sdl3_sys/generated/

atomic.rs

//! Atomic operations.
//!
//! IMPORTANT: If you are not an expert in concurrent lockless programming, you
//! should not be using any functions in this file. You should be protecting
//! your data structures with full mutexes instead.
//!
//! ***Seriously, here be dragons!***
//!
//! You can find out a little more about lockless programming and the subtle
//! issues that can arise here:
//! <https://learn.microsoft.com/en-us/windows/win32/dxtecharts/lockless-programming>
//!
//! There's also lots of good information here:
//!
//! - <https://www.1024cores.net/home/lock-free-algorithms>
//! - <https://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.

use super::stdinc::*;

/// An atomic spinlock.
///
/// 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.
///
/// They are also vulnerable to starvation if the thread holding the lock is
/// lower priority than other threads and doesn't get scheduled. In general you
/// should use mutexes instead, since they have better performance and
/// contention behavior.
///
/// 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.
#[repr(transparent)]
#[derive(Default)]
#[cfg_attr(feature = "debug-impls", derive(Debug))]
pub struct SDL_SpinLock(pub ::core::ffi::c_int);

#[cfg(feature = "metadata")]
impl sdl3_sys::metadata::GroupMetadata for SDL_SpinLock {
    const GROUP_METADATA: &'static sdl3_sys::metadata::Group =
        &crate::metadata::atomic::METADATA_SDL_SpinLock;
}

unsafe extern "C" {
    /// 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!***
    ///
    /// ## Parameters
    /// - `lock`: a pointer to a lock variable.
    ///
    /// ## Return value
    /// Returns true if the lock succeeded, false if the lock is already held.
    ///
    /// ## Thread safety
    /// It is safe to call this function from any thread.
    ///
    /// ## Availability
    /// This function is available since SDL 3.2.0.
    ///
    /// ## See also
    /// - [`SDL_LockSpinlock`]
    /// - [`SDL_UnlockSpinlock`]
    pub fn SDL_TryLockSpinlock(lock: *mut SDL_SpinLock) -> ::core::primitive::bool;
}

unsafe extern "C" {
    /// 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!***
    ///
    /// ## Parameters
    /// - `lock`: a pointer to a lock variable.
    ///
    /// ## Thread safety
    /// It is safe to call this function from any thread.
    ///
    /// ## Availability
    /// This function is available since SDL 3.2.0.
    ///
    /// ## See also
    /// - [`SDL_TryLockSpinlock`]
    /// - [`SDL_UnlockSpinlock`]
    pub fn SDL_LockSpinlock(lock: *mut SDL_SpinLock);
}

unsafe extern "C" {
    /// 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!***
    ///
    /// ## Parameters
    /// - `lock`: a pointer to a lock variable.
    ///
    /// ## Thread safety
    /// It is safe to call this function from any thread.
    ///
    /// ## Availability
    /// This function is available since SDL 3.2.0.
    ///
    /// ## See also
    /// - [`SDL_LockSpinlock`]
    /// - [`SDL_TryLockSpinlock`]
    pub fn SDL_UnlockSpinlock(lock: *mut SDL_SpinLock);
}

apply_cfg!(#[cfg(doc)] => {
    /// Mark a compiler barrier.
    ///
    /// A compiler barrier prevents the compiler from reordering reads and writes
    /// to globally visible variables across the call.
    ///
    /// This macro only prevents the compiler from reordering reads and writes, it
    /// does not prevent the CPU from reordering reads and writes. However, all of
    /// the atomic operations that modify memory are full memory barriers.
    ///
    /// ## Thread safety
    /// Obviously this macro is safe to use from any thread at any
    ///   time, but if you find yourself needing this, you are probably
    ///   dealing with some very sensitive code; be careful!
    ///
    /// ## Availability
    /// This macro is available since SDL 3.2.0.
    #[inline(always)]
    pub fn SDL_CompilerBarrier() {
        ::core::sync::atomic::compiler_fence(::core::sync::atomic::Ordering::SeqCst)
    }
});

apply_cfg!(#[cfg(not(doc))] => {
    apply_cfg!(#[cfg(all(not(any(/* always disabled: __clang__ */)), all(windows, target_env = "msvc")))] => {
        // pragma `intrinsic(_ReadWriteBarrier)`
        #[inline(always)]
        pub fn SDL_CompilerBarrier() {
            ::core::sync::atomic::compiler_fence(::core::sync::atomic::Ordering::SeqCst)
        }
    });

