Package org.python.core.buffer

Class BaseArrayBuffer

java.lang.Object
org.python.core.buffer.BaseBuffer
org.python.core.buffer.Base1DBuffer
org.python.core.buffer.BaseArrayBuffer
All Implemented Interfaces:
AutoCloseable, BufferProtocol, PyBUF, PyBuffer
Direct Known Subclasses:
SimpleBuffer, Strided1DBuffer, ZeroByteBuffer
public abstract class BaseArrayBuffer extends Base1DBuffer
Base implementation of the Buffer API for when the storage implementation is byte[]. The description of BaseBuffer mostly applies. Methods provided or overridden here are appropriate to 1-dimensional arrays, of any item size, backed by byte[].

  • Method Details

    • byteIndex

      public int byteIndex(int... indices) throws IndexOutOfBoundsException
      Description copied from interface: PyBuffer
      Convert a multi-dimensional item index to an absolute byte index in the storage shared by the exporter. The storage exported as a PyBuffer is a linearly-indexed sequence of bytes, although it may not actually be a heap-allocated Java byte[] object. The purpose of this method is to allow the exporter to define the relationship between the item index (as used in PyBuffer.byteAt(int...) and the byte-index (as used with the ByteBuffer returned by PyBuffer.getNIOByteBuffer()).
      Specified by:
      byteIndex in interface PyBuffer
      Overrides:
      byteIndex in class BaseBuffer
      Parameters:
      indices - n-dimensional item-index from consumer
      Returns:
      corresponding byte-index in actual storage
      Throws:
      IndexOutOfBoundsException

    • copyTo

      public void copyTo(int srcIndex, byte[] dest, int destPos, int count) throws IndexOutOfBoundsException
      Copy a simple slice of the buffer-view to the destination byte array, defined by a starting item-index in the source buffer and the count of items to copy. This may validly be done only for a one-dimensional buffer, as the meaning of the starting item-index is otherwise not defined. count*itemsize bytes will be occupied in the destination.

      The default implementation in BaseBuffer deals with the general one-dimensional case of arbitrary item size and stride, but is unable to optimise access to sequential bytes.

      The implementation in BaseArrayBuffer deals with the general one-dimensional case of arbitrary item size and stride.

      Specified by:
      copyTo in interface PyBuffer
      Overrides:
      copyTo in class BaseBuffer
      Parameters:
      srcIndex - starting item-index in the source buffer
      dest - destination byte array
      destPos - byte-index in the destination array of the source item [0,...]
      count - number of items to copy
      Throws:
      IndexOutOfBoundsException - if access out of bounds in source or destination

    • copyFrom

      public void copyFrom(byte[] src, int srcPos, int destIndex, int count) throws IndexOutOfBoundsException, PyException
      Copy from a slice of a (Java) byte array into the buffer starting at a given destination item-index. This may validly be done only for a one-dimensional buffer, as the meaning of the destination index is not otherwise defined. count*itemsize bytes will be read from the source.

      The default implementation in BaseBuffer deals with the general one-dimensional case of arbitrary item size and stride, but is unable to optimise access to sequential bytes.

      The default implementation in BaseArrayBuffer deals with the general one-dimensional case of arbitrary item size and stride.

      Specified by:
      copyFrom in interface PyBuffer
      Overrides:
      copyFrom in class BaseBuffer
      Parameters:
      src - source byte array
      srcPos - location in source of first byte to copy
      destIndex - starting item-index in the destination (i.e. this)
      count - number of items to copy in
      Throws:
      IndexOutOfBoundsException - if access out of bounds in source or destination
      PyException - TypeError if read-only buffer

    • copyFrom

      public void copyFrom(PyBuffer src) throws IndexOutOfBoundsException, PyException
      Description copied from class: BaseBuffer
      Copy the whole of another PyBuffer into this buffer. This may validly be done only for buffers that are consistent in their dimensions. When it is necessary to copy partial buffers, this may be achieved using a buffer slice on the source or destination.

      The default implementation in BaseBuffer deals with the general one-dimensional case of arbitrary item size and stride, but is unable to optimise access to sequential bytes.

      Specified by:
      copyFrom in interface PyBuffer
      Overrides:
      copyFrom in class BaseBuffer
      Parameters:
      src - source buffer
      Throws:
      IndexOutOfBoundsException - if access out of bounds in source or destination
      PyException - TypeError if read-only buffer

    • getBuf

      public PyBuffer.Pointer getBuf()
      Return a structure describing the slice of a byte array that holds the data being exported to the consumer. For a one-dimensional contiguous buffer, assuming the following client code where obj has type BufferProtocol: 
       PyBuffer a = obj.getBuffer(PyBUF.SIMPLE);
 int itemsize = a.getItemsize();
 PyBuffer.Pointer b = a.getBuf();
      the item with index k is in the array b.storage at index [b.offset + k*itemsize] to [b.offset + (k+1)*itemsize - 1] inclusive. And if itemsize==1, the item is simply the byte b.storage[b.offset + k]

      If the buffer is multidimensional or non-contiguous, storage[offset] is still the (first byte of) the item at index [0] or [0,...,0]. However, it is necessary to navigate b.storage using the shape, strides and maybe suboffsets provided by the API.

      BaseArrayBuffer provides a reference to the storage array even when the buffer is intended not to be writable. There can be no enforcement of read-only character once a reference to the byte array has been handed out.

      Specified by:
      getBuf in interface PyBuffer
      Overrides:
      getBuf in class BaseBuffer
      Returns:
      structure defining the byte[] slice that is the shared data