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cpython/Include/pyhash.h at 3.5 · python/cpython · GitHub
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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 PY_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 PY_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
;
#ifdef
PY_UINT64_T
/* two uint64 for SipHash24 */
struct
{
PY_UINT64_T
k0
;
PY_UINT64_T
k1
;
}
siphash
;
#endif
/* 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 provide PY_UINT64_T and doesn'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
# if
(defined(
PY_UINT64_T
)
&&
defined(
PY_UINT32_T
) \
&&
!defined(
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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