diff options
author | Tim Angus <tim@ngus.net> | 2013-01-21 22:40:05 +0000 |
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committer | Tim Angus <tim@ngus.net> | 2014-08-28 11:01:50 +0100 |
commit | 0319df4301e9eca103f35ce2ff7e8f4c7b450c03 (patch) | |
tree | 87334b592f52f1a00c638641e2620cae85870059 /src/SDL2/include/SDL_atomic.h | |
parent | 9cbe2c1a320b30d7d8178123aea01396a996bef4 (diff) |
Update bundled SDL headers/libs
Diffstat (limited to 'src/SDL2/include/SDL_atomic.h')
-rw-r--r-- | src/SDL2/include/SDL_atomic.h | 318 |
1 files changed, 318 insertions, 0 deletions
diff --git a/src/SDL2/include/SDL_atomic.h b/src/SDL2/include/SDL_atomic.h new file mode 100644 index 00000000..4b737f54 --- /dev/null +++ b/src/SDL2/include/SDL_atomic.h @@ -0,0 +1,318 @@ +/* + Simple DirectMedia Layer + Copyright (C) 1997-2012 Sam Lantinga <slouken@libsdl.org> + + This software is provided 'as-is', without any express or implied + warranty. In no event will the authors be held liable for any damages + arising from the use of this software. + + Permission is granted to anyone to use this software for any purpose, + including commercial applications, and to alter it and redistribute it + freely, subject to the following restrictions: + + 1. The origin of this software must not be misrepresented; you must not + claim that you wrote the original software. If you use this software + in a product, an acknowledgment in the product documentation would be + appreciated but is not required. + 2. Altered source versions must be plainly marked as such, and must not be + misrepresented as being the original software. + 3. This notice may not be removed or altered from any source distribution. +*/ + +/** + * \file SDL_atomic.h + * + * Atomic operations. + * + * IMPORTANT: + * If you are not an expert in concurrent lockless programming, you should + * only be using the atomic lock and reference counting functions in this + * file. In all other cases you should be protecting your data structures + * with full mutexes. + * + * The list of "safe" functions to use are: + * SDL_AtomicLock() + * SDL_AtomicUnlock() + * SDL_AtomicIncRef() + * SDL_AtomicDecRef() + * + * Seriously, here be dragons! + * ^^^^^^^^^^^^^^^^^^^^^^^^^^^ + * + * You can find out a little more about lockless programming and the + * subtle issues that can arise here: + * http://msdn.microsoft.com/en-us/library/ee418650%28v=vs.85%29.aspx + * + * There's also lots of good information here: + * http://www.1024cores.net/home/lock-free-algorithms + * + * These operations may or may not actually be implemented using + * processor specific atomic operations. When possible they are + * implemented as true processor specific atomic operations. When that + * is not possible the are implemented using locks that *do* use the + * available atomic operations. + * + * All of the atomic operations that modify memory are full memory barriers. + */ + +#ifndef _SDL_atomic_h_ +#define _SDL_atomic_h_ + +#include "SDL_stdinc.h" +#include "SDL_platform.h" + +#include "begin_code.h" + +/* Need to do this here because intrin.h has C++ code in it */ +/* Visual Studio 2005 has a bug where intrin.h conflicts with winnt.h */ +#if defined(_MSC_VER) && (_MSC_VER >= 1500) +#include <intrin.h> +#define HAVE_MSC_ATOMICS 1 +#endif + +/* Set up for C function definitions, even when using C++ */ +#ifdef __cplusplus +/* *INDENT-OFF* */ +extern "C" { +/* *INDENT-ON* */ +#endif + +/** + * \name SDL AtomicLock + * + * The atomic locks are efficient spinlocks using CPU instructions, + * but are vulnerable to starvation and can spin forever if a thread + * holding a lock has been terminated. For this reason you should + * minimize the code executed inside an atomic lock and never do + * expensive things like API or system calls while holding them. + * + * The atomic locks are not safe to lock recursively. + * + * Porting Note: + * The spin lock functions and type are required and can not be + * emulated because they are used in the atomic emulation code. + */ +/*@{*/ + +typedef int SDL_SpinLock; + +/** + * \brief Try to lock a spin lock by setting it to a non-zero value. + * + * \param lock Points to the lock. + * + * \return SDL_TRUE if the lock succeeded, SDL_FALSE if the lock is already held. + */ +extern DECLSPEC SDL_bool SDLCALL SDL_AtomicTryLock(SDL_SpinLock *lock); + +/** + * \brief Lock a spin lock by setting it to a non-zero value. + * + * \param lock Points to the lock. + */ +extern DECLSPEC void SDLCALL SDL_AtomicLock(SDL_SpinLock *lock); + +/** + * \brief Unlock a spin lock by setting it to 0. Always returns immediately + * + * \param lock Points to the lock. + */ +extern DECLSPEC void SDLCALL SDL_AtomicUnlock(SDL_SpinLock *lock); + +/*@}*//*SDL AtomicLock*/ + + +/** + * The compiler barrier prevents the compiler from reordering + * reads and writes to globally visible variables across the call. + */ +#ifdef _MSC_VER +void _ReadWriteBarrier(void); +#pragma intrinsic(_ReadWriteBarrier) +#define SDL_CompilerBarrier() _ReadWriteBarrier() +#elif defined(__GNUC__) +#define SDL_CompilerBarrier() __asm__ __volatile__ ("" : : : "memory") +#else +#define SDL_CompilerBarrier() \ +({ SDL_SpinLock _tmp = 0; SDL_AtomicLock(&_tmp); SDL_AtomicUnlock(&_tmp); }) +#endif + +/* Platform specific optimized versions of the atomic functions, + * you can disable these by defining SDL_DISABLE_ATOMIC_INLINE + */ +#if defined(SDL_ATOMIC_DISABLED) && SDL_ATOMIC_DISABLED +#define SDL_DISABLE_ATOMIC_INLINE +#endif +#ifndef SDL_DISABLE_ATOMIC_INLINE + +#ifdef HAVE_MSC_ATOMICS + +#define SDL_AtomicSet(a, v) _InterlockedExchange((long*)&(a)->value, (v)) +#define SDL_AtomicAdd(a, v) _InterlockedExchangeAdd((long*)&(a)->value, (v)) +#define SDL_AtomicCAS(a, oldval, newval) (_InterlockedCompareExchange((long*)&(a)->value, (newval), (oldval)) == (oldval)) +#define SDL_AtomicSetPtr(a, v) _InterlockedExchangePointer((a), (v)) +#if _M_IX86 +#define SDL_AtomicCASPtr(a, oldval, newval) (_InterlockedCompareExchange((long*)(a), (long)(newval), (long)(oldval)) == (long)(oldval)) +#else +#define SDL_AtomicCASPtr(a, oldval, newval) (_InterlockedCompareExchangePointer((a), (newval), (oldval)) == (oldval)) +#endif + +#elif defined(__MACOSX__) +#include <libkern/OSAtomic.h> + +#define SDL_AtomicCAS(a, oldval, newval) OSAtomicCompareAndSwap32Barrier((oldval), (newval), &(a)->value) +#ifdef __LP64__ +#define SDL_AtomicCASPtr(a, oldval, newval) OSAtomicCompareAndSwap64Barrier((int64_t)(oldval), (int64_t)(newval), (int64_t*)(a)) +#else +#define SDL_AtomicCASPtr(a, oldval, newval) OSAtomicCompareAndSwap32Barrier((int32_t)(oldval), (int32_t)(newval), (int32_t*)(a)) +#endif + +#elif defined(HAVE_GCC_ATOMICS) + +#define SDL_AtomicSet(a, v) __sync_lock_test_and_set(&(a)->value, v) +#define SDL_AtomicAdd(a, v) __sync_fetch_and_add(&(a)->value, v) +#define