hashtable.)
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*
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* To delete an entry:
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* o unlock the entry if you hold the lock already.
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* o lock hashtable.
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* o lookup hash bin.
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* o lock hash bin.
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* o find entry (if failed, unlock hash, unl bin, exit).
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* o remove entry from hashtable bin overflow chain.
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* o unlock hashtable.
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* o lock entry (writelock).
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* o unlock hash bin.
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* o unlock entry (nobody else should be waiting for this lock,
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* since you removed it from hashtable, and you got writelock while
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* holding the hashbinlock so you are the only one.)
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* Note you are only allowed to obtain a lock while holding hashbinlock.
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* o delete entry.
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*
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* The above sequence is:
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* o race free, works with read, write and delete.
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* o but has a queue, imagine someone needing a writelock on an item.
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* but there are still readlocks. The writelocker waits, but holds
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* the hashbinlock. The next thread that comes in and needs the same
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* hashbin will wait for the lock while holding the hashtable lock.
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* thus halting the entire system on hashtable.
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* This is because of the delete protection.
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* Readlocks will be easier on the rwlock on entries.
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* While the writer is holding writelock, similar problems happen with
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* a reader or writer needing the same item.
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* the scenario requires more than three threads.
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* o so the queue length is 3 threads in a bad situation. The fourth is
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* unable to use the hashtable.
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*
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* If you need to acquire locks on multiple items from the hashtable.
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* o you MUST release all locks on items from the hashtable before
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* doing the next lookup/insert/delete/whatever.
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* o To acquire multiple items you should use a special routine that
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* obtains the locks on those multiple items in one go.
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*/
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#ifndef UTIL_STORAGE_LRUHASH_H
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#define UTIL_STORAGE_LRUHASH_H
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#include "util/locks.h"
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struct lruhash_bin;
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struct lruhash_entry;
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/** default start size for hash arrays */
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#define HASH_DEFAULT_STARTARRAY 1024 /* entries in array */
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/** default max memory for hash arrays */
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#define HASH_DEFAULT_MAXMEM 4*1024*1024 /* bytes */
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/** the type of a hash value */
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typedef uint32_t hashvalue_type;
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/**
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* Type of function that calculates the size of an entry.
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* Result must include the size of struct lruhash_entry.
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* Keys that are identical must also calculate to the same size.
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* size = func(key, data).
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*/
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typedef size_t (*lruhash_sizefunc_type)(void*, void*);
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/** type of function that compares two keys. return 0 if equal. */
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typedef int (*lruhash_compfunc_type)(void*, void*);
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/** old keys are deleted.
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* The RRset type has to revoke its ID number, markdel() is used first.
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* This function is called: func(key, userarg) */
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typedef void (*lruhash_delkeyfunc_type)(void*, void*);
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/** old data is deleted. This function is called: func(data, userarg). */
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typedef void (*lruhash_deldatafunc_type)(void*, void*);
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/** mark a key as pending to be deleted (and not to be used by anyone).
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* called: func(key) */
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typedef void (*lruhash_markdelfunc_type)(void*);
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/**
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* Hash table that keeps LRU list of entries.
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*/
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struct lruhash {
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/** lock for exclusive access, to the lookup array */
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lock_quick_type lock;
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/** the size function for entries in this table */
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lruhash_sizefunc_type sizefunc;
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/** the compare function for entries in this table. */
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lruhash_compfunc_type compfunc;
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/** how to delete keys. */
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lruhash_delkeyfunc_type delkeyfunc;
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/** how to delete data. */
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lruhash_deldatafunc_type deldatafunc;
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/** how to mark a key pending deletion */
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lruhash_markdelfunc_type markdelfunc;
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/** user argument for user functions */
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void* cb_arg;
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/** the size of the lookup array */
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size_t size;
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/** size bitmask - since size is a power of 2 */
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int size_mask;
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/** lookup array of bins */
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struct lruhash_bin* array;
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/** the lru list, start and end, noncyclical double linked list. */
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struct lruhash_entry* lru_start;
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/** lru list end item (least recently used) */
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struct lruhash_entry* lru_end;
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/** the number of entries in the hash table. */
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size_t num;
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/** the amount of space used, roughly the number of bytes in use. */
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size_t space_used;
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/** the amount of space the hash table is maximally allowed to use. */
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size_t space_max;
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};
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/**
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* A single bin with a linked list of entries in it.
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*/
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struct lruhash_bin {
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/**
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* Lock for exclusive access to the linked list
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* This lock makes deletion of items safe in this overflow list.
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*/
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lock_quick_type lock;
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/** linked list of overflow entries */
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struct lruhash_entry* overflow_list;
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};
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/**
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* An entry into the hash table.
