libgo/runtime/go-type-identity.c

   1 /* go-type-identity.c -- hash and equality identity functions.
   2
   3    Copyright 2009 The Go Authors. All rights reserved.
   4    Use of this source code is governed by a BSD-style
   5    license that can be found in the LICENSE file.  */
   6
   7 #include <stddef.h>
   8
   9 #include "config.h"
  10 #include "go-type.h"
  11
  12 /* The 64-bit type.  */
  13
  14 typedef unsigned int DItype __attribute__ ((mode (DI)));
  15
  16 /* An identity hash function for a type.  This is used for types where
  17    we can simply use the type value itself as a hash code.  This is
  18    true of, e.g., integers and pointers.  */
  19
  20 uintptr_t
  21 __go_type_hash_identity (const void *key, uintptr_t key_size)
  22 {
  23   uintptr_t ret;
  24   uintptr_t i;
  25   const unsigned char *p;
  26
  27   if (key_size <= 8)
  28     {
  29       union
  30       {
  31         DItype v;
  32         unsigned char a[8];
  33       } u;
  34       u.v = 0;
  35 #ifdef WORDS_BIGENDIAN
  36       __builtin_memcpy (&u.a[8 - key_size], key, key_size);
  37 #else
  38       __builtin_memcpy (&u.a[0], key, key_size);
  39 #endif
  40       if (sizeof (uintptr_t) >= 8)
  41         return (uintptr_t) u.v;
  42       else
  43         return (uintptr_t) ((u.v >> 32) ^ (u.v & 0xffffffff));
  44     }
  45
  46   ret = 5381;
  47   for (i = 0, p = (const unsigned char *) key; i < key_size; i++, p++)
  48     ret = ret * 33 + *p;
  49   return ret;
  50 }
  51
  52 /* An identity equality function for a type.  This is used for types
  53    where we can check for equality by checking that the values have
  54    the same bits.  */
  55
  56 _Bool
  57 __go_type_equal_identity (const void *k1, const void *k2, uintptr_t key_size)
  58 {
  59   return __builtin_memcmp (k1, k2, key_size) == 0;
  60 }