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#ifndef Py_HASH_H

#define Py_HASH_H

#ifdef __cplusplus

extern "C" {

#endif

/* Helpers for hash functions */

#ifndef Py_LIMITED_API

PyAPI_FUNC(Py_hash_t) _Py_HashDouble(double);

PyAPI_FUNC(Py_hash_t) _Py_HashPointer(void*);

PyAPI_FUNC(Py_hash_t) _Py_HashBytes(const void*, Py_ssize_t);

#endif

/* 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 Objects/object.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_NAN 0

#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.

*/

#ifndef Py_LIMITED_API

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;

PyAPI_DATA(_Py_HashSecret_t) _Py_HashSecret;

#endif

#ifdef Py_DEBUG

PyAPI_DATA(int) _Py_HashSecret_Initialized;

#endif

/* hash function definition */

#ifndef Py_LIMITED_API

typedef struct {

Py_hash_t (*const hash)(const void *, Py_ssize_t);

const char *name;

const int hash_bits;

const int seed_bits;

} PyHash_FuncDef;

PyAPI_FUNC(PyHash_FuncDef*) PyHash_GetFuncDef(void);

#endif

/* cutoff for small string DJBX33A optimization in range [1, cutoff).

*

* About 50% of the strings in a typical Python application are smaller than

* 6 to 7 chars. However DJBX33A is vulnerable to hash collision attacks.

* NEVER use DJBX33A for long strings!

*

* A Py_HASH_CUTOFF of 0 disables small string optimization. 32 bit platforms

* should use a smaller cutoff because it is easier to create colliding

* strings. A cutoff of 7 on 64bit platforms and 5 on 32bit platforms should

* provide a decent safety margin.

*/

#ifndef Py_HASH_CUTOFF

# define Py_HASH_CUTOFF 0

#elif (Py_HASH_CUTOFF > 7 || Py_HASH_CUTOFF < 0)

# error Py_HASH_CUTOFF must in range 0...7.

#endif /* Py_HASH_CUTOFF */

/* hash algorithm selection

*

* The values for Py_HASH_SIPHASH24 and Py_HASH_FNV are hard-coded in the

* configure script.

*

* - FNV is available on all platforms and architectures.

* - SIPHASH24 only works on plaforms that don't require aligned memory for integers.

* - With EXTERNAL embedders can provide an alternative implementation with::

*

* PyHash_FuncDef PyHash_Func = {...};

*

* XXX: Figure out __declspec() for extern PyHash_FuncDef.

*/

#define Py_HASH_EXTERNAL 0

#define Py_HASH_SIPHASH24 1

#define Py_HASH_FNV 2

#ifndef Py_HASH_ALGORITHM

# ifndef HAVE_ALIGNED_REQUIRED

# define Py_HASH_ALGORITHM Py_HASH_SIPHASH24

# else

# define Py_HASH_ALGORITHM Py_HASH_FNV

# endif /* uint64_t && uint32_t && aligned */

#endif /* Py_HASH_ALGORITHM */

#ifdef __cplusplus

}

#endif

#endif /* !Py_HASH_H */