hashtable

hashtable 包括 ：

• 一個 gc 結(jié)構(gòu) ,是幫助垃圾回收而使用的
• 一個聯(lián)合體
• 掩碼
• 桶指針 arData
• 析構(gòu)函數(shù)pDestructor
• 桶的數(shù)目 nTableSize
  ...

// src\Zend\zend_types.h
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;
    Bucket           *arData;
    uint32_t          nNumUsed;
    uint32_t          nNumOfElements;
    uint32_t          nTableSize;
    uint32_t          nInternalPointer;
    zend_long         nNextFreeElement;
    dtor_func_t       pDestructor;
};

然后是Bucket 結(jié)構(gòu)

typedef struct _Bucket {
    zval              val;
    zend_ulong        h;                /* hash value (or numeric index)   */
    zend_string      *key;              /* string key or NULL for numerics */
} Bucket;

然后是zval

typedef struct _zval_struct     zval;

struct _zval_struct {
    zend_value        value;            /* value */
    union {
        struct {
            ZEND_ENDIAN_LOHI_4(
                zend_uchar    type,         /* active type */
                zend_uchar    type_flags,
                zend_uchar    const_flags,
                zend_uchar    reserved)     /* call info for EX(This) */
        } v;
        uint32_t type_info;
    } u1;
    union {
        uint32_t     next;                 /* hash collision chain */
        uint32_t     cache_slot;           /* literal cache slot */
        uint32_t     lineno;               /* line number (for ast nodes) */
        uint32_t     num_args;             /* arguments number for EX(This) */
        uint32_t     fe_pos;               /* foreach position */
        uint32_t     fe_iter_idx;          /* foreach iterator index */
        uint32_t     access_flags;         /* class constant access flags */
        uint32_t     property_guard;       /* single property guard */
        uint32_t     extra;                /* not further specified */
    } u2;
};

繼續(xù)上面的結(jié)構(gòu) _zval_struct , 我的代碼的版本是php 7.1.8， 然后看到 ·_zval_struct 由以下幾個部分組成

• zend_val
• 聯(lián)合體 u1
• 聯(lián)合體u2
  u2 有一個next 的值可以實(shí)現(xiàn)關(guān)聯(lián)數(shù)組相關(guān)的操作

zend_value; 然后到了zend_value
zend_value 是一個聯(lián)合體,7.18 繼續(xù)對zend_value 進(jìn)行優(yōu)化,縮小了zend_value的大小,可以節(jié)省非常多的內(nèi)存

typedef union _zend_value {
    zend_long         lval;             /* long value */
    double            dval;             /* double value */
    zend_refcounted  *counted;
    zend_string      *str;
    zend_array       *arr;
    zend_object      *obj;
    zend_resource    *res;
    zend_reference   *ref;
    zend_ast_ref     *ast;
    zval             *zv;
    void             *ptr;
    zend_class_entry *ce;
    zend_function    *func;
    struct {
        uint32_t w1;
        uint32_t w2;
    } ww;
} zend_value;