PHP数组的存储
PHP数组是PHP最复杂的数据结构，没有之一，如果能把数据彻底搞透，那么其他的数据结构也能理解的差不多了。
数据结构
typedef struct _Bucket {
zval val;
zend_ulong h; /* hash value (or numeric index) */
zend_string *key; /* string key or NULL for numerics */
} Bucket;
typedef struct _zend_array HashTable;
struct _zend_array {
zend_refcounted_h gc;
union {
struct {
ZEND_ENDIAN_LOHI_4(
zend_uchar flags,
zend_uchar nApplyCount,
zend_uchar nIteratorsCount,
zend_uchar consistency)
} v;
uint32_t flags;
} u;
uint32_t nTableMask; // 中间映射表，用来映射在arData的存储位置
Bucket *arData; // 元素的存储数据结构，默认指向第一个元素
uint32_t nNumUsed; // arData使用的个数
uint32_t nNumOfElements; // 数组的个数
uint32_t nTableSize; // 数组的大小
uint32_t nInternalPointer;
zend_long nNextFreeElement;
dtor_func_t pDestructor;
};数组的初始化
ZEND_API void ZEND_FASTCALL _zend_hash_init(HashTable *ht, uint32_t nSize, dtor_func_t pDestructor, zend_bool persistent ZEND_FILE_LINE_DC)
{
GC_REFCOUNT(ht) = 1;
GC_TYPE_INFO(ht) = IS_ARRAY;
ht->u.flags = (persistent ? HASH_FLAG_PERSISTENT : 0) | HASH_FLAG_APPLY_PROTECTION | HASH_FLAG_STATIC_KEYS;
ht->nTableMask = HT_MIN_MASK;
HT_SET_DATA_ADDR(ht, &uninitialized_bucket);
ht->nNumUsed = 0;
ht->nNumOfElements = 0;
ht->nInternalPointer = HT_INVALID_IDX;
ht->nNextFreeElement = 0;
ht->pDestructor = pDestructor;
ht->nTableSize = zend_hash_check_size(nSize);
}
static zend_always_inline void zend_hash_real_init_ex(HashTable *ht, int packed)
{
HT_ASSERT(GC_REFCOUNT(ht) == 1);
ZEND_ASSERT(!((ht)->u.flags & HASH_FLAG_INITIALIZED));
if (packed) {
HT_SET_DATA_ADDR(ht, pemalloc(HT_SIZE(ht), (ht)->u.flags & HASH_FLAG_PERSISTENT));
(ht)->u.flags |= HASH_FLAG_INITIALIZED | HASH_FLAG_PACKED;
HT_HASH_RESET_PACKED(ht);
} else {
(ht)->nTableMask = -(ht)->nTableSize;
HT_SET_DATA_ADDR(ht, pemalloc(HT_SIZE(ht), (ht)->u.flags & HASH_FLAG_PERSISTENT));
(ht)->u.flags |= HASH_FLAG_INITIALIZED;
if (EXPECTED(ht->nTableMask == (uint32_t)-8)) {
Bucket *arData = ht->arData;
HT_HASH_EX(arData, -8) = -1;
HT_HASH_EX(arData, -7) = -1;
HT_HASH_EX(arData, -6) = -1;
HT_HASH_EX(arData, -5) = -1;
HT_HASH_EX(arData, -4) = -1;
HT_HASH_EX(arData, -3) = -1;
HT_HASH_EX(arData, -2) = -1;
HT_HASH_EX(arData, -1) = -1;
} else {
HT_HASH_RESET(ht);
}
}
}
在初始化之前，会先调用_zend_hash_init进行一些简单的初始化操作，但是这部分做的事情比较少，只是初始化了nTableSize=8，arData的内存大小是根据这个值确定的，它的大小是8的幂次方，最小为8；
其他的初始化操作，是通过zend_hash_real_init_ex函数进行的：
- 首先，将u.flags设置为
初始化的状态 - 将映射关系nTableMask设置为nTableSize大小的相反数
- 申请地址空间，设备的地址空间大小是nTableMask和nTableSize的两个地址空间大小
- 设置arData的每个元素的值为-1
数组的赋值_zend_hash_add_or_update_i
static zend_always_inline zval *_zend_hash_add_or_update_i(HashTable *ht, zend_string *key, zval *pData, uint32_t flag ZEND_FILE_LINE_DC)
{
zend_ulong h;
uint32_t nIndex;
uint32_t idx;
Bucket *p;
IS_CONSISTENT(ht);
HT_ASSERT(GC_REFCOUNT(ht) == 1);
if (UNEXPECTED(!(ht->u.flags & HASH_FLAG_INITIALIZED))) {
CHECK_INIT(ht, 0);
goto add_to_hash;
} else if (ht->u.flags & HASH_FLAG_PACKED) {
zend_hash_packed_to_hash(ht);
} else if ((flag & HASH_ADD_NEW) == 0) {
p = zend_hash_find_bucket(ht, key);
if (p) {
zval *data;
if (flag & HASH_ADD) {
if (!(flag & HASH_UPDATE_INDIRECT)) {
return NULL;
}
ZEND_ASSERT(&p->val != pData);
data = &p->val;
if (Z_TYPE_P(data) == IS_INDIRECT) {
data = Z_INDIRECT_P(data);
if (Z_TYPE_P(data) != IS_UNDEF) {
return NULL;
}
} else {
return NULL;
}
} else {
ZEND_ASSERT(&p->val != pData);
data = &p->val;
if ((flag & HASH_UPDATE_INDIRECT) && Z_TYPE_P(data) == IS_INDIRECT) {
data = Z_INDIRECT_P(data);
}
}
if (ht->pDestructor) {
ht->pDestructor(data);
}
ZVAL_COPY_VALUE(data, pData);
return data;
}
}
ZEND_HASH_IF_FULL_DO_RESIZE(ht); /* If the Hash table is full, resize it */
add_to_hash:
idx = ht->nNumUsed++;
ht->nNumOfElements++;
if (ht->nInternalPointer == HT_INVALID_IDX) {
ht->nInternalPointer = idx;
}
zend_hash_iterators_update(ht, HT_INVALID_IDX, idx);
p = ht->arData + idx;
p->key = key;
if (!ZSTR_IS_INTERNED(key)) {
zend_string_addref(key);
ht->u.flags &= ~HASH_FLAG_STATIC_KEYS;
zend_string_hash_val(key);
}
p->h = h = ZSTR_H(key);
ZVAL_COPY_VALUE(&p->val, pData);
nIndex = h | ht->nTableMask;
Z_NEXT(p->val) = HT_HASH(ht, nIndex);
HT_HASH(ht, nIndex) = HT_IDX_TO_HASH(idx);
return &p->val;
}- 首先，在赋值之前，会先判断数组是否已经被初始化过，如果初始化那么就进行赋值的操作
- 赋值的时候，会把nNumUsed进行累加，然后得到arData的位置
- 将赋值的bucket设置hash code和key等成员变量
- 根据hash code，计算出在nTableMask对应的位置为nIndex
- 将arData的位置，存储到nTableMask对应的nIndex的值上面
