cpython/Include/internal/pycore_pyhash.h

#ifndef Py_INTERNAL_PYHASH_H
#define Py_INTERNAL_PYHASH_H

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

/* Helpers for hash functions */
extern Py_hash_t _Py_HashDouble(PyObject *, double);

// Export for '_decimal' shared extension
PyAPI_FUNC(Py_hash_t) _Py_HashPointer(const void*);

// Similar to _Py_HashPointer(), but don't replace -1 with -2
extern Py_hash_t _Py_HashPointerRaw(const void*);

// Export for '_datetime' shared extension
PyAPI_FUNC(Py_hash_t) _Py_HashBytes(const void*, Py_ssize_t);

/* Prime multiplier used in string and various other hashes. */
#define _PyHASH_MULTIPLIER 1000003UL  /* 0xf4243 */

/* Parameters used for the numeric hash implementation.  See notes for
   _Py_HashDouble in Python/pyhash.c.  Numeric hashes are based on
   reduction modulo the prime 2**_PyHASH_BITS - 1. */

#if SIZEOF_VOID_P >= 8
#  define _PyHASH_BITS 61
#else
#  define _PyHASH_BITS 31
#endif

#define _PyHASH_MODULUS (((size_t)1 << _PyHASH_BITS) - 1)
#define _PyHASH_INF 314159
#define _PyHASH_IMAG _PyHASH_MULTIPLIER

/* Hash secret
 *
 * memory layout on 64 bit systems
 *   cccccccc cccccccc cccccccc  uc -- unsigned char[24]
 *   pppppppp ssssssss ........  fnv -- two Py_hash_t
 *   k0k0k0k0 k1k1k1k1 ........  siphash -- two uint64_t
 *   ........ ........ ssssssss  djbx33a -- 16 bytes padding + one Py_hash_t
 *   ........ ........ eeeeeeee  pyexpat XML hash salt
 *
 * memory layout on 32 bit systems
 *   cccccccc cccccccc cccccccc  uc
 *   ppppssss ........ ........  fnv -- two Py_hash_t
 *   k0k0k0k0 k1k1k1k1 ........  siphash -- two uint64_t (*)
 *   ........ ........ ssss....  djbx33a -- 16 bytes padding + one Py_hash_t
 *   ........ ........ eeee....  pyexpat XML hash salt
 *
 * (*) The siphash member may not be available on 32 bit platforms without
 *     an unsigned int64 data type.
 */
typedef union {
    /* ensure 24 bytes */
    unsigned char uc[24];
    /* two Py_hash_t for FNV */
    struct {
        Py_hash_t prefix;
        Py_hash_t suffix;
    } fnv;
    /* two uint64 for SipHash24 */
    struct {
        uint64_t k0;
        uint64_t k1;
    } siphash;
    /* a different (!) Py_hash_t for small string optimization */
    struct {
        unsigned char padding[16];
        Py_hash_t suffix;
    } djbx33a;
    struct {
        unsigned char padding[16];
        Py_hash_t hashsalt;
    } expat;
} _Py_HashSecret_t;

// Export for '_elementtree' shared extension
PyAPI_DATA(_Py_HashSecret_t) _Py_HashSecret;

#ifdef Py_DEBUG
extern int _Py_HashSecret_Initialized;
#endif


struct pyhash_runtime_state {
    struct {
#ifndef MS_WINDOWS
        int fd;
        dev_t st_dev;
        ino_t st_ino;
#else
    // This is a placeholder so the struct isn't empty on Windows.
    int _not_used;
#endif
    } urandom_cache;
};

#ifndef MS_WINDOWS
# define _py_urandom_cache_INIT \
    { \
        .fd = -1, \
    }
#else
# define _py_urandom_cache_INIT {0}
#endif

#define pyhash_state_INIT \
    { \
        .urandom_cache = _py_urandom_cache_INIT, \
    }


extern uint64_t _Py_KeyedHash(uint64_t key, const void *src, Py_ssize_t src_sz);

#endif  // !Py_INTERNAL_PYHASH_H