Package org.gnome.glib

Class Once

java.lang.Object

org.javagi.base.ProxyInstance

org.gnome.glib.Once

All Implemented Interfaces:

Proxy

@Generated("org.javagi.JavaGI")
public class Once
extends ProxyInstance

A GOnce struct controls a one-time initialization function. Any one-time initialization function must have its own unique GOnce struct.

Since:

2.4

Constructor Summary

Constructors

Constructor	Description
Once()	Allocate a new Once.
Once(Arena arena)	Allocate a new Once.
Once(MemorySegment address)	Create a Once proxy instance for the provided memory address.
Once(OnceStatus status, MemorySegment retval)	Allocate a new Once with the fields set to the provided values.
Once(OnceStatus status, MemorySegment retval, Arena arena)	Allocate a new Once with the fields set to the provided values.

Method Summary

Modifier and Type	Method	Description
static MemoryLayout	getMemoryLayout()	The memory layout of the native struct.
@Nullable MemorySegment	impl(@Nullable ThreadFunc func, @Nullable MemorySegment arg)
static boolean	initEnter(Out<MemorySegment> location)	Function to be called when starting a critical initialization section.
static boolean	initEnterImpl(MemorySegment location)
static boolean	initEnterPointer(MemorySegment location)	This functions behaves in the same way as g_once_init_enter(), but can can be used to initialize pointers (or guintptr) instead of gsize.
static void	initLeave(Out<MemorySegment> location, long result)	Counterpart to g_once_init_enter().
static void	initLeavePointer(MemorySegment location, @Nullable MemorySegment result)	Counterpart to g_once_init_enter_pointer().
MemorySegment	readRetval()	Read the value of the field retval.
OnceStatus	readStatus()	Read the value of the field status.
void	writeRetval(MemorySegment retval)	Write a value in the field retval.
void	writeStatus(OnceStatus status)	Write a value in the field status.

Methods inherited from class org.javagi.base.ProxyInstance

equals, handle, hashCode

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Constructor Details

Once

public Once(MemorySegment address)

Create a Once proxy instance for the provided memory address.

Parameters:

address - the memory address of the native object

Once

public Once(Arena arena)

Allocate a new Once.

Parameters:

arena - to control the memory allocation scope

Once

public Once()

Allocate a new Once. The memory is allocated with Arena.ofAuto().

Once

public Once(OnceStatus status,
 MemorySegment retval,
 Arena arena)

Allocate a new Once with the fields set to the provided values.

Parameters:

status - value for the field status

retval - value for the field retval

arena - to control the memory allocation scope

Once

public Once(OnceStatus status,
 MemorySegment retval)

Allocate a new Once with the fields set to the provided values. The memory is allocated with Arena.ofAuto().

Parameters:

status - value for the field status

retval - value for the field retval

Method Details

getMemoryLayout

public static MemoryLayout getMemoryLayout()

The memory layout of the native struct.

Returns:

the memory layout

readStatus

public OnceStatus readStatus()

Read the value of the field status.

Returns:

The value of the field status

writeStatus

public void writeStatus(OnceStatus status)

Write a value in the field status.

Parameters:

status - The new value for the field status

readRetval

public MemorySegment readRetval()

Read the value of the field retval.

Returns:

The value of the field retval

writeRetval

public void writeRetval(MemorySegment retval)

Write a value in the field retval.

Parameters:

retval - The new value for the field retval

initEnter

public static boolean initEnter(Out<MemorySegment> location)

Function to be called when starting a critical initialization section. The argument location must point to a static 0-initialized variable that will be set to a value other than 0 at the end of the initialization section. In combination with g_once_init_leave() and the unique address valueLocation, it can be ensured that an initialization section will be executed only once during a program's life time, and that concurrent threads are blocked until initialization completed. To be used in constructs like this:

  static gsize initialization_value = 0;

   if (g_once_init_enter (&initialization_value))
     {
       gsize setup_value = 42; // initialization code here

       g_once_init_leave (&initialization_value, setup_value);
     }

   // use initialization_value here
 

While location has a volatile qualifier, this is a historical artifact and the pointer passed to it should not be volatile.

Parameters:

location - location of a static initializable variable containing 0

Returns:

true if the initialization section should be entered, false and blocks otherwise

Since:

2.14

initEnterImpl

public static boolean initEnterImpl(MemorySegment location)

initEnterPointer

public static boolean initEnterPointer(MemorySegment location)

This functions behaves in the same way as g_once_init_enter(), but can can be used to initialize pointers (or guintptr) instead of gsize.

  static MyStruct *interesting_struct = NULL;

   if (g_once_init_enter_pointer (&interesting_struct))
     {
       MyStruct *setup_value = allocate_my_struct (); // initialization code here

       g_once_init_leave_pointer (&interesting_struct, g_steal_pointer (&setup_value));
     }

   // use interesting_struct here
 

Parameters:

location - location of a static initializable variable containing NULL

Returns:

true if the initialization section should be entered, false and blocks otherwise

Since:

2.80

initLeave

public static void initLeave(Out<MemorySegment> location,
 long result)

Counterpart to g_once_init_enter(). Expects a location of a static 0-initialized initialization variable, and an initialization value other than 0. Sets the variable to the initialization value, and releases concurrent threads blocking in g_once_init_enter() on this initialization variable.

While location has a volatile qualifier, this is a historical artifact and the pointer passed to it should not be volatile.

Parameters:

location - location of a static initializable variable containing 0

result - new non-0 value for *value_location

Since:

2.14

initLeavePointer

public static void initLeavePointer(MemorySegment location,
 @Nullable MemorySegment result)

Counterpart to g_once_init_enter_pointer(). Expects a location of a static NULL-initialized initialization variable, and an initialization value other than NULL. Sets the variable to the initialization value, and releases concurrent threads blocking in g_once_init_enter_pointer() on this initialization variable.

This functions behaves in the same way as g_once_init_leave(), but can be used to initialize pointers (or guintptr) instead of gsize.

Parameters:

location - location of a static initializable variable containing NULL

result - new non-NULL value for *location

Since:

2.80

impl

public @Nullable MemorySegment impl(@Nullable ThreadFunc func,
 @Nullable MemorySegment arg)