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Get the C API straight 

Python already has sys.hash_info
This commit is contained in:
Christian Heimes 2013-10-06 15:56:00 +02:00
parent 781581bd26
commit 10346678ba
1 changed files with 34 additions and 17 deletions
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51
pep-0456.txt
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@ -310,31 +310,43 @@ hash function
function prototype::
typedef Py_hash_t (*PyHash_Func)(const void *, Py_ssize_t);
typedef Py_hash_t (*PyHash_Func_t)(const void *, Py_ssize_t);
hash function table
-------------------
hash function selection
-----------------------
type definition::
#define PY_HASH_SIPHASH24 0x53495024
#define PY_HASH_FNV 0x464E56
#ifndef PY_HASH_ALGORITHM
#if defined(PY_UINT64_T) && defined(PY_UINT32_T)
#define PY_HASH_ALGORITHM PY_HASH_SIPHASH24
#else
#define PY_HASH_ALGORITHM PY_HASH_FNV
#endif /* uint64_t && uint32_t */
#endif /* PY_HASH_ALGORITHM */
typedef struct {
PyHash_Func hash; /* function pointer */
PyHash_Func_t hash; /* function pointer */
char *name; /* name of the hash algorithm and variant */
int hash_bits; /* internal size of hash value */
int seed_bits; /* size of seed input */
} _PyHash_FuncDef;
} PyHash_FuncDef;
PyAPI_DATA(_PyHash_FuncDef *) _PyHash_Func;
PyAPI_DATA(PyHash_FuncDef) PyHash_Func;
Implementation::
#ifndef PY_HASH_FUNC
#ifdef PY_UINT64_T
_PyHash_Func = {siphash24, "sip24", 64, 128}
#else
_PyHash_Func = {fnv, "fnv", 8 * sizeof(Py_hash_t), 16 * sizeof(Py_hash_t)}
#if PY_HASH_ALGORITHM == PY_HASH_FNV
PyHash_FuncDef PyHash_Func = {fnv, "fnv", 8 * sizeof(Py_hash_t),
16 * sizeof(Py_hash_t)};
#endif
#if PY_HASH_ALGORITHM == PY_HASH_SIPHASH24
PyHash_FuncDef PyHash_Func = {siphash24, "siphash24", 64, 128};
#endif
TODO: select hash algorithm with autoconf variable
@ -346,14 +358,19 @@ Python API addition
sys module
----------
The sys module grows a new struct member with information about the select
algorithm as well as all available algorithms.
The sys module already has a hash_info struct sequence. More fields are added
to the object to reflect the active hash algorithm and its properties.
::
sys.hash_info(algorithm='siphash24',
sys.hash_info(width=64,
modulus=2305843009213693951,
inf=314159,
nan=0,
imag=1000003,
# new fields:
algorithm='siphash24',
hash_bits=64,
hash_output=64, # 8 * sizeof(Py_hash_t)
seed_bits=128)
@ -411,8 +428,8 @@ multiplied with the size of the internal unicode kind::
if (PyUnicode_READY(u) == -1)
return -1;
x = _PyHash_Func->hash(PyUnicode_DATA(u),
PyUnicode_GET_LENGTH(u) * PyUnicode_KIND(u));
x = PyHash_Func.hash(PyUnicode_DATA(u),
PyUnicode_GET_LENGTH(u) * PyUnicode_KIND(u));
generic_hash (Modules/_datetimemodule.c)