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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 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_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 */
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