1 #ifndef Py_HASH_H 2 3 #define Py_HASH_H 4 #ifdef __cplusplus 5 extern "C" { 6 #endif 7 8 /* Helpers for hash functions */ 9 #ifndef Py_LIMITED_API 10 PyAPI_FUNC(Py_hash_t) _Py_HashDouble(double); 11 PyAPI_FUNC(Py_hash_t) _Py_HashPointer(void*); 12 PyAPI_FUNC(Py_hash_t) _Py_HashBytes(const void*, Py_ssize_t); 13 #endif 14 15 /* Prime multiplier used in string and various other hashes. */ 16 #define _PyHASH_MULTIPLIER 1000003UL /* 0xf4243 */ 17 18 /* Parameters used for the numeric hash implementation. See notes for 19 _Py_HashDouble in Objects/object.c. Numeric hashes are based on 20 reduction modulo the prime 2**_PyHASH_BITS - 1. */ 21 22 #if SIZEOF_VOID_P >= 8 23 # define _PyHASH_BITS 61 24 #else 25 # define _PyHASH_BITS 31 26 #endif 27 28 #define _PyHASH_MODULUS (((size_t)1 << _PyHASH_BITS) - 1) 29 #define _PyHASH_INF 314159 30 #define _PyHASH_NAN 0 31 #define _PyHASH_IMAG _PyHASH_MULTIPLIER 32 33 34 /* hash secret 35 * 36 * memory layout on 64 bit systems 37 * cccccccc cccccccc cccccccc uc -- unsigned char[24] 38 * pppppppp ssssssss ........ fnv -- two Py_hash_t 39 * k0k0k0k0 k1k1k1k1 ........ siphash -- two uint64_t 40 * ........ ........ ssssssss djbx33a -- 16 bytes padding + one Py_hash_t 41 * ........ ........ eeeeeeee pyexpat XML hash salt 42 * 43 * memory layout on 32 bit systems 44 * cccccccc cccccccc cccccccc uc 45 * ppppssss ........ ........ fnv -- two Py_hash_t 46 * k0k0k0k0 k1k1k1k1 ........ siphash -- two uint64_t (*) 47 * ........ ........ ssss.... djbx33a -- 16 bytes padding + one Py_hash_t 48 * ........ ........ eeee.... pyexpat XML hash salt 49 * 50 * (*) The siphash member may not be available on 32 bit platforms without 51 * an unsigned int64 data type. 52 */ 53 #ifndef Py_LIMITED_API 54 typedef union { 55 /* ensure 24 bytes */ 56 unsigned char uc[24]; 57 /* two Py_hash_t for FNV */ 58 struct { 59 Py_hash_t prefix; 60 Py_hash_t suffix; 61 } fnv; 62 /* two uint64 for SipHash24 */ 63 struct { 64 uint64_t k0; 65 uint64_t k1; 66 } siphash; 67 /* a different (!) Py_hash_t for small string optimization */ 68 struct { 69 unsigned char padding[16]; 70 Py_hash_t suffix; 71 } djbx33a; 72 struct { 73 unsigned char padding[16]; 74 Py_hash_t hashsalt; 75 } expat; 76 } _Py_HashSecret_t; 77 PyAPI_DATA(_Py_HashSecret_t) _Py_HashSecret; 78 #endif 79 80 #ifdef Py_DEBUG 81 PyAPI_DATA(int) _Py_HashSecret_Initialized; 82 #endif 83 84 85 /* hash function definition */ 86 #ifndef Py_LIMITED_API 87 typedef struct { 88 Py_hash_t (*const hash)(const void *, Py_ssize_t); 89 const char *name; 90 const int hash_bits; 91 const int seed_bits; 92 } PyHash_FuncDef; 93 94 PyAPI_FUNC(PyHash_FuncDef*) PyHash_GetFuncDef(void); 95 #endif 96 97 98 /* cutoff for small string DJBX33A optimization in range [1, cutoff). 99 * 100 * About 50% of the strings in a typical Python application are smaller than 101 * 6 to 7 chars. However DJBX33A is vulnerable to hash collision attacks. 102 * NEVER use DJBX33A for long strings! 103 * 104 * A Py_HASH_CUTOFF of 0 disables small string optimization. 32 bit platforms 105 * should use a smaller cutoff because it is easier to create colliding 106 * strings. A cutoff of 7 on 64bit platforms and 5 on 32bit platforms should 107 * provide a decent safety margin. 108 */ 109 #ifndef Py_HASH_CUTOFF 110 # define Py_HASH_CUTOFF 0 111 #elif (Py_HASH_CUTOFF > 7 || Py_HASH_CUTOFF < 0) 112 # error Py_HASH_CUTOFF must in range 0...7. 113 #endif /* Py_HASH_CUTOFF */ 114 115 116 /* hash algorithm selection 117 * 118 * The values for Py_HASH_SIPHASH24 and Py_HASH_FNV are hard-coded in the 119 * configure script. 120 * 121 * - FNV is available on all platforms and architectures. 122 * - SIPHASH24 only works on plaforms that don't require aligned memory for integers. 123 * - With EXTERNAL embedders can provide an alternative implementation with:: 124 * 125 * PyHash_FuncDef PyHash_Func = {...}; 126 * 127 * XXX: Figure out __declspec() for extern PyHash_FuncDef. 128 */ 129 #define Py_HASH_EXTERNAL 0 130 #define Py_HASH_SIPHASH24 1 131 #define Py_HASH_FNV 2 132 133 #ifndef Py_HASH_ALGORITHM 134 # ifndef HAVE_ALIGNED_REQUIRED 135 # define Py_HASH_ALGORITHM Py_HASH_SIPHASH24 136 # else 137 # define Py_HASH_ALGORITHM Py_HASH_FNV 138 # endif /* uint64_t && uint32_t && aligned */ 139 #endif /* Py_HASH_ALGORITHM */ 140 141 #ifdef __cplusplus 142 } 143 #endif 144 145 #endif /* !Py_HASH_H */ 146