    apply_cfg!(#[cfg(not(all(not(any(/* always disabled: __clang__ */)), all(windows, target_env = "msvc"))))] => {
        apply_cfg!(#[cfg(not(any(doc, target_os = "emscripten")))] => {
            #[inline(always)]
            pub fn SDL_CompilerBarrier() {
                ::core::sync::atomic::compiler_fence(::core::sync::atomic::Ordering::SeqCst)
            }
        });

        apply_cfg!(#[cfg(any(doc, target_os = "emscripten"))] => {
            #[inline(always)]
            pub fn SDL_CompilerBarrier() {
                ::core::sync::atomic::compiler_fence(::core::sync::atomic::Ordering::SeqCst)
            }
        });

    });

});

#[inline(always)]
pub fn SDL_MemoryBarrierRelease() {
    ::core::sync::atomic::fence(::core::sync::atomic::Ordering::Release)
}

unsafe extern "C" {
    /// Insert a memory release barrier (function version).
    ///
    /// Please refer to [`SDL_MemoryBarrierRelease`] for details. This is a function
    /// version, which might be useful if you need to use this functionality from a
    /// scripting language, etc. Also, some of the macro versions call this
    /// function behind the scenes, where more heavy lifting can happen inside of
    /// SDL. Generally, though, an app written in C/C++/etc should use the macro
    /// version, as it will be more efficient.
    ///
    /// ## Thread safety
    /// Obviously this function is safe to use from any thread at any
    ///   time, but if you find yourself needing this, you are probably
    ///   dealing with some very sensitive code; be careful!
    ///
    /// ## Availability
    /// This function is available since SDL 3.2.0.
    ///
    /// ## See also
    /// - [`SDL_MemoryBarrierRelease`]
    pub fn SDL_MemoryBarrierReleaseFunction();
}

#[inline(always)]
pub fn SDL_MemoryBarrierAcquire() {
    ::core::sync::atomic::fence(::core::sync::atomic::Ordering::Acquire)
}

unsafe extern "C" {
    /// Insert a memory acquire barrier (function version).
    ///
    /// Please refer to [`SDL_MemoryBarrierRelease`] for details. This is a function
    /// version, which might be useful if you need to use this functionality from a
    /// scripting language, etc. Also, some of the macro versions call this
    /// function behind the scenes, where more heavy lifting can happen inside of
    /// SDL. Generally, though, an app written in C/C++/etc should use the macro
    /// version, as it will be more efficient.
    ///
    /// ## Thread safety
    /// Obviously this function is safe to use from any thread at any
    ///   time, but if you find yourself needing this, you are probably
    ///   dealing with some very sensitive code; be careful!
    ///
    /// ## Availability
    /// This function is available since SDL 3.2.0.
    ///
    /// ## See also
    /// - [`SDL_MemoryBarrierAcquire`]
    pub fn SDL_MemoryBarrierAcquireFunction();
}

apply_cfg!(#[cfg(doc)] => {
});

apply_cfg!(#[cfg(not(doc))] => {
    apply_cfg!(#[cfg(all(any(any(target_arch = "powerpc", target_arch = "powerpc64"), any(target_arch = "powerpc", target_arch = "powerpc64")), any(/* always disabled: __GNUC__ */)))] => {
    });

    apply_cfg!(#[cfg(not(all(any(any(target_arch = "powerpc", target_arch = "powerpc64"), any(target_arch = "powerpc", target_arch = "powerpc64")), any(/* always disabled: __GNUC__ */))))] => {
    });

});

apply_cfg!(#[cfg(doc)] => {
    /// A macro to insert a CPU-specific "pause" instruction into the program.
    ///
    /// This can be useful in busy-wait loops, as it serves as a hint to the CPU as
    /// to the program's intent; some CPUs can use this to do more efficient
    /// processing. On some platforms, this doesn't do anything, so using this
    /// macro might just be a harmless no-op.
    ///
    /// Note that if you are busy-waiting, there are often more-efficient
    /// approaches with other synchronization primitives: mutexes, semaphores,
    /// condition variables, etc.
    ///
    /// ## Thread safety
    /// This macro is safe to use from any thread.
    ///
    /// ## Availability
    /// This macro is available since SDL 3.2.0.
    #[inline(always)]
    pub fn SDL_CPUPauseInstruction() {
        ::core::hint::spin_loop();
    }
});

apply_cfg!(#[cfg(not(doc))] => {
    apply_cfg!(#[cfg(all(any(any(/* always disabled: __GNUC__ */), any(/* always disabled: __clang__ */)), any(target_arch = "x86", target_arch = "x86_64")))] => {
        #[inline(always)]
        pub fn SDL_CPUPauseInstruction() {
            ::core::hint::spin_loop();
        }
    });

    apply_cfg!(#[cfg(not(all(any(any(/* always disabled: __GNUC__ */), any(/* always disabled: __clang__ */)), any(target_arch = "x86", target_arch = "x86_64"))))] => {
        #[inline(always)]
        pub fn SDL_CPUPauseInstruction() {
            ::core::hint::spin_loop();
        }
    });

