org.python.core

Interface BufferProtocol

All Known Subinterfaces:

PyBuffer

All Known Implementing Classes:

Base1DBuffer, BaseArrayBuffer, BaseBuffer, BaseNIOBuffer, Py2kBuffer, PyArray, PyArrayDerived, PyByteArray, PyByteArrayDerived, PyMemoryView, PyShadowString, PyShadowStringDerived, PyString, PyStringDerived, PyUnicode, PyUnicodeDerived, SimpleBuffer, SimpleNIOBuffer, SimpleStringBuffer, SimpleWritableBuffer, Strided1DBuffer, Strided1DNIOBuffer, Strided1DWritableBuffer, SyspathArchive, ZeroByteBuffer

public interface BufferProtocol

Interface marking an object as capable of exposing its internal state as a PyBuffer.

A few objects implement BufferProtocol (e.g. by inheritance) but cannot actually provide their value as a PyBuffer. These should throw ClassCastException, permitting the idiom:

     try (PyBuffer buf = ((BufferProtocol) obj).getBuffer(PyBUF.SIMPLE)) {
         ... // Do something with buf
     } catch (ClassCastException e) {
         ... // expected bytes object or buffer not obj.getType()
     }
 

The catch is executed identically whether the cause is the explicit cast of obj or getBuffer, and the try-with-resources releases the buffer if one was obtained.

Method Summary

Modifier and Type	Method and Description
PyBuffer	getBuffer(int flags) Method by which the consumer requests the buffer from the exporter.

Method Detail

getBuffer

PyBuffer getBuffer(int flags)
            throws PyException,
                   java.lang.ClassCastException

Method by which the consumer requests the buffer from the exporter. The consumer provides information on its ability to understand buffer navigation. Each consumer requesting a buffer in this way, when it has finished using it, should make a corresponding call to PyBuffer.release() on the buffer it obtained, or PyBuffer.close() using try-with-resources, since some objects alter their behaviour while buffers are exported.

Parameters:

flags - specifying features demanded and the navigational capabilities of the consumer

Returns:

exported buffer

Throws:

PyException - BufferError when expectations do not correspond with the buffer

java.lang.ClassCastException - when the object only formally implements BufferProtocol