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 "go-type.h"
  10
  11 /* The 64-bit type.  */
  12
  13 typedef unsigned int DItype __attribute__ ((mode (DI)));
  14
  15 /* An identity hash function for a type.  This is used for types where
  16    we can simply use the type value itself as a hash code.  This is
  17    true of, e.g., integers and pointers.  */
  18
  19 uintptr_t
  20 __go_type_hash_identity (const void *key, uintptr_t key_size)
  21 {
  22   uintptr_t ret;
  23   uintptr_t i;
  24   const unsigned char *p;
  25
  26   if (key_size <= 8)
  27     {
  28       union
  29       {
  30         DItype v;
  31         unsigned char a[8];
  32       } u;
  33       u.v = 0;
  34       __builtin_memcpy (&u.a, key, key_size);
  35       return (uintptr_t) u.v;
  36     }
  37
  38   ret = 5381;
  39   for (i = 0, p = (const unsigned char *) key; i < key_size; i++, p++)
  40     ret = ret * 33 + *p;
  41   return ret;
  42 }
  43
  44 /* An identity equality function for a type.  This is used for types
  45    where we can check for equality by checking that the values have
  46    the same bits.  */
  47
  48 _Bool
  49 __go_type_equal_identity (const void *k1, const void *k2, uintptr_t key_size)
  50 {
  51   return __builtin_memcmp (k1, k2, key_size) == 0;
  52 }