libpointer

Creates an C pointer object usuable in Nelson.

Syntax

• ptr = libpointer()
• ptr = libpointer(datatype)
• ptr = libpointer(datatype, value)

Input argument

• datatype - a string: data type.
• value - a nelson variable compatible with datatype.

Output argument

• ptr - a libpointer handle.

Description

This is an advanced feature to manipulate C pointers.

ptr = libpointer() creates an NULL pointer.

Examples

p = libpointer('int8Ptr', int8([3 4]));
p.isNull()
p.DataType
p.Value

NLSDYNAMIC_LINK_IMPEXP double *multiplicationDoubleByReference(double *x)
{
    *x *= 2;
    return x;
}

x = 133.3;
xPtr = libpointer('doublePtr', x);
path_ref = modulepath('dynamic_link', 'builtin');
lib = dlopen(path_ref);
f = dlsym(lib, 'multiplicationDoubleByReference', 'libpointer', {'doublePtr'});
[r1, r2] = dlcall(f, xPtr);
r2
% r1 is an libpointer of type '' (voidPointer) and it need to be change type and size.
r1.setdatatype('doublePtr');
r1.reshape(1, 1);
get(r1)

See also

C/Nelson equivalent data types, isNull, libpointer.reshape, libpointer.setdatatype.

History

Author

Allan CORNET