});

/// A type representing an atomic integer value.
///
/// This can be used to manage a value that is synchronized across multiple
/// CPUs without a race condition; when an app sets a value with
/// [`SDL_SetAtomicInt`] all other threads, regardless of the CPU it is running on,
/// will see that value when retrieved with [`SDL_GetAtomicInt`], regardless of CPU
/// caches, etc.
///
/// This is also useful for atomic compare-and-swap operations: a thread can
/// change the value as long as its current value matches expectations. When
/// done in a loop, one can guarantee data consistency across threads without a
/// lock (but the usual warnings apply: if you don't know what you're doing, or
/// you don't do it carefully, you can confidently cause any number of
/// disasters with this, so in most cases, you _should_ use a mutex instead of
/// this!).
///
/// This is a struct so people don't accidentally use numeric operations on it
/// directly. You have to use SDL atomic functions.
///
/// ## Availability
/// This struct is available since SDL 3.2.0.
///
/// ## See also
/// - [`SDL_CompareAndSwapAtomicInt`]
/// - [`SDL_GetAtomicInt`]
/// - [`SDL_SetAtomicInt`]
/// - [`SDL_AddAtomicInt`]
#[repr(C)]
#[derive(Default)]
#[cfg_attr(feature = "debug-impls", derive(Debug))]
pub struct SDL_AtomicInt {
    pub value: ::core::ffi::c_int,
}

unsafe extern "C" {
    /// 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!***
    ///
    /// ## Parameters
    /// - `a`: a pointer to an [`SDL_AtomicInt`] variable to be modified.
    /// - `oldval`: the old value.
    /// - `newval`: the new value.
    ///
    /// ## Return value
    /// Returns true if the atomic variable was set, false otherwise.
    ///
    /// ## Thread safety
    /// It is safe to call this function from any thread.
    ///
    /// ## Availability
    /// This function is available since SDL 3.2.0.
    ///
    /// ## See also
    /// - [`SDL_GetAtomicInt`]
    /// - [`SDL_SetAtomicInt`]
    pub fn SDL_CompareAndSwapAtomicInt(
        a: *mut SDL_AtomicInt,
        oldval: ::core::ffi::c_int,
        newval: ::core::ffi::c_int,
    ) -> ::core::primitive::bool;
}

unsafe extern "C" {
    /// 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!***
    ///
    /// ## Parameters
    /// - `a`: a pointer to an [`SDL_AtomicInt`] variable to be modified.
    /// - `v`: the desired value.
    ///
    /// ## Return value
    /// Returns the previous value of the atomic variable.
    ///
    /// ## Thread safety
    /// It is safe to call this function from any thread.
    ///
    /// ## Availability
    /// This function is available since SDL 3.2.0.
    ///
    /// ## See also
    /// - [`SDL_GetAtomicInt`]
    pub fn SDL_SetAtomicInt(a: *mut SDL_AtomicInt, v: ::core::ffi::c_int) -> ::core::ffi::c_int;
}

unsafe extern "C" {
    /// Get the value of an atomic variable.
    ///
    /// ***Note: If you don't know what this function is for, you shouldn't use
    /// it!***
    ///
    /// ## Parameters
    /// - `a`: a pointer to an [`SDL_AtomicInt`] variable.
    ///
    /// ## Return value
    /// Returns the current value of an atomic variable.
    ///
    /// ## Thread safety
    /// It is safe to call this function from any thread.
    ///
    /// ## Availability
    /// This function is available since SDL 3.2.0.
    ///
    /// ## See also
    /// - [`SDL_SetAtomicInt`]
    pub fn SDL_GetAtomicInt(a: *mut SDL_AtomicInt) -> ::core::ffi::c_int;
}

unsafe extern "C" {
    /// 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!***
    ///
    /// ## Parameters
    /// - `a`: a pointer to an [`SDL_AtomicInt`] variable to be modified.
    /// - `v`: the desired value to add.
    ///
    /// ## Return value
    /// Returns the previous value of the atomic variable.
    ///
    /// ## Thread safety
    /// It is safe to call this function from any thread.
    ///
    /// ## Availability
    /// This function is available since SDL 3.2.0.
    ///
    /// ## See also
    /// - [`SDL_AtomicDecRef`]
    /// - [`SDL_AtomicIncRef`]
    pub fn SDL_AddAtomicInt(a: *mut SDL_AtomicInt, v: ::core::ffi::c_int) -> ::core::ffi::c_int;
}