SDL_AtomicSetPtr(a, v) __sync_lock_test_and_set(a, v) +#define SDL_AtomicCAS(a, oldval, newval) __sync_bool_compare_and_swap(&(a)->value, oldval, newval) +#define SDL_AtomicCASPtr(a, oldval, newval) __sync_bool_compare_and_swap(a, oldval, newval) + +#endif + +#endif /* !SDL_DISABLE_ATOMIC_INLINE */ + + +/** + * \brief A type representing an atomic integer value. It is a struct + * so people don't accidentally use numeric operations on it. + */ +#ifndef SDL_atomic_t_defined +typedef struct { int value; } SDL_atomic_t; +#endif + +/** + * \brief Set an atomic variable to a new value if it is currently an old value. + * + * \return SDL_TRUE if the atomic variable was set, SDL_FALSE otherwise. + * + * \note If you don't know what this function is for, you shouldn't use it! +*/ +#ifndef SDL_AtomicCAS +#define SDL_AtomicCAS SDL_AtomicCAS_ +#endif +extern DECLSPEC SDL_bool SDLCALL SDL_AtomicCAS_(SDL_atomic_t *a, int oldval, int newval); + +/** + * \brief Set an atomic variable to a value. + * + * \return The previous value of the atomic variable. + */ +#ifndef SDL_AtomicSet +static __inline__ int SDL_AtomicSet(SDL_atomic_t *a, int v) +{ + int value; + do { + value = a->value; + } while (!SDL_AtomicCAS(a, value, v)); + return value; +} +#endif + +/** + * \brief Get the value of an atomic variable + */ +#ifndef SDL_AtomicGet +static __inline__ int SDL_AtomicGet(SDL_atomic_t *a) +{ + int value = a->value; + SDL_CompilerBarrier(); + return value; +} +#endif + +/** + * \brief Add to an atomic variable. + * + * \return The previous value of the atomic variable. + * + * \note This same style can be used for any number operation + */ +#ifndef SDL_AtomicAdd +static __inline__ int SDL_AtomicAdd(SDL_atomic_t *a, int v) +{ + int value; + do { + value = a->value; + } while (!SDL_AtomicCAS(a, value, (value + v))); + return value; +} +#endif + +/** + * \brief Increment an atomic variable used as a reference count. + */ +#ifndef SDL_AtomicIncRef +#define SDL_AtomicIncRef(a) SDL_AtomicAdd(a, 1) +#endif + +/** + * \brief Decrement an atomic variable used as a reference count. + * + * \return SDL_TRUE if the variable reached zero after decrementing, + * SDL_FALSE otherwise + */ +#ifndef SDL_AtomicDecRef +#define SDL_AtomicDecRef(a) (SDL_AtomicAdd(a, -1) == 1) +#endif + +/** + * \brief Set a pointer to a new value if it is currently an old value. + * + * \return SDL_TRUE if the pointer was set, SDL_FALSE otherwise. + * + * \note If you don't know what this function is for, you shouldn't use it! +*/ +#ifndef SDL_AtomicCASPtr +#define SDL_AtomicCASPtr SDL_AtomicCASPtr_ +#endif +extern DECLSPEC SDL_bool SDLCALL SDL_AtomicCASPtr_(void* *a, void *oldval, void *newval); + +/** + * \brief Set a pointer to a value atomically. + * + * \return The previous value of the pointer. + */ +#ifndef SDL_AtomicSetPtr +static __inline__ void* SDL_AtomicSetPtr(void* *a, void* v) +{ + void* value; + do { + value = *a; + } while (!SDL_AtomicCASPtr(a, value, v)); + return value; +} +#endif + +/** + * \brief Get the value of a pointer atomically. + */ +#ifndef SDL_AtomicGetPtr +static __inline__ void* SDL_AtomicGetPtr(void* *a) +{ + void* value = *a; + SDL_CompilerBarrier(); + return value; +} +#endif + + +/* Ends C function definitions when using C++ */ +#ifdef __cplusplus +/* *INDENT-OFF* */ +} +/* *INDENT-ON* */ +#endif + +#include "close_code.h" + +#endif /* _SDL_atomic_h_ */ + +/* vi: set ts=4 sw=4 expandtab: */ |