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Filename : apc_cache.h
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/*
  +----------------------------------------------------------------------+
  | APC                                                                  |
  +----------------------------------------------------------------------+
  | Copyright (c) 2006-2011 The PHP Group                                |
  +----------------------------------------------------------------------+
  | This source file is subject to version 3.01 of the PHP license,      |
  | that is bundled with this package in the file LICENSE, and is        |
  | available through the world-wide-web at the following url:           |
  | http://www.php.net/license/3_01.txt.                                 |
  | If you did not receive a copy of the PHP license and are unable to   |
  | obtain it through the world-wide-web, please send a note to          |
  | license@php.net so we can mail you a copy immediately.               |
  +----------------------------------------------------------------------+
  | Authors: Daniel Cowgill <dcowgill@communityconnect.com>              |
  |          Rasmus Lerdorf <rasmus@php.net>                             |
  +----------------------------------------------------------------------+

   This software was contributed to PHP by Community Connect Inc. in 2002
   and revised in 2005 by Yahoo! Inc. to add support for PHP 5.1.
   Future revisions and derivatives of this source code must acknowledge
   Community Connect Inc. as the original contributor of this module by
   leaving this note intact in the source code.

   All other licensing and usage conditions are those of the PHP Group.

 */

#ifndef APC_CACHE_H
#define APC_CACHE_H

#include "apc.h"
#include "apc_sma.h"
#include "apc_lock.h"
#include "apc_globals.h"
#include "TSRM.h"

typedef struct apc_cache_slam_key_t apc_cache_slam_key_t;
struct apc_cache_slam_key_t {
	zend_ulong hash;         /* hash of the key */
	size_t len;              /* length of the key */
	time_t mtime;            /* creation time of this key */
	pid_t owner_pid;         /* the pid that created this key */
#ifdef ZTS
	void ***owner_thread;    /* TSRMLS cache of thread that created this key */
#endif
};

typedef struct apc_cache_entry_t apc_cache_entry_t;
struct apc_cache_entry_t {
	uintptr_t next;          /* offset to next entry (MUST BE THE 1st FIELD OF THE STRUCT!) */
	uintptr_t prev;          /* offset to previous entry / head-pointer of the linked list */
	zend_long ttl;           /* the ttl on this specific entry */
	zend_long ref_count;     /* the reference count of this entry */
	zend_long nhits;         /* number of hits to this entry */
	time_t ctime;            /* time entry was initialized */
	time_t mtime;            /* the mtime of this cached entry */
	time_t dtime;            /* time entry was removed from cache */
	time_t atime;            /* time entry was last accessed */
	zend_long mem_size;      /* memory used */
	zval val;                /* the zval copied at store time */
	zend_string key;         /* entry key (MUST BE THE LAST FIELD OF THE STRUCT!) */
};

/* Any values that must be shared among processes should go in here. */
typedef struct _apc_cache_header_t {
	apc_lock_t lock;                /* header lock */
	zend_long nhits;                /* hit count */
	zend_long nmisses;              /* miss count */
	zend_long ninserts;             /* insert count */
	zend_long ncleanups;            /* default expunge count */
	zend_long ndefragmentations;    /* defragmentation count */
	zend_long nexpunges;            /* real expunge count */
	zend_long nentries;             /* entry count */
	zend_long mem_size;             /* used */
	time_t stime;                   /* start time */
	apc_cache_slam_key_t lastkey;   /* last key inserted (not necessarily without error) */
	uintptr_t gc;                   /* offset in shm to the first entry of gc list */
} apc_cache_header_t;

typedef struct _apc_cache_t {
	apc_cache_header_t* header;   /* cache header (stored in SHM) */
	uintptr_t* slots;             /* array of cache slots (stored in SHM) */
	apc_sma_t* sma;               /* shared memory allocator */
	apc_serializer_t* serializer; /* serializer */
	size_t nslots;                /* number of slots in cache */
	zend_long gc_ttl;             /* maximum time on GC list for a entry */
	zend_long ttl;                /* if slot is needed and entry's access time is older than this ttl, remove it */
	zend_long smart;              /* smart parameter for gc */
	zend_bool defend;             /* defense parameter for runtime */
} apc_cache_t;

typedef zend_bool (*apc_cache_updater_t)(apc_cache_t*, apc_cache_entry_t*, void* data);

typedef zend_bool (*apc_cache_atomic_updater_t)(apc_cache_t*, zend_long*, void* data);

