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Diffstat (limited to 'dependencies/SDL/SDL_atomic.h')
| -rw-r--r-- | dependencies/SDL/SDL_atomic.h | 415 |
1 files changed, 415 insertions, 0 deletions
diff --git a/dependencies/SDL/SDL_atomic.h b/dependencies/SDL/SDL_atomic.h new file mode 100644 index 0000000..f0c05f4 --- /dev/null +++ b/dependencies/SDL/SDL_atomic.h @@ -0,0 +1,415 @@ +/* + Simple DirectMedia Layer + Copyright (C) 1997-2022 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 + * http://preshing.com/ + * + * 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" + +/* Set up for C function definitions, even when using C++ */ +#ifdef __cplusplus +extern "C" { +#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; + +/** + * Try to lock a spin lock by setting it to a non-zero value. + * + * ***Please note that spinlocks are dangerous if you don't know what you're + * doing. Please be careful using any sort of spinlock!*** + * + * \param lock a pointer to a lock variable + * \returns SDL_TRUE if the lock succeeded, SDL_FALSE if the lock is already + * held. + * + * \since This function is available since SDL 2.0.0. + * + * \sa SDL_AtomicLock + * \sa SDL_AtomicUnlock + */ +extern DECLSPEC SDL_bool SDLCALL SDL_AtomicTryLock(SDL_SpinLock *lock); + +/** + * Lock a spin lock by setting it to a non-zero value. + * + * ***Please note that spinlocks are dangerous if you don't know what you're + * doing. Please be careful using any sort of spinlock!*** + * + * \param lock a pointer to a lock variable + * + * \since This function is available since SDL 2.0.0. + * + * \sa SDL_AtomicTryLock + * \sa SDL_AtomicUnlock + */ +extern DECLSPEC void SDLCALL SDL_AtomicLock(SDL_SpinLock *lock); + +/** + * Unlock a spin lock by setting it to 0. + * + * Always returns immediately. + * + * ***Please note that spinlocks are dangerous if you don't know what you're + * doing. Please be careful using any sort of spinlock!*** + * + * \param lock a pointer to a lock variable + * + * \since This function is available since SDL 2.0.0. + * + * \sa SDL_AtomicLock + * \sa SDL_AtomicTryLock + */ +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. + */ +#if defined(_MSC_VER) && (_MSC_VER > 1200) && !defined(__clang__) +void _ReadWriteBarrier(void); +#pragma intrinsic(_ReadWriteBarrier) +#define SDL_CompilerBarrier() _ReadWriteBarrier() +#elif (defined(__GNUC__) && !defined(__EMSCRIPTEN__)) || (defined(__SUNPRO_C) && (__SUNPRO_C >= 0x5120)) +/* This is correct for all CPUs when using GCC or Solaris Studio 12.1+. */ +#define SDL_CompilerBarrier() __asm__ __volatile__ ("" : : : "memory") +#elif defined(__WATCOMC__) +extern __inline void SDL_CompilerBarrier(void); +#pragma aux SDL_CompilerBarrier = "" parm [] modify exact []; +#else +#define SDL_CompilerBarrier() \ +{ SDL_SpinLock _tmp = 0; SDL_AtomicLock(&_tmp); SDL_AtomicUnlock(&_tmp); } +#endif + +/** + * Memory barriers are designed to prevent reads and writes from being + * reordered by the compiler and being seen out of order on multi-core CPUs. + * + * A typical pattern would be for thread A to write some data and a flag, and + * for thread B to read the flag and get the data. In this case you would + * insert a release barrier between writing the data and the flag, + * guaranteeing that the data write completes no later than the flag is + * written, and you would insert an acquire barrier between reading the flag + * and reading the data, to ensure that all the reads associated with the flag + * have completed. + * + * In this pattern you should always see a release barrier paired with an + * acquire barrier and you should gate the data reads/writes with a single + * flag variable. + * + * For more information on these semantics, take a look at the blog post: + * http://preshing.com/20120913/acquire-and-release-semantics + * + * \since This function is available since SDL 2.0.6. + */ +extern DECLSPEC void SDLCALL SDL_MemoryBarrierReleaseFunction(void); +extern DECLSPEC void SDLCALL SDL_MemoryBarrierAcquireFunction(void); + +#if