Package org.gnome.glib

Interface HashFunc

All Superinterfaces:

FunctionPointer

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.

@FunctionalInterface
@Generated("io.github.jwharm.JavaGI")
public interface HashFunc
extends FunctionPointer

Functional interface declaration of the HashFunc callback.

See Also:

• run(java.lang.foreign.MemorySegment)

Method Summary

Modifier and Type	Method	Description
int	run(@Nullable MemorySegment key)	Specifies the type of the hash function which is passed to g_hash_table_new() when a GHashTable is created.
default MemorySegment	toCallback(Arena arena)	Creates a native function pointer to the upcall(java.lang.foreign.MemorySegment) method.
default int	upcall(MemorySegment key)	The upcall method is called from native code.

Method Details

run

int run(@Nullable
 @Nullable MemorySegment key)

Specifies the type of the hash function which is passed to g_hash_table_new() when a GHashTable is created.

The function is passed a key and should return a guint hash value. The functions g_direct_hash(), g_int_hash() and g_str_hash() provide hash functions which can be used when the key is a gpointer, gint*, and gchar* respectively.

g_direct_hash() is also the appropriate hash function for keys of the form GINT_TO_POINTER (n) (or similar macros).

A good hash functions should produce hash values that are evenly distributed over a fairly large range. The modulus is taken with the hash table size (a prime number) to find the 'bucket' to place each key into. The function should also be very fast, since it is called for each key lookup.

Note that the hash functions provided by GLib have these qualities, but are not particularly robust against manufactured keys that cause hash collisions. Therefore, you should consider choosing a more secure hash function when using a GHashTable with keys that originate in untrusted data (such as HTTP requests). Using g_str_hash() in that situation might make your application vulnerable to Algorithmic Complexity Attacks.

The key to choosing a good hash is unpredictability. Even cryptographic hashes are very easy to find collisions for when the remainder is taken modulo a somewhat predictable prime number. There must be an element of randomness that an attacker is unable to guess.

upcall

default int upcall(MemorySegment key)

The upcall method is called from native code. The parameters are marshaled and run(java.lang.foreign.MemorySegment) is executed.

toCallback

default MemorySegment toCallback(Arena arena)

Creates a native function pointer to the upcall(java.lang.foreign.MemorySegment) method.

Specified by:

toCallback in interface FunctionPointer

Parameters:

arena - the function pointer will be allocated in this arena

Returns:

the native function pointer