/*
 * apc_cache_create creates the shared memory cache.
 *
 * This function should be called once per process per cache
 *
 * serializer for APCu is set by globals on MINIT and ensured with apc_cache_serializer
 * during execution. Using apc_cache_serializer avoids race conditions between MINIT/RINIT of
 * APCU and the third party serializer. API users can choose to leave this null to use default
 * PHP serializers, or search the list of serializers for the preferred serializer
 *
 * size_hint is a "hint" at the total number entries that will be expected.
 * It determines the physical size of the hash table. Passing 0 for
 * this argument will use a reasonable default value
 *
 * gc_ttl is the maximum time a cache entry may speed on the garbage
 * collection list. This is basically a work around for the inherent
 * unreliability of our reference counting mechanism (see apc_cache_release).
 *
 * ttl is the maximum time a cache entry can idle in a slot in case the slot
 * is needed.  This helps in cleaning up the cache and ensuring that entries
 * hit frequently stay cached and ones not hit very often eventually disappear.
 *
 * for an explanation of smart, see apc_cache_default_expunge
 *
 * defend enables/disables slam defense for this particular cache
 */
PHP_APCU_API apc_cache_t* apc_cache_create(
        apc_sma_t* sma, apc_serializer_t* serializer, zend_long size_hint,
        zend_long gc_ttl, zend_long ttl, zend_long smart, zend_bool defend);

/*
* apc_cache_preload preloads the data at path into the specified cache
*/
PHP_APCU_API zend_bool apc_cache_preload(apc_cache_t* cache, const char* path);

/*
 * apc_cache_detach detaches from the shared memory cache and cleans up
 * local allocations. Under apache, this function can be safely called by
 * the child processes when they exit.
 */
PHP_APCU_API void apc_cache_detach(apc_cache_t* cache);

/*
 * apc_cache_clear empties a cache. This can safely be called at any time.
 */
PHP_APCU_API void apc_cache_clear(apc_cache_t* cache);

/*
 * apc_cache_store creates key, entry and context in which to make an insertion of val into the specified cache
 */
PHP_APCU_API zend_bool apc_cache_store(
        apc_cache_t* cache, zend_string *key, const zval *val,
        const int32_t ttl, const zend_bool exclusive);

/*
 * apc_cache_update updates an entry in place. The updater function must not bailout.
 * The update is performed under write-lock and doesn't have to be atomic.
 */
PHP_APCU_API zend_bool apc_cache_update(
		apc_cache_t *cache, zend_string *key, apc_cache_updater_t updater, void *data,
		zend_bool insert_if_not_found, zend_long ttl);

/*
 * apc_cache_atomic_update_long updates an integer entry in place. The updater function must
 * perform the update atomically, as the update is performed under read-lock.
 */
PHP_APCU_API zend_bool apc_cache_atomic_update_long(
		apc_cache_t *cache, zend_string *key, apc_cache_atomic_updater_t updater, void *data,
		zend_bool insert_if_not_found, zend_long ttl);

/*
 * apc_cache_fetch fetches an entry from the cache directly into dst
 */
PHP_APCU_API zend_bool apc_cache_fetch(apc_cache_t* cache, zend_string *key, time_t t, zval *dst);

/*
 * apc_cache_exists searches for a cache entry by its hashed identifier,
 * and returns whether the entry exists.
 */
PHP_APCU_API zend_bool apc_cache_exists(apc_cache_t* cache, zend_string *key, time_t t);

/*
 * apc_cache_delete and apc_cache_delete finds an entry in the cache and deletes it.
 */
PHP_APCU_API zend_bool apc_cache_delete(apc_cache_t* cache, zend_string *key);

/*
 * apc_cache_fetch_zval copies a cache entry value to be usable at runtime.
 */
PHP_APCU_API zend_bool apc_cache_entry_fetch_zval(
		apc_cache_t *cache, apc_cache_entry_t *entry, zval *dst);

/*
 * apc_cache_entry_release decrements the reference count associated with a cache
 * entry. Calling apc_cache_rlocked_find_incref automatically increments the reference count,
 * and this function must be called post-execution to return the count to its
 * original value. Failing to do so will prevent the entry from being
 * garbage-collected.
 *
 * entry is the cache entry whose ref count you want to decrement.
 */
PHP_APCU_API void apc_cache_entry_release(apc_cache_t *cache, apc_cache_entry_t *entry);

/*
 * fetches information about the cache provided for userland status functions
 */
PHP_APCU_API zend_bool apc_cache_info(zval *info, apc_cache_t *cache, zend_bool limited);