defined(__GNUC__) && (defined(__powerpc__) || defined(__ppc__)) +#define SDL_MemoryBarrierRelease() __asm__ __volatile__ ("lwsync" : : : "memory") +#define SDL_MemoryBarrierAcquire() __asm__ __volatile__ ("lwsync" : : : "memory") +#elif defined(__GNUC__) && defined(__aarch64__) +#define SDL_MemoryBarrierRelease() __asm__ __volatile__ ("dmb ish" : : : "memory") +#define SDL_MemoryBarrierAcquire() __asm__ __volatile__ ("dmb ish" : : : "memory") +#elif defined(__GNUC__) && defined(__arm__) +#if 0 /* defined(__LINUX__) || defined(__ANDROID__) */ +/* Information from: + https://chromium.googlesource.com/chromium/chromium/+/trunk/base/atomicops_internals_arm_gcc.h#19 + + The Linux kernel provides a helper function which provides the right code for a memory barrier, + hard-coded at address 0xffff0fa0 +*/ +typedef void (*SDL_KernelMemoryBarrierFunc)(); +#define SDL_MemoryBarrierRelease() ((SDL_KernelMemoryBarrierFunc)0xffff0fa0)() +#define SDL_MemoryBarrierAcquire() ((SDL_KernelMemoryBarrierFunc)0xffff0fa0)() +#elif 0 /* defined(__QNXNTO__) */ +#include <sys/cpuinline.h> + +#define SDL_MemoryBarrierRelease() __cpu_membarrier() +#define SDL_MemoryBarrierAcquire() __cpu_membarrier() +#else +#if defined(__ARM_ARCH_7__) || defined(__ARM_ARCH_7A__) || defined(__ARM_ARCH_7EM__) || defined(__ARM_ARCH_7R__) || defined(__ARM_ARCH_7M__) || defined(__ARM_ARCH_7S__) || defined(__ARM_ARCH_8A__) +#define SDL_MemoryBarrierRelease() __asm__ __volatile__ ("dmb ish" : : : "memory") +#define SDL_MemoryBarrierAcquire() __asm__ __volatile__ ("dmb ish" : : : "memory") +#elif defined(__ARM_ARCH_6__) || defined(__ARM_ARCH_6J__) || defined(__ARM_ARCH_6K__) || defined(__ARM_ARCH_6T2__) || defined(__ARM_ARCH_6Z__) || defined(__ARM_ARCH_6ZK__) || defined(__ARM_ARCH_5TE__) +#ifdef __thumb__ +/* The mcr instruction isn't available in thumb mode, use real functions */ +#define SDL_MEMORY_BARRIER_USES_FUNCTION +#define SDL_MemoryBarrierRelease() SDL_MemoryBarrierReleaseFunction() +#define SDL_MemoryBarrierAcquire() SDL_MemoryBarrierAcquireFunction() +#else +#define SDL_MemoryBarrierRelease() __asm__ __volatile__ ("mcr p15, 0, %0, c7, c10, 5" : : "r"(0) : "memory") +#define SDL_MemoryBarrierAcquire() __asm__ __volatile__ ("mcr p15, 0, %0, c7, c10, 5" : : "r"(0) : "memory") +#endif /* __thumb__ */ +#else +#define SDL_MemoryBarrierRelease() __asm__ __volatile__ ("" : : : "memory") +#define SDL_MemoryBarrierAcquire() __asm__ __volatile__ ("" : : : "memory") +#endif /* __LINUX__ || __ANDROID__ */ +#endif /* __GNUC__ && __arm__ */ +#else +#if (defined(__SUNPRO_C) && (__SUNPRO_C >= 0x5120)) +/* This is correct for all CPUs on Solaris when using Solaris Studio 12.1+. */ +#include <mbarrier.h> +#define SDL_MemoryBarrierRelease() __machine_rel_barrier() +#define SDL_MemoryBarrierAcquire() __machine_acq_barrier() +#else +/* This is correct for the x86 and x64 CPUs, and we'll expand this over time. */ +#define SDL_MemoryBarrierRelease() SDL_CompilerBarrier() +#define SDL_MemoryBarrierAcquire() SDL_CompilerBarrier() +#endif +#endif + +/* "REP NOP" is PAUSE, coded for tools that don't know it by that name. */ +#if (defined(__GNUC__) || defined(__clang__)) && (defined(__i386__) || defined(__x86_64__)) + #define SDL_CPUPauseInstruction() __asm__ __volatile__("pause\n") /* Some assemblers can't do REP NOP, so go with PAUSE. */ +#elif (defined(__arm__) && __ARM_ARCH >= 7) || defined(__aarch64__) + #define SDL_CPUPauseInstruction() __asm__ __volatile__("yield" ::: "memory") +#elif (defined(__powerpc__) || defined(__powerpc64__)) + #define SDL_CPUPauseInstruction() __asm__ __volatile__("or 27,27,27"); +#elif defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64)) + #define SDL_CPUPauseInstruction() _mm_pause() /* this is actually "rep nop" and not a SIMD instruction. No inline asm in MSVC x86-64! */ +#elif defined(_MSC_VER) && (defined(_M_ARM) || defined(_M_ARM64)) + #define SDL_CPUPauseInstruction() __yield() +#elif defined(__WATCOMC__) && defined(__386__) + /* watcom assembler rejects PAUSE if CPU < i686, and it refuses REP NOP as an invalid combination. Hardcode the bytes. */ + extern __inline void SDL_CPUPauseInstruction(void); + #pragma aux SDL_CPUPauseInstruction = "db 0f3h,90h" +#else + #define SDL_CPUPauseInstruction() +#endif + + +/** + * \brief A type representing an atomic integer value. It is a struct + * so people don't accidentally use numeric operations on it. + */ +typedef struct { int value; } SDL_atomic_t; + +/** + * Set an atomic variable to a new value if it is currently an old value. + * + * ***Note: If you don't know what this function is for, you shouldn't use + * it!