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* To change overflow_next you need to hold the bin lock.
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* To change the lru items you need to hold the hashtable lock.
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* This structure is designed as part of key struct. And key pointer helps
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* to get the surrounding structure. Data should be allocated on its own.
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*/
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struct lruhash_entry {
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/**
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* rwlock for access to the contents of the entry
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* Note that it does _not_ cover the lru_ and overflow_ ptrs.
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* Even with a writelock, you cannot change hash and key.
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* You need to delete it to change hash or key.
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*/
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lock_rw_type lock;
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/** next entry in overflow chain. Covered by hashlock and binlock. */
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struct lruhash_entry* overflow_next;
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/** next entry in lru chain. covered by hashlock. */
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struct lruhash_entry* lru_next;
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/** prev entry in lru chain. covered by hashlock. */
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struct lruhash_entry* lru_prev;
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/** hash value of the key. It may not change, until entry deleted. */
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hashvalue_type hash;
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/** key */
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void* key;
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/** data */
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void* data;
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};
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/**
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* Create new hash table.
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* @param start_size: size of hashtable array at start, must be power of 2.
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* @param maxmem: maximum amount of memory this table is allowed to use.
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* @param sizefunc: calculates memory usage of entries.
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* @param compfunc: compares entries, 0 on equality.
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* @param delkeyfunc: deletes key.
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* Calling both delkey and deldata will also free the struct lruhash_entry.
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* Make it part of the key structure and delete it in delkeyfunc.
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* @param deldatafunc: deletes data.
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* @param arg: user argument that is passed to user function calls.
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* @return: new hash table or NULL on malloc failure.
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*/
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struct lruhash* lruhash_create(size_t start_size, size_t maxmem,
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lruhash_sizefunc_type sizefunc, lruhash_compfunc_type compfunc,
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lruhash_delkeyfunc_type delkeyfunc,
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lruhash_deldatafunc_type deldatafunc, void* arg);
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/**
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* Delete hash table. Entries are all deleted.
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* @param table: to delete.
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*/
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void lruhash_delete(struct lruhash* table);
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/**
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* Clear hash table. Entries are all deleted, while locking them before
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* doing so. At end the table is empty.
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* @param table: to make empty.
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*/
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void lruhash_clear(struct lruhash* table);
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/**
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* Insert a new element into the hashtable.
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* If key is already present data pointer in that entry is updated.
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* The space calculation function is called with the key, data.
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* If necessary the least recently used entries are deleted to make space.
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* If necessary the hash array is grown up.
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*
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* @param table: hash table.
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* @param hash: hash value. User calculates the hash.
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* @param entry: identifies the entry.
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* If key already present, this entry->key is deleted immediately.
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* But entry->data is set to NULL before deletion, and put into
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* the existing entry. The data is then freed.
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* @param data: the data.
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* @param cb_override: if not null overrides the cb_arg for the deletefunc.
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*/
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void lruhash_insert(struct lruhash* table, hashvalue_type hash,
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struct lruhash_entry* entry, void* data, void* cb_override);
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/**
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* Lookup an entry in the hashtable.
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* At the end of the function you hold a (read/write)lock on the entry.
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* The LRU is updated for the entry (if found).
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* @param table: hash table.
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* @param hash: hash of key.
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* @param key: what to look for, compared against entries in overflow chain.
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* the hash value must be set, and must work with compare function.
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* @param wr: set to true if you desire a writelock on the entry.
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* with a writelock you can update the data part.
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* @return: pointer to the entry or NULL. The entry is locked.
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* The user must unlock the entry when done.
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*/
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struct lruhash_entry* lruhash_lookup(struct lruhash* table,
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hashvalue_type hash, void* key, int wr);
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/**
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* Touch entry, so it becomes the most recently used in the LRU list.
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* Caller must hold hash table lock. The entry must be inserted already.
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* @param table: hash table.
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* @param entry: entry to make first in LRU.
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*/
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void lru_touch(struct lruhash* table, struct lruhash_entry* entry);
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/**
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* Set the markdelfunction (or NULL)
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*/
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void lruhash_setmarkdel(struct lruhash* table, lruhash_markdelfunc_type md);
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/************************* getdns functions ************************/
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/*** these are used by getdns only and not by unbound. ***/
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/**
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* Demote entry, so it becomes the least recently used in the LRU list.
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* Caller must hold hash table lock. The entry must be inserted already.
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* @param table: hash table.
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* @param entry: entry to make last in LRU.
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*/
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void lru_demote(struct lruhash* table, struct lruhash_entry* entry);
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/**
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* Insert a new element into the hashtable, or retrieve the corresponding
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* element of it exits.
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*
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* If key is already present data pointer in that entry is kept.
