cpython/Include/internal/pycore_dict.h

#ifndef Py_INTERNAL_DICT_H
#define Py_INTERNAL_DICT_H
#ifdef __cplusplus
extern "C" {
#endif

#ifndef Py_BUILD_CORE
#  error "this header requires Py_BUILD_CORE define"
#endif


typedef struct {
    /* Cached hash code of me_key. */
    Py_hash_t me_hash;
    PyObject *me_key;
    PyObject *me_value; /* This field is only meaningful for combined tables */
} PyDictKeyEntry;

/* _Py_dict_lookup() returns index of entry which can be used like DK_ENTRIES(dk)[index].
 * -1 when no entry found, -3 when compare raises error.
 */
Py_ssize_t _Py_dict_lookup(PyDictObject *mp, PyObject *key, Py_hash_t hash, PyObject **value_addr);


#define DKIX_EMPTY (-1)
#define DKIX_DUMMY (-2)  /* Used internally */
#define DKIX_ERROR (-3)

typedef enum {
    DICT_KEYS_GENERAL = 0,
    DICT_KEYS_UNICODE = 1,
    DICT_KEYS_SPLIT = 2
} DictKeysKind;

/* See dictobject.c for actual layout of DictKeysObject */
struct _dictkeysobject {
    Py_ssize_t dk_refcnt;

    /* Size of the hash table (dk_indices). It must be a power of 2. */
    uint8_t dk_log2_size;

    /* Kind of keys */
    uint8_t dk_kind;

    /* Version number -- Reset to 0 by any modification to keys */
    uint32_t dk_version;

    /* Number of usable entries in dk_entries. */
    Py_ssize_t dk_usable;

    /* Number of used entries in dk_entries. */
    Py_ssize_t dk_nentries;

    /* Actual hash table of dk_size entries. It holds indices in dk_entries,
       or DKIX_EMPTY(-1) or DKIX_DUMMY(-2).

       Indices must be: 0 <= indice < USABLE_FRACTION(dk_size).

       The size in bytes of an indice depends on dk_size:

       - 1 byte if dk_size <= 0xff (char*)
       - 2 bytes if dk_size <= 0xffff (int16_t*)
       - 4 bytes if dk_size <= 0xffffffff (int32_t*)
       - 8 bytes otherwise (int64_t*)

       Dynamically sized, SIZEOF_VOID_P is minimum. */
    char dk_indices[];  /* char is required to avoid strict aliasing. */

    /* "PyDictKeyEntry dk_entries[dk_usable];" array follows:
       see the DK_ENTRIES() macro */
};

#define DK_LOG_SIZE(dk)  ((dk)->dk_log2_size)
#if SIZEOF_VOID_P > 4
#define DK_SIZE(dk)      (((int64_t)1)<<DK_LOG_SIZE(dk))
#define DK_IXSIZE(dk)                     \
    (DK_LOG_SIZE(dk) <= 7 ?               \
        1 : DK_LOG_SIZE(dk) <= 15 ?       \
            2 : DK_LOG_SIZE(dk) <= 31 ?   \
                4 : sizeof(int64_t))
#else
#define DK_SIZE(dk)      (1<<DK_LOG_SIZE(dk))
#define DK_IXSIZE(dk)                     \
    (DK_LOG_SIZE(dk) <= 7 ?               \
        1 : DK_LOG_SIZE(dk) <= 15 ?       \
            2 : sizeof(int32_t))
#endif
#define DK_ENTRIES(dk) \
    ((PyDictKeyEntry*)(&((int8_t*)((dk)->dk_indices))[DK_SIZE(dk) * DK_IXSIZE(dk)]))


#ifdef __cplusplus
}
#endif
#endif   /* !Py_INTERNAL_DICT_H */