*** + * + * \param a a pointer to an SDL_atomic_t variable to be modified + * \param oldval the old value + * \param newval the new value + * \returns SDL_TRUE if the atomic variable was set, SDL_FALSE otherwise. + * + * \since This function is available since SDL 2.0.0. + * + * \sa SDL_AtomicCASPtr + * \sa SDL_AtomicGet + * \sa SDL_AtomicSet + */ +extern DECLSPEC SDL_bool SDLCALL SDL_AtomicCAS(SDL_atomic_t *a, int oldval, int newval); + +/** + * Set an atomic variable to a value. + * + * This function also acts as a full memory barrier. + * + * ***Note: If you don't know what this function is for, you shouldn't use + * it!*** + * + * \param a a pointer to an SDL_atomic_t variable to be modified + * \param v the desired value + * \returns the previous value of the atomic variable. + * + * \since This function is available since SDL 2.0.2. + * + * \sa SDL_AtomicGet + */ +extern DECLSPEC int SDLCALL SDL_AtomicSet(SDL_atomic_t *a, int v); + +/** + * Get the value of an atomic variable. + * + * ***Note: If you don't know what this function is for, you shouldn't use + * it!*** + * + * \param a a pointer to an SDL_atomic_t variable + * \returns the current value of an atomic variable. + * + * \since This function is available since SDL 2.0.2. + * + * \sa SDL_AtomicSet + */ +extern DECLSPEC int SDLCALL SDL_AtomicGet(SDL_atomic_t *a); + +/** + * Add to an atomic variable. + * + * This function also acts as a full memory barrier. + * + * ***Note: If you don't know what this function is for, you shouldn't use + * it!*** + * + * \param a a pointer to an SDL_atomic_t variable to be modified + * \param v the desired value to add + * \returns the previous value of the atomic variable. + * + * \since This function is available since SDL 2.0.2. + * + * \sa SDL_AtomicDecRef + * \sa SDL_AtomicIncRef + */ +extern DECLSPEC int SDLCALL SDL_AtomicAdd(SDL_atomic_t *a, int v); + +/** + * \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 + +/** + * Set a pointer to a new value if it is currently an old value. + * + * ***Note: If you don't know what this function is for, you shouldn't use + * it!*** + * + * \param a a pointer to a pointer + * \param oldval the old pointer value + * \param newval the new pointer value + * \returns SDL_TRUE if the pointer was set, SDL_FALSE otherwise. + * + * \since This function is available since SDL 2.0.0. + * + * \sa SDL_AtomicCAS + * \sa SDL_AtomicGetPtr + * \sa SDL_AtomicSetPtr + */ +extern DECLSPEC SDL_bool SDLCALL SDL_AtomicCASPtr(void **a, void *oldval, void *newval); + +/** + * Set a pointer to a value atomically. + * + * ***Note: If you don't know what this function is for, you shouldn't use + * it!*** + * + * \param a a pointer to a pointer + * \param v the desired pointer value + * \returns the previous value of the pointer. + * + * \since This function is available since SDL 2.0.2. + * + * \sa SDL_AtomicCASPtr + * \sa SDL_AtomicGetPtr + */ +extern DECLSPEC void* SDLCALL SDL_AtomicSetPtr(void **a, void* v); + +/** + * Get the value of a pointer atomically. + * + * ***Note: If you don't know what this function is for, you shouldn't use + * it!*** + * + * \param a a pointer to a pointer + * \returns the current value of a pointer. + * + * \since This function is available since SDL 2.0.2. + * + * \sa SDL_AtomicCASPtr + * \sa SDL_AtomicSetPtr + */ +extern DECLSPEC void* SDLCALL SDL_AtomicGetPtr(void **a); + +/* Ends C function definitions when using C++ */ +#ifdef __cplusplus +} +#endif + +#include "close_code.h" + +#endif /* SDL_atomic_h_ */ + +/* vi: set ts=4 sw=4 expandtab: */ |