/// Increment an atomic variable used as a reference count.
///
/// ***Note: If you don't know what this macro is for, you shouldn't use it!***
///
/// ## Parameters
/// - `a`: a pointer to an [`SDL_AtomicInt`] to increment.
///
/// ## Return value
/// Returns the previous value of the atomic variable.
///
/// ## Thread safety
/// It is safe to call this macro from any thread.
///
/// ## Availability
/// This macro is available since SDL 3.2.0.
///
/// ## See also
/// - [`SDL_AtomicDecRef`]
#[inline(always)]
pub unsafe fn SDL_AtomicIncRef(a: *mut SDL_AtomicInt) -> ::core::ffi::c_int {
    unsafe { SDL_AddAtomicInt(a, 1) }
}

/// Decrement an atomic variable used as a reference count.
///
/// ***Note: If you don't know what this macro is for, you shouldn't use it!***
///
/// ## Parameters
/// - `a`: a pointer to an [`SDL_AtomicInt`] to decrement.
///
/// ## Return value
/// Returns true if the variable reached zero after decrementing, false
///   otherwise.
///
/// ## Thread safety
/// It is safe to call this macro from any thread.
///
/// ## Availability
/// This macro is available since SDL 3.2.0.
///
/// ## See also
/// - [`SDL_AtomicIncRef`]
#[inline(always)]
pub unsafe fn SDL_AtomicDecRef(a: *mut SDL_AtomicInt) -> ::core::primitive::bool {
    (unsafe { SDL_AddAtomicInt(a, -1_i32) } == 1_i32)
}

/// A type representing an atomic unsigned 32-bit value.
///
/// This can be used to manage a value that is synchronized across multiple
/// CPUs without a race condition; when an app sets a value with
/// [`SDL_SetAtomicU32`] all other threads, regardless of the CPU it is running on,
/// will see that value when retrieved with [`SDL_GetAtomicU32`], regardless of CPU
/// caches, etc.
///
/// This is also useful for atomic compare-and-swap operations: a thread can
/// change the value as long as its current value matches expectations. When
/// done in a loop, one can guarantee data consistency across threads without a
/// lock (but the usual warnings apply: if you don't know what you're doing, or
/// you don't do it carefully, you can confidently cause any number of
/// disasters with this, so in most cases, you _should_ use a mutex instead of
/// this!).
///
/// This is a struct so people don't accidentally use numeric operations on it
/// directly. You have to use SDL atomic functions.
///
/// ## Availability
/// This struct is available since SDL 3.2.0.
///
/// ## See also
/// - [`SDL_CompareAndSwapAtomicU32`]
/// - [`SDL_GetAtomicU32`]
/// - [`SDL_SetAtomicU32`]
#[repr(C)]
#[derive(Default)]
#[cfg_attr(feature = "debug-impls", derive(Debug))]
pub struct SDL_AtomicU32 {
    pub value: Uint32,
}

unsafe extern "C" {
    /// 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!***
    ///
    /// ## Parameters
    /// - `a`: a pointer to an [`SDL_AtomicU32`] variable to be modified.
    /// - `oldval`: the old value.
    /// - `newval`: the new value.
    ///
    /// ## Return value
    /// Returns true if the atomic variable was set, false otherwise.
    ///
    /// ## Thread safety
    /// It is safe to call this function from any thread.
    ///
    /// ## Availability
    /// This function is available since SDL 3.2.0.
    ///
    /// ## See also
    /// - [`SDL_GetAtomicU32`]
    /// - [`SDL_SetAtomicU32`]
    pub fn SDL_CompareAndSwapAtomicU32(
        a: *mut SDL_AtomicU32,
        oldval: Uint32,
        newval: Uint32,
    ) -> ::core::primitive::bool;
}

