the begginning

utils/common/atomicops.h

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+/* Copyright (C) 2014 InfiniDB, Inc.
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License
+   as published by the Free Software Foundation; version 2 of
+   the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+   MA 02110-1301, USA. */
+
+/** @file */
+
+#ifndef COMMON_ATOMICOPS_H__
+#define COMMON_ATOMICOPS_H__
+
+#include <unistd.h>
+#if defined(__linux__)
+#include <stdint.h>
+#endif
+#if !defined(_MSC_VER)
+#include <sched.h>
+#endif
+
+/*
+This is an attempt to wrap the differneces between Windows and Linux around atomic ops.
+Boost has something in interprocess::ipcdetail, but it doesn't have 64-bit API's.
+*/
+
+namespace atomicops
+{
+
+//Returns the resulting, incremented value
+template <typename T>
+inline T atomicInc(volatile T* mem)
+{
+#ifdef _MSC_VER
+	switch (sizeof(T))
+	{
+	case 4:
+	default:
+		return InterlockedIncrement(reinterpret_cast<volatile LONG*>(mem));
+
+	case 8:
+		return InterlockedIncrement64(reinterpret_cast<volatile LONGLONG*>(mem));
+	}
+#else
+	return __sync_add_and_fetch(mem, 1);
+#endif
+}
+
+//decrements, but returns the pre-decrement value
+template <typename T>
+inline T atomicDec(volatile T* mem)
+{
+#ifdef _MSC_VER
+	switch (sizeof(T))
+	{
+	case 4:
+	default:
+		return InterlockedDecrement(reinterpret_cast<volatile LONG*>(mem))+1;
+
+	case 8:
+		return InterlockedDecrement64(reinterpret_cast<volatile LONGLONG*>(mem))+1;
+	}
+#else
+	return __sync_fetch_and_add(mem, -1);
+#endif
+}
+
+//Returns the resulting value (but doesn't need to yet)
+template <typename T>
+inline T atomicAdd(volatile T* mem, T val)
+{
+#ifdef _MSC_VER
+	switch (sizeof(T))
+	{
+	case 4:
+	default:
+		InterlockedExchangeAdd(reinterpret_cast<volatile LONG*>(mem), val);
+		break;
+
+	case 8:
+		InterlockedExchangeAdd64(reinterpret_cast<volatile LONGLONG*>(mem), val);
+		break;
+	}
+	return *mem;
+#else
+	return __sync_add_and_fetch(mem, val);
+#endif
+}
+
+//Returns the resulting value
+template <typename T>
+inline T atomicSub(volatile T* mem, T val)
+{
+#ifdef _MSC_VER
+	switch (sizeof(T))
+	{
+	case 4:
+	default:
+		InterlockedExchangeAdd(reinterpret_cast<volatile LONG*>(mem), -(static_cast<LONG>(val)));
+		break;
+	case 8:
+		InterlockedExchangeAdd64(reinterpret_cast<volatile LONGLONG*>(mem), -(static_cast<LONGLONG>(val)));
+		break;
+	}
+	return *mem;
+#else
+	return __sync_sub_and_fetch(mem, val);
+#endif
+}
+
+//Implements a memory barrier
+inline void atomicMb()
+{
+#ifdef _MSC_VER
+	MemoryBarrier();
+#else
+	__sync_synchronize();
+#endif
+}
+
+//Returns true iff the CAS took place, that is
+// if (*mem == comp) {
+//   *mem = swap;
+//   return true;
+// } else {
+//   return false;
+// }
+template <typename T>
+inline bool atomicCAS(volatile T* mem, T comp, T swap)
+{
+#ifdef _MSC_VER
+	switch (sizeof(T))
+	{
+	case 4:
+	default:
+		//The function returns the initial value of the mem parameter
+		return (InterlockedCompareExchange(reinterpret_cast<volatile LONG*>(mem), swap, comp) == comp);
+
+	case 8:
+		return (InterlockedCompareExchange64(reinterpret_cast<volatile LONGLONG*>(mem), swap, comp) == comp);
+	}
+#else
+	//If the current value of *mem is comp, then write swap into *comp. Return true if the comparison is successful and swap was written.
+	return __sync_bool_compare_and_swap(mem, comp, swap);
+#endif
+}
+
+//Implements a scheduler yield
+inline void atomicYield()
+{
+#ifdef _MSC_VER
+	SwitchToThread();
+#else
+	sched_yield();
+#endif
+}
+
+}
+
+#endif