include/python3.13/pyhash.h

0001 #ifndef Py_HASH_H
0002 #define Py_HASH_H
0003 #ifdef __cplusplus
0004 extern "C" {
0005 #endif
0006
0007 /* Cutoff for small string DJBX33A optimization in range [1, cutoff).
0008  *
0009  * About 50% of the strings in a typical Python application are smaller than
0010  * 6 to 7 chars. However DJBX33A is vulnerable to hash collision attacks.
0011  * NEVER use DJBX33A for long strings!
0012  *
0013  * A Py_HASH_CUTOFF of 0 disables small string optimization. 32 bit platforms
0014  * should use a smaller cutoff because it is easier to create colliding
0015  * strings. A cutoff of 7 on 64bit platforms and 5 on 32bit platforms should
0016  * provide a decent safety margin.
0017  */
0018 #ifndef Py_HASH_CUTOFF
0019 #  define Py_HASH_CUTOFF 0
0020 #elif (Py_HASH_CUTOFF > 7 || Py_HASH_CUTOFF < 0)
0021 #  error Py_HASH_CUTOFF must in range 0...7.
0022 #endif /* Py_HASH_CUTOFF */
0023
0024
0025 /* Hash algorithm selection
0026  *
0027  * The values for Py_HASH_* are hard-coded in the
0028  * configure script.
0029  *
0030  * - FNV and SIPHASH* are available on all platforms and architectures.
0031  * - With EXTERNAL embedders can provide an alternative implementation with::
0032  *
0033  *     PyHash_FuncDef PyHash_Func = {...};
0034  *
0035  * XXX: Figure out __declspec() for extern PyHash_FuncDef.
0036  */
0037 #define Py_HASH_EXTERNAL 0
0038 #define Py_HASH_SIPHASH24 1
0039 #define Py_HASH_FNV 2
0040 #define Py_HASH_SIPHASH13 3
0041
0042 #ifndef Py_HASH_ALGORITHM
0043 #  ifndef HAVE_ALIGNED_REQUIRED
0044 #    define Py_HASH_ALGORITHM Py_HASH_SIPHASH13
0045 #  else
0046 #    define Py_HASH_ALGORITHM Py_HASH_FNV
0047 #  endif /* uint64_t && uint32_t && aligned */
0048 #endif /* Py_HASH_ALGORITHM */
0049
0050 #ifndef Py_LIMITED_API
0051 #  define Py_CPYTHON_HASH_H
0052 #  include "cpython/pyhash.h"
0053 #  undef Py_CPYTHON_HASH_H
0054 #endif
0055
0056 #ifdef __cplusplus
0057 }
0058 #endif
0059 #endif  // !Py_HASH_H