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* If it is not present, a new entry is created. In that case,
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* the space calculation function is called with the key, data.
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* If necessary the least recently used entries are deleted to make space.
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* If necessary the hash array is grown up.
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*
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* @param table: hash table.
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* @param hash: hash value. User calculates the hash.
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* @param entry: identifies the entry.
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* @param data: the data.
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* @param cb_arg: if not null overrides the cb_arg for the deletefunc.
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* @return: pointer to the existing entry if the key was already present,
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* or to the entry argument if it was not.
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*/
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struct lruhash_entry* lruhash_insert_or_retrieve(struct lruhash* table, hashvalue_type hash,
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struct lruhash_entry* entry, void* data, void* cb_arg);
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/************************* Internal functions ************************/
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/*** these are only exposed for unit tests. ***/
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/**
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* Remove entry from hashtable. Does nothing if not found in hashtable.
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* Delfunc is called for the entry.
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* @param table: hash table.
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* @param hash: hash of key.
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* @param key: what to look for.
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*/
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void lruhash_remove(struct lruhash* table, hashvalue_type hash, void* key);
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/** init the hash bins for the table */
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void bin_init(struct lruhash_bin* array, size_t size);
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/** delete the hash bin and entries inside it */
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void bin_delete(struct lruhash* table, struct lruhash_bin* bin);
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/**
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* Find entry in hash bin. You must have locked the bin.
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* @param table: hash table with function pointers.
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* @param bin: hash bin to look into.
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* @param hash: hash value to look for.
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* @param key: key to look for.
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* @return: the entry or NULL if not found.
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*/
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struct lruhash_entry* bin_find_entry(struct lruhash* table,
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struct lruhash_bin* bin, hashvalue_type hash, void* key);
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/**
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* Remove entry from bin overflow chain.
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* You must have locked the bin.
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* @param bin: hash bin to look into.
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* @param entry: entry ptr that needs removal.
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*/
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void bin_overflow_remove(struct lruhash_bin* bin,
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struct lruhash_entry* entry);
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/**
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* Split hash bin into two new ones. Based on increased size_mask.
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* Caller must hold hash table lock.
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* At the end the routine acquires all hashbin locks (in the old array).
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* This makes it wait for other threads to finish with the bins.
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* So the bins are ready to be deleted after this function.
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* @param table: hash table with function pointers.
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* @param newa: new increased array.
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* @param newmask: new lookup mask.
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*/
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void bin_split(struct lruhash* table, struct lruhash_bin* newa,
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int newmask);
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/**
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* Try to make space available by deleting old entries.
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* Assumes that the lock on the hashtable is being held by caller.
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* Caller must not hold bin locks.
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* @param table: hash table.
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* @param list: list of entries that are to be deleted later.
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* Entries have been removed from the hash table and writelock is held.
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*/
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void reclaim_space(struct lruhash* table, struct lruhash_entry** list);
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/**
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* Grow the table lookup array. Becomes twice as large.
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* Caller must hold the hash table lock. Must not hold any bin locks.
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* Tries to grow, on malloc failure, nothing happened.
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* @param table: hash table.
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*/
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void table_grow(struct lruhash* table);
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/**
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* Put entry at front of lru. entry must be unlinked from lru.
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* Caller must hold hash table lock.
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* @param table: hash table with lru head and tail.
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* @param entry: entry to make most recently used.
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*/
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void lru_front(struct lruhash* table, struct lruhash_entry* entry);
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/**
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* Remove entry from lru list.
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* Caller must hold hash table lock.
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* @param table: hash table with lru head and tail.
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* @param entry: entry to remove from lru.
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*/
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void lru_remove(struct lruhash* table, struct lruhash_entry* entry);
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/**
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* Output debug info to the log as to state of the hash table.
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* @param table: hash table.
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* @param id: string printed with table to identify the hash table.
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* @param extended: set to true to print statistics on overflow bin lengths.
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*/
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void lruhash_status(struct lruhash* table, const char* id, int extended);
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/**
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* Get memory in use now by the lruhash table.
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* @param table: hash table. Will be locked before use. And unlocked after.
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* @return size in bytes.
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*/
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size_t lruhash_get_mem(struct lruhash* table);
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/**
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* Traverse a lruhash. Call back for every element in the table.
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* @param h: hash table. Locked before use.
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* @param wr: if true writelock is obtained on element, otherwise readlock.
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* @param func: function for every element. Do not lock or unlock elements.
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* @param arg: user argument to func.
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*/
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void lruhash_traverse(struct lruhash* h, int wr,
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void (*func)(struct lruhash_entry*, void*), void* arg);
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#endif /* UTIL_STORAGE_LRUHASH_H */
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