1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 // 5 // The purpose of this file is to supply the macro definintions necessary 6 // to make third_party/dmg_fp/dtoa.cc threadsafe. 7 #include "base/lazy_instance.h" 8 #include "base/logging.h" 9 #include "base/synchronization/lock.h" 10 11 // We need two locks because they're sometimes grabbed at the same time. 12 // A single lock would lead to an attempted recursive grab. 13 static base::LazyInstance<base::Lock>::Leaky 14 dtoa_lock_0 = LAZY_INSTANCE_INITIALIZER; 15 static base::LazyInstance<base::Lock>::Leaky 16 dtoa_lock_1 = LAZY_INSTANCE_INITIALIZER; 17 18 /* 19 * This define and the code below is to trigger thread-safe behavior 20 * in dtoa.cc, per this comment from the file: 21 * 22 * #define MULTIPLE_THREADS if the system offers preemptively scheduled 23 * multiple threads. In this case, you must provide (or suitably 24 * #define) two locks, acquired by ACQUIRE_DTOA_LOCK(n) and freed 25 * by FREE_DTOA_LOCK(n) for n = 0 or 1. (The second lock, accessed 26 * in pow5mult, ensures lazy evaluation of only one copy of high 27 * powers of 5; omitting this lock would introduce a small 28 * probability of wasting memory, but would otherwise be harmless.) 29 * You must also invoke freedtoa(s) to free the value s returned by 30 * dtoa. You may do so whether or not MULTIPLE_THREADS is #defined. 31 */ 32 #define MULTIPLE_THREADS 33 34 inline static void ACQUIRE_DTOA_LOCK(size_t n) { 35 DCHECK(n < 2); 36 base::Lock* lock = n == 0 ? dtoa_lock_0.Pointer() : dtoa_lock_1.Pointer(); 37 lock->Acquire(); 38 } 39 40 inline static void FREE_DTOA_LOCK(size_t n) { 41 DCHECK(n < 2); 42 base::Lock* lock = n == 0 ? dtoa_lock_0.Pointer() : dtoa_lock_1.Pointer(); 43 lock->Release(); 44 } 45 46 #include "base/third_party/dmg_fp/dtoa.cc" 47
