Package Summary Overview Summary

Package Summary Overview Summary

Module java.base
Package java.lang.foreign

# Interface MemorySegment.Scope

Enclosing interface:
  `MemorySegment`

public static sealed interface MemorySegment.Scope
A scope models the lifetime of all the memory segments associated with it. That is, a memory segment cannot be accessed if its associated scope is not alive. Scope instances can be compared for equality. That is, two scopes are considered equals(Object) if they denote the same lifetime.

The lifetime of a memory segment can be either unbounded or bounded. An unbounded lifetime is modelled with the global scope . The global scope is always `alive`. As such, a segment associated with the global scope features trivial temporal bounds, and is always accessible. Segments associated with the global scope are:

- Segments obtained from the global arena ;
- Segments obtained from a raw address, using the `MemorySegment.ofAddress(long)` factory; and
- Zero-length memory segments.

Conversely, a bounded lifetime is modelled with a segment scope that can be invalidated, either `explicitly`, or automatically, by the garbage collector. A segment scope that is invalidated automatically is an automatic scope . An automatic scope is always `alive` as long as it is reachable. Segments associated with an automatic scope are:

- Segments obtained from an automatic arena ;
- Segments obtained from a Java array, e.g. using the `MemorySegment.ofArray(int[])` factory;
- Segments obtained from a buffer, using the `MemorySegment.ofBuffer(Buffer)` factory; and
- Segments obtained from loader lookup .

If two memory segments are obtained from the same buffer or array, the automatic scopes associated with said segments are considered equal, as the two segments have the same lifetime:

    byte[] arr = new byte[10];
    MemorySegment segment1 = MemorySegment.ofArray(arr);
    MemorySegment segment2 = MemorySegment.ofArray(arr);
    assert segment1.scope().equals(segment2.scope());

- ## Method Summary

  Modifier and Type
  Method
  Description
  `boolean`
  `equals (Object that)`
  Returns `true`, if the provided object is also a scope, which models the same lifetime as that modelled by this scope.
  `int`
  `hashCode()`
  Returns the hash code of this scope object.
  `boolean`
  `isAlive()`
  Returns `true`, if the regions of memory backing the memory segments associated with this scope are still valid.

- ## Method Details

  - ### isAlive

    boolean isAlive()
    Returns `true`, if the regions of memory backing the memory segments associated with this scope are still valid.
    Returns:
      `true`, if the regions of memory backing the memory segments associated with this scope are still valid

  - ### equals

    boolean equals (Object that)
    Returns `true`, if the provided object is also a scope, which models the same lifetime as that modelled by this scope.. In that case, it is always the case that `this.isAlive() == ((Scope)that).isAlive()` .
    Overrides:
      `equals` in class `Object`
    Parameters:
      `that` - the object to be tested.
    Returns:
      `true`, if the provided object is also a scope, which models the same lifetime as that modelled by this scope
    See Also:
      - `Object.hashCode()`
      - `HashMap`

  - ### hashCode

    int hashCode()
    Returns the hash code of this scope object.
    Overrides:
      `hashCode` in class `Object`
    Returns:
      the hash code of this scope object.
    See Also:
      - `equals(Object)`
    Implementation Requirements:
      Implementations of this method obey the general contract of `Object.hashCode()`.