/*
 * fetches information about the key provided
 */
PHP_APCU_API void apc_cache_stat(apc_cache_t *cache, zend_string *key, zval *stat);

/*
* apc_cache_defense: guard against slamming a key
* will return true if the following conditions are met:
*  - the key provided has a matching hash and length to the last key inserted into cache
*  - the last key has a different owner
* in ZTS mode, TSRM determines owner
* in non-ZTS mode, PID determines owner
* Note: this function sets the owner of key during execution
*/
PHP_APCU_API zend_bool apc_cache_defense(apc_cache_t *cache, zend_string *key, time_t t);

/*
* apc_cache_serializer sets the serializer for a cache, and by proxy contexts created for the cache.
* Note: this avoids race conditions between third party serializers and APCu
*/
PHP_APCU_API void apc_cache_serializer(apc_cache_t* cache, const char* name);

/*
* The remaining functions allow a third party to reimplement expunge
*
* Look at the source of apc_cache_default_expunge for what is expected of this function
*
* The default behaviour of expunge is explained below, should no combination of those options
* be suitable, you will need to reimplement apc_cache_default_expunge and pass it to your
* call to apc_sma_api_impl, this will replace the default functionality.
* The functions below you can use during your own implementation of expunge to gain more
* control over how the expunge process works ...
*
* Note: beware of locking (copy it exactly), setting states is also important
*/

/*
* apc_cache_default_expunge() is executed by the sma layer when there is not enough
* free shared memory to satisfy an allocation request. It attempts to free memory
* (e.g., by removing entries) so that the allocation request can be satisfied.
*
* Where smart is not set:
*  1) Perform cleanup of stale entries
*  2) If available memory is less than the size requested, run full expunge
*
* Where smart is set:
*  1) Perform cleanup of stale entries
*  2) If available memory is less than the size requested * smart, run full expunge
*
* The TTL of an entry takes precedence over the TTL of a cache
*/
PHP_APCU_API zend_bool apc_cache_default_expunge(apc_cache_t* cache, size_t size);

/*
* apc_cache_entry: generate and create or fetch an entry
*
* @see https://github.com/krakjoe/apcu/issues/142
*/
PHP_APCU_API void apc_cache_entry(apc_cache_t *cache, zend_string *key, zend_fcall_info *fci, zend_fcall_info_cache *fcc, zend_long ttl, zend_long now, zval *return_value);

/* apcu_entry() holds a write lock on the cache while executing user code.
 * That code may call other apcu_* functions, which also try to acquire a
 * read or write lock, which would deadlock. As such, don't try to acquire a
 * lock if the current thread is inside apcu_entry().
 *
 * Whether the current thread is inside apcu_entry() is tracked by APCG(entry_level).
 * This breaks the self-contained apc_cache_t abstraction, but is currently
 * necessary because the entry_level needs to be tracked per-thread, while
 * apc_cache_t is a per-process structure.
 */

static inline zend_bool apc_cache_wlock(apc_cache_t *cache) {
	if (!APCG(entry_level)) {
		return WLOCK(&cache->header->lock);
	}
	return 1;
}

static inline void apc_cache_wunlock(apc_cache_t *cache) {
	if (!APCG(entry_level)) {
		WUNLOCK(&cache->header->lock);
	}
}

static inline zend_bool apc_cache_rlock(apc_cache_t *cache) {
	if (!APCG(entry_level)) {
		return RLOCK(&cache->header->lock);
	}
	return 1;
}

static inline void apc_cache_runlock(apc_cache_t *cache) {
	if (!APCG(entry_level)) {
		RUNLOCK(&cache->header->lock);
	}
}

/* APC_ENTRY_SIZE takes into account the trailing key-string + terminating 0-byte */
#define APC_ENTRY_SIZE(key_len) (ZEND_MM_ALIGNED_SIZE(XtOffsetOf(apc_cache_entry_t, key.val) + key_len + 1))

/* ENTRYAT and ENTRYOF are used to convert between offsets and pointers to cache entries.
 * Both expect the presence of cache->header that points to the cache header in the
 * shared memory segment. */
#define ENTRYAT(offset) ((apc_cache_entry_t *)((uintptr_t)cache->header + (uintptr_t)offset))
#define ENTRYOF(entry) (((uintptr_t)entry) - (uintptr_t)cache->header)

#endif

/*
 * Local variables:
 * tab-width: 4
 * c-basic-offset: 4
 * End:
 * vim>600: noexpandtab sw=4 ts=4 sts=4 fdm=marker
 * vim<600: noexpandtab sw=4 ts=4 sts=4
 */