unsafe extern "C" {
    /// 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!***
    ///
    /// ## Parameters
    /// - `a`: a pointer to an [`SDL_AtomicU32`] variable to be modified.
    /// - `v`: the desired value.
    ///
    /// ## Return value
    /// Returns the previous value of the atomic variable.
    ///
    /// ## Thread safety
    /// It is safe to call this function from any thread.
    ///
    /// ## Availability
    /// This function is available since SDL 3.2.0.
    ///
    /// ## See also
    /// - [`SDL_GetAtomicU32`]
    pub fn SDL_SetAtomicU32(a: *mut SDL_AtomicU32, v: Uint32) -> Uint32;
}

unsafe extern "C" {
    /// Get the value of an atomic variable.
    ///
    /// ***Note: If you don't know what this function is for, you shouldn't use
    /// it!***
    ///
    /// ## Parameters
    /// - `a`: a pointer to an [`SDL_AtomicU32`] variable.
    ///
    /// ## Return value
    /// Returns the current value of an atomic variable.
    ///
    /// ## Thread safety
    /// It is safe to call this function from any thread.
    ///
    /// ## Availability
    /// This function is available since SDL 3.2.0.
    ///
    /// ## See also
    /// - [`SDL_SetAtomicU32`]
    pub fn SDL_GetAtomicU32(a: *mut SDL_AtomicU32) -> Uint32;
}

unsafe extern "C" {
    /// 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!***
    ///
    /// ## Parameters
    /// - `a`: a pointer to an [`SDL_AtomicU32`] variable to be modified.
    /// - `v`: the desired value to add or subtract.
    ///
    /// ## Return value
    /// Returns the previous value of the atomic variable.
    ///
    /// ## Thread safety
    /// It is safe to call this function from any thread.
    ///
    /// ## Availability
    /// This function is available since SDL 3.4.0.
    pub fn SDL_AddAtomicU32(a: *mut SDL_AtomicU32, v: ::core::ffi::c_int) -> Uint32;
}

unsafe extern "C" {
    /// 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!***
    ///
    /// ## Parameters
    /// - `a`: a pointer to a pointer.
    /// - `oldval`: the old pointer value.
    /// - `newval`: the new pointer value.
    ///
    /// ## Return value
    /// Returns true if the pointer was set, false otherwise.
    ///
    /// ## Thread safety
    /// It is safe to call this function from any thread.
    ///
    /// ## Availability
    /// This function is available since SDL 3.2.0.
    ///
    /// ## See also
    /// - [`SDL_CompareAndSwapAtomicInt`]
    /// - [`SDL_GetAtomicPointer`]
    /// - [`SDL_SetAtomicPointer`]
    pub fn SDL_CompareAndSwapAtomicPointer(
        a: *mut *mut ::core::ffi::c_void,
        oldval: *mut ::core::ffi::c_void,
        newval: *mut ::core::ffi::c_void,
    ) -> ::core::primitive::bool;
}

unsafe extern "C" {
    /// Set a pointer to a value atomically.
    ///
    /// ***Note: If you don't know what this function is for, you shouldn't use
    /// it!***
    ///
    /// ## Parameters
    /// - `a`: a pointer to a pointer.
    /// - `v`: the desired pointer value.
    ///
    /// ## Return value
    /// Returns the previous value of the pointer.
    ///
    /// ## Thread safety
    /// It is safe to call this function from any thread.
    ///
    /// ## Availability
    /// This function is available since SDL 3.2.0.
    ///
    /// ## See also
    /// - [`SDL_CompareAndSwapAtomicPointer`]
    /// - [`SDL_GetAtomicPointer`]
    pub fn SDL_SetAtomicPointer(
        a: *mut *mut ::core::ffi::c_void,
        v: *mut ::core::ffi::c_void,
    ) -> *mut ::core::ffi::c_void;
}

unsafe extern "C" {
    /// Get the value of a pointer atomically.
    ///
    /// ***Note: If you don't know what this function is for, you shouldn't use
    /// it!***
    ///
    /// ## Parameters
    /// - `a`: a pointer to a pointer.
    ///
    /// ## Return value
    /// Returns the current value of a pointer.
    ///
    /// ## Thread safety
    /// It is safe to call this function from any thread.
    ///
    /// ## Availability
    /// This function is available since SDL 3.2.0.
    ///
    /// ## See also
    /// - [`SDL_CompareAndSwapAtomicPointer`]
    /// - [`SDL_SetAtomicPointer`]
    pub fn SDL_GetAtomicPointer(a: *mut *mut ::core::ffi::c_void) -> *mut ::core::ffi::c_void;
}

#[cfg(doc)]
use crate::everything::*;