php-src/Zend/zend_string.c

/*
   +----------------------------------------------------------------------+
   | Zend Engine                                                          |
   +----------------------------------------------------------------------+
   | Copyright (c) 1998-2017 Zend Technologies Ltd. (http://www.zend.com) |
   +----------------------------------------------------------------------+
   | This source file is subject to version 2.00 of the Zend 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.zend.com/license/2_00.txt.                                |
   | If you did not receive a copy of the Zend license and are unable to  |
   | obtain it through the world-wide-web, please send a note to          |
   | license@zend.com so we can mail you a copy immediately.              |
   +----------------------------------------------------------------------+
   | Authors: Dmitry Stogov <dmitry@zend.com>                             |
   +----------------------------------------------------------------------+
*/

/* $Id: $ */

#include "zend.h"
#include "zend_globals.h"

ZEND_API zend_string *(*zend_new_interned_string)(zend_string *str);

static zend_string *zend_new_interned_string_permanent(zend_string *str);
static zend_string *zend_new_interned_string_request(zend_string *str);

/* Any strings interned in the startup phase. Common to all the threads,
   won't be free'd until process exit. If we want an ability to 
   add permanent strings even after startup, it would be still
   possible on costs of locking in the thread safe builds. */
static HashTable interned_strings_permanent;

static zend_new_interned_string_func_t interned_string_request_handler = zend_new_interned_string_request;
static zend_string_copy_storage_func_t interned_string_copy_storage = NULL;

ZEND_API zend_string  *zend_empty_string = NULL;
ZEND_API zend_string  *zend_one_char_string[256];
ZEND_API zend_string **zend_known_strings = NULL;

ZEND_API zend_ulong zend_hash_func(const char *str, size_t len)
{
	return zend_inline_hash_func(str, len);
}

static void _str_dtor(zval *zv)
{
	zend_string *str = Z_STR_P(zv);
	pefree(str, GC_FLAGS(str) & IS_STR_PERSISTENT);
}

static const char *known_strings[] = {
#define _ZEND_STR_DSC(id, str) str,
ZEND_KNOWN_STRINGS(_ZEND_STR_DSC)
#undef _ZEND_STR_DSC
	NULL
};

static void zend_init_interned_strings_ht(HashTable *interned_strings, int permanent)
{
	zend_hash_init(interned_strings, 1024, NULL, _str_dtor, permanent);

	interned_strings->nTableMask = -interned_strings->nTableSize;
	HT_SET_DATA_ADDR(interned_strings, pemalloc(HT_SIZE(interned_strings), permanent));
	HT_HASH_RESET(interned_strings);
	interned_strings->u.flags |= HASH_FLAG_INITIALIZED;
}

ZEND_API void zend_interned_strings_init(void)
{
	char s[2];
	int i;
	zend_string *str;

	zend_init_interned_strings_ht(&interned_strings_permanent, 1);

	zend_new_interned_string = zend_new_interned_string_permanent;

	/* interned empty string */
	str = zend_string_alloc(sizeof("")-1, 1);
	ZSTR_VAL(str)[0] = '\000';
	zend_empty_string = zend_new_interned_string_permanent(str);

	s[1] = 0;
	for (i = 0; i < 256; i++) {
		s[0] = i;
		zend_one_char_string[i] = zend_new_interned_string_permanent(zend_string_init(s, 1, 1));
	}

	/* known strings */
	zend_known_strings = pemalloc(sizeof(zend_string*) * ((sizeof(known_strings) / sizeof(known_strings[0]) - 1)), 1);
	for (i = 0; i < (sizeof(known_strings) / sizeof(known_strings[0])) - 1; i++) {
		str = zend_string_init(known_strings[i], strlen(known_strings[i]), 1);
		zend_known_strings[i] = zend_new_interned_string_permanent(str);
	}
}

ZEND_API void zend_interned_strings_dtor(void)
{
	zend_hash_destroy(&interned_strings_permanent);

	free(zend_known_strings);
	zend_known_strings = NULL;
}

static zend_always_inline zend_string *zend_interned_string_ht_lookup(zend_string *str, HashTable *interned_strings)
{
	zend_ulong h;
	uint32_t nIndex;
	uint32_t idx;
	Bucket *p;

	h = zend_string_hash_val(str);
	nIndex = h | interned_strings->nTableMask;
	idx = HT_HASH(interned_strings, nIndex);
	while (idx != HT_INVALID_IDX) {
		p = HT_HASH_TO_BUCKET(interned_strings, idx);
		if ((p->h == h) && (ZSTR_LEN(p->key) == ZSTR_LEN(str))) {
			if (!memcmp(ZSTR_VAL(p->key), ZSTR_VAL(str), ZSTR_LEN(str))) {
				return p->key;
			}
		}
		idx = Z_NEXT(p->val);
	}

