1 /* 2 * Copyright 2017 Google Inc. 3 * 4 * Use of this source code is governed by a BSD-style license that can 5 * be found in the LICENSE file. 6 * 7 */ 8 9 #pragma once 10 11 // 12 // 13 // 14 15 #include "skc.h" 16 #include "weakref.h" 17 #include "macros.h" 18 19 // 20 // WEAKREF 21 // 22 23 #define SKC_WEAKREF_INDEX_BITS 16 // max bits for a weakref index -- this could/should be 12 bits 24 #define SKC_WEAKREF_INDEX_COUNT (1u << SKC_WEAKREF_INDEX_BITS) 25 26 #define SKC_WEAKREF_INDEX_MASK SKC_BITS_TO_MASK(SKC_WEAKREF_INDEX_BITS) 27 #define SKC_WEAKREF_EPOCH_MASK SKC_BITS_TO_MASK_AT_64(64-SKC_WEAKREF_INDEX_BITS,SKC_WEAKREF_INDEX_BITS) 28 29 #define SKC_WEAKREF_EPOCH_INIT 0ul 30 #define SKC_WEAKREF_EPOCH_ONE SKC_BITS_TO_MASK_AT_64(1,SKC_WEAKREF_INDEX_BITS) 31 32 // 33 // FIXME -- ASSUMES LITTLE-ENDIAN 34 // 35 36 union skc_weakref 37 { 38 skc_weakref_t u64; // 64-bits containing refutation epoch and an index 39 40 struct { 41 skc_uint index : SKC_WEAKREF_INDEX_BITS; 42 skc_uint na_lo : 32 - SKC_WEAKREF_INDEX_BITS; 43 skc_uint na_hi; 44 }; 45 46 struct { 47 skc_ulong : SKC_WEAKREF_INDEX_BITS; 48 skc_ulong epoch : 64 - SKC_WEAKREF_INDEX_BITS; 49 }; 50 }; 51 52 SKC_STATIC_ASSERT(sizeof(skc_weakref_t) == sizeof(skc_ulong)); 53 SKC_STATIC_ASSERT(sizeof(union skc_weakref) == sizeof(skc_ulong)); 54 55 // 56 // 57 // 58 59 void skc_weakref_epoch_init(skc_epoch_t * const epoch)60skc_weakref_epoch_init(skc_epoch_t * const epoch) 61 { 62 *epoch = SKC_WEAKREF_EPOCH_INIT; 63 } 64 65 void skc_weakref_epoch_inc(skc_epoch_t * const epoch)66skc_weakref_epoch_inc(skc_epoch_t * const epoch) 67 { 68 *epoch += SKC_WEAKREF_EPOCH_ONE; 69 } 70 71 void skc_weakref_init(skc_weakref_t * const weakref,skc_epoch_t * const epoch,skc_uint const index)72skc_weakref_init(skc_weakref_t * const weakref, 73 skc_epoch_t * const epoch, 74 skc_uint const index) 75 { 76 *weakref = *epoch | (index & SKC_WEAKREF_INDEX_MASK); 77 } 78 79 bool skc_weakref_is_invalid(skc_weakref_t const * const weakref,skc_epoch_t const * const epoch)80skc_weakref_is_invalid(skc_weakref_t const * const weakref, 81 skc_epoch_t const * const epoch) 82 { 83 return ((*weakref ^ *epoch) & SKC_WEAKREF_EPOCH_MASK) != 0UL; 84 } 85 86 skc_uint skc_weakref_index(skc_weakref_t const * const weakref)87skc_weakref_index(skc_weakref_t const * const weakref) 88 { 89 // truncate to word and mask 90 return (skc_uint)*weakref & SKC_WEAKREF_INDEX_MASK; 91 } 92 93 // 94 // 95 // 96