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 "runtime.h"
  10 #include "go-type.h"
  11
  12 /* An identity hash function for a type.  This is used for types where
  13    we can simply use the type value itself as a hash code.  This is
  14    true of, e.g., integers and pointers.  */
  15
  16 uintptr_t
  17 __go_type_hash_identity (const void *key, uintptr_t key_size)
  18 {
  19   uintptr_t ret;
  20   uintptr_t i;
  21   const unsigned char *p;
  22
  23   if (key_size <= 8)
  24     {
  25       union
  26       {
  27         uint64 v;
  28         unsigned char a[8];
  29       } u;
  30       u.v = 0;
  31 #ifdef WORDS_BIGENDIAN
  32       __builtin_memcpy (&u.a[8 - key_size], key, key_size);
  33 #else
  34       __builtin_memcpy (&u.a[0], key, key_size);
  35 #endif
  36       if (sizeof (uintptr_t) >= 8)
  37         return (uintptr_t) u.v;
  38       else
  39         return (uintptr_t) ((u.v >> 32) ^ (u.v & 0xffffffff));
  40     }
  41
  42   ret = 5381;
  43   for (i = 0, p = (const unsigned char *) key; i < key_size; i++, p++)
  44     ret = ret * 33 + *p;
  45   return ret;
  46 }
  47
  48 /* An identity equality function for a type.  This is used for types
  49    where we can check for equality by checking that the values have
  50    the same bits.  */
  51
  52 _Bool
  53 __go_type_equal_identity (const void *k1, const void *k2, uintptr_t key_size)
  54 {
  55   return __builtin_memcmp (k1, k2, key_size) == 0;
  56 }