	return NULL;
}

static zend_never_inline void zend_string_table_grow(HashTable *interned_strings)
{
	if (EXPECTED(interned_strings->nTableSize < HT_MAX_SIZE)) {	/* Let's double the table size */
		void *new_data;
		void *old_data = HT_GET_DATA_ADDR(interned_strings);
		Bucket *old_buckets = interned_strings->arData;

		interned_strings->nTableSize += interned_strings->nTableSize;
		interned_strings->nTableMask = -interned_strings->nTableSize;
		new_data = pemalloc(HT_SIZE(interned_strings), interned_strings->u.flags & HASH_FLAG_PERSISTENT);

		HT_SET_DATA_ADDR(interned_strings, new_data);
		memcpy(interned_strings->arData, old_buckets, sizeof(Bucket) * interned_strings->nNumUsed);
		pefree(old_data, interned_strings->u.flags & HASH_FLAG_PERSISTENT);
		zend_hash_rehash(interned_strings);
	}
}

/* This function might be not thread safe at least because it would update the
   hash val in the passed string. Be sure it is called in the appropriate context. */
static zend_always_inline zend_string *zend_add_interned_string(zend_string *str, HashTable *interned_strings, uint32_t flags)
{
	zend_ulong h;
	uint32_t nIndex;
	uint32_t idx;
	Bucket *p;

	h = zend_string_hash_val(str);

	GC_REFCOUNT(str) = 1;
	GC_FLAGS(str) |= IS_STR_INTERNED | flags;

	if (UNEXPECTED(interned_strings->nNumUsed >= interned_strings->nTableSize)) {
		zend_string_table_grow(interned_strings);
	}

	idx = interned_strings->nNumUsed++;
	interned_strings->nNumOfElements++;
	p = interned_strings->arData + idx;
	p->h = h;
	p->key = str;
	Z_STR(p->val) = str;
	Z_TYPE_INFO(p->val) = IS_INTERNED_STRING_EX;
	nIndex = h | interned_strings->nTableMask;
	Z_NEXT(p->val) = HT_HASH(interned_strings, nIndex);
	HT_HASH(interned_strings, nIndex) = HT_IDX_TO_HASH(idx);

	return str;
}

ZEND_API zend_string *zend_interned_string_find_permanent(zend_string *str)
{
	return zend_interned_string_ht_lookup(str, &interned_strings_permanent);
}


static zend_string *zend_new_interned_string_permanent(zend_string *str)
{
	zend_string *ret;

	if (ZSTR_IS_INTERNED(str)) {
		return str;
	}

	ret = zend_interned_string_ht_lookup(str, &interned_strings_permanent);
	if (ret) {
		zend_string_release(str);
		return ret;
	}

	return zend_add_interned_string(str, &interned_strings_permanent, IS_STR_PERMANENT);
}

static zend_string *zend_new_interned_string_request(zend_string *str)
{
	zend_string *ret;

	if (ZSTR_IS_INTERNED(str)) {
		return str;
	}

	/* Check for permanent strings, the table is readonly at this point. */
	ret = zend_interned_string_ht_lookup(str, &interned_strings_permanent);
	if (ret) {
		zend_string_release(str);
		return ret;
	}

	ret = zend_interned_string_ht_lookup(str, &CG(interned_strings));
	if (ret) {
		zend_string_release(str);
		return ret;
	}

	/* Create a short living interned, freed after the request. */
	ret = zend_add_interned_string(str, &CG(interned_strings), 0);

	return ret;
}

ZEND_API void zend_interned_strings_activate(void)
{
	zend_init_interned_strings_ht(&CG(interned_strings), 0);
}

ZEND_API void zend_interned_strings_deactivate(void)
{
	zend_hash_destroy(&CG(interned_strings));
}

ZEND_API void zend_interned_strings_set_request_storage_handler(zend_new_interned_string_func_t handler)
{
	interned_string_request_handler = handler;
}

ZEND_API void zend_interned_strings_set_permanent_storage_copy_handler(zend_string_copy_storage_func_t handler)
{
	interned_string_copy_storage = handler;
}

ZEND_API void zend_interned_strings_switch_storage(void)
{
	if (interned_string_copy_storage) {
		interned_string_copy_storage();
	}
	zend_new_interned_string = interned_string_request_handler;
}

/*
 * Local variables:
 * tab-width: 4
 * c-basic-offset: 4
 * indent-tabs-mode: t
 * End:
 */